Showing papers in "European Journal of Applied Physiology in 2019"

RR interval signal quality of a heart rate monitor and an ECG Holter at rest and during exercise.

Abstract: This study was designed to examine the RR interval signal qualities of a Holter device and a heart rate chest belt monitor at rest and during exercise. Ten healthy individuals completed five low- to high-intensity activities while simultaneously using the medilog® AR12plus Holter monitor and the Polar H10 heart rate monitor. The RR interval signal quality was based on the quantification of the missing RR intervals and RR interval detection errors. Therefore, both measurement systems were compared against visual inspection of the raw electrocardiography signal. The missing and wrong R-wave peak detections were counted manually for both measurement systems. RR interval signal quality was defined as the relative number of correctly detected RR intervals. Overall, RR interval signal qualities of 94.6% and 99.6% were demonstrated for the medilog® AR12plus and the Polar H10. During the high-intensity activities, the RR interval signal quality of the medilog® AR12plus dropped to 89.8%, whereas the Polar H10 maintained a signal quality of 99.4%. The correlation between both systems was high (r = 0.997, p > 0.001). The excellent RR interval signal quality during low- to moderate-intensity activities in the medilog® AR12plus and during low- to high-intensity activities in the Polar H10 demonstrates both measurement systems’ validity for the detection of RR intervals throughout a wide range of activities. A simple chest strap such as the Polar H10 might be recommended as the gold standard for RR interval assessments if intense activities with strong body movements are investigated.

Mechanisms of vitamin D on skeletal muscle function: oxidative stress, energy metabolism and anabolic state.

Abstract: This review provides a current perspective on the mechanism of vitamin D on skeletal muscle function with the emphasis on oxidative stress, muscle anabolic state and muscle energy metabolism. It focuses on several aspects related to cellular and molecular physiology such as VDR as the trigger point of vitamin D action, oxidative stress as a consequence of vitamin D deficiency. The interaction between vitamin D deficiency and mitochondrial function as well as skeletal muscle atrophy signalling pathways have been studied and clarified in the last years. To the best of our knowledge, we summarize key knowledge and knowledge gaps regarding the mechanism(s) of action of vitamin D in skeletal muscle. Vitamin D deficiency is associated with oxidative stress in skeletal muscle that influences the mitochondrial function and affects the development of skeletal muscle atrophy. Namely, vitamin D deficiency decreases oxygen consumption rate and induces disruption of mitochondrial function. These deleterious consequences on muscle may be associated through the vitamin D receptor (VDR) action. Moreover, vitamin D deficiency may contribute to the development of muscle atrophy. The possible signalling pathway triggering the expression of Atrogin-1 involves Src-ERK1/2-Akt- FOXO causing protein degradation. Based on the current knowledge we propose that vitamin D deficiency results from the loss of VDR function and it could be partly responsible for the development of neurodegenerative diseases in human beings.

Iron considerations for the athlete: A narrative review

Abstract: Iron plays a significant role in the body, and is specifically important to athletes, since it is a dominant feature in processes such as oxygen transport and energy metabolism. Despite its importance, athlete populations, especially females and endurance athletes, are commonly diagnosed with iron deficiency, suggesting an association between sport performance and iron regulation. Although iron deficiency is most common in female athletes (~ 15–35% athlete cohorts deficient), approximately 5–11% of male athlete cohorts also present with this issue. Furthermore, interest has grown in the mechanisms that influence iron absorption in athletes over the last decade, with the link between iron regulation and exercise becoming a research focus. Specifically, exercise-induced increases in the master iron regulatory hormone, hepcidin, has been highlighted as a contributing factor towards altered iron metabolism in athletes. To date, a plethora of research has been conducted, including investigation into the impact that sex hormones, diet (e.g. macronutrient manipulation), training and environmental stress (e.g. hypoxia due to altitude training) have on an athlete’s iron status, with numerous recommendations proposed for consideration. This review summarises the current state of research with respect to the aforementioned factors, drawing conclusions and recommendations for future work.

Four weeks of probiotic supplementation reduces GI symptoms during a marathon race

Abstract: To evaluate the effects of probiotic supplementation on gastrointestinal (GI) symptoms, circulatory markers of GI permeability, damage, and markers of immune response during a marathon race. Twenty-four recreational runners were randomly assigned to either supplement with a probiotic (PRO) capsule [25 billion CFU Lactobacillus acidophilus (CUL60 and CUL21), Bifidobacterium bifidum (CUL20), and Bifidobacterium animalis subs p. Lactis (CUL34)] or placebo (PLC) for 28 days prior to a marathon race. GI symptoms were recorded during the supplement period and during the race. Serum lactulose:rhamnose ratio, and plasma intestinal-fatty acid binding protein, sCD14, and cytokines were measured pre- and post-races. Prevalence of moderate GI symptoms reported were lower during the third and fourth weeks of the supplement period compared to the first and second weeks in PRO (p 0.05). During the marathon, GI symptom severity during the final third was significantly lower in PRO compared to PLC (p = 0.010). The lower symptom severity was associated with a significant difference in reduction of average speed from the first to the last third of the race between PLC (− 14.2 ± 5.8%) and PRO (− 7.9 ± 7.5%) (p = 0.04), although there was no difference in finish times between groups (p > 0.05). Circulatory measures increased to a similar extent between PRO and PLC (p > 0.05). Probiotics supplementation was associated with a lower incidence and severity of GI symptoms in marathon runners, although the exact mechanisms are yet to be elucidated. Reducing GI symptoms during marathon running may help maintain running pace during the latter stages of racing.

