Showing papers in "European Journal of Applied Physiology in 2017"

Doubly labelled water assessment of energy expenditure: principle, practice, and promise

Abstract: The doubly labelled water method for the assessment of energy expenditure was first published in 1955, application in humans started in 1982, and it has become the gold standard for human energy requirement under daily living conditions The method involves enriching the body water of a subject with heavy hydrogen (2H) and heavy oxygen (18O), and then determining the difference in washout kinetics between both isotopes, being a function of carbon dioxide production In practice, subjects get a measured amount of doubly labelled water (2H 2 18 O) to increase background enrichment of body water for 18O of 2000 ppm with at least 180 ppm and background enrichment of body water for 2H of 150 ppm with 120 ppm Subsequently, the difference between the apparent turnover rates of the hydrogen and oxygen of body water is assessed from blood-, saliva-, or urine samples, collected at the start and end of the observation interval of 1–3 weeks Samples are analyzed for 18O and 2H with isotope ratio mass spectrometry The doubly labelled water method is the indicated method to measure energy expenditure in any environment, especially with regard to activity energy expenditure, without interference with the behavior of the subjects Applications include the assessment of energy requirement from total energy expenditure, validation of dietary assessment methods and validation of physical activity assessment methods with doubly labelled water measured energy expenditure as reference, and studies on body mass regulation with energy expenditure as a determinant of energy balance

Time course of recovery following resistance training leading or not to failure.

Abstract: To describe the acute and delayed time course of recovery following resistance training (RT) protocols differing in the number of repetitions (R) performed in each set (S) out of the maximum possible number (P) Ten resistance-trained men undertook three RT protocols [S × R(P)]: (1) 3 × 5(10), (2) 6 × 5(10), and (3) 3 × 10(10) in the bench press (BP) and full squat (SQ) exercises Selected mechanical and biochemical variables were assessed at seven time points (from − 12 h to + 72 h post-exercise) Countermovement jump height (CMJ) and movement velocity against the load that elicited a 1 m s−1 mean propulsive velocity (V1) and 75% 1RM in the BP and SQ were used as mechanical indicators of neuromuscular performance Training to muscle failure in each set [3 × 10(10)], even when compared to completing the same total exercise volume [6 × 5(10)], resulted in a significantly higher acute decline of CMJ and velocity against the V1 and 75% 1RM loads in both BP and SQ In contrast, recovery from the 3 × 5(10) and 6 × 5(10) protocols was significantly faster between 24 and 48 h post-exercise compared to 3 × 10(10) Markers of acute (ammonia, growth hormone) and delayed (creatine kinase) fatigue showed a markedly different course of recovery between protocols, suggesting that training to failure slows down recovery up to 24–48 h post-exercise RT leading to failure considerably increases the time needed for the recovery of neuromuscular function and metabolic and hormonal homeostasis Avoiding failure would allow athletes to be in a better neuromuscular condition to undertake a new training session or competition in a shorter period of time

Direct calorimetry: a brief historical review of its use in the study of human metabolism and thermoregulation.

Abstract: Direct calorimetry is the gold standard means of measuring human metabolic rate and its use has been fundamental for understanding metabolism in health and disease. While metabolic rate is now more commonly estimated indirectly from measures of the oxygen consumed during respiration, direct calorimetry provides the user with the unique capacity to quantify the heat produced from aerobic and anaerobic metabolism by measuring heat exchange between the body and the environment. This review provides a brief historical overview of the fundamental concepts which underlie direct calorimetry, of pioneer scientists which developed these concepts into functional pieces of equipment and the subsequent use of direct calorimetry to advance our understanding of energy balance, nutrition, and the pathogenesis of metabolic diseases. Attention is directed to seminal studies that successfully employed direct calorimetry to verify that the law of energy conservation also applies to human beings and to establish the validity of indirect calorimetry. Finally, we discuss the more recent use of direct calorimetry for the measurement of whole-body heat exchange and body heat storage in the study of human thermoregulation.

The effect of Nordic hamstring strength training on muscle architecture, stiffness, and strength.

Abstract: Hamstring strain injury is a frequent and serious injury in competitive and recreational sports. While Nordic hamstring (NH) eccentric strength training is an effective hamstring injury-prevention method, the protective mechanism of this exercise is not understood. Strength training increases muscle strength, but also alters muscle architecture and stiffness; all three factors may be associated with reducing muscle injuries. The purpose of this study was to examine the effects of NH eccentric strength training on hamstring muscle architecture, stiffness, and strength. Twenty healthy participants were randomly assigned to an eccentric training group or control group. Control participants performed static stretching, while experimental participants performed static stretching and NH training for 6 weeks. Pre- and post-intervention measurements included: hamstring muscle architecture and stiffness using ultrasound imaging and elastography, and maximal hamstring strength measured on a dynamometer. The experimental group, but not the control group, increased volume (131.5 vs. 145.2 cm3, p < 0.001) and physiological cross-sectional area (16.1 vs. 18.1 cm2, p = 0.032). There were no significant changes to muscle fascicle length, stiffness, or eccentric hamstring strength. The NH intervention was an effective training method for muscle hypertrophy, but, contrary to common literature findings for other modes of eccentric training, did not increase fascicle length. The data suggest that the mechanism behind NH eccentric strength training mitigating hamstring injury risk could be increasing volume rather than increasing muscle length. Future research is, therefore, warranted to determine if muscle hypertrophy induced by NH training lowers future hamstring strain injury risk.

