Biomechanical and Skeletal Muscle Determinants of Maximum Running Speed with Aging

Unique enlargement of human soleus muscle for bipedalism at the expense of the ease of leg swing

Humans exhibit unique skeletal muscle morphologies that are known to matter in upright bipedalism. However, their relevance to the ease of leg swing, which limits locomotion performance, remains unclear. Here, we aimed to examine muscle mass distribution within the human leg and the effect of each muscle on the ease of leg swing. We calculated the mass, center of mass position, and moment of inertia around the hip extension-flexion axis for all leg muscles by using a publicly available dataset of the 3D reconstruction of the musculoskeletal components in human male and female legs. The leg muscles showed a top-heavy-bottom-light tapering trend; muscles far from the hip joint tended to have smaller masses. Interestingly, however, the soleus exhibited sizable mass for its location. Consequently, the moment of inertia of the soleus was exceptionally greatest, accounting for approximately one-quarter of that of all muscles. These results indicate that compared to the other muscles the soleus muscle has a much larger effect on the leg moment of inertia and uniquely makes humans difficult to swing the leg, although the leg muscles basically show the top-heavy bottom-light tapering trend favoring the leg swing. Our findings highlight a novel functional consequence of human body evolution, suggesting that muscular enlargement for postural stability and endurance capacity has compromised the locomotion speed during the adaptation to bipedalism.

Reliability of muscle thickness and muscle echo intensity evaluation of the posterior medial tibia in long-distance athletes using an ultrasound imaging device

OBJECTIVE

We aimed to verify the reliability of muscle thickness and luminance evaluation of the deep leg muscles using an ultrasound device.

DESIGN

Cohort study.

SETTING

Track and field, Participants: high school track and field long distance athletes (N = 10, female: 50.0%, age = 16.0 ± 2.8 years, BMI = 18.2 ± 2.3 kg/m2) PARTICIPANTS: This study included Japanese high school track and long-distance field athletes.

MAIN OUTCOME MEASURES

The thickness and echo intensity of tibialis posterior, flexor digitorum longus, and soleus muscles in the posterior medial tibia were clarified.

RESULTS

The echo intensity evaluation of the tibialis posterior muscle showed an additive error.

CONCLUSION

The study suggested that the results could be clinically applied clinically, except for the evaluation of echo intensity of the posterior tibialis muscle.

Effects of resistance training on heat shock response (HSR), HSP70 expression, oxidative stress, inflammation, and metabolism in middle-aged people

Resistance training (RT) can increase the heat shock response (HSR) in the elderly. As middle-aged subjects already suffer physiological declines related to aging, it is hypothesized that RT may increase the HSR in these people. To assess the effects of resistance training on heat shock response, intra and extracellular HSP70, oxidative stress, inflammation, body composition, and metabolism in middle-aged subjects. Sixteen volunteers (40 - 59 years) were allocated to two groups: the trained group (n = 7), which performed 12 weeks of RT; and the physically inactive-control group (n = 9), which did not perform any type of exercise. The RT program consisted of 9 whole-body exercises (using standard gym equipment) and functional exercises, carried out 3 times/week. Before and after the intervention, body composition, muscle mass, strength, functional capacity, and blood sample measurements (lipid profile, glucose, insulin, oxidative damage, TNF-α, the HSR, HSP70 expression in leukocytes, and HSP72 in plasma) were performed. The HSR analysis demonstrated that this response is maintained at normal levels in middle-aged people and that RT did not cause any improvement. Also, RT increases muscle mass, strength, and functional capacity. Despite no additional changes of RT on the antioxidant defenses (catalase, glutathione peroxidase, and reductase) or inflammation, lipid peroxidation was diminished by RT (group x time interaction, p = 0.009), indicating that other antioxidant defenses may be improved after RT. HSR is preserved in middle-aged subjects without metabolic complications. In addition, RT reduces lipid peroxidation and can retard muscle mass and strength loss related to the aging process.

Longitudinal development of physical, perceptual-cognitive and skill predictors of talent in academy and professional female football players

Existing literature on talent development predominantly focuses on male athletes, with limited representation of female athletes. This study aims to address this gap by examining the long-term development of female football players in an elite club. Routine lab-based assessments were conducted on 238 athletes across six teams for 7 years to determine how physical, perceptual-cognitive, and skill performance predictors fluctuated with player age and developmental stage (sampling 9-11y, specializing 12-14y, investment 15-18y, and performance +18y). The developmental stage was a significant predictor of improved performance for each talent indicator (p < .001), with each consecutive stage significantly outperforming the previous stage in all domains with moderate to large effect sizes (0.07-0.40 ηp2). Improvement rate was higher in young adolescence (<15) and slower approaching adulthood (>18y). Playing position influenced performance scores on several physical and technical skill predictors (p ≤ .001), but not perceptual-cognitive ones (p ≥ .11). Players progressed continuously from the sampling to the performance stage, contradicting previously reported plateaus observed when athletes reached the investment stage. Benchmark data are provided across age and playing position to better understand what is required for successful participation at an elite level at varying age groups in female soccer.

High-velocity resistance training improves executive function in mobility-limited older adults

OBJECTIVES

To examine the effect of high-velocity resistance training (HVRT) on the executive function of middle-aged and older adults with and without mobility limitations.

METHODS

Participants (n = 41, female: 48.9%) completed a supervised 12-week HVRT intervention (2 sessions/week; at 40-60% of one-repetition maximum). The sample included 17 middle-aged adults (40-55 years); 16 older adults (>60 years) and 8 mobility-limited older adults (LIM). Executive function was assessed before and after the intervention period and was reported as z-scores. Maximal dynamic strength, peak power, quadriceps muscle thickness, maximal isometric voluntary contraction (MVIC), and functional performance were also measured pre and post intervention. Training-related adaptations in cognitive measures were calculated using a Generalized Estimating Equation model.

RESULTS

HVRT improved executive function in LIM (adjusted marginal mean differences [AMMD]: 0.21; 95%CI: 0.04, 0.38; p = 0.040) although no effect on middle-aged (AMMD: 0.04; 95%CI: -0.09; 0.17; p = 0.533) and older (AMMD: -0.11; 95%CI: -0.25; 0.02; p = 0.107) participants was observed. Improvements in maximal dynamic strength, peak power, MVIC, quadriceps muscle thickness, and functional performance were all associated with changes in executive function, and changes in the first four also seem to mediate the association between changes in functional performance and executive function.

CONCLUSIONS

HVRT-induced improvement in executive function of mobility-limited older adults were mediated by changes in lower-body muscle strength, power, and muscle thickness. Our findings reinforce the relevance of muscle-strengthening exercises to preserve cognition and mobility in older adults.