Effects of squat training with different depths on lower limb muscle volumes

Abstract: The purpose of this study was to compare the effects of squat training with different depths on lower limb muscle volumes. Seventeen males were randomly assigned to a full squat training group (FST, n = 8) or half squat training group (HST, n = 9). They completed 10 weeks (2 days per week) of squat training. The muscle volumes (by magnetic resonance imaging) of the knee extensor, hamstring, adductor, and gluteus maximus muscles and the one repetition maximum (1RM) of full and half squats were measured before and after training. The relative increase in 1RM of full squat was significantly greater in FST (31.8 ± 14.9%) than in HST (11.3 ± 8.6%) (p = 0.003), whereas there was no difference in the relative increase in 1RM of half squat between FST (24.2 ± 7.1%) and HST (32.0 ± 12.1%) (p = 0.132). The volumes of knee extensor muscles significantly increased by 4.9 ± 2.6% in FST (p < 0.001) and 4.6 ± 3.1% in HST (p = 0.003), whereas that of rectus femoris and hamstring muscles did not change in either group. The volumes of adductor and gluteus maximus muscles significantly increased in FST (6.2 ± 2.6% and 6.7 ± 3.5%) and HST (2.7 ± 3.1% and 2.2 ± 2.6%). In addition, relative increases in adductor (p = 0.026) and gluteus maximus (p = 0.008) muscle volumes were significantly greater in FST than in HST. The results suggest that full squat training is more effective for developing the lower limb muscles excluding the rectus femoris and hamstring muscles.

Energy system contribution during competitive cross-country skiing.

Abstract: Energy system contribution during cross-country (XC) skiing races is dependent on several factors, including the race duration, track profile, and sub-techniques applied, and their subsequent effects on the use of the upper and lower body. This review provides a scientific synopsis of the interactions of energy system contributions from a physiological, technical, and tactical perspective. On average, the aerobic proportion of the total energy expended during XC skiing competitions is comparable to the values for other sports with similar racing times. However, during both sprint (≤ 1.8 km) and distance races (≥ 10 and 15 km, women and men, respectively) a high aerobic turnover interacts with subsequent periods of very high work rates at ~ 120 to 160% of VO2peak during the uphill sections of the race. The repeated intensity fluctuations are possible due to the nature of skiing, which involves intermittent downhills where skiers can recover. Thus, the combination of high and sustained aerobic energy turnover and repeated work rates above VO2peak, interspersed with short recovery periods, distinguishes XC skiing from most other endurance sports. The substantially increased average speed in races over recent decades, frequent competitions in mass starts and sprints, and the greater importance of short periods at high speeds in various sub-techniques, have demanded changes in the physiological, technical, and tactical abilities needed to achieve world-class level within the specific disciplines.

More than a ‘speed gene’: ACTN3 R577X genotype, trainability, muscle damage, and the risk for injuries

Abstract: A common null polymorphism (rs1815739; R577X) in the gene that codes for α-actinin-3 (ACTN3) has been related to different aspects of exercise performance. Individuals who are homozygous for the X allele are unable to express the α-actinin-3 protein in the muscle as opposed to those with the RX or RR genotype. α-actinin-3 deficiency in the muscle does not result in any disease. However, the different ACTN3 genotypes can modify the functioning of skeletal muscle during exercise through structural, metabolic or signaling changes, as shown in both humans and in the mouse model. Specifically, the ACTN3 RR genotype might favor the ability to generate powerful and forceful muscle contractions. Leading to an overall advantage of the RR genotype for enhanced performance in some speed and power-oriented sports. In addition, RR genotype might also favor the ability to withstand exercise-induced muscle damage, while the beneficial influence of the XX genotype on aerobic exercise performance needs to be validated in human studies. More information is required to unveil the association of ACTN3 genotype with trainability and injury risk during acute or chronic exercise.

Exercise intensity effects on total sweat electrolyte losses and regional vs. whole-body sweat [Na+], [Cl-], and [K+].

Abstract: To quantify total sweat electrolyte losses at two relative exercise intensities and determine the effect of workload on the relation between regional (REG) and whole body (WB) sweat electrolyte concentrations. Eleven recreational athletes (7 men, 4 women; 71.5 ± 8.4 kg) completed two randomized trials cycling (30 °C, 44% rh) for 90 min at 45% (LOW) and 65% (MOD) of VO2max in a plastic isolation chamber to determine WB sweat [Na+] and [Cl−] using the washdown technique. REG sweat [Na+] and [Cl−] were measured at 11 REG sites using absorbent patches. Total sweat electrolyte losses were the product of WB sweat loss (WBSL) and WB sweat electrolyte concentrations. WBSL (0.86 ± 0.15 vs. 1.27 ± 0.24 L), WB sweat [Na+] (32.6 ± 14.3 vs. 52.7 ± 14.6 mmol/L), WB sweat [Cl−] (29.8 ± 13.6 vs. 52.5 ± 15.6 mmol/L), total sweat Na+ loss (659 ± 340 vs. 1565 ± 590 mg), and total sweat Cl− loss (931 ± 494 vs. 2378 ± 853 mg) increased significantly (p < 0.05) from LOW to MOD. REG sweat [Na+] and [Cl−] increased from LOW to MOD at all sites except thigh and calf. Intensity had a significant effect on the regression model predicting WB from REG at the ventral wrist, lower back, thigh, and calf for sweat [Na+] and [Cl−]. Total sweat Na+ and Cl− losses increased by ~ 150% with increased exercise intensity. Regression equations can be used to predict WB sweat [Na+] and [Cl−] from some REG sites (e.g., dorsal forearm) irrespective of intensity (between 45 and 65% VO2max), but other sites (especially ventral wrist, lower back, thigh, and calf) require separate prediction equations accounting for workload.