Cross-education of muscular strength following unilateral resistance training: a meta-analysis

Abstract: Cross-education (CE) of strength is a well-known phenomenon whereby exercise of one limb can induce strength gains in the contralateral untrained limb. The only available meta-analyses on CE, which date back to a decade ago, estimated a modest 7.8% increase in contralateral strength following unilateral training. However, in recent years new evidences have outlined larger contralateral gains, which deserve to be systematically evaluated. Therefore, the aim of this meta-analysis was to appraise current data on CE and determine its overall magnitude of effect. Five databases were searched from inception to December 2016. All randomized controlled trials focusing on unilateral resistance training were carefully checked by two reviewers who also assessed the eligibility of the identified trials and extracted data independently. The risk of bias was assessed using the Cochrane Risk-of-Bias tool. Thirty-one studies entered the meta-analysis. Data from 785 subjects were pooled and subgroup analyses by body region (upper/lower limb) and type of training (isometric/concentric/eccentric/isotonic–dynamic) were performed. The pooled estimate of CE was a significant 11.9% contralateral increase (95% CI 9.1–14.8; p < 0.00001; upper limb: + 9.4%, p < 0.00001; lower limb: + 16.4%, p < 0.00001). Significant CE effects were induced by isometric (8.2%; p = 0.0003), concentric (11.3%; p < 0.00001), eccentric (17.7%; p = 0.003) and isotonic–dynamic training (15.9%; p < 0.00001), although a high risk of bias was detected across the studies. Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.

An acute session of roller massage prolongs voluntary torque development and diminishes evoked pain

Abstract: Roller massage (RM) has been reported to reduce pain associated with exercise-induced muscle soreness and increase range of motion without force or activation impairments. The objective was to examine RM effects on evoked pain and contractile properties. Twelve men received three sets of 30-s RM at a perceived discomfort level of 7/10 on a visual analogue scale on the ipsilateral (IPSI-R) stimulated plantar flexors (PF), contralateral PF (CONTRA-R), Sham (light rolling on stimulated PF), or Control. At pre-test, post-test, and 5-min post-test, they received evoked maximal twitch, tetanus, and 70% maximal tetanic stimulation, and performed a maximal voluntary isometric contraction (MVIC). Data analysis included perceived pain and contractile properties. The 70% tetanus illustrated significant 9–10% increases in pain perception with Sham and Control at post- and 5-min post-test, respectively (p < 0.01). There was no pain augmentation with IPSI-R and CONTRA-R. There were no main effects or interactions for most contractile properties. However, MVIC force developed in the first 200 ms showed 9.5% (p = 0.1) and 19.1% (p = 0.03) decreases with IPSI-R at post-test and 5-min post-test. Data suggest that RM-induced neural inhibition decreased MVIC F200 and nullified the testing-induced increase in evoked pain associated with 70% tetanic stimulation.

Transcutaneous electrical nerve stimulation reduces exercise-induced perceived pain and improves endurance exercise performance

Abstract: Muscle pain is a natural consequence of intense and prolonged exercise and has been suggested to be a limiter of performance. Transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC) have been shown to reduce both chronic and acute pain in a variety of conditions. This study sought to ascertain whether TENS and IFC could reduce exercise-induced pain (EIP) and whether this would affect exercise performance. It was hypothesised that TENS and IFC would reduce EIP and result in an improved exercise performance. In two parts, 18 (Part I) and 22 (Part II) healthy male and female participants completed an isometric contraction of the dominant bicep until exhaustion (Part I) and a 16.1 km cycling time trial as quickly as they could (Part II) whilst receiving TENS, IFC, and a SHAM placebo in a repeated measures, randomised cross-over, and placebo-controlled design. Perceived EIP was recorded in both tasks using a validated subjective scale. In Part I, TENS significantly reduced perceived EIP (mean reduction of 12%) during the isometric contraction (P = 0.006) and significantly improved participants’ time to exhaustion by a mean of 38% (P = 0.02). In Part II, TENS significantly improved (P = 0.003) participants’ time trial completion time (~2% improvement) through an increased mean power output. These findings demonstrate that TENS can attenuate perceived EIP in a healthy population and that doing so significantly improves endurance performance in both submaximal isometric single limb exercise and whole-body dynamic exercise.

High-intensity aerobic interval training improves aerobic fitness and HbA1c among persons diagnosed with type 2 diabetes

Abstract: It remains to be established how high-intensity aerobic interval training (HAIT) affects risk factors associated with type 2 diabetes (TD2). This study investigated effects of HAIT on maximal oxygen uptake (VO2max), glycated Hemoglobin type A1C (HbA1c), insulin resistance (IR), fat oxidation (FatOx), body weight (BW), percent body fat (%BF), lactate threshold (LT), blood pressure (BP), and blood lipid profile (BLP) among persons with T2D. Results were compared to the effects after a moderate-intensity training (MIT) program. Thirty-eight individuals with T2D completed 12 weeks of supervised training. HAIT consisted of 4 × 4 min of walking or running uphill at 85–95% of maximal heart rate, and MIT consisted of continuous walking at 70–75% of maximal heart rate. A 21% increase in VO2max (from 25.6 to 30.9 ml kg−1 min−1, p < 0.001), and a reduction in HbA1c by −0.58% points (from 7.78 to 7.20%, p < 0.001) was found in HAIT. BW and body mass index (BMI) was reduced by 1.9% (p < 0.01). There was a tendency towards an improved FatOx at 60% VO2max (14%, p = 0.065). These improvements were significant different from MIT. Both HAIT and MIT increased velocity at LT, and reduced %BF, waist circumference, hip circumference, and BP, with no significant differences between the two groups. Correlations were found between change in VO2max and change in HbA1c when the two intervention groups were combined (R = −0.52, p < 0.01). HAIT is an effective exercise strategy to improve aerobic fitness and reduce risk factors associated with T2D.

