Showing papers in "Isokinetics and Exercise Science in 2021"
TL;DR: In this paper, the accuracy of the estimation of the free-weight bench press 1RM between six velocity-based 1RM prediction methods was compared to the actual and predicted 1RM.
Abstract: BACKGROUND: More practical and less fatiguing strategies have been developed to accurately predict the one-repetition maximum (1RM). OBJETIVE: To compare the accuracy of the estimation of the free-weight bench press 1RM between six velocity-based 1RM prediction methods. METHODS: Sixteen men performed an incremental loading test until 1RM on two separate occasions. The first session served to determine the minimal velocity threshold (MVT). The second session was used to determine the validity of the six 1RM prediction methods based on 2 repetition criteria (fastest or average velocity) and 3 MVTs (general MVT of 0.17 m⋅s-1, individual MVT of the preliminary session, and individual MVT of the validity session). Five loads (≈ 2540557085% of 1RM) were used to assess the individualized load-velocity relationships. RESULTS: The absolute difference between the actual and predicted 1RM were low (range = 2.7–3.7%) and did not reveal a significant main effect for repetition criterion (P= 0.402), MVT (P= 0.173) or their two-way interaction (P= 0.354). Furthermore, all 1RM prediction methods accurately estimated bench press 1RM (P⩾ 0.556; ES ⩽ 0.02; r⩾ 0.99). CONCLUSIONS: The individualized load-velocity relationship provides an accurate prediction of the 1RM during the free-weight bench press exercise, while the repetition criteria and MVT do not appear to meaningfully affect the prediction accuracy.
8 citations
7 citations
TL;DR: In this article, the effect of additional plyometric training in rhythmic gymnastics on the reactive jumping performance and strength of the lower leg muscles was examined, and a significant increase in work performed during plantarflexion was found in the EG for the right leg (pre: 24.9 J; post: 29.7 J; p< 0.01).
Abstract: BACKGROUND: Reactive performance is an important component of rhythmic gymnastics. So far, it is unclear whether additional plyometric training in female gymnasts shows an increase in performance. OBJECTIVE: The aim of the study was to examine the effect of additional plyometric training in rhythmic gymnastics on the reactive jumping performance and strength of the lower leg muscles. METHODS: Fifteen rhythmic gymnasts (age: 12.3 ± 2.6 years, height: 1.47 ± 0.12 m, body weight: 37.3 ± 9.3 kg, BMI: 16.7 ± 2.1 kg*m-2; competition level: national and international championships, Tanner stages I–III) participated in the study. The athletes were assigned to an experimental (EG) and a control group (CG). The EG performed plyometric exercises three times per week in addition to the regular training. Before and after six weeks of training the reactive jump performance, the work of dorsi flexors and plantar flexors performed during isokinetic plantarflexion, as well as the performance in two sport-specific tests were measured. RESULTS: In contrast to the CG, in the EG the jump height (pre: 24.8; post: 27.25 cm; p< 0.05) and the reactive-strength-index (pre: 1.01; post: 1.19; p< 0.01) increased significantly. The EG achieved significant improvements in the counter movement jump test (pre: 27.0 cm; post: 31.5 cm; p< 0.01) and in the sport specific double rope jump test (jumps per minute, pre: 18.0; post: 23.0; p< 0.01). Furthermore, a significant increase in work performed during plantarflexion was found in the EG for the right leg (pre: 24.9 J; post: 29.7 J; p< 0.01) and a tendency to increase for the left leg (pre: 26.4 J; post: 37.7 J; p= 0.05). CONCLUSION: Both reactive strength and dynamic force can be efficiently increased by plyometric training. It may be recommended to include plyometric exercises in the training regime of rhythmic gymnasts.
4 citations
TL;DR: The abdominal crunch with transversus abdominis pre-activation increases the inter-rectus distance in comparison with rest and with abdominal crunch in the U point, which increases the knowledge about the behaviour of the linea alba and inter- rectus distance during abdominal exercises.
Abstract: BACKGROUND: The effects of abdominal exercises on the inter-rectus distance are unclear. OBJECTIVE: To compare the inter-rectus distance at rest and during different abdominal exercises: abdominal crunch, abdominal crunch with transversus abdominis pre-activation and hypopressive exercise. METHODS: A transversal experimental study was carried out in 98 healthy adults without diastasis recti abdominis were recruited. Measurements were assessed using ultrasound imaging, and two points were evaluated: just above the umbilicus (U point) and halfway between the U point and the xiphoid (UX point). The inter-rectus distance was measured at rest and during the abdominal exercises. RESULTS: The abdominal crunch with transversus abdominis pre-activation increases the inter-rectus distance in comparison with rest and with abdominal crunch in the U point. CONCLUSION: These results increase the knowledge about the behaviour of the linea alba and inter-rectus distance during abdominal exercises, with practical applications in the rehabilitation of the abdominal wall and low back.
4 citations
TL;DR: Clinically, belts with capacitive force sensors can be used as a feedback tool to train abdominal wall activation and compare changes in muscle activation during respiration while breathing under a load, and during instructed breathing.
Abstract: BACKGROUND: The abdominal muscles play an important respiratory and stabilization role, and in coordination with other muscles regulate intra-abdominal pressure (IAP) to stabilize the spine. OBJECTIVE: To examine a new, non-invasive method to measure activation of the abdominal wall and compare changes in muscle activation during respiration while breathing under a load, and during instructed breathing. METHODS: Thirty-five healthy individuals completed this observational crossover study. Two capacitive force sensors registered the abdominal wall force during resting breathing stereotype, instructed breathing stereotype and under a load. RESULTS: Mean abdominal wall force increased significantly on both sensors when holding the load compared to resting breathing (Upper Sensor: P< 0.0005, d=-0.46, Lower Sensor: P< 0.0005, d=-0.56). The pressure on both sensors also significantly increased during instructed breathing compared to resting breathing (US: P< 0.0005, d=-0.76, LS: P< 0.0005, d=-0.78). CONCLUSIONS: The use of capacitive force-sensors represent a new, non-invasive method to measure abdominal wall activity. Clinically, belts with capacitive force sensors can be used as a feedback tool to train abdominal wall activation.