Effects of upper-body, lower-body, or combined resistance training on the ratio of follistatin and myostatin in middle-aged men.

Abstract: Due to the mechanistic role of myostatin and follistatin in modulating muscle mass, shifts in the follistatin to myostatin ratio (F:M) may help explain changes in muscular size in response to resistance training (RT). The present study examined whether differential responses in follistatin and myostatin occur based on the amount of active musculature in a RT program in middle-aged men. Forty middle-aged men (age = 46.5 ± 3.1 years) were randomly assigned to 1 of 4 groups, upper-body RT (UB; n = 10), lower-body RT (LB; n = 10), combined RT (UB + LB; n = 10) or control (C; n = 10). The training protocol consisted of three exercise sessions per week for 8 weeks. Blood samples were obtained at baseline and 48 h after the final session of the training program. Muscle mass significantly increased (p < 0.05) following UB = 0.76 ± 0.46 kg, LB = 0.90 ± 0.29 kg, UB + LB = 1.38 ± 0.70 kg, compared to no changes after control. Serum follistatin increased in the LB = 0.24 ± 0.06 ng mL−1, UB = 0.27 ± 0.17 ng mL−1, UB + LB = 0.50 ± 0.18 ng mL−1, while serum myostatin decreased in the LB = − 0.11 ± 0.08 ng mL−1 and UB + LB = − 0.34 ± 0.23 ng mL−1, but not UB = 0.07 ± 0.16 ng mL−1. Further, change in concentration following training was larger between UB + LB and either LB or UB alone for both follistatin and myostatin. Both UB and LB increase muscle mass and alter the F: M ratio; however, the change in these endocrine markers is approximately twice as large if UB and LB is combined. The endocrine response to RT of myostatin and follistatin may depend on the volume of muscle mass activated during training.

A review on crosstalk in myographic signals

Abstract: Crosstalk in myographic signals is a major hindrance to the understanding of local information related to individual muscle function. This review aims to analyse the problem of crosstalk in electromyography and mechanomyography. An initial search of the SCOPUS database using an appropriate set of keywords yielded 290 studies, and 59 potential studies were selected after all the records were screened using the eligibility criteria. This review on crosstalk revealed that signal contamination due to crosstalk remains a major challenge in the application of surface myography techniques. Various methods have been employed in previous studies to identify, quantify and reduce crosstalk in surface myographic signals. Although correlation-based methods for crosstalk quantification are easy to use, there is a possibility that co-contraction could be interpreted as crosstalk. High-definition EMG has emerged as a new technique that has been successfully applied to reduce crosstalk. The phenomenon of crosstalk needs to be investigated carefully because it depends on many factors related to muscle task and physiology. This review article not only provides a good summary of the literature on crosstalk in myographic signals but also discusses new directions related to techniques for crosstalk identification, quantification and reduction. The review also provides insights into muscle-related issues that impact crosstalk in myographic signals.

The skeletal muscle fiber: a mechanically sensitive cell.

Abstract: The plasticity of skeletal muscle, whether an increase in size, change in metabolism, or alteration in structural properties, is in a continuous state of flux largely dependent upon physical activity. Much of the past research has expounded upon these ever-changing aspects of the muscle fiber following exercise. Specifically, endocrine and paracrine signaling have been heavily investigated lending to much of the past literature comprised of such endocrinological dynamics following muscle activity. Mechanotransduction, the ability of a cell to convert a mechanical stimulus into an intracellular biochemical response, has garnered much less attention. Recent work, however, has demonstrated the physical continuity of the muscle fiber, specifically demonstrating a continuous physical link between the extracellular matrix (ECM), cytoskeleton, and nuclear matrix as a means to rapidly regulate gene expression following a mechanical stimulus. Similarly, research has shown mechanical stimuli to directly influence cytoplasmic signaling whether through oxidative adaptations, increased muscle size, or enhanced muscle integrity. Regrettably, minimal research has investigated the role that exercise may play within the mechanotransducing signaling cascades. This proposed line of study may prove paramount as muscle-related diseases greatly impact one's ability to lead an independent lifestyle along with contributing a substantial burden upon the economy. Thus, this review explores both biophysical and biochemical mechanotransduction, and how these signaling pathways may be influenced following exercise.

Sprint running: from fundamental mechanics to practice-a review.