Acute and chronic neuromuscular adaptations to local vibration training

Abstract: Vibratory stimuli are thought to have the potential to promote neural and/or muscular (re)conditioning. This has been well described for whole-body vibration (WBV), which is commonly used as a training method to improve strength and/or functional abilities. Yet, this technique may present some limitations, especially in clinical settings where patients are unable to maintain an active position during the vibration exposure. Thus, a local vibration (LV) technique, which consists of applying portable vibrators directly over the tendon or muscle belly without active contribution from the participant, may present an alternative to WBV. The purpose of this narrative review is (1) to provide a comprehensive overview of the literature related to the acute and chronic neuromuscular changes associated with LV, and (2) to show that LV training may be an innovative and efficient alternative method to the ‘classic’ training programs, including in the context of muscle deconditioning prevention or rehabilitation. An acute LV application (one bout of 20–60 min) may be considered as a significant neuromuscular workload, as demonstrated by an impairment of force generating capacity and LV-induced neural changes. Accordingly, it has been reported that a training period of LV is efficient in improving muscular performance over a wide range of training (duration, number of session) and vibration (frequency, amplitude, site of application) parameters. The functional improvements are principally triggered by adaptations within the central nervous system. A model illustrating the current research on LV-induced adaptations is provided.

Comparison of the recovery response from high-intensity and high-volume resistance exercise in trained men

Abstract: The purpose of this study was to compare the physiological responses of a high-volume (HV; 8 sets of 10 repetitions) versus high-intensity (HI; 8 sets of 3 repetitions) exercise protocol in resistance-trained men. Twelve men (24.5 ± 4.2 years; 82.3 ± 8.4 kg; 175.2 ± 5.5 cm) with 6.3 ± 3.4 years of resistance training experience performed each protocol in a counterbalanced, randomized order. Performance [counter movement jump peak power (CMJP), isokinetic (ISOK) and isometric leg extension (MVIC), isometric mid-thigh pull (IMTP), and isometric squat (ISQ)] and muscle morphological [cross-sectional area (CSA) of vastus lateralis] assessments were performed at baseline (BL), 30-min (P-30 min), 24-h (P-24 h), 48-h (P-48 h), and 72-h (P-72 h) post-exercise for each testing session. In addition, endocrine (testosterone and cortisol), inflammatory [interleukin-6 (IL-6) and C-reactive protein (CRP)], and markers of muscle damage [creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin (Mb)] were assessed at the same time points. Significantly greater reductions in CMJP (p < 0.001), and peak torque during both ISOK (p = 0.003) and MVIC (p = 0.008) at P-30 min were detected in HV compared to HI protocol. MVIC was still impaired at P-72 h following the HV protocol, while no differences were noted following HI. Markers of muscle damage (LDH, CK, and Mb) were significantly elevated following both HV and HI (p < 0.05), while cortisol and IL-6 concentrations were significantly elevated at P-30 min following HV only (p < 0.001 and p < 0.05, respectively). Results indicate that high-volume resistance exercise results in greater performance deficits, and a greater extent of muscle damage, than a bout of high-intensity resistance exercise.

Changes in agonist neural drive, hypertrophy and pre-training strength all contribute to the individual strength gains after resistance training.

Abstract: Whilst neural and morphological adaptations following resistance training (RT) have been investigated extensively at a group level, relatively little is known about the contribution of specific physiological mechanisms, or pre-training strength, to the individual changes in strength following training. This study investigated the contribution of multiple underpinning neural [agonist EMG (QEMGMVT), antagonist EMG (HEMGANTAG)] and morphological variables [total quadriceps volume (QUADSVOL), and muscle fascicle pennation angle (QUADSθ p)], as well as pre-training strength, to the individual changes in strength after 12 weeks of knee extensor RT. Twenty-eight healthy young men completed 12 weeks of isometric knee extensor RT (3/week). Isometric maximum voluntary torque (MVT) was assessed pre- and post-RT, as were simultaneous neural drive to the agonist (QEMGMVT) and antagonist (HEMGANTAG). In addition QUADSVOL was determined with MRI and QUADSθ p with B-mode ultrasound. Percentage changes (∆) in MVT were correlated to ∆QEMGMVT (r = 0.576, P = 0.001), ∆QUADSVOL (r = 0.461, P = 0.014), and pre-training MVT (r = −0.429, P = 0.023), but not ∆HEMGANTAG (r = 0.298, P = 0.123) or ∆QUADSθ p (r = −0.207, P = 0.291). Multiple regression analysis revealed 59.9% of the total variance in ∆MVT after RT to be explained by ∆QEMGMVT (30.6%), ∆QUADSVOL (18.7%), and pre-training MVT (10.6%). Changes in agonist neural drive, quadriceps muscle volume and pre-training strength combined to explain the majority of the variance in strength changes after knee extensor RT (~60%) and adaptations in agonist neural drive were the most important single predictor during this short-term intervention.

