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Purpose: The aim of the present study was to investigate whether exercise-induced muscle damage (EIMD) influences cardiovascular responses to isometric exercise and post-exercise circulatory occlusion (PECO). We hypothesized that EIMD would increase muscle afferent sensitivity and, accordingly, increase blood pressure responses to exercise and PECO. Methods: Eleven male and nine female participants performed unilateral isometric knee extension at 30% of maximal voluntary contraction (MVC) for 3-min. A thigh cuff was rapidly inflated to 250 mmHg for two min PECO, followed by 3 min recovery. Heart rate and blood pressure were monitored beat-by-beat, with stroke volume and cardiac output estimated from the Modelflow algorithm. Measurements were taken before and 48 h after completing eccentric knee-extension contractions to induce muscle damage (EIMD). Results: EIMD caused 21% decrease in MVC (baseline: 634.6 ± 229.3 N, 48 h: 504.0 ± 160 N), and a 17-fold increase in perceived soreness using a visual-analogue scale (0–100 mm; VASSQ) (both p < 0.001). CV responses to exercise and PECO were not different between pre and post EIMD. However, mean arterial pressure (MAP) was higher during the recovery phase after EIMD (p < 0.05). Significant associations were found between increases in MAP during exercise and VASSQ, Rate of Perceived Exertion (RPE) and Pain after EIMD only (all p < 0.05). Conclusion: The MAP correlations with muscle soreness, RPE and Pain during contractions of damaged muscles suggests that higher afferent activity was associated with higher MAP responses to exercise.

Long-term exercise training has been considered as an effective strategy to counteract age-related hormonal declines and minimise muscle atrophy. However, human data relating circulating hormone levels with motor nerve function are scant. The aims of the study were to explore associations between circulating sex hormone levels and motor unit (MU) characteristics in older men, including masters athletes competing in endurance and power events. Forty-three older men (mean ± SD age: 69.9 ± 4.6 years) were studied based on competitive status. The serum concentrations of dehydroepiandrosterone (DHEA), total testosterone (T) and estradiol were quantified using liquid chromatography mass spectrometry. Intramuscular electromyographic signals were recorded from vastus lateralis (VL) during 25% of maximum voluntary isometric contractions and processed to extract MU firing rate (FR), and motor unit potential (MUP) features. After adjusting for athletic status, MU FR was positively associated with DHEA levels (p = 0.019). Higher testosterone and estradiol were associated with lower MUP complexity; these relationships remained significant after adjusting for athletic status (p = 0.006 and p = 0.019, respectively). Circulating DHEA was positively associated with MU firing rate in these older men. Higher testosterone levels were associated with reduced MUP complexity, indicating reduced electrophysiological temporal dispersion, which is related to decreased differences in conduction times along axonal branches and/or MU fibres. Although evident in males only, this work highlights the potential of hormone administration as a therapeutic interventional strategy specifically targeting human motor units in older age.

The age-related decline in muscle function, particularly muscle power, is associated with increased risk of important clinical outcomes. Physical activity is an important determinant of muscle function, and different types of physical activity e.g. power-based versus endurance-based exercise appear to have differential effects on muscle power. Cross-sectional studies suggest that participation in power-based exercise is associated with greater muscle power across adulthood but this has not been investigated longitudinally. We recruited eighty-nine male and female power and endurance master athletes (sprint and distance runners respectively, baseline age 35–90y). Using jumping mechanography, we measured lower limb muscle function during a vertical jump including at least two testing sessions longitudinally over 4.5 ± 2.4y. We examined effects of time, discipline (power/endurance) and sex in addition to two- and three-way interactions using linear mixed-effects models. Peak relative power, relative force and jump height, but not Esslingen Fitness Index (indicating peak power relative to sex and age-matched reference data) declined with time. Peak power, force, height and EFI were greater in power than endurance athletes. There were no sex, discipline or sex*discipline interactions with time for any variable, suggesting that changes were similar over time for athletes of both sexes and disciplines. Advantages in lower limb muscle function in power athletes were maintained with time, in line with previous cross-sectional studies. These results suggest that improvements in lower limb function in less active older individuals following power-based training persist with continued adherence, although this requires further investigation in interventional studies.

Electrophysiological alterations of the neuromuscular junction (NMJ) and motor unit potential (MUP) with unloading are poorly studied. We aimed to investigate these aspects and the underlying molecular mechanisms with short-term unloading and active recovery (AR). Eleven healthy males underwent a 10-day unilateral lower limb suspension (ULLS) period, followed by 21-day AR based on resistance exercise. Quadriceps femoris (QF) cross-sectional area (CSA) and isometric maximum voluntary contraction (MVC) were evaluated. Intramuscular electromyographic recordings were obtained during 10% and 25% MVC isometric contractions from the vastus lateralis (VL). Biomarkers of NMJ molecular instability (serum c-terminal agrin fragment, CAF), axonal damage (neurofilament light chain) and denervation status were assessed from blood samples and VL biopsies. NMJ and ion channel transcriptomic profiles were investigated by RNA-sequencing. QF CSA and MVC decreased with ULLS. Increased CAF and altered NMJ transcriptome with unloading suggested the emergence of NMJ molecular instability, which was not associated with impaired NMJ transmission stability. Instead, increased MUP complexity and decreased motor unit firing rates were found after ULLS. Downregulation of ion channel gene expression was found together with increased neurofilament light chain concentration and partial denervation. The AR period restored most of these neuromuscular alterations. In conclusion, the human NMJ is destabilized at the molecular level but shows functional resilience to a 10-day unloading period at least at relatively low contraction intensities. However, MUP properties are altered by ULLS, possibly due to alterations in ion channel dynamics and initial axonal damage and denervation. These changes are fully reversed by 21 days of AR. (Figure presented.). Key points: We used integrative electrophysiological and molecular approaches to comprehensively investigate changes in neuromuscular integrity and functi

Objective: To determine cardiorespiratory fitness and neuromuscular function of people with CFS and FMS compared to healthy individuals. Design: Systematic review and meta-analysis. Data sources: PubMed, Medline, CINAHL, AMED, Cochrane Central Register of Controlled Trials (CENTRAL), and PEDro from inception to June 2022. Eligible criteria for selecting studies: Studies were included if presenting baseline data on cardiorespiratory fitness and/or neuromuscular function from observational or interventional studies of patients diagnosed with FMS or CFS. Participants were aged 18 years or older, with results also provided for healthy controls. Risk of bias assessment was conducted using the Quality Assessment Tool for Quantitative Studies (EPHPP). Results: 99 studies including 9853 participants (5808 patients; 4405 healthy controls) met our eligibility criteria. Random effects meta-analysis showed lower cardiorespiratory fitness (VO2max, anaerobic threshold, peak lactate) and neuromuscular function (MVC, fatigability, voluntary activation, muscle volume, muscle mass, rate of perceived exertion) in CFS and FMS compared to controls: all with moderate to high effect sizes. Discussion: Our results demonstrate lower cardiorespiratory fitness and muscle function in those living with FMS or CFS when compared to controls. There were indications of dysregulated neuro-muscular interactions including heightened perceptions of effort, reduced ability to activate the available musculature during exercise and reduced tolerance of exercise. Trail registration: PROSPERO registration number: (CRD42020184108).