Anthropometric profiles and body composition of male runners at different distances

Anthropometric parameters are crucial prerequisite to achieve success in professional running sports. However, it is not clear how these parameters are relevant for athletes performing on a less demanding sport level as academic competitions. To help coaches and selectors working on this level, we have explored anthropometric variables and body composition in 68 academic athletes: 26 sprinters, 22 middle distance runners, and 20 long distance runners. Sprinters have a more massive body shape, shorter lower legs in relation to the length of the thigh, broader shoulders and narrower hips, greater musculature and cellular mass. A slender figure, a longer shin, and the greatest subcutaneous fat and extracellular mass characterize long-distance runners. Middle-distance runners are the slimmest, and have a narrow trunk and little subcutaneous fat. Sprinters and long-distance runners are mesomorphic, while middle-distance runners present more mixed mesomorph-ectomorph type. The principal component analysis highlighted the importance of the overall size of the body, limbs musculature and the length of the lower limb together with its segments, and also body fatness. This approach emphasized the morphological distinctiveness of runners at particular distances and allows the use of somatic features as predictors of running performance.

A hybrid linear discriminant analysis and genetic algorithm to create a linear model of aging when performing motor tasks through inertial sensors positioned on the hand and forearm

BACKGROUND

During the aging process, cognitive functions and performance of the muscular and neural system show signs of decline, thus making the elderly more susceptible to disease and death. These alterations, which occur with advanced age, affect functional performance in both the lower and upper members, and consequently human motor functions. Objective measurements are important tools to help understand and characterize the dysfunctions and limitations that occur due to neuromuscular changes related to advancing age. Therefore, the objective of this study is to attest to the difference between groups of young and old individuals through manual movements and whether the combination of features can produce a linear correlation concerning the different age groups.

METHODS

This study counted on 99 participants, these were divided into 8 groups, which were grouped by age. The data collection was performed using inertial sensors (positioned on the back of the hand and on the back of the forearm). Firstly, the participants were divided into groups of young and elderly to verify if the groups could be distinguished through the features alone. Following this, the features were combined using the linear discriminant analysis (LDA), which gave rise to a singular feature called the LDA-value that aided in verifying the correlation between the different age ranges and the LDA-value.

RESULTS

The results demonstrated that 125 features are able to distinguish the difference between the groups of young and elderly individuals. The use of the LDA-value allows for the obtaining of a linear model of the changes that occur with aging in the performance of tasks in line with advancing age, the correlation obtained, using Pearson's coefficient, was 0.86.

CONCLUSION

When we compare only the young and elderly groups, the results indicate that there is a difference in the way tasks are performed between young and elderly individuals. When the 8 groups were analyzed, the linear correlation obtained was strong, with the LDA-value being effective in obtaining a linear correlation of the eight groups, demonstrating that although the features alone do not demonstrate gradual changes as a function of age, their combination established these changes.

Task-related and task-unrelated thoughts in runners and equestrians: Measurement issues in evaluations of thought content

Much of the thought content and mind-wandering literature examines self-reported thought content's relationship with performance criteria in limited ways. Furthermore, retrospective reports about thought content may be influenced by the quality of one's performance. We explored these method issues in a cross-sectional study of individuals competing in a trail race and an equestrian event. Our results demonstrated that self-reports of thought content differed based on the performance context: whereas runners' task-related and task-unrelated thoughts were negatively correlated, equestrians' thought content showed no relationship. Moreover, equestrians in general reported fewer task-related and task-unrelated thoughts than runners. Finally, objective performance predicted task-unrelated thought (but not task-related thought) among runners, and an exploratory mediation test suggested the effect was partially mediated by performance awareness. We discuss the applied implications of this research for human performance practitioners.

Predicting Maximum Oxygen Uptake from Non-Exercise and Submaximal Exercise Tests in Paraplegic Men with Spinal Cord Injury

This study aimed to develop prediction equations for maximum oxygen uptake (VO₂max) based on non-exercise (anthropometric) and submaximal exercise (anthropometric and physiological) variables in paraplegic men with a spinal cord injury. All participants were tested on an arm ergometer using a maximal graded exercise test. Anthropometric variables such as age, height, weight, body fat, body mass index, body fat percentage, and arm muscle mass and physiological variables such as VO₂, VCO₂, and heart rate at 3 and 6 min of graded exercise tests were included in the multiple linear regression analysis. The prediction equations revealed the following. Regarding non-exercise variables, VO₂max was correlated with age and weight (equation R = 0.771, R² = 0.595, SEE= 3.187). Regarding submaximal variables, VO₂max was correlated with weight and VO₂ and VCO₂ at 6 min (equation R = 0.892, R² = 0.796, SEE = 2.309). In conclusion, our prediction equations can be used as a cardiopulmonary function evaluation tool to estimate VO₂max simply and conveniently using the anthropometric and physiological characteristics of paraplegic men with spinal cord injuries.

Impact of Resistance Training Volume on Physical and Perceptual Outcomes of Breast Cancer Survivors Submitted to a Combined Training Program: A Randomized, Single-Blinded Study

BACKGROUND

To determine the effect of resistance training volume on physical and perceptual outcomes of breast cancer survivors submitted to a combined training program.

DESIGN

Randomized single-blinded study.

METHODS

Nineteen breast cancer survivor women were randomized to a single-set (SS) or a multiple-set (MS) group. Both groups completed an 8-week combined training intervention in which the SS and MS groups performed 1 and 3 sets per resistance exercise, respectively. The following outcomes were assessed preintervention and postintervention: maximal knee extension dynamic strength (1-repetition maximum), quadriceps muscle thickness, peak oxygen uptake, time to exhaustion, cancer-related fatigue, and quality of life.

RESULTS

Both interventions increased knee extension 1-repetition maximum (SS: 29.8% [37.5%]; MS: 19.3% [11.8%]), quadriceps muscle thickness (9.4% [4.1%]; 8.9% [5.9%]), and quality of life (4.3% [6.3%]; 7.9% [9.0%]), with no difference between the groups. However, only MS improved cancer-related fatigue (-2.1% [1.7%]) and time to exhaustion (21.3% [14.9%]), whereas peak oxygen uptake remained unchanged in both groups.

CONCLUSIONS

Cancer-related fatigue and time to exhaustion, improved only in the MS group after the intervention. On the other hand, similar knee extension 1-repetition maximum, quadriceps muscle thickness, and quality of life improvements were observed in breast cancer survivors irrespective of the resistance training volume performed.

Relationship Between Dual-Energy X-Ray Absorptiometry, Ultrasonography, and Anthropometry Methods to Estimate Muscle Mass and Muscle Quality in Older Adults

Decreased muscle quality (MQ) may explain functional capacity impairments during aging. Thus, it is essential to verify the interaction between MQ and functional capacity in older adults. We investigated the relationship between MQ and functional capacity in older adults (n = 34; 66.3 ± 4.6 year). MQ was estimated by maximum strength of knee extensors normalized to thigh muscle mass. Maximum strength was assessed on an isokinetic dynamometer (peak torque), while dual-energy X-ray absorptiometry (DXA), ultrasonography, and anthropometry were used to determine thigh muscle mass. Functional capacity was verified by 30-s sit to stand and timed up and go tests. Significant correlations were found between MQ assessed by DXA with 30-s sit to stand (r = .35; p < .05) and timed up and go (r = -.47; p < .05), and MQ assessed by anthropometry with timed up and go (r = -.41; p < .05), but not between MQ assessed by ultrasonography with functional capacity (p > .05). No significant relationship between muscle mass with functional capacity was observed. Thus, MQ assessed by DXA and MQ assessed by anthropometry may partially explain functional capacity in older adults. Interestingly, muscle mass alone did not explain performance in functional tests in this population.