Abstract: In this review, we examine the literature in light of the mechanical principles that govern linear accelerated running. While the scientific literature concerning sprint mechanics is comprehensive, these principles of fundamental mechanics present some pitfalls which can (and does) lead to misinterpretations of findings. Various models of sprint mechanics, most of which build on the spring-mass paradigm, are discussed with reference to both the insight they provide and their limitations. Although much research confirms that sprinters to some extent behave like a spring-mass system with regard to gross kinematics (step length, step rate, ground contact time, and lower limb deformation), the laws of motion, supported by empirical evidence, show that applying the spring-mass model for accelerated running has flaws. It is essential to appreciate that models are pre-set interpretations of reality; finding that a model describes the motor behaviour well is not proof of the mechanism behind the model. Recent efforts to relate sprinting mechanics to metabolic demands are promising, but have the same limitation of being model based. Furthermore, a large proportion of recent literature focuses on the interaction between total and horizontal (end-goal) force. We argue that this approach has limitations concerning fundamental sprinting mechanics. Moreover, power analysis based on isolated end-goal force is flawed. In closing, some prominent practical concepts and didactics in sprint running are discussed in light of the mechanical principles presented. Ultimately, whereas the basic principles of sprinting are relatively simple, the way an athlete manages the mechanical constraints and opportunities is far more complex.

Does an increase in energy return and/or longitudinal bending stiffness shoe features reduce the energetic cost of running?

Abstract: This study focused on the effects of shoe energy return and shoe longitudinal bending stiffness on the energetic cost and biomechanics of running. The energetic cost of running and biomechanical variables altering running economy (ground contact times, stride frequency, vertical and leg stiffness, ground reaction force impulses, alignment between the resultant ground reaction force and the leg) were measured for nineteen male recreational runners. Participants ran overground under their ventilatory anaerobic threshold (10.8 ± 1.1 km h−1 on average) using four shoe prototypes with features combining low or high magnitudes of energy return and longitudinal bending stiffness. Neither the energy return, nor the longitudinal bending stiffness, or the interaction of these shoe features altered the energetic cost of running. High energy return shoes induced significant increased ground contact time from 274.5 ± 18.3 to 277.1 ± 18.7 ms, and significant decreased stride frequency from 1.34 ± 0.05 to 1.33 ± 0.05 Hz. High bending stiffness shoes induced significant increased ground contact time from 273.8 ± 18.2 to 277.9 ± 18.7 ms, significant increased vertical stiffness from 23.2 ± 3.4 to 23.8 ± 3.0 kN m−1, and significant decreased net vertical impulse from 245.4 ± 17.2 to 241.7 ± 17.5 BW ms. Increased energy return and longitudinal bending stiffness induced subtle changes in the running biomechanics, but did not induce any decrease in the energetic cost of running.

Development of peak oxygen uptake from 11-16 years determined using both treadmill and cycle ergometry.

Abstract: To investigate the development of peak oxygen uptake ( $$\dot{{V}}{\text{O}}_{2}$$ ) assessed on both a treadmill and a cycle ergometer in relation with sex and concurrent changes in age, body mass, fat-free mass (FFM), and maturity status and to evaluate currently proposed ‘clinical red flags’ or health-related cut-points for peak $$\dot{{V}}{\text{O}}_{2}$$ . Multiplicative multilevel modelling, which enables the effects of variables to be partitioned concurrently within an allometric framework, was used to analyze the peak $$\dot{{V}}{\text{O}}_{2}$$ s of 138 (72 boys) students initially aged 11–14 years and tested on three annual occasions. Models were founded on 640 (340 from boys) determinations of peak $$\dot{{V}}{\text{O}}_{2}$$ , supported by anthropometric measures and maturity status. Mean peak $$\dot{{V}}{\text{O}}_{2}$$ s were 11–14% higher on a treadmill. The data did not meet the statistical assumptions underpinning ratio scaling of peak $$\dot{{V}}{\text{O}}_{2}$$ with body mass. With body mass appropriately controlled for boys’ peak $$\dot{{V}}{\text{O}}_{2}$$ s were higher than girls’ values and the difference increased with age. The development of peak $$\dot{{V}}{\text{O}}_{2}$$ was sex-specific, but within sex models were similar on both ergometers with FFM the dominant anthropometric factor. Data should not be pooled for analysis but data from either ergometer can be used independently to interpret the development of peak $$\dot{{V}}{\text{O}}_{2}$$ in youth. On both ergometers and in both sexes, FFM is the most powerful morphological influence on the development of peak $$\dot{{V}}{\text{O}}_{2}$$ . ‘Clinical red flags’ or health-related cut-points proposed without consideration of exercise mode and founded on peak $$\dot{{V}}{\text{O}}_{2}$$ in ratio with body mass are fallacious.

Heart rate recovery after maximal exercise is impaired in healthy young adults born preterm.

Abstract: The long-term implications of premature birth on autonomic nervous system (ANS) function are unclear. Heart rate recovery (HRR) following maximal exercise is a simple tool to evaluate ANS function and is a strong predictor of cardiovascular disease. Our objective was to determine whether HRR is impaired in young adults born preterm (PYA). Individuals born between 1989 and 1991 were recruited from the Newborn Lung Project, a prospectively followed cohort of subjects born preterm weighing 0.05). Autonomic dysfunction as seen in this study has been associated with increased rates of cardiovascular disease in non-preterm populations, suggesting further study of the mechanisms of autonomic dysfunction after preterm birth.