Background: An exaggerated exercise blood pressure (BP) is associated with a reduced exercise capacity. However, its connection to physical performance during competition is unknown. Aim: To examine BP responses to ischaemic handgrip exercise in Master athletes (MA) with and without underlying morbidities and to assess their association with athletic performance during the World Master Track Cycling Championships 2019. Methods: Forty-eight Master cyclists [age 59 ± 13yrs; weekly training volume 10.4 ± 4.1 h/week; handgrip maximum voluntary contraction (MVC) 46.3 ± 11.5 kg] divided into 2 matched groups (24 healthy MA and 24 MA with morbidity) and 10 healthy middle-aged non-athlete controls (age 48.3 ± 8.3 years; MVC 40.4 ± 14.8 kg) performed 5 min of forearm occlusion including 1 min handgrip isometric contraction (40%MVC) followed by 5 min recovery. Continuous beat-by-beat BP was recorded using finger plethysmography. Age-graded performance (AGP) was calculated to compare race performances among MA. Healthy Master cyclists were further grouped into middle-age (age 46.2 ± 6.4 years; N:12) and old-age (age 65.0 ± 7.7 years; N:12) for comparison with middle-aged non-athlete controls. Results: Healthy and morbidity MA groups showed similar BP responses during forearm occlusion and AGP (90.1 ± 4.3% and 91.0 ± 5.3%, p > 0.05, respectively). Healthy and morbidity MA showed modest correlation between the BP rising slope for 40%MVC ischaemic exercise and AGP (r = 0.5, p < 0.05). MA showed accelerated SBP recovery after cessation of ischaemic handgrip exercise compared to healthy non-athlete controls. Conclusion: Our findings associate long-term athletic training with improved BP recovery following ischaemic exercise regardless of age or reported morbidity. Exaggerated BP in Master cyclists during ischaemic exercise was associated with lower AGP during the World Master Cycling Championships.

Background: An exaggerated exercise blood pressure (BP) is associated with a reduced exercise capacity. However, its connection to physical performance during competition is unknown. Aim: To examine BP responses to ischaemic handgrip exercise in Master athletes (MA) with and without underlying morbidities and to assess their association with athletic performance during the World Master Track Cycling Championships 2019. Methods: Forty-eight Master cyclists [age 59 ± 13yrs; weekly training volume 10.4 ± 4.1 h/week; handgrip maximum voluntary contraction (MVC) 46.3 ± 11.5 kg] divided into 2 matched groups (24 healthy MA and 24 MA with morbidity) and 10 healthy middle-aged non-athlete controls (age 48.3 ± 8.3 years; MVC 40.4 ± 14.8 kg) performed 5 min of forearm occlusion including 1 min handgrip isometric contraction (40%MVC) followed by 5 min recovery. Continuous beat-by-beat BP was recorded using finger plethysmography. Age-graded performance (AGP) was calculated to compare race performances among MA. Healthy Master cyclists were further grouped into middle-age (age 46.2 ± 6.4 years; N:12) and old-age (age 65.0 ± 7.7 years; N:12) for comparison with middle-aged non-athlete controls. Results: Healthy and morbidity MA groups showed similar BP responses during forearm occlusion and AGP (90.1 ± 4.3% and 91.0 ± 5.3%, p > 0.05, respectively). Healthy and morbidity MA showed modest correlation between the BP rising slope for 40%MVC ischaemic exercise and AGP (r = 0.5, p < 0.05). MA showed accelerated SBP recovery after cessation of ischaemic handgrip exercise compared to healthy non-athlete controls. Conclusion: Our findings associate long-term athletic training with improved BP recovery following ischaemic exercise regardless of age or reported morbidity. Exaggerated BP in Master cyclists during ischaemic exercise was associated with lower AGP during the World Master Cycling Championships.

Motor unit (MU) expansion enables rescue of denervated muscle fibres helping to ameliorate age-related muscle atrophy, with evidence to suggest master athletes are more successful at this remodelling. Electrophysiological data has suggested MUs located superficially are larger than those located deeper within young muscle. However, the effects of ageing and exercise on MU heterogeneity across deep and superficial aspects of vastus lateralis (VL) remain unclear. Intramuscular electromyography was used to record individual MU potentials (MUPs) and near fibre MUPs (NFMs) from deep and superficial regions of the VL during 25% maximum voluntary contractions, in 83 males (15 young (Y), 17 young athletes (YA), 22 old (O) and 29 master athletes (MA)). MUP size and complexity were assessed using area and number of turns, respectively. Multilevel mixed effects linear regression models were performed to investigate the effects of depth in each group. MUP area was greater in deep compared with superficial MUs in Y (p<0.001) and O (p=0.012) but not in YA (p=0.071) or MA (p=0.653). MUP amplitude and NF MUP area were greater, and MUPs were more complex in deep MUPs from Y, YA and O (all p<0.05) but did not differ across depth in MA (all p>0.07). These data suggest MU characteristics differ according to depth within the VL which may be influenced by both ageing and exercise. A more homogenous distribution of MUP size and complexity across muscle depths in older athletes may be a result of a greater degree of age-related MU adaptations.

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for males and females. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship and fatigability adaptations to 12 weeks SIT.Sixteen males and fifteen females (mean (SEM) age: 41 (±2.5) yrs) completed measurements of total body composition assessed by DXA, quadriceps muscle cross-sectional area (CSAQ) assessed by MRI, the knee extensor torque-velocity relationship (covering 0 - 240°·sec) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·sec. SIT consisted of 4 x 20 second sprints on a cycle ergometer set at an initial power output of 175% of power at VO2max, three times per week for 12 weeks.CSAQ increased by 5% (p=0.023) and fatigue resistance improved 4.8% (p=0.048), with no sex differences in these adaptations (sex comparisons: p=0.140 and p=0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both males and females (p>0.05 for all velocities).12 weeks SIT, totalling 4 minutes very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in males and females, but did not significantly increase torque in males or females. These results suggest that SIT is a time-effective training modality for males and females to increase leg muscle size and fatigue resistance.