4 citations
TL;DR: Based on inter-rater reliability and DNS brace correlations with trained DNS professionals, the IAPRT, Diaphragm test, and Hip Flexion test may prove useful when assessing asymptomatic individuals.
Abstract: BACKGROUND: The evaluation of postural trunk muscle function is a critical component of clinical assessment in patients with musculoskeletal pain and dysfunction. Postural activation of the trunk muscles has been evaluated by various methods. This study evaluates the correlation between subjective assessment of postural trunk muscle function with an objective measurement of abdominal wall expansion. METHODS: Twenty-five healthy participants (16 women, 9 men, age 22.4 years) were assessed. The subjective assessment was performed by two experienced Dynamic Neuromuscular Stabilization (DNS) clinicians evaluating the quality of trunk stabilization using five postural stability tests through palpation and observation. Interrater reliability was determined using an intraclass correlation coefficients (ICC). Objective measurement was performed using a new device (DNS Brace) which externally measures abdominal wall pressure. Spearman rank correlations were calculated for both palpation and observation measures with DNS Brace data. RESULTS: The interrater reliability (ICC2,k) estimates demonstrated moderate reliability in palpation measures for three DNS tests: Hip flexion test, Diaphragm test, & Intra-abdominal pressure regulation test (IAPRT) (ICC = 0.645–0.707). For observation measures, good reliability was found in IAPRT (ICC = 0.835), and three tests demonstrated moderate reliability: Hip flexion test, Diaphragm test, & Breathing Stereotype (ICC = 0.577–0.695). Correlation analysis demonstrated several moderate to strong correlations between palpation and DNS brace values (Assessor 1): IAPRT, rs= 0.580, p= 0.002, Diaphragm test, rs= 0.543, p= 0.005, (Assessor 2): IAPRT, rs= 0.776, p< 0.001, Breathing Stereotype, rs= 0.625, p= 0.001, Diaphragm test, rs= 0.519, p= 0.008, Hip Flexion test, rs= 0.536, p= 0.006, and Arm Elevation test, rs= 0.460, p= 0.021. For observation, several moderate correlations were demonstrated with DNS brace values (Assessor 1): Arm Elevation test, rs= 0.472, p= 0.017, (Assessor 2) Diaphragm test, rs= 0.540, p= 0.005, IAPRT rs= 0.475, p= 0.016, Hip Flexion test, rs= 0.485, p= 0.014, and Arm Elevation, rs= 0.451, p= 0.024. CONCLUSION: Based on inter-rater reliability and DNS brace correlations with trained DNS professionals, the IAPRT, Diaphragm test, and Hip Flexion test may prove useful when assessing asymptomatic individuals. More research is needed in order to establish the utility of DNS brace and clinical testing both in asymptomatic and back pain populations. DNS tests must be supplemented by further examinations for definitive clinical decision making.
4 citations
TL;DR: In this paper, the authors compared the acute physiological and neuromuscular responses and time-motion characteristics during small-sided games played with and without wildcard players, and found that the inclusion of wild-card players during smallsided games caused a reduction in perceptual, physiological demands and time motion parameters when compared to control condition.
Abstract: BACKGROUND: Small-sided games are a popular training method that have shown its effectiveness in improving athletic performance in football players. OBJECTIVE: To compare the acute physiological and neuromuscular responses and time-motion characteristics during small-sided games played with and without wildcard players. METHODS: Sixteen amateur male football players completed two small-sided games protocol: 4-a-side and 4-a-side with wildcard players. Time-motion characteristics during games, muscular performance parameters before and after small-sided games protocols, physiological response in terms of heart rate and muscle oximetry and rate of perceived exertion were collected. RESULTS: Both small-sided games formats induced changes in sprint performance (before-after comparison), in the rate of perceived exertion, heart rate-related variables and time-motion parameters (p< 0.05). In a comparison between small-sided games formats, lower values of oxygen saturation, heart rate, rate of perceived exertion and time-motion parameters (p< 0.05) were reported during small-sided games with wildcard players in both working and recovery periods. CONCLUSIONS: The inclusion of wildcard players during small-sided games cause a reduction in perceptual, physiological demands and time-motion parameters when compared to control condition.
4 citations
TL;DR: Resistance exercise to muscular failure induced greater CMJ height decrement and internal training load perception than non-failure exercise, with RP-F leading to a higher acute neuromuscular performance impairment.
Abstract: BACKGROUND: Traditional and rest-pause systems are commonly used during resistance training. These systems have different rest times between repetitions that might affect neuromuscular status and fatigue level. OBJECTIVE: This study compared the acute effects of traditional and rest-pause resistance exercise done to muscular failure on countermovement jump (CMJ) performance. METHODS: Twenty-nine recreationally strength-trained adults of both sexes aged from 18 to 33 years old performed four experimental resistance exercise sessions (half back-squat exercise) in a randomized order. The experimental conditions were: Traditional system to muscular failure (TR-F; 4 × 15 [15RM]) or non-failure (TR-NF; 5 × 12 [15RM]), and rest-pause system to muscular failure (RP-F; 60 reps with 30 s rest between each failure) or non-failure (RP-NF; 60 reps with 10.2 s rest between each repetition). CMJ height was measured at pre-experiment, Post-15 s, and Post-30 min. Perceived recovery was assessed at pre-experiment, lactate concentration Post-2 min, and rating of perceived exertion Post-30 min. RESULTS: CMJ height decrease occurred at Post-15 s and 30 min for the TR-F, TR-NF, and RP-F sessions (p< 0.05). Interaction effects (p< 0.05) showed exercise to muscle failure (TR-F and RP-F) induced greater neuromuscular decrement at Post-15 s, with RP-F leading to a higher CMJ performance impairment at Post-30 min (p< 0.001). Higher blood lactate concentrations were found following TR-F, TR-NF, and RP-F (p< 0.05) than RP-NF conditions, whereas greater internal training load perception was reported after training to muscular failure (p< 0.05) than non-failure exercise. CONCLUSION: Resistance exercise to muscular failure induced greater CMJ height decrement and internal training load perception than non-failure exercise, with RP-F leading to a higher acute neuromuscular performance impairment.