Physiological comparison between non-athletes, endurance, power and team athletes

Abstract: We hypothesized that endurance athletes have lower muscle power than power athletes due to a combination of weaker and slower muscles, while their higher endurance is attributable to better oxygen extraction, reflecting a higher muscle oxidative capacity and larger stroke volume. Endurance (n = 87; distance runners, road cyclists, paddlers, skiers), power (n = 77; sprinters, throwers, combat sport athletes, body builders), team (n = 64; basketball, soccer, volleyball) and non-athletes (n = 223) performed a countermovement jump and an incremental running test to estimate their maximal anaerobic and aerobic power (VO2max), respectively. Dynamometry and M-mode echocardiography were used to measure muscle strength and stroke volume. The VO2max (L min-1) was larger in endurance and team athletes than in power athletes and non-athletes (p < 0.05). Athletes had a larger stroke volume, left ventricular mass and left ventricular wall thickness than non-athletes (p < 0.02), but there were no significant differences between athlete groups. The higher anaerobic power in power and team athletes than in endurance athletes and non-athletes (p < 0.001) was associated with a larger force (p < 0.001), but not faster contractile properties. Endurance athletes (20.6%) had a higher (p < 0.05) aerobic:anaerobic power ratio than controls and power and team athletes (14.0-15.3%). The larger oxygen pulse, without significant differences in stroke volume, in endurance than power athletes indicates a larger oxygen extraction during exercise. Power athletes had stronger, but not faster, muscles than endurance athletes. The similar VO2max in endurance and team athletes and similar jump power in team and power athletes suggest that concurrent training does not necessarily impair power or endurance performance.

Muscle quality as a complementary prognostic tool in conjunction with sarcopenia assessment in younger and older individuals

Abstract: This pilot study investigated differences in lean tissue mass, muscle strength, muscle quality (strength per unit of muscle mass; MQ), and functional performance in healthy younger and older individuals. The most robust predictors of appendicular lean mass (ALM) were then determined in each group. Fifty younger (18–45 years) and 50 older (60–80 years) participants completed tests of upper and lower body strength alongside body composition by dual-energy X-ray absorptiometry from which upper- and lower-body MQ were estimated. Available cut-points for older people were used to determine low upper-body MQ in both groups. Low lower-body MQ was determined as at least two standard deviations below the mean of the younger group. Functional performance was assessed by gait speed. Sarcopenia was identified using two established definitions. Upper and lower body strength, ALM, lower-body MQ and gait speed were significantly higher in the younger group (all p < 0.002). Sarcopenia was identified in 2–4% of the older group. Low upper-body MQ was evident in 32% and 42% of the younger and older group, respectively. Low lower-body MQ was observed in 4% of younger participants, and 50% of older participants. In both groups, the most robust predictors of ALM were upper and lower body strength (young R2 = 0.74, 0.82; older R2 = 0.68, 0.72). Low MQ despite low prevalence rates of sarcopenia in both groups suggests a need for age-specific MQ cut-points. Muscle quality assessments might be useful complementary prognostic tools alongside existing sarcopenia definitions.

Mitochondrial health and muscle plasticity after spinal cord injury

Abstract: Mitochondria are responsible for aerobic respiration and large-scale ATP production in almost all cells of the body. Their function is decreased in many neurodegenerative and cardiovascular disease states, in metabolic disorders such as type II diabetes and obesity, and as a normal component of aging. Disuse of skeletal muscle from immobilization or unloading triggers alterations of mitochondrial density and activity. Resultant mitochondrial dysfunction after paralysis, which precedes muscle atrophy, may augment subsequent release of reactive oxygen species leading to protein ubiquitination and degradation. Spinal cord injury is a unique form of disuse atrophy as there is a complete or partial disruption in tonic communication between the central nervous system (CNS) and skeletal muscle. Paralysis, unloading and disruption of CNS communication result in a rapid decline in skeletal muscle function and metabolic status with disruption in activity of peroxisome-proliferator-activated receptor-gamma co-activator 1 alpha and calcineurin, key regulators of mitochondrial health and function. External interventions, both acute and chronical with training using body-weight-assisted treadmill training or electrical stimulation have consistently demonstrated adaptations in skeletal muscle mitochondria, and expression of the genes and proteins required for mitochondrial oxidation of fats and carbohydrates to ATP, water, and carbon dioxide. The purpose of this mini-review is to highlight our current understanding as to how paralysis mechanistically triggers downstream regulation in mitochondrial density and activity and to discuss how mitochondrial dysfunction may contribute to skeletal muscle atrophy.

Whole body cryotherapy, cold water immersion, or a placebo following resistance exercise: a case of mind over matter?

Abstract: The use of cryotherapy as a recovery intervention is prevalent amongst athletes. Performance of high volume, heavy load resistance exercise is known to result in disturbances of muscle function, perceptual responses and blood borne parameters. Therefore, this study investigated the influence of cold water immersion (CWI), whole body cryotherapy (WBC) or a placebo (PL) intervention on markers of recovery following an acute resistance training session. 24 resistance trained males were matched into a CWI (10 min at 10 °C), WBC (3- and 4 min at − 85 °C) or PL group before completing a lower body resistance training session. Perceptions of soreness and training stress, markers of muscle function, inflammation and efflux of intracellular proteins were assessed before, and up to 72 h post exercise. The training session resulted in increased soreness, disturbances of muscle function, and increased inflammation and efflux of intracellular proteins. Although WBC attenuated soreness at 24 h, and positively influenced peak force at 48 h compared to CWI and PL, many of the remaining outcomes were trivial, unclear or favoured the PL condition. With the exception of CRP at 24 h, neither cryotherapy intervention attenuated the inflammatory response compared to PL. There was some evidence to suggest that WBC is more effective than CWI at attenuating select perceptual and functional responses following resistance training. However, neither cryotherapy intervention was more effective than the placebo treatment at accelerating recovery. The implications of these findings should be carefully considered by individuals employing cryotherapy as a recovery strategy following heavy load resistance training.