Relationship Between Age and Running Kinematics in Female Recreational Runners

Sex-based analyses are important when studying running kinematics. Females experience a unique aging process and demonstrate differences in running biomechanics from males. The purpose was to determine the relationship between age and running kinematics in female runners. Forty-six female runners (18-65 y) ran at self-selected jogging and maximal speed on a treadmill. Lower-extremity joint kinematics were calculated, and 2 principal component analyses (jogging speed and maximal speed) were performed from kinematic variables. Regression was used to examine the relationship between age and identified components, and between age and the variables with the highest loadings within these components. For jogging speed, there was a positive relationship between age and ankle varus at initial contact and a negative relationship between age and peak eversion, hip adduction, knee flexion, dorsiflexion, and hip adduction at initial contact (Ps < .05). For maximal speed, initial contact ankle frontal plane angle became more positive with age, and there was a negative relationship with age and peak eversion, dorsiflexion and knee flexion, and knee flexion and hip adduction at initial contact (Ps < .05). Primarily distal joint angles decreased with increasing age in female recreational runners at self-selected running speeds.

Running in the wild: Energetics explain ecological running speeds

Human runners have long been thought to have the ability to consume a near-constant amount of energy per distance traveled, regardless of speed, allowing speed to be adapted to particular task demands with minimal energetic consequence.^1-3 However, recent and more precise laboratory measures indicate that humans may in fact have an energy-optimal running speed.^4-6 Here, we characterize runners' speeds in a free-living environment and determine if preferred speed is consistent with task- or energy-dependent objectives. We analyzed a large-scale dataset of free-living runners, which was collected via a commercial fitness tracking device, and found that individual runners preferred a particular speed that did not change across commonly run distances. We compared the data from lab experiments that measured participants' energy-optimal running speeds with the free-living preferred speeds of age- and gender-matched runners in our dataset and found the speeds to be indistinguishable. Human runners prefer a particular running speed that is independent of task distance and is consistent with the objective of minimizing energy expenditure. Our findings offer an insight into the biological objectives that shape human running preferences in the real world-an important consideration when examining human ecology or creating training strategies to improve performance and prevent injury.

High-velocity resistance training mitigates physiological and functional impairments in middle-aged and older adults with and without mobility-limitation

The aim of the present study was to compare the neuromuscular, morphological, and functional responses to a high-velocity resistance training (HVRT) program between three cohorts: middle-aged adults (40–55 years, n = 18), healthy older adults (> 60 years, n = 18), and mobility-limited older adults (n = 8). Participants were tested before and after a 4-week control period and then assigned to a 12-week HVRT intervention. Investigated outcomes included ultrasound-derived muscle thickness and quality, maximal dynamic strength (1RM), maximal voluntary isometric contraction (MVIC), and muscle activation (sEMG), as well as muscle power and functional performance. After the intervention, quadriceps muscle thickness, 1RM, and sEMG improved in all three groups (all p < 0.05), whereas muscle quality improved only in middle-aged and older participants (p ≤ 0.001), and MVIC only in middle-aged and mobility-limited older adults (p < 0.05). With a few exceptions, peak power improved in all groups from 30–90% 1RM (p < 0.05) both when tested relative to pre-training or post-training 1RM workloads (all p < 0.05). Both mobility-limited older adults and older adults improved their short physical performance battery score (p < 0.05). Chair stand, stair climb, maximal gait speed, and timed up-and-go performance, on the other hand, improved in all three groups (p < 0.05), but no change was observed for habitual gait speed and 6-min walk test performance. Overall, our results demonstrate that a HVRT intervention can build a stronger foundation in middle-aged individuals so that they can better deal with age-related impairments at the same time that it can mitigate already present physiological and functional impairments in older adults with and without mobility-limitation.

Is musculoskeletal pain related to locomotive syndrome even in young and middle-aged adults?

OBJECTIVES

Locomotive syndrome (LS) is the leading cause of persons needing long-term care in old age and is characterized by locomotive organ impairment including musculoskeletal pain. The aim was to examine the association between musculoskeletal pain and LS in young and middle-aged persons.

METHODS

A total of 836 participants (male 667, female 169; mean age 44.4 years) were examined in this cross-sectional study. The LS was evaluated by three screening tools: the two-step test, the stand-up test, and the 25-question Geriatric Locomotive Function Scale. Musculoskeletal pain, exercise habits, physical function (walkability and muscle strength), and physical activity were also assessed.

RESULTS

The LS was found in 22.8% of participants. The number with musculoskeletal pain was significantly higher in those with the LS. A significant correlation was found between the degree of musculoskeletal pain and exercise habits. Less regular exercise was significantly associated with higher LS prevalence. Physical activity and function were greater in participants with more regular exercise.

CONCLUSION

Musculoskeletal pain was significantly related to LS even in young and middle-aged persons. The present results suggest that control of musculoskeletal pain and improvement of exercise habits in young and middle-aged persons might help prevent the LS.

Methodological Proposal for Strength and Power Training in Older Athletes: A Narrative Review

INTRODUCTION

Within the adult population, it is not uncommon to meet older athletes who challenge the negative stereotypes associated with aging. Although their physical performance is superior to their sedentary counterparts, they are not immune to impaired neuromuscular function, leading to a decreased physical capacity and an increased risk of injuries. Despite the abundant information about the benefits of strength/power training in advanced ages, there are no methodological proposals that guide physical activity professionals to program this type of training.

OBJECTIVE

This study aimed to review the factors related to the decrease in sports performance within older athletes and the benefits of a strength/power program in order to provide a methodological proposal to organize training in this population.

METHODS

This is a review article. First, databases from PubMed, Science Direct, and SPORTSDiscus and search engines, namely Google Scholar and Scielo, were reviewed, using standard keywords such as strength and power training, evaluation of physical performance, neuromuscular function, and risk of injury in the elderly athlete. All related articles published during the period 1963 to 2020 were considered. A total of 1837 documents were found. By removing 1715 unrelated documents, 122 articles were included in the study after revision control.

RESULTS

Strength/power training is key to alleviating the loss of performance in older athletes and the benefits in neuromuscular function, which helps reduce the rate of serious injuries, maintaining sports practice for a longer period of time. In order to design an appropriate program, a prior evaluation of the individual's physical-technical level must be carried out, respecting the biologicalpedagogical principles and safety regulations.

CONCLUSION

The methodological proposal delivered in this review can serve as a technical guide for physical activity professionals, which will be able to structure the strength/power training and thus preserve the sports practice in older athletes for a longer time.