4 citations
TL;DR: In this article, post-activation potentiation (PAP) exercises at the end of warm-up may increase muscles nerve conduction speed and per consequent improve speed, strength and explosive power performances.
Abstract: BACKGROUND: The use of post-activation potentiation (PAP) exercises at the end of the warm-up may increase muscles nerve conduction speed and per consequent improve speed, strength and explosive power performances. OBJECTIVE: To assess the effect of PAP during warm-up using vertical or horizontal drop jumps on repeated sprints performance combined with countermovement jump in young handball players. METHODS: 12 young handball players participated in this study. Participants realized 3 randomized warm-up protocols: a warm-up without PAP, a warm-up with PAP using vertical drop jumps, and a warm-up with PAP using horizontal drop jumps. After the assigned PAP protocol, the subject realized a counter movement jump as a reference value (CMJr), and thereafter repeated sprint tests with and without changing of direction (six maximal 2 × 12.5 m shuttle sprints and six maximal 25 m straight sprints, respectively) combined with vertical jumping. RESULTS: Horizontal drop jump during warm-up showed larger improvements in repeated sprints performance with and without change of direction for the parameters best time and mean time, compared with warm up without drop jumps (p< 0.01) and warm up with vertical drop jumps (p< 0.05). Vertical drop jump performance during warm-up induced greater gains in countermovement jump reference value in comparison with warm up without drop jump (p< 0.01), or warm up with horizontal drop jump (p< 0.01). CONCLUSION: PAP during warm-up using horizontal drop jump improves repeated sprints performance with and without changing of direction while PAP using vertical drop jump improves CMJ reference value.
3 citations
TL;DR: The results of the present study suggest that the differential activation/movement pattern of the D and ND leg muscles do not lead to anatomical, dynamic and functional lower extremities asymmetries.
Abstract: BACKGROUND: Data about lower extremities’ strength and power asymmetries in fencers, and their relationships to fencing performance are limited and inconsistent. OBJECTIVE: The aim of the present study was to investigate asymmetries, between dominant (D) and non-dom (ND) legs of elite young male and female fencers, in relation to performance in fencing specific tests. METHODS: Anthropometric characteristics, unilateral vertical-horizontal jumping, isokinetic strength, lunge and step lunge performances were evaluated in 16 male and 22 female elite fencers. RESULTS: Significant differences between genders were found for all anthropometric measurements (p< 0.05). No significant bilateral asymmetries and gender x laterality effects were observed (p> 0.05). Fencing performance was negatively correlated with the D leg’s flexion/extension (F/E) ratio at 300∘/s (r: -0.564 to -0.619, p< 0.05). In addition, D leg’s F/E ratio at 300∘/s was positively related to lung peak velocity and power in female fencers (r: 0.562–0.649; p< 0.05). Finally, only in female fencers, unilateral triple hop distance was significantly related to lung peak velocity and power (r: 0.442–0.500; p< 0.05). CONCLUSIONS: The results of the present study suggest that the differential activation/movement pattern of the D and ND leg muscles do not lead to anatomical, dynamic and functional lower extremities asymmetries.
3 citations
TL;DR: In juvenile football players, weight-free vibration training at 40 Hz and 50 Hz improves peak torque of the knee extensors at 60∘/s and 240∙/s, while training at 50Hz improves endurance of the knees extensor.
Abstract: BACKGROUND: Vibration training can affect strength improvement. However, the role of the vibration frequency, in terms of knee muscle strength, is unclear. OBJECTIVE: To evaluate the effect of vibration training with the same amplitude and different frequencies on the isokinetic muscle strength of the knee in juvenile football players. METHODS: Juvenile football players were divided into four groups: low frequency (n= 13, 25 Hz), medium frequency (n= 14, 40 Hz), high frequency (n= 14, 50 Hz), and control (n= 13). The frequency groups completed 12 weeks of weight-free vibration training (three times/week) with the same amplitude (3 mm) but different frequency. RESULTS: Compared with baseline, the peak extension torque of the knee at 60∘/s and 240∘/s increased by 8.4% and 12.9%, respectively, in the medium-frequency group, and by 8.9% and 15.5%, respectively, in the high-frequency group. The extensor endurance (the ability of joint muscle groups to maintain a force output over time) of the knee in the high-frequency group increased by 4.3%. At 12 weeks, the high-frequency group had greater knee extensor endurance than the low- and medium-frequency groups. CONCLUSION: In juvenile football players, weight-free vibration training at 40 Hz and 50 Hz improves peak torque of the knee extensors at 60∘/s and 240∘/s, while training at 50 Hz improves endurance of the knee extensors.
TL;DR: The findings derived from the isometric strength tests are not related to those obtained from specific volleyball performance tests, however, the advantages of isometric tests and their findings may be of a comparative clinical value in management of sports injury in volleyball players.