Do metabolites that are produced during resistance exercise enhance muscle hypertrophy

Abstract: Many reviews conclude that metabolites play an important role with respect to muscle hypertrophy during resistance exercise, but their actual physiologic contribution remains unknown. Some have suggested that metabolites may work independently of muscle contraction, while others have suggested that metabolites may play a secondary role in their ability to augment muscle activation via inducing fatigue. Interestingly, the studies used as support for an anabolic role of metabolites use protocols that are not actually designed to test the importance of metabolites independent of muscle contraction. While there is some evidence in vitro that metabolites may induce muscle hypertrophy, the only study attempting to answer this question in humans found no added benefit of pooling metabolites within the muscle post-exercise. As load-induced muscle hypertrophy is thought to work via mechanotransduction (as opposed to being metabolically driven), it seems likely that metabolites simply augment muscle activation and cause the mechanotransduction cascade in a larger proportion of muscle fibers, thereby producing greater muscle growth. A sufficient time under tension also appears necessary, as measurable muscle growth is not observed after repeated maximal testing. Based on current evidence, it is our opinion that metabolites produced during resistance exercise do not have anabolic properties per se, but may be anabolic in their ability to augment muscle activation. Future studies are needed to compare protocols which produce similar levels of muscle activation, but differ in the magnitude of metabolites produced, or duration in which the exercised muscles are exposed to metabolites.

The effect of treadmill and overground walking on preferred walking speed and gait kinematics in healthy, physically active older adults.

Abstract: Preferred walking speed (PWS) represents a performance measure of mobility in older individuals. PWS is usually assessed during overground (via a 2–40 m walkway) or treadmill walking in older adults. The aim of this study was to compare the effect of treadmill and overground walking on preferred walking speed, spatiotemporal parameters and foot kinematics in healthy, physically active older and young adults after adequate treadmill familiarization. PWS and spatiotemporal parameters were assessed during overground (PWSO) and treadmill (PWST) walking using two wearable inertial sensor systems and were compared between 25 older (72.2 ± 4.0, range 66–80 years) and 20 young (24.4 ± 2.1, range 20–30 years) adults. In the two groups, PWSO (older: 1.45 ± 0.17 m.s−1; young: 1.37 ± 0.16 m.s−1) was significantly faster than PWST (older: 1.31 ± 0.15 m.s−1; young: 1.25 ± 0.17 m.s−1; P < 0.001), with no significant difference between the groups in either walking condition (P = 0.11). The older adults walked with a significantly greater stride frequency (+8%; P ≤ 0.001) and lower plantarflexion angle (−5%; P ≤ 0.001) than the young participants under both walking conditions. In both groups, treadmill walking was characterized by significantly increased stance (+1%; P = 0.02) and double support (+1%; P = 0.04) duration, as well as reduced swing duration (−1%; P = 0.02) and heel-strike pitch angle (−8%; P < 0.001). Our findings showed that healthy and physically active older and young adults who were adequately familiarized to the treadmill selected a slower PWS on the treadmill than during overground walking with small “safety-related” gait kinematic adaptations. Therefore, treadmill can be used for assessing PWS and gait kinematics in physically active older adults.

Crescent pyramid and drop-set systems do not promote greater strength gains, muscle hypertrophy, and changes on muscle architecture compared with traditional resistance training in well-trained men

Abstract: The aim of this study was to compare the effects of crescent pyramid (CP) and drop-set (DS) systems with traditional resistance training (TRAD) with equalized total training volume (TTV) on maximum dynamic strength (1-RM), muscle cross-sectional area (CSA), pennation angle (PA), and fascicle length (FL). Thirty-two volunteers had their legs randomized in a within-subject design in TRAD (3–5 sets of 6–12 repetitions at 75% 1-RM), CP (3–5 sets of 6–15 repetitions at 65–85% 1-RM), and DS (3–5 sets of ~50–75% 1-RM to muscle failure) protocols. Each leg was trained for 12 weeks. Participants had one leg fixed in the TRAD while the contralateral leg performed either CP or DS to allow for TTV equalization. The CSA increased significantly and similarly for all protocols (TRAD: 7.6%; CP: 7.5%; DS: 7.8%). All protocols showed significant and similar increases in leg press (TRAD = 25.9%; CP = 25.9%; DS = 24.9%) and leg extension 1-RM loads (TRAD = 16.6%; CP = 16.4%; DS = 17.1%). All protocols increased PA (TRAD = 10.6%; CP = 11.0%; DS = 10.3%) and FL (TRAD = 8.9%; CP = 8.9%; DS = 9.1%) similarly. CP and DS systems do not promote greater gains in strength, muscle hypertrophy and changes in muscle architecture compared to traditional resistance training.

The presence of symptoms of testosterone deficiency in the exercise-hypogonadal male condition and the role of nutrition

Abstract: High volumes of aerobic exercise have been associated with reduced testosterone (T), known as the exercise-hypogonadal male condition (EHMC). Although the presence of low T has been identified, few studies have assessed the presence of androgen-deficient symptoms. The purpose of this investigation is to assess men exhibiting EHMC and evaluate their hypothalamic–pituitary–gonadal axis, the presence of hypogonadal symptoms, and also investigate a possible contribution of inadequate nutrition to the condition. A cross-sectional design compared 9 long-distance runners exhibiting EHMC to 8 non-active controls. Comparisons included serum T, luteinizing hormone (LH), follicle-stimulating hormone, and cortisol, the Aging Male Symptoms (AMS) questionnaire score, bone mineral density (BMD), and a food frequency questionnaire. Mean T was significantly reduced in the EHMC group (EHMC 9.2 nmol L−1 vs. CONT 16.2 nmol L−1). The EHMC group demonstrated significantly higher AMS scores (EHMC 27.1 ± 7.3 vs. CONT 19.7 ± 2.5). There were no differences in bone density, although 3 cases of osteopenia were noted for EHMC in the lumbar spine, 1 in the right femur, and 1 in the radius. Energy availability was significantly reduced in EHMC (EHMC 27.2 ± 12.7 vs. CONT 45.4 ± 18.2 kcal d FFM−1). Men exhibiting EHMC do appear to present with symptoms associated with androgen deficiency. For the most part, these symptoms are limited to those reported on the AMS questionnaire, although there are also some cases of clinically low BMD. It is possible that inadequate energy intake is contributing to this condition.