Intra-rater and inter-rater reliability of the process of obtaining cross-sectional area and echo intensity measurements of muscles from ultrasound images

Introduction: The use of ultrasound images for analyzing muscle quality and size is continuing to grow in the literature. However, many of these manuscripts fail to properly describe their measurement techniques and steps involved in analyzing ultrasound images. Aim of this study: To evaluate the intra- and inter-rater reliability of the steps involved when analyzing ultrasound images to measure cross-sectional area and echo intensity. Material and methods: Twenty ultrasound images of the rectus femoris and vastus lateralis images were blinded and replicated, and then analyzed by experienced raters. The raters then were asked to analyze the images using open-source software for scaling measurements, subcutaneous fat thickness, cross-sectional area, and echo intensity. Matched image values for each measurement where compared for intra- and inter-rater reliability. Results: Intra-rater reliability ranged from fair (ICC_3,1 = 0.32) to high (0.98), with echo intensity values being the least reliable (>0.55), and scaling and depth measurements being the most reliable (<0.85). Inter-rater reliability ranged from good (0.77) to high (0.97). Conclusion: Ultrasound-derived measures of cross-sectional area and echo intensity can be measured reliably, with echo intensity being the most difficult to replicate. However, reliability measures are unique to the rater and study and, therefore, should be clearly reported in every paper.

Why Are Masters Sprinters Slower Than Their Younger Counterparts? Physiological, Biomechanical, and Motor Control Related Implications for Training Program Design

Elite sprint performances typically peak during an athlete's 20s and decline thereafter with age. The mechanisms underpinning this sprint performance decline are often reported to be strength-based in nature with reductions in strength capacities driving increases in ground contact time and decreases in stride lengths and frequency. However, an as-of-yet underexplored aspect of Masters sprint performance is that of age-related degradation in neuromuscular infrastructure, which manifests as a decline in both strength and movement coordination. Here, the authors explore reductions in sprint performance in Masters athletes in a holistic fashion, blending discussion of strength and power changes with neuromuscular alterations along with mechanical and technical age-related alterations. In doing so, the authors provide recommendations to Masters sprinters-and the aging population, in general-as to how best to support sprint ability and general function with age, identifying nutritional interventions that support performance and function and suggesting useful programming strategies and injury-reduction techniques.

Age and training volume influence joint kinetics during running

Recently, we proposed the hypothesis that weekly running volume and preferred running pace may play a role in preserving ankle joint kinetics in middle-age runners as ankle joint kinetics were generally similar in young and middle-aged runners with similar running volume and preferred pace. To further address this hypothesis, we compared lower extremity joint kinetics between high and low training volume runners in both young and middle-aged groups. Joint kinetics calculated from 3D kinematic and ground reaction force data during over-ground running at 2.7 m·s^-1 from young and middle-aged runners who ran low or high weekly volume were analyzed. A two-factor analysis of variance was used to compare joint kinetics between age and running volume groups. Positive hip work was greater in middle-aged compared to young runners (P = .005). Plantarflexor torque (P = .009) and positive ankle work (P = .042) were greater in young compared to middle-aged runners. Positive ankle work was also greater in the high compared to the low volume group (P = .021). Finally, age by volume interactions were found for knee extensor torque (P = .024), negative knee work (P = .018), and positive knee work (P = .019) but not for ankle and hip joint kinetics. These findings suggest less distal-to-proximal difference in positive joint work with high running volume in both young and middle-aged runners as a result of greater power generation at the ankle. Given the age main effects, our findings are also the first to suggest the age-related distal-to-proximal shift in joint kinetics appears in middle-aged runners.

Effects of Traditional and Vascular Restricted Strength Training Program With Equalized Volume on Isometric and Dynamic Strength, Muscle Thickness, Electromyographic Activity, and Endothelial Function Adaptations in Young Adults

Ramis, TR, Muller, CHdL, Boeno, FP, Teixeira, BC, Rech, A, Pompermayer, MG, Medeiros, NdS, Oliveira, ÁRd, Pinto, RS, and Ribeiro, JL. Effects of traditional and vascular restricted strength training program with equalized volume on isometric and dynamic strength, muscle thickness, electromyographic activity, and endothelial function adaptations in young adults. J Strength Cond Res 34(3): 689-698, 2020-The purpose of the study was to evaluate and compare the acute and chronic effects of partial vascular occlusion training in young, physically active adults. Neuromuscular, morphological, and endothelial function responses were compared between high-intensity resistance training (HI-RT) and low-intensity resistance training with partial vascular occlusion (LI-BFR), despite the same training volume. The 28 subjects (age, 23.96 ± 2.67 years) were randomly assigned into 2 groups: LI-BFR (n = 15) and HI-RT (n = 13). Both groups performed unilateral exercise of elbow flexion (EF) and knee extension (KE) 3 times per week for 8 weeks. This study was approved by the ethics committee. Flow-mediated dilation showed a significant difference in baseline and post-training in the LI-BFR group (4.44 ± 0.51 vs. 6.35 ± 2.08 mm, respectively). For nitrite/nitrate concentrations only, there was a significant difference when comparing pre- and post-acute exercise in both groups. The torque and rep. Sixty percent 1 repetition maximum had improvements in both groups. There were differences between groups only in isometric delta EF and isokinetic delta KE (EF 3.42 ± 5.09 and 9.61 ± 7.52 N·m; KE 12.78 ± 25.61 and 42.69 ± 35.68 N·m; LI-BFR and HI-RT groups, respectively). There was a significant increase of muscle thickness in both groups. An increase of both isokinetic and isometric electromyography (EMG) of biceps of the HI-RT group was observed. The same was observed for the LI-BFR group regarding isokinetic and isometric EMG of vastus lateralis. Thus, in addition to strength and hypertrophy gains, this study also shows benefits related to vascular function. For practical applications, this study demonstrates a clinical importance of LI-BFR training as an alternative methodology.

The physical demands of mixed martial arts: A narrative review using the ARMSS model to provide a hierarchy of evidence

The physical demands of mixed martial arts (MMA) training and competition is not yet well quantified. The Applied Research Model for the Sport Sciences (ARMSS) provides a framework through which to conduct sport science, determining pertinent questions to test research findings in real-world settings. The aim of this review was to evaluate MMA research within the context of ARMSS to critically analyse our understanding of the physical requirements of MMA training and competition. Research databases were searched, with 70 peer-reviewed articles being discussed in relation to the specific stage of the ARMSS in which their results best fit. MMA research was found to be mostly foundational and descriptive in nature and has generally not developed along systematic lines. The internal and external loads and responses to training and competition have not been adequately identified. Therefore, it is not currently possible to state which variables are key predictors of success, or how coaches can optimally manipulate these variables. We propose that MMA research be refocused to be conducted within ARMSS. Specifically, stage 2 studies describing the physical, physiological and technical demands of MMA training and competition, and stage 3 studies determining the physiological predictors of performance should be initially prioritised.