Abstract: BACKGROUND: Volleyball player’s performance depends on a combination of technical-tactical skills and an optimum level of general and specific physical fitness. OBJECTIVE: The purpose of the study was to compare the results of three isometric strength tests with the results of four specific volleyball performance tests using a novel Multidimensional Modelling Approach. METHODS: In a cross-sectional study 80 male (age = 16.2 ± 1.7 yrs.) and 116 female (age = 16.1 ± 1.5 yrs.) volleyball players performed two testing sessions consisting of ankle extensor, handgrip, and lumbar isometric strength tests, followed by countermovement tests, modified X test and medicine ball throw. RESULTS: Principal Component Analysis, with 51.38% to 64.87% of variances explained, was used to group results from multiple tests into a single score: isometric force (Fmax Score), rate of force development (RFDmax Score), and specific performance tests (Specific Score). Calculated Fmax Score, and RFDmax Score values showed low (r= 0.310–0.416), but statistically significant (p< 0.01) correlations with Specific Score. Regression analysis showed 17.3% and 9.6% influence of Fmax and 16.9% and 10.1% influence of RFDmax on specific abilities for male and female sample respectively. CONCLUSIONS: The findings derived from the isometric strength tests are not related to those obtained from specific volleyball performance tests. However, the advantages of isometric tests and their findings may be of a comparative clinical value in management of sports injury in volleyball players.
TL;DR: Both HIPW and LIPW may be effective in enhancing the pre-training or pre-competition practices in off-season for national-level field hockey athletes, however, the individualization of HIPW is highly recommended in order to maintain PAP effects for 10-m sprint times, 30-m Sprint times and agility times throughout the 10 minutes when compared to LipW.
Abstract: BACKGROUND: Postactivation potentiation (PAP) is an acute and temporary enhancement of muscular performance resulting from previous muscular contraction. Extensive research exists examining the PAP effect after a heavy resistance exercise but there is limited research examining the PAP effect after a plyometric stimulus to the pre-competition practices (e.g., warm-up) of well-trained athletes. OBJECTIVE: The purpose of this study was to investigate the acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes at recovery time of immediately, 5 minutes and 10 minutes. METHODS: In a randomized crossover design, ten male national-level field hockey athletes performed 30-m sprint (with 10-m split) and agility test at baseline, immediately (∼ 15 sec), 5 minutes and 10 minutes after a high-intensity plyometric warm-up (HIPW), a low-intensity plyometric warm-up (LIPW) and a control trial (CT). RESULTS: Mean 10-m sprint times, 30-m sprint times and agility times were similar between trials at baseline (p> 0.05). Significant trial x time interactions (p⩽ 0.05) were observed for 10-m sprint time, 30-m sprint time and agility time. 10-m sprint times were significantly decreased after HIPW at all time-points and LIPW at immediately time-point, relative to baseline (p⩽ 0.05). HIPW 10-m sprint times were faster at all time-points and LIPW sprint time was faster at 10 minutes when compared with CT (p⩽ 0.05). Thirty-meter sprint times were significantly decreased after HIPW and LIPW at all time-points, relative to baseline (p⩽ 0.05). HIPW 30-m sprint times at all time-points and LIPW at both the 5 and 10 minute time-points were faster than CT (p⩽ 0.05). Agility times were significantly decreased after HIPW at all time-points and LIPW at both the immediately and 5 minutes time-points, relative to baseline (p⩽ 0.05). HIPW and LIPW agility times were faster than CT, at all time-points (p⩽ 0.05). CONCLUSIONS: Both HIPW and LIPW may be effective in enhancing the pre-training or pre-competition practices in off-season for national-level field hockey athletes. However, the individualization of HIPW is highly recommended in order to maintain PAP effects for 10-m sprint times, 30-m sprint times and agility times throughout the 10 minutes when compared to LIPW.
TL;DR: In this article, the effects of repeated sprint training with a change of direction on isokinetic strength parameters in well-trained youth soccer players were evaluated for a period of eight weeks, including three sets of six, 40 m (20 + 20 m) shuttle sprints twice a week for eight weeks.
Abstract: BACKGROUND: Sprint drills are part of the soccer training routine for their resemblance to match activities. There is a lack of information in the literature about the changes in isokinetic skeletal muscle strength in response to sprint training. OBJECTIVE: This study evaluates the effects of eight weeks, on-season repeated sprint training with a change of direction on isokinetic strength parameters in well-trained youth soccer players. METHODS: Nineteen well-trained youth soccer players volunteered to participate in the study. The training program included three sets of six, 40 m (20 + 20 m) shuttle sprints twice a week for eight weeks. Isokinetic peak moment, work, and power of knee extensors and flexors were measured at angular velocities of 60, 180 and 240∘/s. Pre- and post-training valid isokinetic sector data were compared. RESULTS: Following the training period, dominant and non-dominant legs’ peak moment, work, and power values for both extensor and flexor muscle groups improved significantly at various angular velocities. CONCLUSIONS: Isokinetic strength enhancement may be explained with the induction of muscle hypertrophy following a prolonged period of sprint training.
TL;DR: In this paper, the authors compared the performance of the CrossFit Barbara and the traditional resistance training methods to maintain the strength performance of national kickboxers, and found that the former was more effective in maintaining strength endurance performances, and the latter in maintaining maximum strength performances.
Abstract: BACKGROUND: The inability of athletes to train or the decrease in the intensity and frequency of training may cause athletes to lose performance. Particularly in view of the current COVID-19 pandemic, maintaining strength outside the normal framework provides an advantage to athletes for the next competitions. OBJECTIVE: To compare the CrossFit Barbara which can be applied easily at home during the off-season or some situations such as the epidemic limitation to classic resistance training methods used to maintain the strength performance of national kickboxers. METHODS: Forty-three national kickboxers, CrossFit (CF, n= 22), and resistance training (RT, n= 21), participated in this study. While CF performed 20 pull-ups, 30 push-ups, 40 sit-ups, and 50 squat exercises, RT performed bench press, lat pull down, leg press, biceps curl, and triceps extension exercises twice per week for six weeks. Before and after the six weeks, the following variables were measured;body mass (BM) and body fat percentage (FP), VO2max, bench press (BP), squat (SQ), leg strength (LS), hand grip strength (HGS), pull-up, push-up and counter movement jump (CMJ). RESULTS: BP (p p> 0.05). In the RT, the pull-up and push-up variables decreased significantly (p p> 0.05). CONCLUSION: CF Barbara workout was more effective in maintaining strength endurance performances, and RT in maintaining maximum strength performances. According to the individual performance needs of athletes, reasonable training method can be used to prevent performance decrement in the strength domain.