Intestinal fatty acid-binding protein and gut permeability responses to exercise

Abstract: Intestinal cell damage due to physiological stressors (e.g. heat, oxidative, hypoperfusion/ischaemic) may contribute to increased intestinal permeability. The aim of this study was to assess changes in plasma intestinal fatty acid-binding protein (I-FABP) in response to exercise (with bovine colostrum supplementation, Col, positive control) and compare this to intestinal barrier integrity/permeability (5 h urinary lactulose/rhamnose ratio, L/R). In a double-blind, placebo-controlled, crossover design, 18 males completed two experimental arms (14 days of 20 g/day supplementation with Col or placebo, Plac). For each arm participants performed two baseline (resting) intestinal permeability assessments (L/R) pre-supplementation and one post-exercise following supplementation. Blood samples were collected pre- and post-exercise to determine I-FABP concentration. Two-way repeated measures ANOVA revealed an arm × time interaction for L/R and I-FABP (P < 0.001). Post hoc analyses showed urinary L/R increased post-exercise in Plac (273% of pre, P < 0.001) and Col (148% of pre, P < 0.001) with post-exercise values significantly lower with Col (P < 0.001). Plasma I-FABP increased post-exercise in Plac (191% of pre-exercise, P = 0.002) but not in the Col arm (107%, P = 0.862) with post-exercise values significantly lower with Col (P = 0.013). Correlations between the increase in I-FABP and L/R were evident for visit one (P = 0.044) but not visit two (P = 0.200) although overall plots/patterns do appear similar for each. These findings suggest that exercise-induced intestinal cellular damage/injury is partly implicated in changes in permeability but other factors must also contribute.

Oral l-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion

Abstract: The study investigated the effect of a non-thermal cooling agent, l-menthol, on exercise at a fixed subjective rating of perceived exertion (RPE) in a hot environment Eight male participants completed two trials at an exercise intensity between ‘hard’ and ‘very hard’, equating to 16 on the RPE scale at ~35 °C Participants were instructed to continually adjust their power output to maintain an RPE of 16 throughout the exercise trial, stopping once power output had fallen by 30% In a randomized crossover design, either l-menthol or placebo mouthwash was administered prior to exercise and at 10 min intervals Power output, $$\dot{V}$$ O2, heart rate, core and skin temperature was monitored, alongside thermal sensation and thermal comfort Isokinetic peak power sprints were conducted prior to and immediately after the fixed RPE trial Exercise time was greater (23:23 ± 3:36 vs 21:44 ± 2:32 min; P = 0049) and average power output increased (173 ± 24 vs 167 ± 24 W; P = 0044) in the l-menthol condition Peak isokinetic sprint power declined from pre-post trial in the l-menthol l (90%; P = 0015) but not in the placebo condition (34%; P = 0275) Thermal sensation was lower in the l-menthol condition (P = 0036), despite no changes in skin or core temperature (P > 005) These results indicate that a non-thermal cooling mouth rinse lowered thermal sensation, resulting in an elevated work rate, which extended exercise time in the heat at a fixed RPE

Exercise and gastrointestinal symptoms: running-induced changes in intestinal permeability and markers of gastrointestinal function in asymptomatic and symptomatic runners.

Abstract: Athletes frequently experience gastrointestinal (GI) symptoms during training and competition. Although the prevalence of exercise-induced GI symptoms is high, the mechanisms leading to GI distress during exercise are not fully understood. The aim of this study was to identify running-induced changes in intestinal permeability and markers of GI function and investigate their association with gastrointestinal symptoms. We recruited 17 active runners who we allocated as either asymptomatic or symptomatic based on their history of experiencing GI symptoms during running. The participants took part in a running test where they were asked to run for 90 min at 80% of their best 10 km race speed. Intestinal permeability was measured at baseline and after the running test. Levels of serum intestinal fatty acid-binding protein (I-FABP), zonulin, bacterial lipopolysaccharide (LPS), and fecal calprotectin were also measured at baseline and after the running test. Running induced a significant increase in intestinal permeability and serum I-FABP concentration but there were no differences between asymptomatic and symptomatic runners. Serum LPS activity did not change from baseline following the running test but the symptomatic group exhibited higher LPS activity at baseline compared to the asymptomatic runners. Running for 90 min at a challenging pace causes small intestinal damage and increases intestinal permeability. However, these alterations in GI function do not appear to correlate with the development of GI symptoms during running.