Ankle kinetics and plantarflexor morphology in older runners with different lifetime running exposures

Running promotes better cardiovascular health and has positive effects on the musculoskeletal system in older adults. However, older adults have lower ankle plantarflexor torques and positive powers during running, and exhibit changes in plantarflexor morphology than young adults. Since older runners who run as much as younger runners exhibit youthful ankle mechanical outputs, running exposure may preserve the locomotor factors that mediate running speed. The purpose of this study was to compare ankle mechanical output during running and plantarflexor morphological characteristics between older runners who have low or high lifetime running exposure. Ten older runners with low lifetime running exposure and nine older runners with high lifetime running exposure performed over-ground running trials at 3.0 m/s (±5%) while kinematic and ground reaction force (GRF) data were collected and used to compute joint angular kinetics. Right medial gastrocnemius morphological characteristics were assessed using ultrasonography at rest and during isometric contractions. Ankle torques, powers, and plantarflexor morphology were compared between groups. Older runners with different lifetime running exposures ran with similar ankle mechanical output (i.e. no effect of running exposure) (p > .05) and exhibited similar medial gastrocnemius morphology during isometric testing. The findings from this study demonstrate that lifetime running exposure does not appear to influence ankle mechanical output or plantarflexor morphology in middle-aged runners.

Biomechanics of starting, sprinting and submaximal running in athletes with brain impairment: A systematic review

OBJECTIVES

Para athletes with brain impairment are affected by hypertonia, ataxia and athetosis, which adversely affect starting, sprinting and submaximal running. The aim was to identify and synthesise evidence from studies that have compared the biomechanics of runners with brain impairments (RBI) and non-disabled runners (NDR).

DESIGN

Systematic review.

METHODS

Five journal databases were systematically searched from inception to March 2020. Included studies compared the biomechanics of RBI (aged>14 years) and NDR performing either block-starts, sprinting, or submaximal running.

RESULTS

Eight studies were included, analysing a total of 100 RBI (78M:22F; 18-38 years) diagnosed with either cerebral palsy (n=44) or traumatic brain injury (n=56). Studies analysed block-starts (n=3), overground sprinting (n=3) and submaximal running (n=2), and submaximal treadmill running (n=1). Horizontal velocity during starts, sprinting and self-selected submaximal speeds were lower in RBI. During sprinting and submaximal running, compared with NDR, RBI had shorter stride length, step length, and flight time, increased ground-contact time, increased cadence, and reduced ankle and hip range of motion. In submaximal running, RBI had decreased ankle-power generation at toe-off.

CONCLUSIONS

There is limited research and small sample sizes in this area. However, preliminary evidence suggests that RBI had lower sprint speeds and biomechanical characteristics typical of submaximal running speeds in NDR, including increased ground-contact times and reduced stride length, step length, and flight times. Meaningful interpretation of biomechanical findings in RBI is impeded by impairment variability (type, severity and distribution), and methods which permit valid, reliable impairment stratification in larger samples are required.

Sprint and Strength Training Modulates Autophagy and Proteostasis in Aging Sprinters

PURPOSE

Exercise and aging may modulate muscle protein homeostasis and autophagy, but few studies examine highly trained middle-age or older individuals. This study elucidated the effects of a new long-term training stimulus on markers of muscle autophagy and unfolded protein response (UPR) and on sprint running performance in masters sprinters.

METHODS

Thirty-two male competitive sprinters (age 40-76 yr) were randomly divided into experimental (EX) and control (CTRL) groups. The EX training program was a combination of heavy and explosive strength and sprint exercises aimed at improving sprint performance. Fifteen and thirteen participants completed the 20-wk intervention period in EX and CTRL, respectively. The latter were told to continue their routine exercises. Key protein markers were analyzed by Western blotting from vastus lateralis (VL) muscle biopsies. The muscle thickness of VL was analyzed by ultrasonography and sprint performance by a 60-m running test.

RESULTS

EX induced improvement in 60-m sprint performance when compared with controls (time-group, P = 0.003) without changes in VL muscle thickness. Content of lipidated microtubule-associated protein 1A/1B-light chain 3 (LC3-II) increased in EX (P = 0.022), suggesting increased autophagosome content. In addition, an autophagosome clearance marker sequestosome 1 (p62) decreased in EX (P = 0.006). Markers of UPR selectively modulated with decreases (e.g., ATF4, P = 0.003) and increases (e.g., EIF2α, P = 0.019) observed in EX.

CONCLUSIONS

These findings suggest that a new intensive training stimulus that combines strength training with sprint training may increase muscle autophagosome content in a basal state without any evidence of impaired autophagosome clearance in masters sprinters. Simultaneously, the combined training may have a selective effect on the content of UPR signaling components.

Water-based continuous and interval training in older women: Cardiorespiratory and neuromuscular outcomes (WATER study)

The purpose of this study was to investigate the effects of two water-based aerobic programs on cardiorespiratory and neuromuscular outcomes in older women. Forty-one women (60 to 75 years old) volunteered to participate in the study. Participants were randomized into a water-based continuous (CTG; n = 21; 63.9 ± 2.5 years) or an interval (ITG; n = 20; 64.8 ± 3.6 years) aerobic training group. Both training programs were performed for 12 weeks (45-min sessions twice a week), with exercise intensity based on rating of perceived exertion (Borg's RPE 6-20 Scale). Pre and post training assessments of cardiorespiratory and neuromuscular outcomes were performed. Data analyses were conducted using Generalized Estimating Equations and Bonferroni post-hoc test (α = 0.05). After the intervention, the CTG and the ITG displayed similar improvements in time to exhaustion (8% vs. 11%), peak oxygen uptake (9% vs. 7%), maximal dynamic knee extension strength (5% vs. 6%), dynamic muscular endurance of knee extensors (10% vs. 11%), maximal vastus lateralis electromyographic signal amplitude (13% vs. 35%), as well as an increase in muscle thickness (5% vs. 6%) and decrease in muscle echo intensity (-2% vs. -3%) of the quadriceps femoris. In conclusion, older women benefited from water-based exercise training prescribed based on participants' RPE, with both the interval and the continuous training programs resulting in similar increases in the cardiorespiratory and neuromuscular parameters.

Enhanced Echo Intensity of Skeletal Muscle Is Associated With Exercise Intolerance in Patients With Heart Failure

BACKGROUND

Skeletal muscle is quantitatively and qualitatively impaired in patients with heart failure (HF), which is closely linked to lowered exercise capacity. Ultrasonography (US) for skeletal muscle has emerged as a useful, noninvasive tool to evaluate muscle quality and quantity. Here we investigated whether muscle quality based on US-derived echo intensity (EI) is associated with exercise capacity in patients with HF.

METHODS AND RESULTS

Fifty-eight patients with HF (61 ± 12 years) and 28 control subjects (58 ± 14 years) were studied. The quadriceps femoris echo intensity (QEI) was significantly higher and the quadriceps femoris muscle thickness (QMT) was significantly lower in the patients with HF than the controls (88.3 ± 13.4 vs 81.1 ± 7.5, P= .010; 5.21 ± 1.10 vs 6.54 ±1.34 cm, P< .001, respectively). By univariate analysis, QEI was significantly correlated with age, peak oxygen uptake (VO₂), and New York Heart Association class in the HF group. A multivariable analysis revealed that the QEI was independently associated with peak VO₂ after adjustment for age, gender, body mass index, and QMT: β-coefficient = -11.80, 95%CI (-20.73, -2.86), P= .011.