© 2019 Elsevier Inc. One of the hallmarks of ageing is muscle wasting that may be preceded by morphological changes, such as capillary rarefaction. Muscle-specific changes in morphology in early ageing may differ between locomotor and respiratory muscles. To investigate this, we compared capillarization, fiber type composition, fiber cross-sectional area (FCSA) and oxidative capacity of individual fibers of the soleus (n = 6/5 for 20- and 79 weeks, respectively), extensor digitorum longus (EDL: n = 3/3) and diaphragm (n = 7/5) muscles in 20- (mature) and 79-week-old (early ageing) CD-1 female mice. There was no significant loss of soleus and EDL mass. The FCSA was larger and the capillary density lower at 79 than 20 weeks in the diaphragm, while in the EDL the opposite was found (both p ≤ 0.002) with no significant ageing-related differences in the soleus. The heterogeneity in capillary spacing, which may negatively impact on muscle oxygenation, was highest in muscles from 20-week-old mice, irrespective of muscle (p ≤ 0.011). Succinate dehydrogenase activity, indicative of oxidative capacity, and capillary to fiber ratio did not significantly change with age in any muscle. At all ages, the capillary supply to a fiber was positively related to FCSA in each muscle. We conclude that despite previously reported early age-related reductions in specific tension in both locomotor and respiratory muscles, morphological changes show a muscle-specific pattern in early ageing CD-1 mice. Specifically, early ageing was associated with 1) diaphragm hypertrophy 2) and fiber atrophy in the EDL that was not accompanied by angiogenesis, capillary rarefaction or reductions in oxidative capacity.

© 2019 Piasecki, Ireland, Piasecki, Deere, Hannam, Tobias and McPhee. Masters endurance runners can epitomize healthy aging; being reflective of the physiological processes of aging without the compounded effects of inactivity. The primary aim of the present study was to determine, using cross-sectional data, whether individuals taking up training after the age of 50 years can achieve the same level of athletic performance and musculoskeletal characteristics in their older age as those who trained all of their adult lives. A total of 150 master endurance runners [age 68 (5) years; 111 male, 39 female] were divided into early starters (training all of their adulthood) and late starters (started training after age 50 years). A comparative non-athletic group of 59 healthy older adults [age 73 (4) years; 30 female, 29 male] were additionally included for analysis. Training intensity, age-graded performance (AGP) and musculoskeletal assessments were performed. Results showed that there was no difference between athlete groups for training intensity or age-graded performance, despite the 30-year difference in training history. Body fat percentage and leg lean mass did not differ between athlete groups, but were 17% lower and 12% greater, respectively, in athlete groups compared with controls. Power normalized to body mass did not differ between any groups. Spine BMD was lower in late starters than controls, while early starters did not differ from late starters or controls. Hip BMD did not differ between any of the groups. These findings show that the Masters athletes we studied that started intense endurance running after the age of 50 years had lower body fat and higher leg lean mass compared to non-athletes. Body composition and athletic performance of the late starters was very similar to those who trained all of their adult lives.

The evidence concerning the effects of exercise in older age on motor unit (MU) numbers, muscle fiber denervation and reinnervation cycles is inconclusive and it remains unknown whether any effects are dependent on the type of exercise undertaken or are localized to highly used muscles. MU characteristics of the vastus lateralis (VL) were assessed using surface and intramuscular electromyography in eighty-five participants, divided into sub groups based on age (young, old) and athletic discipline (control, endurance, power). In a separate study of the biceps brachii (BB), the same characteristics were compared in the favored and non-favored arms in eleven masters tennis players. Muscle size was assessed using MRI and ultrasound. In the VL, the CSA was greater in young compared to old, and power athletes had the largest CSA within their age groups. Motor unit potential (MUP) size was larger in all old compared to young (p < 0.001), with interaction contrasts showing this age-related difference was greater for endurance and power athletes than controls, and MUP size was greater in old athletes compared to old controls. In the BB, thickness did not differ between favored and non-favored arms (p = 0.575), but MUP size was larger in the favored arm (p < 0.001). Long-term athletic training does not prevent age-related loss of muscle size in the VL or BB, regardless of athletic discipline, but may facilitate more successful axonal sprouting and reinnervation of denervated fibers. These effects may be localized to muscles most involved in the exercise.

Lower physical activity levels in old age are thought to contribute to the age-related decline in peak aerobic and anaerobic power. Master athletes maintain high levels of physical activity with advancing age and endurance or power training may influence the extent to which these physical functions decline with advancing age. To investigate, 37-90-year-old power (n=20, 45% female) and endurance (n=19, 58% female) master athletes were recruited. Maximal aerobic power was assessed when cycling two-legged (VO2 Peak2-leg ) and cycling one-legged (VO2 Peak1-leg ), while peak jumping (anaerobic) power was assessed by a countermovement jump. Men and women had a similar VO2 Peak2-leg (mL·kg-1 ·min-1 , p=0.138) and similar ratio of VO2 Peak1-leg to VO2 Peak2-leg (p=0.959) and similar ratio of peak aerobic to anaerobic power (p=0.261). The VO2 Peak2-leg (mL·kg-1 ·min-1 ) was 17% (p=0.022) and the peak rate of fat oxidation (FATmax) during steady-state cycling was 45% higher in endurance than power athletes (p=0.001). The anaerobic power was 33% higher in power than endurance athletes (p=0.022). The VO2 Peak1-leg :VO2 Peak2-leg ratio did not differ significantly between disciplines, but the aerobic to anaerobic power ratio was 40% higher in endurance than power athletes (p=0.002). Anaerobic power, VO2 Peak2-leg , VO2 Peak1-leg and power at FATmax decreased by around 7-14% per decade in male and female power and endurance athletes. The cross-sectional data from 37-90-year-old master athletes in the present study indicates that peak anaerobic and aerobic power decline by around 7-14% per decade and this does not differ between athletic disciplines or sexes. This article is protected by copyright. All rights reserved.