Increase in echo intensity and extracellular-to-intracellular water ratio is independently associated with muscle weakness in elderly women

Abstract: The changes in muscle composition and its heterogeneity during aging are associated with muscle weakness in elderly persons independent of decreases in muscle mass or muscle thickness (MT). Both the assessment of echo intensity (EI) with ultrasound imaging and the evaluation of the extracellular water/intracellular water (ECW/ICW) ratio with segmental bioelectrical impedance spectroscopy (BIS) are non-invasive and convenient methods and seem valuable for muscle quality determination. However, no previous study has evaluated both EI and the ECW/ICW ratio simultaneously to investigate their relationship to muscle strength. The purpose of the present study was to investigate whether both EI and the ECW/ICW ratio are independently associated with muscle strength in elderly women. A total of 179 elderly women with a mean age of 74.1 ± 4.9 years, living independently in the community, were enrolled. The MT and EI of the quadriceps femoris were measured using transverse ultrasound imaging. The ECW/ICW ratio in the upper thigh was calculated from segmental BIS. The maximum knee extensor strength and the presence of knee pain were also assessed. Knee extensor strength showed a significant positive correlation with MT, and significant negative correlations with EI, the ECW/ICW ratio, and age. Stepwise regression analysis revealed that knee extensor strength in elderly women was predicted by MT, EI, and the ECW/ICW ratio. This study suggests that the simultaneous application of EI and the ECW/ICW ratio is useful in assessing muscle strength, and accurately estimates the changes in muscle quality related to muscle weakness.

Dietary nitrate supplementation enhances short but not longer duration running time-trial performance.

Abstract: This study evaluated the effects of dietary nitrate (NO3 −) supplementation on physiological functioning and exercise performance in trained runners/triathletes conducting short and longer-distance treadmill running time-trials (TT). Eight trained male runners or triathletes completed four exercise performance tests comprising a 10 min warm up followed by either a 1500 or 10,000 m treadmill TT. Exercise performance tests were preceded 3 h before the exercise by supplementation with either 140 ml concentrated nitrate-rich (~12.5 mmol nitrate) (BRJ) or nitrate-deplete (~0.01 mmol nitrate) (PLA) beetroot juice. BRJ supplementation significantly elevated plasma [NO2 −] (P < 0.05). Resting blood pressure and exercise $$\dot{\text{V}}{{\text{O}}_{\text{2}}}$$ were not significantly different between BRJ and PLA (P > 0.05). However, post-exercise blood [lactate] was significantly greater in BRJ following the 1500 m TT (6.6 ± 1.2 vs. 6.1 ± 1.5 mM; P 0.05). Performance in the 1500 m TT was significantly faster in BRJ vs. PLA (319.6 ± 36.2 vs. 325.7 ± 38.8 s; P 0.05). Acute BRJ supplementation significantly enhanced 1500 m, but not 10,000 m TT performance. These findings suggest that BRJ might be ergogenic during shorter distance TTs which allow for a high work rate, but not during longer distance TTs, completed at a lower work rate.

Effects of resistance training at different loads on inflammatory markers in young adults

Abstract: Suppressing inflammaging at an early stage in life via exercise might prevent chronic diseases later in life. The aim was to investigate the influence of resistance training at different external loads on inflammatory markers in healthy young adults. Serum was collected for basal levels of cytokines (IL-1beta, IL-6, IL-8, sTNFR1, IL-1RA, IL-10 and GM-CSF) before and after 9 weeks exercise from 36 young (22 ± 2 years) healthy subjects who were randomized to three times weekly supervised resistance training at either HImax (n = 12, 1 × 10–12 repetitions at 80% 1RM), LO (n = 12, 1 × 10–12 repetitions at 40% 1RM), or LOmax (n = 12, 1 × 10–12 repetitions at 40% 1RM preceded by 60 repetitions at 20–25% 1RM) respectively. Overall, IL-8 increased (p < 0.001) and IL-6 decreased (p = 0.001) after training, but no significant time*group interaction was found (respectively, p = 0.283 and p = 0.058 for IL-8 and IL-6). When analyzed separately, IL-8 increased significantly in HImax (p = 0.022) and LOmax (p = 0.024); and IL-6 decreased significantly in LOmax (p = 0.009) and LO (p = 0.013). No significant overall time effect was observed for sTNFR1 and IL-1RA; however, in HImax sTNFR1 (p = 0.031) and IL-1RA (p = 0.014) increased significantly, but remained unchanged in LOmax and LO. IL-1beta, IL-10 and GM-CSF levels remained undetectable in most participants. Nine weeks of resistance training—irrespective of the external load—have beneficial effects on circulating IL-8 and IL-6. In addition, training at high external load increases the anti-inflammatory cytokines sTNFR1 and IL-1RA. The results of this study show that resistance training has anti-inflammatory effects in healthy young persons and that the response of the different inflammatory mediators depends on the magnitude of the external load.

Shear wave elastography reveals different degrees of passive and active stiffness of the neck extensor muscles.

Abstract: Purpose: The neck extensor muscles contribute to spinal support and posture while performing head and neck motion. Muscle stiffness relates to passive elasticity (support) and active tensioning (posture and movement) of muscle. It was hypothesized that support and motion requirements are reflected in the distribution of stiffness between superficial and deep neck extensor muscles. Methods: In ten healthy participants, shear modulus (stiffness) of five neck extensor muscles was determined in prone at rest and during isometric head lift at three intensities using shear wave elastography. Results: Shear modulus differed between muscles (P < 0.001), and was larger for the deeper muscles: (median (interquartile range)) trapezius 7.7 kPa (4.4), splenius capitis 6.5 kPa (2.5), semispinalis capitis 8.9 kPa (2.8), semispinalis cervicis 9.5 kPa (2.5), multifidus 14.9 kPa (1.4). Shear modulus differed between the resting condition and head lift (P < 0.001) but not between levels of head lift intensity. Conclusion: Shear wave elastography revealed highest passive and active stiffness of the deep neck extensor muscles most close to the spine. The highest active increase of stiffness during the head lift was found in the semispinalis cervicis muscle. The non-invasive, clinically applicable estimates of muscle stiffness have potential for the assessment of muscular changes associated with neck pain/injury.