CONCLUSION

Enhanced EI in skeletal muscle was independently associated with lowered exercise capacity in HF. The measurement of EI is low-cost, easily accessible, and suitable for assessment of HF-related alterations in skeletal muscle quality.

Photobiomodulation Therapy Does Not Attenuate Fatigue and Muscle Damage in Judo Athletes: A Randomized, Triple-Blind, Placebo-Controlled Trial

Fatigue and muscle damage negatively affect performance in lower limb exercises involving the stretch-shortening cycle in judo athletes during competition and training sessions. Photobiomodulation therapy has emerged as an effective non-invasive strategy to attenuate fatigue and muscle damage when applied before different types of exercises. Our objective was to investigate the effects of photobiomodulation therapy on fatigue and muscle damage in judo athletes. Sixteen judo athletes participated in the study (23.1 ± 3.8 years, 77.9 ± 14.9 kg, 173.1 ± 8.9 cm, 17.5 ± 7.3 body fat%, 12.9 ± 5.0 years of practice). Each participant received, in a randomized manner, photobiomodulation in one limb and placebo in the contralateral limb on the same day. Thereafter, subjects performed a stretch-shortening cycle protocol to induce muscle fatigue and damage. Countermovement jump (impulse, peak power, peak velocity, and peak force), echo intensity (rectus femoris and vastus lateralis), and muscle soreness were assessed at different time points before, during, immediately post, and 24 and 48 h after the protocol. Muscle fatigue was detected due to reductions in countermovement jump impulse (14.7 ± 9.8 and 15.9 ± 15.5%), peak power (12.9 ± 8.5 and 11.9 ± 6.9%), peak velocity (8.6 ± 8.1 and 6.5 ± 6.0%), and peak force (7.0 ± 5.3 and 8.0 ± 6.1%) after the protocol (p < 0.001), for placebo and photobiomodulation therapy, respectively. Muscle damage was detected due to reductions in countermovement jump impulse (−6.1 ± 19.2% and −4.5 ± 9.2%, p < 0.05), increases in echo intensity (rectus femoris, 21.0 ± 11.9 and 20.8 ± 9.0%; and vastus lateralis, 22.4 ± 23.2%; and 16.7 ± 23.8%; p < 0.001), and quadriceps muscle soreness (3.6 ± 1.6 and 3.5 ± 1.7 a.u; p < 0.011), 48 h after the protocol, for placebo and photobiomodulation therapy, respectively. No differences were observed between photobiomodulation therapy and placebo at any time points for any variables (p > 0.05), indicating no positive effect favoring photobiomodulation therapy. In conclusion, our findings suggest no effect of photobiomodulation therapy applied before exercise to reduce lower limb muscle fatigue and damage during and following a stretch-shortening cycle protocol in judo athletes.

Age-Related Changes of Sprint Kinematics

The sprint performance of master athletes decreases with age, but little is known about possible contributions of changes in sprint kinematics. The aim of this study was to assess the influence of age, sex and sprinting kinematics on sprint performance. To investigate this, in 199 men (30–89 years) and 81 women (33–76 years), bending over, brake, propulsion, leg stiffness and hip flexion angles were assessed during a sprint stride using high-resolution video analyses. Propulsion angle (men 25 ± 4.2, women 23.7 ± 4) was larger and hip flexion angle (men 25.3 ± 7.3, women 28 ± 5.7) was smaller in men than in women (both p < 0.001). Bending over angle (p = 0.004), brake angle (p = 0.004) and hip flexion angle (p < 0.001) increased, whereas propulsion angle (p < 0.001) and leg stiffness angle (p = 0.001) decreased with age, irrespective of sex. While performance was mainly determined by age (R² = 0.501, p < 0.001) and sex (adjusted R² = 0.642), hip flexion angle (adjusted R² = 0.686) and bending over angle (adjusted R² = 0.705) contributed also to performance in 60-m sprint. In 200-m sprint, in addition to age and sex, only hip flexion angle (age: R² = 0.506; age + sex adjusted: R² = 641; age + sex + hip flexion adjusted: R² = 0.655) contributed to performance. In conclusion, the kinematics of sprinting differ between sexes and change with age. The aging-related changes of sprinting kinematics have a minor contribution to the aging-related decline in performance.

Sprint running: from fundamental mechanics to practice-a review

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.

An Increase in Fat Mass Index Predicts a Deterioration of Running Speed

A low fat mass is associated with a good running performance. This study explores whether modifications in body composition predicted changes in running speed. We included people who underwent several measurements of body composition by bioelectrical impedance analysis between 1999 and 2016, at the “Course de l’Escalade”, taking place yearly in Geneva. Body composition was reported as a fat-free mass index (FFMI) and fat mass index (FMI). Running distances (men: 7.2 km; women: 4.8 km) and running times were used to calculate speed in km/h. We performed multivariate linear mixed regression models to determine whether modifications of body mass index, FFMI, FMI or the combination of FFMI and FMI predicted changes in running speed. The study population included 377 women (1419 observations) and 509 men (2161 observations). Changes in running speed were best predicted by the combination of FFMI and FMI. Running speed improved with a reduction of FMI in both sexes (women: ß −0.31; 95% CI −0.35 to −0.27, p < 0.001. men: ß −0.43; 95% CI −0.48 to −0.39, p < 0.001) and a reduction of FFMI in men (ß −0.20; 95% CI −0.26 to −0.15, p < 0.001). Adjusted for body composition, the decline in running performance occurred from 50 years onward, but appeared earlier with a body mass, FFMI or FMI above the median value at baseline. Changes of running speed are determined mostly by changes in FMI. The decline in running performance occurs from 50 years onward but appears earlier in people with a high body mass index, FFMI or FMI at baseline.

The Physiology and Biomechanics of the Master Runner

The Master runner (age 35 y and above) represents a unique athletic patient. Lifelong participation in endurance running slows the inevitable age-related decline in aerobic function and muscular strength. Still, the Master runner does not escape the inevitable effects of aging. Master runners experience a steady decline in running performance, that is, typical and maximal running speeds, after the age of 50 years of age. Age-related declines in running performance are driven by a host of factors, including declining cardiovascular function, reduced muscular capacity, altered biomechanics, and greater susceptibility to running-related injury. This review discusses age-related changes in physiology, biomechanics, and running injury susceptibility and practical strategies to maximize running participation in the Master runner.