Exercise can improve psychiatric symptoms, neurocognitive functioning and physical health in schizophrenia. However, the effects in early psychosis have not been explored. This study aimed to assess the feasibility of an exercise intervention for early psychosis and to determine if it was associated with changes in physical and mental health. Methods: Thirty-one patients with first-episode psychosis (FEP) were recruited from early intervention services to a 10-week exercise intervention. The intervention group received individualized training programmes, aiming to achieve ≥90 min of moderate-to-vigorous activity each week, using exercise programmes tailored to individual preferences and needs. A comparison FEP sample from the same services (n = 7) received treatment as usual. Results: Rates of consent and retention in the exercise group were 94% and 81%, respectively. Participants achieved an average of 107 min of moderate-to-vigorous exercise per week. Positive and Negative Syndrome Scale total scores reduced by 13.3 points after 10 weeks of exercise, which was significantly greater than the treatment as usual comparison group (P = 0.010). The greatest differences were observed in negative symptoms, which reduced by 33% in the intervention group (P = 0.013). Significant improvements were also observed in psychosocial functioning and verbal short-term memory. Increases in cardiovascular fitness and processing speed were positively associated with the amounts of exercise achieved by participants. Conclusion: Individualized exercise training could provide a feasible treatment option for improving symptomatic, neurocognitive and metabolic outcomes in FEP.

The contributions of fiber atrophy, fiber loss, in situ specific force, and voluntary activation to weakness in sarcopenia remain unclear. To investigate, 40 older (20 women; age 72 ± 4 years) and 31 younger adults (15 women, age 22 ± 3 years) completed measurements. The knee extensor maximal voluntary torque (MVC) was measured as well as voluntary activation, patella tendon moment arm length, muscle volume, and fascicle architecture to estimate in situ specific force. Fiber cross-sectional area (FCSA), fiber numbers, and connective tissue contents were also estimated from vastus lateralis biopsies. The MVC, quadriceps volume, and specific force were 39%, 28%, and 17% lower, respectively, in old compared with young, but voluntary activation was not different. The difference in muscle size was due in almost equal proportions to lower type II FCSA and fewer fibers. Five years later (n = 23) the MVC, muscle volume and voluntary activation in old decreased an additional 12%, 6%, and 4%, respectively, but there was no further change in specific force. In situ specific force declines relatively early in older age and reduced voluntary activation occurs later, but the overall weakness in sarcopenia is mainly related to loss of both type I and II fibers and type II fiber atrophy.

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for males and females. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship and fatigability adaptations to 12 weeks SIT.Sixteen males and fifteen females (mean (SEM) age: 41 (±2.5) yrs) completed measurements of total body composition assessed by DXA, quadriceps muscle cross-sectional area (CSAQ) assessed by MRI, the knee extensor torque-velocity relationship (covering 0 - 240°·sec) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·sec. SIT consisted of 4 x 20 second sprints on a cycle ergometer set at an initial power output of 175% of power at VO2max, three times per week for 12 weeks.CSAQ increased by 5% (p=0.023) and fatigue resistance improved 4.8% (p=0.048), with no sex differences in these adaptations (sex comparisons: p=0.140 and p=0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both males and females (p>0.05 for all velocities).12 weeks SIT, totalling 4 minutes very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in males and females, but did not significantly increase torque in males or females. These results suggest that SIT is a time-effective training modality for males and females to increase leg muscle size and fatigue resistance.

Rationale: Downregulation of the pacemaking ion channel, HCN4, and the corresponding ionic current, If, underlies exercise training-induced sinus bradycardia in rodents. If this occurs in humans, it could explain the increased incidence of bradyarrhythmias in veteran athletes and it will be important to understand the underlying processes. Objective: To test the role of HCN4 in the training-induced bradycardia in human athletes and investigate the role of micro-RNAs (miRs) in the repression of HCN4. Methods and Results: As in rodents, the intrinsic heart rate was significantly lower in human athletes than non-athletes and in all subjects the rate-lowering effect of the HCN selective blocker, ivabradine, was significantly correlated with the intrinsic heart rate, consistent with HCN repression in athletes. Next generation sequencing and qPCR showed remodelling of miRs in the sinus node of swim-trained mice. Computational predictions highlighted a prominent role for miR-423-5p. Interaction between miR-423-5p and HCN4 was confirmed by a dose-dependent reduction in HCN4 3'-UTR luciferase reporter activity on co-transfection with precursor miR-423-5p (abolished by mutation of predicted recognition elements). Knockdown of miR-423-5p with antimiR-423-5p reversed training-induced bradycardia via rescue of HCN4 and If Further experiments showed that, in the sinus node of swim-trained mice, upregulation of miR-423-5p (intronic miR) and its host gene, NSRP1, is driven by an upregulation of the transcription factor Nkx2.5. Conclusions: HCN remodelling likely occurs in human athletes as well as rodent models. miR-423-5p contributes to training-induced bradycardia by targeting HCN4. This work presents the first evidence of miR control of HCN4 and heart rate. miR-423-5p could be a therapeutic target for pathological sinus node dysfunction in veteran athletes.

© 2017 The Authors. Background: Handgrip strength (HGS) is used to identify individuals with low muscle strength (dynapenia). The influence of the number of attempts on maximal HGS is not yet known and may differ depending on age and health status. This study aimed to assess how many attempts of HGS are required to obtain maximal HGS. Methods: Three cohorts (939 individuals) differing in age and health status were included. HGS was assessed three times and explored as continuous and dichotomous variable. Paired t-test, intraclass correlation coefficients (ICC) and Bland-Altman analysis were used to test reproducibility of HGS. The number of individuals with misclassified dynapenia at attempts 1 and 2 with respect to attempt 3 were assessed. Results: Results showed the same pattern in all three cohorts. Maximal HGS at attempts 1 and 2 was higher than at attempt 3 on population level (P < 0.001 for all three cohorts). ICC values between all attempts were above 0.8, indicating moderate to high reproducibility. Bland-Altman analysis showed that 41.0 to 58.9% of individuals had the highest HGS at attempt 2 and 12.4 to 37.2% at attempt 3. The percentage of individuals with a maximal HGS above the gender-specific cut-off value at attempt 3 compared with attempts 1 and 2 ranged from 0 to 50.0%, with a higher percentage of misclassification in middle-aged and older populations. Conclusions: Maximal HGS is dependent on the number of attempts, independent of age and health status. To assess maximal HGS, at least three attempts are needed if HGS is considered to be a continuous variable. If HGS is considered as a discrete variable to assess dynapenia, two attempts are sufficient to assess dynapenia in younger populations. Misclassification should be taken into account in middle-aged and older populations.