A tale of three cuffs: the hemodynamics of blood flow restriction

Abstract: The blood flow response to relative levels of blood flow restriction (BFR) across varying cuff widths is not well documented. With the variety of cuff widths and pressures reported in the literature, the effects of different cuffs and pressures on blood flow require investigation. To measure blood pressure using three commonly used BFR cuffs, examine possible venous/arterial restriction pressures, and measure hemodynamic responses to relative levels of BFR using these same cuffs. 43 participants (Experiment 1, brachial artery blood pressure assessed) and 38 participants (Experiment 2, brachial artery blood flow assessed using ultrasound, cuff placed at proximal portion of arm) volunteered for this study. Blood pressure measurement was higher in the 5 cm cuff than in the 10 and 12 cm cuffs. Sub-diastolic relative pressures appear to occur predominantly at 70% of AOP) are surpassed. Calculated mean shear rate decreases in a similar fashion as blood flow. Under relative levels of restriction, pressures from 40 to 90% of AOP appear to decrease blood flow to a similar degree in these three cuffs. Relative pressures appear to elicit a similar blood flow stimulus when accounting for cuff width and participant characteristics.

Post-absorptive muscle protein turnover affects resistance training hypertrophy.

Abstract: Acute bouts of resistance exercise and subsequent training alters protein turnover in skeletal muscle. The mechanisms responsible for the changes in basal post-absorptive protein turnover and its impact on muscle hypertrophy following resistance exercise training are unknown. Our goal was to determine whether post-absorptive muscle protein turnover following 12 weeks of resistance exercise training (RET) plays a role in muscle hypertrophy. In addition, we were interested in determining potential molecular mechanisms responsible for altering post-training muscle protein turnover. Healthy young men (n = 31) participated in supervised whole body progressive RET at 60–80% 1 repetition maximum (1-RM), 3 days/week for 3 months. Pre- and post-training vastus lateralis muscle biopsies and blood samples taken during an infusion of 13C6 and 15N phenylalanine and were used to assess skeletal muscle protein turnover in the post-absorptive state. Lean body mass (LBM), muscle strength (determined by dynamometry), vastus lateralis muscle thickness (MT), myofiber type-specific cross-sectional area (CSA), and mRNA were assessed pre- and post-RET. RET increased strength (12–40%), LBM (~5%), MT (~15%) and myofiber CSA (~20%) (p < 0.05). Muscle protein synthesis (MPS) increased 24% while muscle protein breakdown (MPB) decreased 21%, respectively. These changes in protein turnover resulted in an improved net muscle protein balance in the basal state following RET. Further, the change in basal MPS is positively associated (r = 0.555, p = 0.003) with the change in muscle thickness. Post-absorptive muscle protein turnover is associated with muscle hypertrophy during resistance exercise training.

Home-based isometric exercise training induced reductions resting blood pressure

Abstract: Isometric exercise training (IET) reduces resting blood pressure (BP). Most previous protocols impose exercise barriers which undermine its effectiveness as a potential physical therapy for altering BP. An inexpensive, home-based programme would promote IET as a valuable tool in the fight against hypertension. The aims of this study were: (a) to investigate whether home-based wall squat training could successfully reduce resting BP and (b) to explore the physiological variables that might mediate a change in resting BP. Twenty-eight healthy normotensive males were randomly assigned to a control and a 4 week home-based IET intervention using a crossover design with a 4 week ‘washout’ period in-between. Wall squat training was completed 3 × weekly over 4 weeks with 48 h between sessions. Each session comprised 4 × 2 min bouts of wall squat exercise performed at a participant-specific knee joint angle relative to a target HR of 95% HRpeak, with 2 min rest between bouts. Resting heart rate, BP, cardiac output, total peripheral resistance, and stroke volume were taken at baseline and post each condition. Resting BP (systolic −4 ± 5, diastolic −3 ± 3 and mean arterial −3 ± 3 mmHg), cardiac output (−0.54 ± 0.66 L min−1) and heart rate (−5 ± 7 beats min−1) were all reduced following IET, with no change in total peripheral resistance or stroke volume compared to the control. These findings suggest that the wall squat provides an effective method for reducing resting BP in the home resulting primarily from a reduction in resting heart rate.

The assessment of neuromuscular fatigue during 120 min of simulated soccer exercise

Abstract: Purpose This investigation examined the development of neuromuscular fatigue during a simulated soccer match incorporating a period of extra time (ET) and the reliability of these responses on repeated test occasions.

Cortical voluntary activation testing methodology impacts central fatigue

Abstract: Currently, cortical voluntary activation (VATMS) is assessed by superimposing transcranial magnetic stimulation (TMS) on a maximal voluntary contraction (MVC), 75% MVC and 50% MVC, each contraction being interspersed with 5–10 s of relaxation. Here, we assessed whether this traditional approach (TRADI) underestimates central fatigue due to this short recovery compared to a continuous method (CONTI). VATMS, motor-evoked potential (MEP), and cortical silent period (CSP) of the vastus lateralis were determined in 12 young healthy adults before and after a 2-min sustained MVC of knee extensors in two randomly assigned sessions. In TRADI, evaluations comprised a 7-s rest between the three contractions (100, 75, and 50% MVC) and evaluation following the 2-min sustained MVC started after a minimal rest (3–4 s). In CONTI, evaluations were performed with no rest allowed between the three levels of contraction, and evaluation after the 2-min sustained MVC commenced without any rest. MVC was equally depressed at the end of the 2 min in both conditions. Post 2-min sustained MVC, VATMS change was greater in CONTI than in TRADI (−29 (15)% [−42, −17] vs. −9 (4)% [−13, −5], respectively, P < 0.001). Differences were also observed between TRADI and CONTI for MEP and CSP immediately after the fatiguing exercise. All differences between the two methods disappeared after 2 min of recovery. After a 2-min sustained MVC, a few seconds of recovery change the amount of measured VATMS and associated parameters of central fatigue. The continuous method should be preferred to determine deficits in voluntary activation.