Peak Age and Performance Progression in World-Class Track-and-Field Athletes

The aim of this study was to quantify peak age and improvements over the preceding years to peak age in elite athletic contestants according to athlete performance level, sex, and discipline. Individual season bests for world-ranked top 100 athletes from 2002 to 2016 (14,937 athletes and 57,049 individual results) were downloaded from the International Association of Athletics Federations’ website. Individual performance trends were generated by fitting a quadratic curve separately to each athlete’s performance and age data using a linear modeling procedure. Mean peak age was typically 25–27 y, but somewhat higher for marathon and male throwers (∼28–29 y). Women reached greater peak age than men in the hurdles and middle- and long-distance running events (mean difference, ±90% CL: 0.6, ±0.3 to 1.9, ±0.3 y: small to moderate). Male throwers had greater peak age than corresponding women (1.3, ±0.3 y: small). Throwers displayed the greatest performance improvements over the 5 y prior to peak age (mean [SD]: 7.0% [2.9%]), clearly ahead of jumpers, long-distance runners, hurdlers, middle-distance runners, and sprinters (3.4, ±0.2% to 5.2, ±0.2%; moderate to large). Similarly, top 10 athletes showed greater improvements than top 11–100 athletes in all events (1.0, ±0.9% to 1.8, ±1.1%; small) except throws. Women improved more than men in all events (0.4, ±0.2% to 2.9, ±0.4%) except sprints. This study provides novel insight on performance development in athletic contestants that are useful for practitioners when setting goals and evaluating strategies for achieving success.

Genetic variant in the β2 -adrenergic receptor (Arg16Gly) influences fat-free mass, muscle strength and motor unit behaviour in young men

NEW FINDINGS

What is the central question of this study? Does a common genetic variant in the β₂ -adrenergic receptor (β₂ -AR) have effects on skeletal muscle function in young, healthy men? What is the main finding and its importance? This study provides preliminary evidence that β₂ -AR Arg16Gly genotype has a significant effect on fat-free mass, muscle strength and motor unit behaviour in recreationally trained men. These data might have important clinical and exercise-related implications. For example, β₂ -AR (rs1042713) genotype might influence the responsiveness of skeletal muscle to clinical or exercise-based interventions or β-AR agonist treatment.

ABSTRACT

This study explored whether the β₂ -adrenergic receptor (β₂ -AR) single nucleotide polymorphism at amino acid 16 (Arg16Gly) has functional effects on skeletal muscle mass, torque production and motor unit behaviour in young, healthy men. Twenty-eight recreationally active men (mean ± SD 23.1 ± 1.3 years of age) were genotyped for Arg16Gly polymorphisms of β₂ -AR as arginine homozygous (ArgArg; n = 5), glycine homozygous (GlyGly; n = 11) or arginine-glycine heterozygous (ArgGly; n = 12). The participants then completed body composition testing, assessments of leg extensor size and echo intensity, and evoked and voluntary isometric leg-extension muscle actions. During the evoked muscle actions, peak twitch torque, peak rate of torque development and peak relaxation rate were assessed. During the voluntary muscle actions, maximal voluntary isometric (MVIC) strength was assessed, and surface EMG signals were obtained during submaximal isometric muscle actions and later decomposed to examine motor unit firing behaviour. Fat-free mass and MVIC strength were greater (P = 0.004, d = 1.74 and P = 0.026, d = 1.10, respectively) in those expressing the GlyGly versus ArgArg allele. The slope of the mean firing rate versus recruitment threshold relationship was more negative in the GlyGly than the ArgArg allele carriers (P = 0.012, d = 1.68) at 50% MVIC, but was less negative in GlyGly and ArgGly versus ArgArg allele carriers (P = 0.013 and 0.016, respectively; d = 1.34 and 1.20, respectively) at 70% MVIC. These data provide preliminary evidence that β₂ -AR Arg16Gly genotype has a significant effect on fat-free mass, muscle strength and motor unit behaviour in humans.

Differential effects of speed on two-dimensional foot strike pattern during barefoot and shod running in recreationally active men

The majority of barefoot running studies have not considered speed as an influential factor on foot strike pattern. The aim of this study was to investigate differences in foot strike pattern and spatiotemporal characteristics between barefoot and shod overground running at varying speeds. We first determined maximal running speed (Vm) over 50 m in 15 recreationally active men who self-reported as habitual rearfoot strikers. Participants then completed shod and barefoot running trials at different speeds equivalent to approximately 90%, 80%, 70% and 60% of Vm. Sagittal plane two-dimensional (2D) foot-ground contact angle, ankle plantar-dorsi flexion angle, contact time, flight time, step length and step rate variables for each trial were recorded. A significant interaction effect of running speed and footwear condition (p < 0.05) on foot-ground contact angle, ankle plantar-dorsi flexion angle and contact time was observed. There was a main effect of running speed (p < 0.01) on flight time, step length and step rate. There was a main effect of footwear condition on step length (p < 0.01). Participants were more inclined to plantarflex the ankle and contact the ground with the forefoot at higher percentages of Vm, especially when running barefoot.

Physiological and Biomechanical Mechanisms of Distance Specific Human Running Performance

SYNOPSIS

Running events range from 60-m sprints to ultra-marathons covering 100 miles or more, which presents an interesting diversity in terms of the parameters for successful performance. Here, we review the physiological and biomechanical variations underlying elite human running performance in sprint to ultramarathon distances. Maximal running speeds observed in sprint disciplines are achieved by high vertical ground reaction forces applied over short contact times. To create this high force output, sprint events rely heavily on anaerobic metabolism, as well as a high number and large cross-sectional area of type II fibers in the leg muscles. Middle distance running performance is characterized by intermediates of biomechanical and physiological parameters, with the possibility of unique combinations of each leading to high-level performance. The relatively fast velocities in mid-distance events require a high mechanical power output, though ground reaction forces are less than in sprinting. Elite mid-distance runners exhibit local muscle adaptations that, along with a large anaerobic capacity, provide the ability to generate a high power output. Aerobic capacity starts to become an important aspect of performance in middle distance events, especially as distance increases. In distance running events, V˙O2max is an important determinant of performance, but is relatively homogeneous in elite runners. V˙O2 and velocity at lactate threshold have been shown to be superior predictors of elite distance running performance. Ultramarathons are relatively new running events, as such, less is known about physiological and biomechanical parameters that underlie ultra-marathon performance. However, it is clear that performance in these events is related to aerobic capacity, fuel utilization, and fatigue resistance.

Associations Between Individual Lower-Limb Muscle Volumes and 100-m Sprint Time in Male Sprinters

PURPOSE

To elucidate the relationship between the muscularity of individual lower-limb muscles and 100-m-race time (t₁₀₀) in young-adult male sprinters.

METHODS

Thirty-one young-adult male sprinters took part in this study (age 19.9 ± 1.4 y, height 173.5 ± 4.6 cm, body mass 67.0 ± 4.9 kg, t₁₀₀ 10.23-11.71 s). Cross-sectional images from the origin to insertion of 12 lower-limb muscles were obtained with via magnetic resonance imaging (MRI). The absolute volume of each muscle, the ratio of total volume of measured muscles to body mass, the ratio of individual muscle volume to body mass, and the ratio between 2 individual muscle volumes were calculated as indices of muscularity using the images. A stepwise multiple-regression analysis was performed to examine the association between the indices and t₁₀₀.