Contradictory results have been reported on the impact of ageing on structure and functions of skeletal muscle fibres likely due to complex interplay between ageing and other phenomena such as disuse and diseases. Here we recruited healthy, physically and socially active young (YO) and elderly (EL) men in order to study aging per se without the confounding effects of impaired physical function. In vivo analyses of quadriceps and in vitro analyses of vastus lateralis muscle biopsies were performed. In EL subjects, our results show that: (i) quadriceps volume, maximum voluntary torque (MVC), and patellar tendon force (Ft) were significantly lower; (ii) muscle fibres went through significant atrophy and impairment of specific force (Po/CSA) and unloaded shortening velocity (Vo); (iii) myosin/actin ratio and myosin content in individual muscle fibres were not altered; (iv) muscle proteome went through quantitative adaptations, namely an up-regulation of the content of several groups of proteins among which myofibrillar proteins and antioxidant defence systems; (v) muscle proteome went through qualitative adaptations, namely phosphorylation of several proteins, including Myosin Light Chain-2 slow and Troponin T and carbonylation of Myosin Heavy Chains. The present results indicate that impairment of individual muscle fibres structure and function is a major feature of ageing per se and that qualitative adaptations of muscle proteome are likely more involved than quantitative adaptations in determining such phenomenon. This article is protected by copyright. All rights reserved.

Summary: This observational study assessed vertical impacts experienced in older adults as part of their day-to-day physical activity using accelerometry and questionnaire data. Population-based older adults experienced very limited high-impact activity. The accelerometry method utilised appeared to be valid based on comparisons between different cohorts and with self-reported activity. Introduction: We aimed to validate a novel method for evaluating day-to-day higher impact weight-bearing physical activity (PA) in older adults, thought to be important in protecting against osteoporosis, by comparing results between four cohorts varying in age and activity levels, and with self-reported PA levels. Methods: Participants were from three population-based cohorts, MRC National Survey of Health and Development (NSHD), Hertfordshire Cohort Study (HCS) and Cohort for Skeletal Health in Bristol and Avon (COSHIBA), and the Master Athlete Cohort (MAC). Y-axis peaks (reflecting the vertical when an individual is upright) from a triaxial accelerometer (sampling frequency 50 Hz, range 0–16 g) worn at the waist for 7 days were classified as low (0.5–1.0 g), medium (1.0–1.5 g) or higher (≥1.5 g) impacts. Results: There were a median of 90, 41 and 39 higher impacts/week in NSHD (age 69.5), COSHIBA (age 76.8) and HCS (age 78.5) participants, respectively (total n = 1512). In contrast, MAC participants (age 68.5) had a median of 14,322 higher impacts/week. In the three population cohorts combined, based on comparison of beta coefficients, moderate-high-impact activities as assessed by PA questionnaire were suggestive of stronger association with higher impacts from accelerometers (0.25 [0.17, 0.34]), compared with medium (0.18 [0.09, 0.27]) and low impacts (0.13 [0.07,0.19]) (beta coefficient, with 95 % CI). Likewise in MAC, reported moderate-high-impact activities showed a stronger association with higher impacts (0.26 [0.14, 0.37]), compared with medium (0.14 [0.05, 0.22]) and low

As muscle capillarization is related to the oxidative capacity of the muscle and the size of muscle fibres, capillary rarefaction may contribute to sarcopenia and functional impairment in older adults. Therefore, it is important to assess how ageing affects muscle capillarization and the interrelationship between fibre capillary supply with the oxidative capacity and size of the fibres.Muscle biopsies from healthy recreationally active young (22 years; 14 men and 5 women) and older (74 years; 22 men and 6 women) people were assessed for muscle capillarization and the distribution of capillaries with the method of capillary domains. Oxidative capacity of muscle fibres was assessed with quantitative histochemistry for succinate dehydrogenase (SDH) activity.There was no significant age-related reduction in muscle fibre oxidative capacity. Despite 18% type II fibre atrophy (P = 0.019) and 23% fewer capillaries per fibre (P < 0.002) in the old people, there was no significant difference in capillary distribution between young and old people, irrespective of sex. The capillary supply to a fibre was primarily determined by fibre size and only to a small extent by oxidative capacity, irrespective of age and sex. Based on SDH, the maximal oxygen consumption supported by a capillary did not differ significantly between young and old people.The similar quantitative and qualitative distribution of capillaries within muscle from healthy recreationally active older people and young adults indicates that the age-related capillary rarefaction, which does occur, nevertheless maintains the coupling between skeletal muscle fibre size and capillarization during healthy ageing.

© 2017 International Osteoporosis Foundation and National Osteoporosis Foundation Summary: Bone mineral density declines with increasing older age. We examined the levels of circulating factors known to regulate bone metabolism in healthy young and older adults. The circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin were positively associated with whole-body bone mineral density (WBMD) in older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young. Introduction: This study aims to investigate the relationship between whole-body bone mineral density (WBMD) and levels of circulating factors with known roles in bone remodelling during ‘healthy’ ageing. Methods: WBMD and fasting plasma concentrations of dickkopf-1, fibroblast growth factor-23, osteocalcin, osteoprotegerin, osteopontin and sclerostin were measured in 272 older subjects (69 to 81 years; 52% female) and 171 younger subjects (18–30 years; 53% female). Results: WBMD was lower in old than young. Circulating osteocalcin was lower in old compared with young, while dickkopf-1, osteoprotegerin and sclerostin were higher in old compared with young. These circulating factors were each positively associated with WBMD in the older adults and the relationships remained after adjustment for covariates (r values ranging from 0.174 to 0.254, all p < 0.01). In multivariate regression, the body mass index, circulating sclerostin and whole-body lean mass together accounted for 13.8% of the variation with WBMD in the older adults. In young adults, dickkopf-1 and body mass index together accounted for 7.7% of variation in WBMD. Conclusion: Circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin are positively associated with WBMD in community-dwelling older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young.

Introduction: cognitive deterioration and reductions of bone health coincide with increasing age. We examine the relationship between bone composition and plasma markers of bone remodelling with measures of cognitive performance in healthy adults. Methods: this cross-sectional study included 225 old (52% women, mean age: 74.4 ± 3.3 years) and 134 young (52% women, mean age: 23.4 ± 2.7 years) adult participants from the MyoAge project. Whole body bone mineral density was measured by dualenergy X-ray absorptiometry. Blood analyses included a panel of bone-related peptides (dickkopf-1, osteoprotegerin, osteocalcin (OC), osteopontin, sclerostin, parathyroid hormone and fibroblast growth factor 23), as well as serum calcium and 25-hydroxy vitamin D assays. A selection of cognitive domains (working memory capacity, episodic memory, executive functioning and global cognition) was assessed with a standardised neuropsychological test battery. Results: adjusting for covariates and multiple testing revealed that plasma OC levels were positively associated with measures of executive functioning (β = 0.444, P < 0.001) and global cognition (β = 0.381, P = 0.001) in the older women. Discussion: these correlative results demonstrate a positive association between OC, a factor known to regulate bone remodelling, with cognitive performance in older non-demented women. Further work should address possible mechanistic interpretations in humans.