TL;DR: In this article, the authors examined the relationship between trunk flexion strength and throwing velocity in elite handball players, using women as a model, and found no significant association between any measure of trunk flexions and the throwing velocity for either throwing technique.
Abstract: BACKGROUND: The relationship between strength and throwing velocity is much investigated in handball, but core strength is largely ignored. Only four studies have investigated the effect of core training on handball throwing velocity, reporting conflicting results in amateur players. However, lack of specificity and deficient technical execution of throwing in amateurs can obscure the results. OBJECTIVE: To examine the direct association between trunk flexion strength and throwing velocity in elite handball players, using women as a model. METHODS: Sixteen women players from an elite-level Norwegian handball team participated in the study. Strength in trunk flexion, shoulder extension, internal shoulder rotation, and forearm pronation was assessed using isokinetic dynamometer measurements (peak moment, total work, angular impulse). Throwing velocity in both the standing throw with run-up and the jump throw was determined from motion capture measurements. To account for arm strength, the association between trunk flexion strength and throwing velocity was examined using partial correlation analyses. RESULTS: No significant association was found between any measure of trunk flexion strength and throwing velocity for either throwing technique (explained variance ⩽ 13.7%). CONCLUSIONS: The results indicate that isolated, dynamic trunk flexion strength is not a differentiating factor for handball throwing velocity in elite women players.
TL;DR: PS, PL and PD are all suitable to evaluate strength endurance, however, PD may be preferred to evaluate the upper body, if velocity also needs to be taken into account.
Abstract: BACKGROUND: The hand-grip strength test has been widely adopted to evaluate upper limb strength. Other field based tests as push-ups and pull-ups are commonly used for the same purpose. It is however unclear if these may be used interchangeably for upper body strength evaluation. OBJECTIVE: The purpose of this investigation was to evaluate strength endurance of the upper body and understand which test could be the most appropriate for upper body evaluation. METHODS: Thirty-eight healthy young male participants were tested with three tests comprised of: 1) push-ups (PS), 2) pull-ups (PL) and 3) parallel dips (PD) performed to exhaustion. Grip strength (GS), total number of repetitions, time-to-complete the test, repetition cadence and rate of perceived exertion (RPE) were also retrieved for investigation. RESULTS: Repetitions, time-to-complete the test and repetition cadence significantly differed across the three tests (p< 0.001). No difference in the RPE was present. No correlation was present between GS and the other tests. No correlation was present between RPE and performance values and time-to-complete the tests. BMI was positively correlated to RPE in all tests. All tests strongly correlate to each other (PS vs. PL r= 0.55; PS vs. PD r= 0.64; PL vs. PD r= 0.70) and to time-to-complete the test (PS r= 0.79; PL r= 0.69; PD r= 0.66). Only the results of the PD correlate to their respective repetition cadence (r= 0.66). CONCLUSIONS: GS is not suitable to evaluate strength endurance. PS, PL and PD are all suitable to evaluate strength endurance. However, PD may be preferred to evaluate the upper body, if velocity also needs to be taken into account.
TL;DR: The provided MRD values allow to detect significant individual changes in VA, as expected after training and rehabilitation programs.
Abstract: BACKGROUND: A method of measurement of voluntary activation (VA, percent of full muscle recruitment) during isometric and isokinetic concentric contractions of the quadriceps femoris (QF) at 60∘/s and 120∘/s was previously validated. OBJECTIVE: This study aimed to quantify the test-retest minimal real difference (MRD) of VA during isometric (ISOM) and isokinetic concentric contractions of QF (100∘/s, ISOK) in a sample of healthy individuals. METHODS: VA was measured through the interpolated twitch technique. Pairs of electrical stimuli were delivered to the QF at 40∘ of knee flexion during maximal voluntary contractions. Twenty-five healthy participants (20–38 years, 12 women, 13 men) completed two testing sessions with a 14-day interval. VA values were linearized through logit transformation (VAl). The MRD was estimated from intraclass correlation coefficients (model 2.1). RESULTS: The VA (median, range) was 84.20% (38.2–99.9%) in ISOM and 94.22% (33.8–100%) in ISOK. MRD was 0.78 and 1.12 logit for ISOM and ISOK, respectively. As an example, in terms of percent VA these values correspond to a change from 76% to 95% and from 79% to 98% in ISOM and in ISOK, respectively. CONCLUSIONS: The provided MRD values allow to detect significant individual changes in VA, as expected after training and rehabilitation programs.
TL;DR: SFEs, with or without TPT, may offer an effective treatment for PwMLBP with foot over-pronation, based on the effect size, SFEs significantly improved all the variables of interest.
Abstract: BACKGROUND: Abnormal foot mechanics in foot over-pronation has an identified relationship with mechanical low back pain (MLBP). OBJECTIVE: To explore the use of short foot exercises (SFEs) as a standalone treatment for MLBP with foot over-pronation. METHODS: Forty-six patients with MLBP (PwMLBP) presenting with and foot over-pronation were analyzed. They were randomized into the SFE (short foot exercise), SFE plus traditional physical therapy treatment (SFE+TPT), and control (CG) groups. Functional disability and pain level were measured using the Oswestry Disability Index (ODI) and visual analog scale (VAS), respectively. Ultrasonography measured the cross-sectional area (CSA) of the abductor hallucis (AbdH) muscle. The foot posture and navicular drop (ND) were investigated using the foot posture index-6 (FPI) score and ND test, respectively. RESULTS: The CSA of the AbdH and VAS scores improved significantly (p< 0.001) between the groups, more in the SFE+TPT group than in the SFE group (p< 0.001). The ND, FPI, and ODI measures improved significantly among the groups (p< 0.001), with no significant difference (p> 0.002) between the SFE and SFE+TPT groups. The CG did not show significant differences in the outcome measures (p> 0.002). Based on the effect size, SFEs significantly improved all the variables of interest (d>1). CONCLUSION: SFEs, with or without TPT may offer an effective treatment for PwMLBP with foot over-pronation.