Effect of an acute dose of omega-3 fish oil following exercise-induced muscle damage.

Abstract: The purpose of this double-blind, placebo-controlled study was to examine the effect of two fish oil supplements, one high in EPA (750 mg EPA, 50 mg DHA) and one low in EPA (150 mg EPA, 100 mg DHA), taken acutely as a recovery strategy following EIMD. Twenty-seven physically active males (26 ± 4 year, 1.77 ± 0.07 m, 80 ± 10 kg) completed 100 plyometric drop jumps to induce muscle damage. Perceptual (perceived soreness) and functional (isokinetic muscle strength at 60° and 180° s−1, squat jump performance and countermovement jump performance) indices of EIMD were recorded before, and 1, 24, 48, 72, and 96h after the damaging protocol. Immediately after the damaging protocol, volunteers ingested either a placebo (Con), a low-EPA fish oil (Low EPA) or a high-EPA fish oil (High EPA) at a dose of 1 g per 10 kg body mass. A significant group main effect was observed for squat jump, with the High EPA group performing better than Con and Low EPA groups (average performance decrement, 2.1, 8.3 and 9.8%, respectively), and similar findings were observed for countermovement jump performance, (average performance decrement, 1.7, 6.8 and 6.8%, respectively, p = 0.07). Significant time, but no interaction main effects were observed for all functional and perceptual indices measured, although large effect sizes demonstrate a possible ameliorating effect of high dose of EPA fish supplementation (effect sizes ≥0.14). This study indicates that an acute dose of high-EPA fish oil may ameliorate the functional changes following EIMD.

The effects of traditional, superset, and tri-set resistance training structures on perceived intensity and physiological responses

Abstract: Investigate the acute and short-term (i.e., 24 h) effects of traditional (TRAD), superset (SS), and tri-set (TRI) resistance training protocols on perceptions of intensity and physiological responses. Fourteen male participants completed a familiarisation session and three resistance training protocols (i.e., TRAD, SS, and TRI) in a randomised-crossover design. Rating of perceived exertion, lactate concentration ([Lac]), creatine kinase concentration ([CK]), countermovement jump (CMJ), testosterone, and cortisol concentrations was measured pre, immediately, and 24-h post the resistance training sessions with magnitude-based inferences assessing changes/differences within/between protocols. TRI reported possible to almost certainly greater efficiency and rate of perceived exertion, although session perceived load was very likely lower. SS and TRI had very likely to almost certainly greater lactate responses during the protocols, with changes in [CK] being very likely and likely increased at 24 h, respectively. At 24-h post-training, CMJ variables in the TRAD protocol had returned to baseline; however, SS and TRI were still possibly to likely reduced. Possible increases in testosterone immediately post SS and TRI protocols were reported, with SS showing possible increases at 24-h post-training. TRAD and SS showed almost certain and likely decreases in cortisol immediately post, respectively, with TRAD reporting likely decreases at 24-h post-training. SS and TRI can enhance training efficiency and reduce training time. However, acute and short-term physiological responses differ between protocols. Athletes can utilise SS and TRI resistance training, but may require additional recovery post-training to minimise effects of fatigue.

Biochemical responses and physical performance during high-intensity resistance circuit training in hypoxia and normoxia.

Abstract: The aim of this study was to analyze the effect of hypoxia on metabolic and acid–base balance, blood oxygenation, electrolyte, and half-squat performance variables during high-resistance circuit (HRC) training. Twelve resistance-trained subjects participated in this study. After a 6RM testing session, participants performed three randomized trials of HRC: normoxia (NORM: FiO2 = 0.21), moderate hypoxia (MH: FiO2 = 0.16), or high hypoxia (HH: FiO2 = 0.13), separated by 72 h of recovery in normoxic conditions. HRC consisted of two blocks of three exercises (Block 1: bench press, deadlift and elbow flexion; Block 2: half-squat, triceps extension, and ankle extension). Each exercise was performed at 6RM. Rest periods lasted for 35 s between exercises, 3 min between sets, and 5 min between blocks. Peak and mean force and power were determined during half-squat. Metabolic, acid–base balance, blood oxygenation and electrolyte variables, arterial oxygen saturation (SaO2), and rating of perceived exertion (RPE) were measured following each block. During the first set, peak force and power were significantly lower in HH than MH and NORM; whereas in the second set, mean and peak force and power were significantly lower in HH than NORM. At the end of the HRC training session, blood lactate and RPE in HH were significantly higher than in MH and NORM. SaO2, pH, HCO3 −, and pO2 values were significantly lower in all hypoxic conditions than in NORM. These results indicate that simulated hypoxia during HRC exercise reduce blood oxygenation, pH, and HCO3 −, and increased blood lactate ultimately decreasing muscular performance.