We aimed to quantify the ACE I/D and ACTN3 R577X (rs1815739) genetic variants in elite rugby athletes (rugby union and league) and compare genotype frequencies to controls and between playing positions. The rugby athlete cohort consisted of 507 Caucasian men, including 431 rugby union athletes that for some analyses were divided into backs and forwards and into specific positional groups: front five, back row, half backs, centers, and back three. Controls were 710 Caucasian men and women. Real-time PCR of genomic DNA was used to determine genotypes using TaqMan probes and groups were compared using χ(2) and odds ratio (OR) statistics. Correction of P values for multiple comparisons was according to Benjamini-Hochberg. There was no difference in ACE I/D genotype between groups. ACTN3 XX genotype tended to be underrepresented in rugby union backs (15.7%) compared with forwards (24.8%, P = 0.06). Interestingly, the 69 back three players (wings and full backs) in rugby union included only six XX genotype individuals (8.7%), with the R allele more common in the back three (68.8%) than controls (58.0%; χ(2) = 6.672, P = 0.04; OR = 1.60) and forwards (47.5%; χ(2) = 11.768, P = 0.01; OR = 2.00). Association of ACTN3 R577X with playing position in elite rugby union athletes suggests inherited fatigue resistance is more prevalent in forwards, while inherited sprint ability is more prevalent in backs, especially wings and full backs. These results also demonstrate the advantage of focusing genetic studies on a large cohort within a single sport, especially when intrasport positional differences exist, instead of combining several sports with varied demands and athlete characteristics.

The aim of this study was to compare postural sway during a series of static balancing tasks and during five chair rises between healthy young (mean (SEM) age 26(1) yrs), healthy old (age 67(1) yrs) and master athlete runners (age 67(1) yrs; competing and training for the previous 51(5) yrs) using the Microsoft Kinect One. The healthy old had more sway than young in all balance tasks. The master athletes had similar sway to young during two-leg balancing and one leg standing with eyes open. When balancing on one-leg with eyes closed, both the healthy old and the master athletes had around 17-fold more sway than young. The healthy old and master athletes also had less anterio-posterior movement during chair rising compared with young. These results suggest that masters runners are not spared from the age-associated decline in postural stability and may benefit from specific balance training.

© 2015 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism.Background & aims: Consensus on the definition of malnutrition has not yet been reached. Recently, The European Society for Clinical Nutrition and Metabolism (ESPEN) proposed a consensus definition of malnutrition. The aim of the present study was to describe the prevalence of malnutrition according to the ESPEN definition in four diverse populations. Methods: In total, 349 acutely ill middle-aged patients, 135 geriatric outpatients, 306 healthy old individuals and 179 healthy young individuals were included in the study. Subjects were screened for risk of malnutrition using the SNAQ. The ESPEN definition of malnutrition, i.e. low BMI (< 18.5 kg/m2) or a combination of unintentional weight loss and low FFMI or low BMI was applied to all subjects. Results: Screening identified 0, 0.5, 10 and 30% of the healthy young, the healthy old, the geriatric outpatients and the acutely ill middle-aged patients as being at risk of malnutrition. The prevalence of malnutrition ranged from 0% in the healthy young, 0.5% in healthy old individuals, 6% in the geriatric outpatients to 14% in the acutely ill middle-aged patients. Prevalence of low FFMI was observed in all four populations (14-33%), but concurred less frequently with weight loss (0-13%). Conclusions: Using the ESPEN definition, 0%-14% malnutrition was found in the diverse populations. Further work is needed to fully address the validity of a two-step approach, including risk assessment as an initial step in screening and defining malnutrition. Furthermore, assessing the predictive validity of the ESPEN definition is needed.

Muscle motor unit numbers decrease markedly in old age, while remaining motor units are enlarged and can have reduced neuromuscular junction transmission stability. However, it is possible that regular intense physical activity throughout life can attenuate this remodeling. The aim of this study was to compare the number, size, and neuromuscular junction transmission stability of tibialis anterior (TA) motor units in healthy young and older men with those of exceptionally active master runners. The distribution of motor unit potential (MUP) size was determined from intramuscular electromyographic signals recorded in healthy male Young (mean ± SD, 26 ± 5 years), Old (71 ± 4 years) and Master Athletes (69 ± 3 years). Relative differences between groups in numbers of motor units was assessed using two methods, one comparing MUP size and muscle cross-sectional area (CSA) determined with MRI, the other comparing surface recorded MUPs with maximal compound muscle action potentials and commonly known as a "motor unit number estimate (MUNE)". Near fiber (NF) jiggle was measured to assess neuromuscular junction transmission stability. TA CSA did not differ between groups. MUNE values for the Old and Master Athletes were 45% and 40%, respectively, of the Young. Intramuscular MUPs of Old and Master Athletes were 43% and 56% larger than Young. NF jiggle was slightly higher in the Master Athletes, with no difference between Young and Old. These results show substantial and similar motor unit loss and remodeling in Master Athletes and Old individuals compared with Young, which suggests that lifelong training does not attenuate the age-related loss of motor units.

Background The purpose of this study was to examine whether very short duration, very high intensity sprint interval training (SIT) leads to loss of body fat mass in association with improvements to VO2max and fatty acid oxidation, and to assess the extent of sex dimorphism in these physiological responses. Methods A total of 24 men and 17 women (mean (SEM) age: 39 (±2) years; body mass index 24.6 (0.6)) completed measurements of the maximal rate of oxygen uptake (VO2max) and fatty acid oxidation (FATmax). Body fat and lean mass were measured by dual emission x-ray absorptiometry, and fasting blood lipid, glucose and insulin profiles were assessed before and after training. SIT consisted of 4×20 s sprints on a cycle ergometer at approximately 175% VO2max, three times per week for 12 weeks. Results Fat mass decreased by 1.0 kg, although men lost statistically significantly more fat than women both when expressed in Kg and as % body fat. VO2max increased by around 9%, but women improved VO2max significantly more than men. FATmax improved by around 13%, but fasting plasma glucose, insulin, total triglyceride, total cholesterol and high-density lipoprotein (HDL) did not change after training, while low-density lipoprotein decreased by 8% (p=0.028) and the HDL:Total Cholesterol ratio improved by 6%. There were no sex differences in these metabolic responses to training. Conclusions These results show lower body fat %, and higher rates of fatty acid oxidation and VO2max after 12 weeks of training for just 4 min per week. Notably, women improved VO2max more than men, while men lost more fat than women.