TL;DR: CODS correlate with SJ and CMJ, in particular, SJ influence CODS independently of gender, and multiple regression model documented that only SJ significantly influenced CODs performance in male and female.
Abstract: BACKGROUND: Explosive strength and change of direction speed (CODS) are relevant physical abilities in karate. OBJECTIVE: To examine the relationship between the characteristics of explosive strength and the 5-m linear sprint (5M) with CODS performance and ii) to examine the influential characteristics of explosive strength on CODS performance. METHODS: Eighteen cadet and junior karate athletes, eight females and ten males were evaluated. The physical abilities assessments included: squat jump (SJ), countermovement jump (CMJ), 5M and CODS. Also, pre-stretch percentage increase (PSA), eccentric utilization index (EUR) reactive strength index (RSI) were calculated. RESULTS: Superior performance (p< 0.05) was documented in SJ, CMJ and CODS in male vs. female. Also, significant correlations between CODS with SJ and CMJ (r=-0.70 to -0.80; R2=-0.51 to -0.73; p< 0.05, respectively) and correlations (r=-0.14 to -0.22; R2= 0.01 to 0.04; p> 0.05) between CODS with RSI, EUR and PSA. Multiple regression model documented that only SJ significantly influenced CODS performance in male (R2= 60%; p= 0.009) and female (R2= 71%; p= 0.001). CONCLUSION: CODS correlate with SJ and CMJ. In particular, SJ influence CODS independently of gender.
TL;DR: The current study revealed that plyometric training as a single component may not guarantee the development of low-risk landing mechanics for young female athletes.
Abstract: BACKGROUND: It remains unclear if plyometric training as a single component could improve landing mechanics that are potentially associated with lower risk of ACL injury in the long term OBJECTIVE: The purpose of this study was to investigate the influence of experience undertaking plyometrics on landing biomechanics in female athletes. METHODS: Non-jumpers with little experience in plyometric training (12 female college swimmers) and jumpers with five years of experience in plyometric training (12 female college long jumpers and high jumpers) were recruited to participate in two testing sessions: an isokinetic muscle force test for the dominant leg at 120∘/s and a 40-cm drop landing test. An independent t test was applied to detect any significant effects between cohorts for selected muscle force, kinematic, kinetic, and electromyography variables. RESULTS: While female jumpers exhibited greater quadriceps eccentric strength (P= 0.013) and hamstring concentric strength (P= 0.023) during isokinetic testing than female swimmers, no significant differences were observed in kinematics, kinetics, and muscle activities during both drop landing and drop jumping. CONCLUSIONS: The results suggest that the female jumpers did not present any training-induced modification in landing mechanics regarding reducing injury risks compared with the swimmers. The current study revealed that plyometric training as a single component may not guarantee the development of low-risk landing mechanics for young female athletes.
TL;DR: In this article, the authors present reference values for tests of muscle function, and to study the relationship to a commonly used tool of generic health related quality of life (HRQL) in older Swedish adults.
Abstract: BACKGROUND: Life expectancy among older adults has dramatically increased and they are one of the fastest growing populations worldwide. Maintaining quality of life and the ability to live independently are often of greater importance than overall life expectancy. OBJECTIVE: To present reference values for tests of muscle function, and to study the relationship to a commonly used tool of generic health related quality of life (HRQL) in older Swedish adults. METHODS: The study consisted of 192 individuals (105 women) aged between 65 and 80. The tests included hand grip and isometric knee extension strength measurements, the standing heel rise test and a 30 m walking test. Health-related quality of life (HRQOL) was evaluated using the SF-36. RESULTS: Reference values for the measured parameters are presented. There were high correlations (n= 192) between handgrip and leg extension strength (r= 0.72–0.75; p< 0.01). The walking test’s self-selected speed demonstrated the strongest correlation with the physical component summary of the SF-36 (r= 0.57; p< 0.01) and with maximal speed, moderate correlations were demonstrated with muscle strength (r= 0.43–0.56; p< 0.01) and the heel rise test (r= 0.45; p< 0.01). CONCLUSIONS: This study presents reference values for simple tests of muscle function which are relatively easy to perform, used in a Swedish clinical setting performing screening for older adults.
TL;DR: Verbal encouragement appears to be effective in maintaining central activation, but is insufficient for promoting strength, which supports the idea that peripheral contributing factors play a larger role in force production when performing multiple sets of exercises.
Abstract: BACKGROUND: Although the common practice of verbal encouragement is scientifically supported, its effect on the maintenance of force output in fatiguing exertions is unknown. OBJECTIVE: To examine the effects of verbal encouragement on exercise-induced quadriceps and knee joint function during three sets of knee extension exercise. METHODS: Sixty-five healthy males (23.3 years, 175.8 cm, 75.3 kg) underwent testing using the administration of verbal encouragement (n= 32) or not (n= 33) during assessment of quadriceps and knee joint function. Assessments were performed at baseline and times 1, 2, and 3. The knee concentric isokinetic extension at 60∘/s, was performed between the time points. For quadriceps function, maximal isometric strength and activation (central activation ratio) were recorded. Absolute error values on knee flexion replications at 15∘ or 45∘ were recorded for knee joint function. RESULTS: There was no verbal encouragement effect over three sets of exercise in quadriceps strength (condition × time: F3,189= 1.71, p= 0.17) and knee flexion replication (condition × time for 15∘: F3,189= 0.11, p= 0.96; 45∘: F3,189= 0.63, p= 0.6). However, subjects who had received verbal encouragement maintained quadriceps activation (condition × time: F3,189= 5.49, p= 0.001). Specifically, quadriceps activation in the verbal condition was 3.0% higher at time 2 (p= 0.01) and 4.7% higher at time 3 (p= 0.0003) versus in the non-verbal condition. CONCLUSIONS: Verbal encouragement appears to be effective in maintaining central activation, but is insufficient for promoting strength. This supports the idea that peripheral contributing factors play a larger role in force production when performing multiple sets of exercises.