RESULTS

A stepwise multiple-regression analysis produced an equation (adjusted R² = .234) with the gluteus maximus-to-quadriceps femoris muscle-volume ratio (β = -0.509, P = .003) as the explanatory variable.

CONCLUSIONS

Individual differences in 100-m-race performance cannot be explained by the muscularity of specific muscles, and 23% of the variability in the performance can be explained by the relative difference between the muscularity of gluteus maximus and quadriceps femoris; faster runners have a greater gluteus maximus relative to quadriceps femoris.

Effect of strength training on sleep apnea severity in the elderly: study protocol for a randomized controlled trial

BACKGROUND

Obstructive sleep apnea (OSA) occurs due to sleep-induced upper airway muscle relaxation resulting in increased pharyngeal collapsibility. Clinical trials have shown a favorable effect of exercise training on OSA severity in middle-aged adults. Aging is characterized by motor-unit loss. Force training may affect the whole body muscle tone. We hypothesize that interventions increasing muscle strength might propagate to motor units at the abductor pharyngeal muscles, reducing collapsibility and, hence, sleep apnea severity in elderly patients with obstructive sleep apnea.

METHODS/DESIGN

This is a randomized clinical trial including patients between 65 and 80 years of age, with obstructive sleep apnea, and an apnea-hypopnea index (AHI) between 20 and 50 events/hour, diagnosed by out-of-center in-home type III polysomnography. Forty subjects will be included and randomly assigned to two equal sized groups. The participants allocated to the intervention group will attend two sessions per week of one-hour strength training for the legs, arms, chest, back, and abdomen and the controls will receive advice on lifestyle change. The primary outcome measure of the study will be the change in apnea-hypopnea index and the secondary outcomes will be the body composition, evaluated by anthropometric and bioelectrical impedance variables; maximum dynamic force, appraised by one-repetition maximum strength test; muscle quality and thickness by ultrasound; physical function assessed by sit-to-stand test, timed up and go test, handgrip strength test. The study duration will be 12 weeks. Intention-to-treat and per-protocol analyses will be performed.

DISCUSSION

The high prevalence of obstructive sleep apnea in elderly people is a public health issue. OSA is a recognized cause of cardiovascular disease and reduces quality of life due to sleepiness and fatigue. Exercise is a low-cost intervention that could help to detain the trend towards age-dependent loss of pharyngeal motor units and progressive severity of obstructive sleep apnea. Home-based strength exercises may represent a more practical approach than aerobic exercise for elderly patients. If the results confirm our hypothesis, further research on the clinical application of our findings will be warranted.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02742792 . Registered on 1 April 2016.

Sprint mechanics return to competition follow-up after hamstring injury on a professional soccer player: A case study with an inertial sensor unit based methodological approach

BACKGROUND

The present research aimed to describe an inertial unit (IU)-based sprint mechanics evaluation model for assessing players' readiness to return to competition after suffering a grade I hamstring injury.

METHODS

A professional male football player (age 19years; height 177cm; weight 70kg, midfielder, Spanish, 3° Division) with a grade 1 biceps femoris injury was evaluated at pre-season, at return to play after injury and at the end of the competitive season. Sprint mechanics were analyzed via the use of an inertial orientation tracker (Xsens Technologies B.V. Enschede, Netherlands) attached over the L3-L4 region of the subject's lumbar spine. Sprint mechanics such as horizontal components of ground reaction force were assessed in both legs during sprinting actions. Findings and interpretation: Both the coefficient of the horizontal force application (SFV) and the ratio of forces (DRF) applied at increasing velocity were decreased in the injured limb compared with the contralateral healthy limb at the return to play evaluation (73% and 76% reductions, respectively) and returned to symmetrical levels at the end-season evaluation.

Sprint Acceleration Mechanics in Masters Athletes

PURPOSE

The best sprint performances are usually reached between the ages of 20 and 30 yr; however, even in well-trained individuals, performance continues to decrease with age. Although this inevitable decrease in performance has been related to reductions in muscular force, velocity, and power capabilities, these measures have not been assessed in the specific context of sprinting. The aim of this study was to investigate the mechanical outputs of sprinting acceleration among masters sprinters to better understand the mechanical underpinnings of the age-related decrease in sprint performance.

METHODS

The study took place during an international masters competition, with testing performed at the end of the warm-up for official sprint races. Horizontal ground reaction force, velocity, mechanical power outputs, and mechanical effectiveness of force application were estimated from running velocity-time data during a 30-m sprint acceleration in 27 male sprinters (39-96 yr). Data were presented in the form of age-related changes and compared with elite young sprinters data.

RESULTS

Maximal force, velocity, and power outputs decreased linearly with age (all r > 0.84, P < 0.001), at a rate of ~1% per year. Maximal power of the oldest subject tested was approximately one-ninth of that of younger world-class sprinters (3.57 vs 32.1 W·kg). Although the maximal effectiveness of horizontal force application also decreased with age, its decrease with increasing velocity within the sprint acceleration was not age dependent.

CONCLUSIONS

In addition to lower neuromuscular force, velocity, and power outputs, masters sprinters had a comparatively lower effectiveness of force application, especially at the beginning of the sprint.

Sprint mechanics evaluation using inertial sensor-based technology: A laboratory validation study

Advances in micro-electromechanical systems have turned magnetic inertial measurement units (MIMUs) into a suitable tool for vertical jumping biomechanical evaluation. Thus, this study aimed to determine whether appropriate reliability and agreement reports could also be obtained when analyzing 20-m sprint mechanics. Four bouts of 20-m sprints were evaluated to determine whether the data provided by a MIMU placed at the lumbar spine could reliably assess sprint mechanics and to examine the validity of the MIMU sensor compared to force plate recordings. Maximal power (P₀ ), force (F₀ ), and velocity (V₀ ), as well as other mechanical determinants of sprint performance associated with the force-velocity, power-velocity, and ratio of forces-velocity, such as applied horizontal force loss (S_fv ) and decrease in ratio of forces (D_rf ), were calculated and compared between instrumentations. Extremely large-to-very large correlation levels between MIMU sensor-based sprint mechanics variables and force plate recordings were obtained (mean±SD, force plate vs MIMU; V_0, 8.61±0.85 vs 8.42±0.69; F₀ , 383±110 vs 391±103; P₀ , 873±246 vs 799±241; S_fv, -44.6±12.7 vs -46.2±10.7), ranging from 0.88 to 0.94, except for D_rf, which showed weak-to-moderate correlation level (r=.45; -6.32±1.08 vs -5.76±0.68). Step-averaged force values measured with both systems were highly correlated (r=.88), with a regression slope close to the identity (1.01). Bland and Altman graphical representation showed a no random distribution of measured force values. Finally, very large-to-extremely large retest correlation coefficients were found for the intertrial reliability of MIMU measurements of sprint performance variables (r value ranging from .72 to .96). Therefore, MIMUs showed appropriate validity and reliability values for 20-m sprint performance variables.