Physical activity (PA) may need to produce high impacts to be osteogenic. The aim of this study was to identify threshold(s) for defining high impact PA for future analyses in the VIBE (Vertical Impact and Bone in the Elderly) study, based on home recordings with triaxial accelerometers. Recordings were obtained from 19 Master Athlete Cohort (MAC; mean 67.6 years) and 15 Hertfordshire Cohort Study (HCS; mean 77.7 years) participants. Data cleaning protocols were developed to exclude artifacts. Accelerations expressed in g units were categorized into three bands selected from the distribution of positive Y-axis peak accelerations. Data were available for 6.6 and 4.4 days from MAC and HCS participants respectively, with approximately 14 hr recording daily. Three-fold more 0.5-1.0g impacts were observed in MAC versus HCS, 20-fold more 1.0-1.5g impacts, and 140-fold more impacts ≥ 1.5g. Our analysis protocol successfully distinguishes PA levels in active and sedentary older individuals.

Declining muscle mass and function is one of the main drivers of loss of independence in the elderly. Sarcopenia is associated with numerous cellular and endocrine perturbations, and it remains challenging to identify those changes that play a causal role and could serve as targets for therapeutic intervention. In this study, we uncovered a remarkable differential susceptibility of certain muscles to age-related decline. Aging rats specifically lose muscle mass and function in the hindlimbs, but not in the forelimbs. By performing a comprehensive comparative analysis of these muscles, we demonstrate that regional susceptibility to sarcopenia is dependent on neuromuscular junction fragmentation, loss of motoneuron innervation, and reduced excitability. Remarkably, muscle loss in elderly humans also differs in vastus lateralis and tibialis anterior muscles in direct relation to neuromuscular dysfunction. By comparing gene expression in susceptible and non-susceptible muscles, we identified a specific transcriptomic signature of neuromuscular impairment. Importantly, differential molecular profiling of the associated peripheral nerves revealed fundamental changes in cholesterol biosynthetic pathways. Altogether our results provide compelling evidence that susceptibility to sarcopenia is tightly linked to neuromuscular decline in rats and humans, and identify dysregulation of sterol metabolism in the peripheral nervous system as an early event in this process.

Regular physical activity helps to improve physical and mental functions as well as reverse some effects of chronic disease to keep older people mobile and independent. Despite the highly publicised benefits of physical activity, the overwhelming majority of older people in the United Kingdom do not meet the minimum physical activity levels needed to maintain health. The sedentary lifestyles that predominate in older age results in premature onset of ill health, disease and frailty. Local authorities have a responsibility to promote physical activity amongst older people, but knowing how to stimulate regular activity at the population-level is challenging. The physiological rationale for physical activity, risks of adverse events, societal and psychological factors are discussed with a view to inform public health initiatives for the relatively healthy older person as well as those with physical frailty. The evidence shows that regular physical activity is safe for healthy and for frail older people and the risks of developing major cardiovascular and metabolic diseases, obesity, falls, cognitive impairments, osteoporosis and muscular weakness are decreased by regularly completing activities ranging from low intensity walking through to more vigorous sports and resistance exercises. Yet, participation in physical activities remains low amongst older adults, particularly those living in less affluent areas. Older people may be encouraged to increase their activities if influenced by clinicians, family or friends, keeping costs low and enjoyment high, facilitating group-based activities and raising self-efficacy for exercise.

BACKGROUND & AIM: Sarcopenia, the age-related decrease in muscle mass, strength, and function, is a main cause of reduced mobility, increased falls, fractures and nursing home admissions. Cross-sectional and prospective studies indicate that sarcopenia may be influenced in part by reversible factors like nutritional intake. The aim of this study was to compare functional and nutritional status, body composition, and quality of life of older adults between age and sex-matched older adults with and without sarcopenia. METHODS: In a multi-centre setting, non-sarcopenic older adults (n = 66, mean ± SD: 71 ± 4 y), i.e. Short Physical Performance Battery (SPPB): 11-12 and normal skeletal muscle mass index, were recruited to match 1:1 by age and sex to previously recruited adults with sarcopenia: SPPB 4-9 and low skeletal muscle mass index. Health-related quality of life, self-reported physical activity levels and dietary intakes were measured using the EQ-5D scale and index, Physical Activity Scale for the Elderly (PASE), and 3-day prospective diet records, respectively. Concentrations of 25-OH-vitamin D, α-tocopherol (adjusted for cholesterol), folate, and vitamin B-12 were assessed in serum samples. RESULTS: In addition to the defined components of sarcopenia, i.e. muscle mass, strength and function, reported physical activity levels and health-related quality of life were lower in the sarcopenic adults (p < 0.001). For similar energy intakes (mean ± SD: sarcopenic, 1710 ± 418; non-sarcopenic, 1745 ± 513, p = 0.50), the sarcopenic group consumed less protein/kg (-6%), vitamin D (-38%), vitamin B-12 (-22%), magnesium (-6%), phosphorus (-5%), and selenium (-2%) (all p < 0.05) compared to the non-sarcopenic controls. The serum concentration of vitamin B-12 was 15% lower in the sarcopenic group (p = 0.015), and all other nutrient concentrations were similar between groups. CONCLUSIONS: In non-malnourished older adults with and without sarcopenia, we observed that sarcopenia

Voluntary control of skeletal muscle enables humans to interact with and manipulate the environment. Lower muscle mass, weakness and poor coordination are common complaints in older age and reduce physical capabilities. Attention has focused on ways of maintaining muscle size and strength by exercise, diet or hormone replacement. Without appropriate neural innervation, however, muscle cannot function. Emerging evidence points to a neural basis of muscle loss. Motor unit number estimates indicate that by age around 71 years, healthy older people have around 40 % fewer motor units. The surviving low- and moderate-threshold motor units recruited for moderate intensity contractions are enlarged by around 50 % and show increased fibre density, presumably due to collateral reinnervation of denervated fibres. Motor unit potentials show increased complexity and the stability of neuromuscular junction transmissions is decreased. The available evidence is limited by a lack of longitudinal studies, relatively small sample sizes, a tendency to examine the small peripheral muscles and relatively few investigations into the consequences of motor unit remodelling for muscle size and control of movements in older age. Loss of motor neurons and remodelling of surviving motor units constitutes the major change in ageing muscles and probably contributes to muscle loss and functional impairments. The deterioration and remodelling of motor units likely imposes constraints on the way in which the central nervous system controls movements.