TL;DR: A combination of 70% of total occlusion pressure with 30% 1RM could be beneficial in PwKOA in improving pain, and increasing the quadriceps strength.
Abstract: BACKGROUND: Knee osteoarthritis (KOA) is one of the most common chronic diseases impacting millions of elderly people. OBJECTIVES: The study compared the effects of two intensities of partial blood flow restriction (BFR) with low-intensity resistance training on quadriceps strength and cross-sectional area (CSA), and pain in people with knee osteoarthritis (PwKOA). METHODS: Thirty-five PwKOA, aged 50–65, participated. Quadriceps CSA was measured by ultrasonography, quadriceps strength – by isokinetic dynamometry and pain by VAS. These outcome variables were obtained at the beginning of the study and re-evaluated eight weeks after the intervention. RESULTS: An interaction effect was present for quadriceps CSA (P= 0.042) and quadriceps strength (P= 0.006), showing that using 70% of total occlusion pressure with 30% 1RM had a more significant effect. Knee pain improved significantly through the main effect of BFR (P< 0.001), and low-intensity resistance training (P= 0.011). Pain improved more at 70% of total occlusion pressure, with 30% of 1RM (2.5 ± 1.06) than 50% total occlusion pressure with 10% of 1RM (5.77 ± 1.46). CONCLUSION: A combination of 70% of total occlusion pressure with 30% 1RM could be beneficial in PwKOA in improving pain, and increasing the quadriceps strength. The changes in the quadriceps strength could be a predictor for knee pain.
TL;DR: Investigation of the effects of three different cryo-compressive modalities applied at the knee on the isokinetic strength of the quadriceps over a re-warming period found caution for immediately returning to sport following cryotherapy is required and influenced by type of cooling on muscle strength responses.
Abstract: BACKGROUND: The effects of contemporary cryo-compression devices on function are limited compared to traditional applications of cooling. Development of cooling protocols are warranted. OBJECTIVE: To investigate the effects of three different cryo-compressive modalities applied at the knee on the isokinetic strength of the quadriceps over a re-warming period. METHODS: Eleven healthy male participants took part (23 ± 14 years; 78.3 ± 14.5 Kg; 180 ± 9.5 cm) randomly assigned to receive all modalities (Game Ready® (GR), Swellaway® (SA), Wetted Ice (WI)) applied for 15-min, separated by 1-week. Skin surface temperature (Tsk) via thermography and the concentric peak moment (PM) of the quadriceps at 60 and 180∘/s were collected pre-, immediately-post and at 20-min post-intervention. RESULTS: Significant reductions occurred in Tsk across all timepoints for all modalities (p=⩽ 0.05). Significant reductions in PM for WI were noted across all timepoints and PM for GR and SA immediately-post (p=⩽ 0.05) only. CONCLUSION: Precaution for immediately returning to sport following cryotherapy is required and influenced by type of cooling on muscle strength responses. Alternate targeted treatment modalities to minimise deferred deleterious effects on muscle strength may be considered. Research into length of application, periodisation and location is warranted for the development of such contemporary cryo-compressive modalities in applied practice.
TL;DR: In this paper, the strongest indicators of weightlifting performance (WPER) and the relationship between competition performance and strength-power tests in junior female weightlifters were determined and the strongest predictor of WPER were Wingate leg peak power and countermovement jump height (CMJ).
Abstract: BACKGROUND: Strength-power tests are commonly used to monitor performance improvement and to assess preparedness for competition in weightlifters. Previous studies were limited to male weightlifters, consisted of a small number of tests, or used small samples of female weightlifters. OBJECTIVE: The purpose of this study is to determine the strongest indicators of weightlifting performance (WPER) and to reveal the relationships between competition performance and strength-power tests in junior female weightlifters. METHODS: Forty-two female weightlifters (age: 17.8 ± 2.3 years, body mass: 56.6 ± 8.1 kg; height: 156.1 ± 5.8) participated in this study. Participants were tested on a series of performance indicators including Wingate anaerobic power (lower and upper body), isokinetic leg force, vertical jumps, handgrip strength, and isometric leg strength following a national weightlifting competition. Competition performance was calculated with the Sinclair equation. Pearson correlation analysis was used to reveal the relationships between strength-power variables and Sinclair score, and Ridge regression analysis was used to determine the strongest indicators of WPER. RESULTS: The main results showed that Wingate leg peak power (L-PP) and countermovement jump height (CMJ) were the strongest indicators for WPER. They accounted for 74% of the common variance. Additionally, there was a significant correlation between strength-power variables (r= 0.41–0.846) and Sinclair score. CONCLUSIONS: This study’s findings suggest that the strongest predictors of WPER are L-PP and CMJ, and these tests can be used to monitor WPER in junior female weightlifters.
TL;DR: Findings in this study support the use of different types of breathing depending on the muscle to be activated or the sex, helping health care professionals to address their interventions on the abdominal muscles with a more focused approach.