The interactions of physical activity, exercise and genetics and their associations with bone mineral density: implications for injury risk in elite athletes

Abstract: Low bone mineral density (BMD) is established as a primary predictor of osteoporotic risk and can also have substantial implications for athlete health and injury risk in the elite sporting environment. BMD is a highly multi-factorial phenotype influenced by diet, hormonal characteristics and physical activity. The interrelationships between such factors, and a strong genetic component, suggested to be around 50–85% at various anatomical sites, determine skeletal health throughout life. Genome-wide association studies and case–control designs have revealed many loci associated with variation in BMD. However, a number of the candidate genes identified at these loci have no known associated biological function or have yet to be replicated in subsequent investigations. Furthermore, few investigations have considered gene–environment interactions—in particular, whether specific genes may be sensitive to mechanical loading from physical activity and the outcome of such an interaction for BMD and potential injury risk. Therefore, this review considers the importance of physical activity on BMD, genetic associations with BMD and how subsequent investigation requires consideration of the interaction between these determinants. Future research using well-defined independent cohorts such as elite athletes, who experience much greater mechanical stress than most, to study such phenotypes, can provide a greater understanding of these factors as well as the biological underpinnings of such a physiologically “extreme” population. Subsequently, modification of training, exercise or rehabilitation programmes based on genetic characteristics could have substantial implications in both the sporting and public health domains once the fundamental research has been conducted successfully.

Ischemic preconditioning and exercise performance: shedding light through smallest worthwhile change.

Abstract: Ischemic preconditioning (IPC) has been suggested as a potential ergogenic aid to improve exercise performance, although controversial findings exist. The controversies may be explained by several factors, including the mode of exercise, the ratio between the magnitude of improvement, or the error of measurement and physiological meaning. However, a relevant aspect has been lacking in the literature: the interpretation of the findings considering statistical tests and adequate effect size (ES) according to the fitness level of individuals. Thus, we performed a systematic review with meta-analysis to update the effects of IPC on exercise performance and physiological responses, using traditional statistics (P values), ES, and smallest worth change (SWC) approach contextualizing the IPC application to applied Sports and Exercise performance. Forty-five studies met the inclusion criteria. Overall, the results show that IPC has a minimal or nonsignificant effect on performance considering the fitness level of the individuals, using statistical approaches (i.e., tests with P value, ES, and SWC). Therefore, IPC procedures should be revised and refined in future studies to evaluate if IPC promotes positive effects on performance in a real-world scenario with more consistent interpretation.

Bone mineral density, energy availability, and dietary restraint in collegiate cross-country runners and non-running controls

Abstract: Weight-bearing activities such as running have been shown to be osteogenic. However, investigations have also shown that running may lead to site-specific deficiencies in bone mineral density (BMD) as well as overall low BMD. The purpose of this investigation was to evaluate and compare the BMD of female and male collegiate cross-country runners with non-running controls. In addition, energy availability and disordered eating attitudes and behaviors were assessed. BMD of 60 collegiate cross-country runners and 47 BMI and age-matched non-running controls were measured via DXA scans. Participants completed a Block 2014 Food Frequency Questionnaire and Eating Disorder Examination Questionnaire. Controlling for fat-free mass (FFM), male runners showed greater BMD at the femoral neck (0.934 ± 0.029 vs. 0.866 ± 0.028 g cm2, p < 0.05), total hip (1.119 ± 0.023 vs. 1.038 ± 0.021 g cm2, p < 0.05), and whole body (1.119 ± 0.023 vs. 1.038 ± 0.021 g cm2, p < 0.05) than male controls. The female runners had greater whole-body BMD than female controls (1.143 ± 0.018 vs. 1.087 ± 0.022 g cm2, p < 0.05). Runners scored significantly higher than controls in dietary restraint (1.134 ± 1.24 vs. 0.451 ± 0.75, p < 0.05), male runners were significantly higher than male controls in eating concern (1.344 ± 1.08 vs. 0.113 ± 0.27, p < 0.05) and female runners were significantly higher than male runners in shape concern (1.056 ± 1.27 vs. 0.242 ± 0.31, p < 0.05). Forty-two percent of the male runners and 29% of female runners had an energy availability of less than 30 kcals kg−1FFM. It appears that distance running has beneficial effects on whole-body BMD and site-specific areas. Further research is warranted to further clarify the health effects of eating behaviors and EA of distance runners.

The effects of a 12-week jump rope exercise program on abdominal adiposity, vasoactive substances, inflammation, and vascular function in adolescent girls with prehypertension

Abstract: The Following error was published on page 578. The incorrect IRB number under "Participants" section was accidently reported.

Changes in oxidative stress, inflammation and muscle damage markers following eccentric versus concentric cycling in older adults.