Older people experience skeletal muscle wasting, in part due to impaired proliferative capacity of quiescent skeletal muscle satellite cells which can be reversed by exposure to young blood. To investigate the role of immune cells in muscle regeneration, we isolated lymphocytes from whole blood of young and older healthy volunteers and cultured them with, or without, anti-CD3/CD28 activators to induce release of cytokines, interleukins, and growth factors into the media. The secreted proteins were collected to prepare a conditioned media, which was subsequently used to culture C2C12 myoblasts. The conditioned media from the activated young lymphocytes increased the rate of proliferation of myoblasts by around threefold (P < 0.005) and caused an approximate fourfold (P < 0.005) increase in migration compared with nonactivated lymphocyte control media. These responses were characterized by minimal myotube formation (2%), low fusion index (5%), low myosin heavy chain content, and substantial migration. In contrast, myoblasts treated with conditioned media from activated old lymphocytes exhibited a high degree of differentiation, and multi-nucleated myotube formation that was comparable to control conditions, thus showing no effect on proliferation or migration of myoblasts. These results indicate that secreted proteins from lymphocytes of young people enhance the muscle cell proliferation and migration, whereas secreted proteins from lymphocytes of older people may contribute to the attenuated skeletal muscle satellite cell proliferation and migration.

INTRODUCTION: The anterior thigh muscles are particularly susceptible to muscle loss and weakness during ageing, but it remains unclear how this is associated with changes to neuromuscular structure and function in terms of motor unit (MU) number, size and MU potential (MUP) stability. METHODS: Intramuscular and surface electromyographic (EMG) signals were recorded from the vastus lateralis (VL) during voluntary contractions held at 25% maximal knee extensor strength in 22 young (25.3 ± 4.8yrs) and 20 physically active older men (71.4 ± 6.2yrs). MUP size, firing rates, phases, turns and near fibre (NF) jiggle were determined and motor unit number estimates (MUNEs) were made by comparing average surface MUP with maximal electrically-evoked compound muscle action potentials. Quadriceps cross-sectional area was measured by magnetic resonance imaging. RESULTS: 379 individual MUs were sampled in young and 346 in older men. Compared with young, the older MUs had 8% lower firing rates and larger MUP size (∼+25%) as well as increased complexity evidenced as, phases (+13%), turns (+20%) and NF jiggle (+11%) (all P < 0.0005). The MUNE values (derived from the area of muscle in range of the surface-electrode) in older subjects were around 70% of the young (P < 0.05). Taking into consideration the 30% smaller cross-sectional area of the VL, the total number of MUs in the older muscles was between 50-60% lower than in the young (P < 0.0005). CONCLUSION: A large portion of the VL MU pool is lost in older men and those recruited during moderate intensity contractions were enlarged and less stable. These MU changes were evident before clinically relevant changes to muscle function were apparent; nevertheless, the changes in MU number and size are likely to be a prelude to future movement problems. This article is protected by copyright. All rights reserved.

Consensus on clinically valid diagnostic criteria for sarcopenia requires a systematical assessment of the association of its candidate measures of muscle mass, muscle strength, and physical performance on one side and muscle-related clinical parameters on the other side. In this study, we systematically assessed associations between serum albumin as a muscle-related parameter and muscle measures in 172 healthy young (aged 18-30 years) and 271 old participants (aged 69-81 year) from the European MYOAGE study. Muscle measures included relative muscle mass, i.e., total- and appendicular lean mass (ALM) percentage, absolute muscle mass, i.e., ALM/height(2) and total lean mass in kilograms, handgrip strength, and walking speed. Muscle measures were standardized and analyzed in multivariate linear regression models, stratified by age. Adjustment models included age, body composition, C-reactive protein and lifestyle factors. In young participants, serum albumin was positively associated with lean mass percentage (p = 0.007) and with ALM percentage (p = 0.001). In old participants, serum albumin was not associated with any of the muscle measures. In conclusion, the association between serum albumin and muscle measures was only found in healthy young participants and the strongest for measures of relative muscle mass.

Introduction: Susceptibility to muscle fatigue during aging could depend on muscle activation patterns. Methods: Young (mean age, 22 years) and older (mean age 70 years) men and women completed two fatigue tests of knee extensor muscles using voluntary and electrically stimulated contractions. Results: Older subjects displayed a shift to the left of the torque-frequency relationship and held a sustained voluntary isometric contraction at 50% maximal strength for significantly longer than young (P < 0.001). Young and old showed similar fatigue during electrically induced, intermittent isometric contractions (1-s on, 1-s off for 2 min), but women fatigued less than men (P = 0.001). Stronger muscles fatigued more quickly, and slower contractile properties were associated with longer sustained contractions. Conclusions: The slowing and weakness of older muscle was associated with superior fatigue resistance during sustained isometric contractions. Young and old showed similar fatigue following a series of brief, intermittent contractions, but women fatigued less than men.

Recent works on human action recognition have focused on representing and classifying articulated body motion. These methods require a detailed knowledge of the action composition both in the spatial and temporal domains, which is a difficult task, most notably under real-time conditions. As such, there has been a recent shift towards the exemplar paradigm as an efficient low-level and invariant modelling approach. Motivated by recent success, we believe a real-time solution to the problem of human action recognition can be achieved. In this work, we present an exemplar-based approach where only a single action sequence is used to model an action class. Notably, rotations for each pose are parameterised in Exponential Map form. Delegate exemplars are selected using k-means clustering, where the cluster criteria is selected automatically. For each cluster, a delegate is identified and denoted as the exemplar by means of a similarity function. The number of exemplars is adaptive based on the complexity of the action sequence. For recognition, Dynamic Time Warping and template matching is employed to compare the similarity between a streamed observation and the action model. Experimental results using motion capture demonstrate our approach is superior to current state-of-the-art, with the additional ability to handle large and varied action sequences.

OBJECTIVES: Magnetic resonance imaging (MRI) and dual-energy x-ray absorptiometry (DXA) were used to examine the thigh lean mass in young and old men and women. METHODS: A whole-body DXA scan was used to estimate thigh lean mass in young (20 men; 22.4±3.1y; 18 women; 22.1±2.0y) and older adults (25 men; 72.3±4.9y; 28 women; 72.0±4.5y). Thigh lean mass determined with a thigh scan on the DXA or full thigh MRI scans were compared. RESULTS: Although the thigh lean mass quantified by DXA and MRI in young and older participants were correlated (R(2)=0.88; p<0.001) the magnitude of the differences in thigh lean mass between young and old was smaller with DXA than MRI (old vs. young men 79.5±13.1% and 73.4±11.2%; old vs. young women 88.6±11.8% and 79.4±12.3%, respectively). Detailed analysis of MRI revealed 30% smaller quadriceps muscles in the older than young individuals, while the other thigh muscles were only 18% smaller. CONCLUSIONS: DXA underestimates the age-related loss of thigh muscle mass in comparison to MRI. The quadriceps muscles were more susceptible to age-related atrophy compared with other thigh muscles.