Abstract: BACKGROUND: The underlying morphology and behavior of abdominal muscles during breathing are still lacking in knowledge in healthy population. OBJECTIVE: To analyze the effects of three different types of breathing on the architectural characteristics of abdominal muscles. METHODS: Ninety-eight healthy subjects were measured to assess the effects of breathing on the abdominal muscles, subjects performed three different types of breathing and the muscular thickness was measured with ultrasound imaging, analyzing also the differences between sexes. RESULTS: During the three different types of breathing and in comparison with the resting state, an increase of the thickness has been reported in the transversus abdominis (p< 0.001; effect size = 2.44, very large) and internal oblique (p< 0.001; effect size = 1.04, moderate) in both sexes, but with a higher increase in men. External oblique and rectus abdominis increased their thickness through breathing only while the lips were with pursed (p< 0.05) with trivial effect sizes and only differences between sexes were found in rectus abdominis. CONCLUSIONS: All breathings activated the deepest abdominal muscles, but the most superficial were only activated with lips pursed. Moreover, men appeared to activate more the deepest abdominal muscles but also the rectus abdominis. Findings in this study support the use of different types of breathing depending on the muscle to be activated or the sex, helping health care professionals to address their interventions on the abdominal muscles with a more focused approach.
TL;DR: It is recommended that AH be performed for the selective contraction of TrA during ASLR, and that AB be performed in stabilization exercises for the prevention of the pelvic rotation during active ASLR.
Abstract: BACKGROUND: Active straight leg-raise (ASLR) is often performed to strengthen abdominal muscles. The correct execution and maximum benefit of the ASLR can be achieved using abdominal hollowing (AH) and abdominal bracing (AB) exercises. OBJECTIVE: To compare the effects of AH and AB on transverse abdominis (TrA), internal oblique, and external oblique thicknesses, as well as on the pelvic rotation angle, in healthy women during active ASLR. METHODS: The participants in this study were assigned randomly to either the AH (n= 15) or AB groups (n= 15). During ASLR, abdominal muscle thickness was measured using ultrasound and pelvic rotation was measured using a Smart KEMA device. Each trial was repeated three times for 5 s each. RESULTS: The thickness of the TrA was significantly greater during ASLR with AH than during ASLR with AB (p< 0.001). In contrast, there was no respective significant change in the thickness of the external oblique (p> 0.0.311) or internal oblique (p> 0.818). Pelvic rotation angle was significantly reduced during ASLR with AB, compared with ASLR with AH (p< 0.018). CONCLUSIONS: We recommend that AH be performed for the selective contraction of TrA during ASLR, and that AB be performed for the prevention of the pelvic rotation during ASLR. Therefore, AH and AB should be separately done in stabilization exercises.
TL;DR: Only some of the parameters derived either from the short concentric and eccentric strength evaluation protocol or the fatigability resistance evaluation protocol may be interchangeable providing transposition formulas are applied.
Abstract: BACKGROUND: Isokinetic evaluation is considered the gold standard in muscle strength measurement due to its sensitivity, intra-dynamometer reproducibility and usefulness in the injury prevention screening and follow up of subjects with musculoskeletal pathologies, neurological disease or after surgical operation. However, can one switch among different isokinetic dynamometers for the purpose of knee muscles evaluation? OBJECTIVES: To comprehensively evaluate the compatibility of the isokinetic short concentric and eccentric strength evaluation protocol and of the fatigability resistance evaluation between three different isokinetic devices. METHODS: Eighteen recreationally active men underwent three isokinetic knee testing sessions on three different isokinetic devices with 7–10 days of rest between each session. Relative (Pearson’s r product-moment correlation coefficient – PCC) and absolute (standard error of measurement – SEM, Cohen effect sizes (d) and probabilistic inferences – MBI) parameters of reproducibility were determined to assess the inter-dynamometer agreement. RESULTS: For the short concentric and eccentric strength evaluation protocol, the extensors in concentric mode and the flexors in eccentric mode can be compared (eventually with transposition formulas provided) between Biodex, Con-Trex and Cybex (almost all PCC ⩾ 0.80). The DCR could be compared between Con-Trex and Cybex and between Biodex and Cybex pairs (eventually with transposition formula provided). For the fatigability resistance evaluation protocol, the total sum can be compared for extensors (eventually with transposition formulas provided) for PM for all dynamometer pairs considered and, in the case of MW, only for Biodex and Con-Trex (PCC ⩾ 0.80). CONCLUSIONS: Only some of the parameters derived either from the short concentric and eccentric strength evaluation protocol or the fatigability resistance evaluation protocol may be interchangeable providing transposition formulas are applied. Otherwise, isokinetic findings are largely system-dependent save some specific instances.
TL;DR: Acute and delayed neuromuscular impairment may be observed after both exercise regimens, but high-intensity training using vertical jumps seems to induce a more pronounced impairment than running.
Abstract: BACKGROUND: Repetitive stretch-shortening cycle exercises generate high rates of mechanical work and consequently induce substantial muscular fatigue related to delayed neuromuscular functions. OBJECTIVE: To investigate the neuromuscular impairment after high-intensity exercise protocols involving different gravity loads in stretch-shortening cycle – running (RUN) and vertical jumps (VJ). METHODS: Twenty-two healthy men, divided into two groups, VJ and RUN participated in this study. The individuals performed a training session involving six bouts of 30 s of VJ or RUN. The isokinetic PM (PM) of the knee extensors and flexor muscles, rate of perceived exertion and delayed onset muscle soreness (DOMS) were evaluated at pre, post, 24 h and 48 h post-training. RESULTS: The concentric and eccentric PM of the extensor in the RUN group was reduced until 24 h, while in the VJ a decrement was observed until 48 h. Following running, the PM of the flexors decreased until 48 h, while for VJ there was an eccentric PM decrement at 48 h. The DOMS increased at the anterior thigh and only after VJ training for 48 h. CONCLUSION: Acute and delayed neuromuscular impairment may be observed after both exercise regimens, but high-intensity training using vertical jumps seems to induce a more pronounced impairment than running.