Abstract: To compare concentric and eccentric cycling performed by older adults for metabolic demand and post-exercise oxidative stress, inflammation and muscle damage. Eight male and two female healthy older adults (60.4 ± 6.8 years) performed 30 min of moderate-intensity concentric (CONC-M: 50% maximum power output; POmax) and eccentric cycling (ECC-M: 50% POmax) and high-intensity eccentric cycling (ECC-H: 100% POmax) in a randomized order. Average power output (PO), oxygen consumption (VO2), heart rate (HR) and rate of perceived exertion were recorded during cycling. Some indirect markers of muscle damage were assessed before, and immediately, 24 and 48 h after cycling. Markers of oxidative stress (malondialdehyde: MDA, protein carbonyl), antioxidant (total antioxidant capacity, glutathione peroxidase activity: GPx) and inflammation (IL-6, TNF-α) were measured before and 5 min after cycling. PO in ECC-H (202.6 ± 78.5 W) was > 50% greater (P < 0.05) than that of CONC-M (98.6 ± 33.1 W) and ECC-M (112.0 ± 42.1 W). VO2 and HR were also greater (P < 0.05) for ECC-H than CONC-M (50% and 17%, respectively) and ECC-M (40% and 23%, respectively). Muscle strength loss at 1 day post-exercise (8–22%), peak soreness (10–62 mm) and creatine kinase activity (30–250 IU/L) after ECC-H were greater (P < 0.05) than those after ECC-M and CONC-M. MDA decreased (P < 0.05) after CONC-M (− 28%) and ECC-M (− 22%), but not after ECC-H. GPx activity increased after all exercises similarly (20–27%). IL-6 increased (P < 0.05) only after ECC-H (18%). Oxidative stress was minimal after eccentric cycling, but high-intensity eccentric cycling induced moderate muscle damage and inflammation, which is not desirable for older individuals.

The time course and mechanisms of change in biomarkers of joint metabolism in response to acute exercise and chronic training in physiologic and pathological conditions

Abstract: The benefits of exercise across the lifespan and for a wide spectrum of health and diseases are well known. However, there remains less clarity as to the effects of both acute and chronic exercise on joint health. Serum biomarkers of joint metabolism are sensitive to change and have the potential to differentiate between normal and adverse adaptations to acute and chronic load. Therefore, the primary objective of this review is to evaluate how serum biomarkers can inform our understanding of how exercise affects joint metabolism. A comprehensive literature search was completed to identify joint biomarkers previously used to investigate acute and chronic exercise training. Identified biomarkers included those related to joint cartilage, bone, synovium, synovial fluid, and inflammation. However, current research has largely focused on the response of serum cartilage oligomeric matrix protein (COMP) to acute loading in healthy young individuals. Studies demonstrate how acute loading transiently increases serum COMP (i.e., cartilage metabolism), which is mostly dependent on the duration of exercise. This response does not appear to be associated with any lasting deleterious changes, cartilage degradation, or osteoarthritis. Several promising biomarkers for assessing joint metabolism exist and may in future enhance our understanding of the physiological response to acute and chronic exercise. Defining ‘normal’ and ‘abnormal’ biomarker responses to exercise and methodological standardisation would greatly improve the potential of research in this area to understand mechanisms and inform practice.

High-intensity interval exercise promotes post-exercise hypotension of greater magnitude compared to moderate-intensity continuous exercise

Abstract: Physical exercise is associated with reduced blood pressure (BP). Moderate-intensity continuous exercise (MCE) promotes post-exercise hypotension (PEH), which is highly recommended to hypertensive patients. However, recent studies with high-intensity interval exercise (HIIE) have shown significant results in cardiovascular disease. Thus, this study aimed to analyze PEH in hypertensive subjects submitted to HIIE and compare it to post MCE hypotension. 20 hypertensive adults (51 ± 8 years), treated with antihypertensive medications, were submitted to two different exercise protocols and a control session. The MCE was performed at 60–70% of VO2 reserve, while HIIE was composed of five bouts of 3 min at 85–95% VO2 reserve with 2 min at 50% of VO2 reserve. The following variables were evaluated during exercise, pre- and post-session: clinical BP, heart rate (HR), double product, perception of effort, body mass, height and body mass index. Systolic BP decreased after exercise in both sessions, showing greater decrease after HIIE (− 7 ± 10 and − 11 ± 12 mmHg, after MCE and HIIE, respectively, p ≤ 0.01). Diastolic BP also decreased after both sessions, but there were no significant differences between the two sessions (− 4 ± 8 and − 7 ± 8 mmHg, after MCE and HIIE, respectively). Both exercise sessions produced PEH, but HIIE generated a greater magnitude of hypotension. The HIIE protocol performed in this study caused a greater cardiovascular stress during exercise; however, it was safe for the studied population and efficient for reducing BP after exercise.

Resistance training induced changes in strength and specific force at the fiber and whole muscle level: a meta-analysis

Abstract: Considerable debate exists as to whether increases in strength that occur with resistance exercise are the result of increases in muscle size. Most studies have attempted to answer this question using assessments of whole muscle size and voluntary muscle strength, but examining changes at the individual muscle fiber level may also provide some insight. The purpose of this meta-analysis was to compare adaptations at the whole muscle and individual fiber level. A meta-analysis was conducted in February, 2018 including all previously published papers and was analyzed using a random effects model. There were no differences (p = 0.88) when comparing hypertrophy at the whole muscle (4.6%) and individual fiber level (7.0%), but significantly larger (p < 0.001) strength gains were observed at the whole muscle level (43.3%) relative to the individual fiber (19.5%). Additionally, there was an increase in the specific tension of type 1 muscle fibers (p = 0.013), but not type 2 muscle fibers (p = 0.23) which was driven by similar increases in strength (type 1: 17.5%, type 2A: 17.7%), despite differences in muscle size (type 1: 6.7%, type 2A: 12.1%). These results support the hypothesis that the neural adaptations play a large role in increasing isotonic whole muscle strength, but also demonstrate that an improvement in specific tension of type 1 muscle fibers is present. These results would suggest that some mechanism intrinsic to the muscle fiber, and independent of muscle growth, may also be contributing to strength increases in response to resistance exercise providing an avenue for future research.

Exploring the effect of exercise training on testicular function.

Abstract: The impact of exercise training on testicular function is relatively ill-defined. To gain new insights into this important topic, published data, deriving from both humans and animal studies, were critically analyzed. The effects of exercise on the hypothalamus–pituitary–gonadal axis, influenced by the type, intensity and duration of the exercise program, can be evaluated in terms of total and free testosterone and/or luteinizing hormone and follicle-stimulating hormone serum levels and sperm parameters. High-intensity exercise promotes a common decrease in these parameters, and therefore, negatively impacts upon testicular function. However, published data for moderate-intensity exercise training are inconsistent. Conversely, there is consistent evidence to support the benefits of exercise training to prevent and/or counteract the impairment of testis function caused by aging, obesity and doxorubicin treatment. This positive effect is likely the consequence of decreased oxidative stress and inflammatory status. In the future, it will be important to clarify the molecular mechanisms which explain these reported discrepancies and to establish guidelines for an active lifestyle to promote healthy testicular function.

Oxidative stress assessment in breath-hold diving.

Abstract: Breath-hold diving results in significant changes in blood gases’ levels. Challenging variations in oxygen partial pressures may induce reactive oxygen species (ROS) production that exacerbate oxidative stress and, consequently, affect endothelial function. The aim of this study was to investigate the effects of breath-hold diving on oxidative stress damage, assessing ROS production. Nitric oxide metabolites, inducible nitric oxide synthase (iNOS), aminothiols, and renal function were evaluated too as markers of redox status and renal damage. ROS production was assessed with electron paramagnetic resonance. Oxidative status values were measured at pre- and post-40 m dive in a deep swimming pool (Y-40) from six divers (mean age 46.6 ± 9.3 years; height 176 ± 4 cm; BMI 25 ± 2.9 kg/m2). Significant (p < 0.05) increases at post-dive of ROS production rate (0.158 ± 0.003 vs 0.195 ± 0.006 μmol min−1), lipid peroxidation (8-isoprostane: 375.67 ± 195.62 vs 420.49 ± 232.31 pg mg−1 creatinine), nitrate (27.91 ± 19.71 vs 30.80 ± 20.44 μM), iNOS (31.30 ± 4.52 vs 35.68 ± 6.72 IU mL−1) and neopterin concentration (96.20 ± 40.41 vs 118.76 ± 27.84 μmol mol−1 creatinine) were recorded. Conversely, the antioxidant capacity significantly decreased (3.423 ± 0.089 vs 3.015 ± 0.284 mM) after immersion. Overproduction of ROS and consequent oxidative damage to lipids of membrane and antioxidant capacity decreasing reflect also a hypoxic condition, which in the breath-hold diving typically occurs in the last few meters below the surface. iNOS produces NO in large quantities under the examined extreme conditions. Neopterin and creatinine concentration level increased, suggesting an “impairment of renal function” as a likely physiological response to PaO2 variations during dive activity.

In vivo assessment of muscle mitochondrial function in healthy, young males in relation to parameters of aerobic fitness.

Abstract: The recovery of muscle oxygen consumption (m $$\dot{V}$$ O2) after exercise provides a measure of skeletal muscle mitochondrial capacity, as more and better-functioning mitochondria will be able to restore m $$\dot{V}$$ O2 faster to the pre-exercise state. The aim was to measure muscle mitochondrial capacity using near-infrared spectroscopy (NIRS) within a healthy, normally active population and relate this to parameters of aerobic fitness, investigating the applicability and relevance of using NIRS to assess muscle mitochondrial capacity non-invasively. Mitochondrial capacity was analysed in the gastrocnemius and flexor digitorum superficialis (FDS) muscles of eight relatively high-aerobic fitness ( $$\dot{V}$$ O2peak ≥ 57 mL/kg/min) and eight relatively low-aerobic fitness male subjects ( $$\dot{V}$$ O2peak ≤ 47 mL/kg/min). Recovery of whole body $$\dot{V}$$ O2, i.e. excess post-exercise oxygen consumption (EPOC) was analysed after a cycling protocol. Mitochondrial capacity, as analysed using NIRS, was significantly higher in high-fitness individuals compared to low-fitness individuals in the gastrocnemius, but not in the FDS (p = 0.0036 and p = 0.20, respectively). Mitochondrial capacity in the gastrocnemius was significantly correlated with $$\dot{V}$$ O2peak (R2 = 0.57, p = 0.0019). Whole body $$\dot{V}$$ O2 recovery was significantly faster in the high-fitness individuals (p = 0.0048), and correlated significantly with mitochondrial capacity in the gastrocnemius (R2 = 0.34, p = 0.028). NIRS measurements can be used to assess differences in mitochondrial muscle oxygen consumption within a relatively normal, healthy population. Furthermore, mitochondrial capacity correlated with parameters of aerobic fitness ( $$\dot{V}$$ O2peak and EPOC), emphasising the physiological relevance of the NIRS measurements.