Jonathon Senefeld

FATIGUE AND RECOVERY FROM DYNAMIC CONTRACTIONS IN MEN AND WOMEN DIFFER FOR ARM AND LEG MUSCLES

Introduction: Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Methods: Sixteen men and 19 women performed 90 isotonic contractions at maximal voluntary shortening velocity (maximal velocity concentric contractions, MVCC) with the elbow flexor and knee extensor muscles (separate days) at a load equivalent to 20% maximal voluntary isometric contraction (MVIC). Results: Power (from MVCCs) decreased similarly for men and women for both muscles (P > 0.05). Men and women had similar declines in MVIC of elbow flexors, but men had greater reductions in knee extensor MVIC force and MVIC electromyogram activity than women (P < 0.05). The decline in MVIC and power was greater, and force recovery was slower for the elbow flexors compared with knee extensors. Conclusions: The gender difference in muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. Muscle Nerve 48: 436–439, 2013

Sex differences in elite swimming with advanced age are less than marathon running

The sex difference in marathon performance increases with finishing place and age of the runner but whether this occurs among swimmers is unknown. The purpose was to compare sex differences in swimming velocity across world record place (1st–10th), age group (25–89 years), and event distance. We also compared sex differences between freestyle swimming and marathon running. The worlds top 10 swimming times of both sexes for World Championship freestyle stroke, backstroke, breaststroke, and butterfly events and the worlds top 10 marathon times in 5‐year age groups were obtained. Men were faster than women for freestyle (12.4 ± 4.2%), backstroke (12.8 ± 3.0%), and breaststroke (14.5 ± 3.2%), with the greatest sex differences for butterfly (16.7 ± 5.5%). The sex difference in swimming velocity increased across world record place for freestyle (P < 0.001), breaststroke, and butterfly for all age groups and distances (P < 0.001) because of a greater relative drop‐off between first and 10th place for women. The sex difference in marathon running increased with the world record place and the sex difference for marathon running was greater than for swimming (P < 0.001). The sex difference in swimming increased with world record place and age, but was less than for marathon running. Collectively, these results suggest more depth in womens swimming than marathon running.

Age Differences in Dynamic Fatigability and Variability of Arm and Leg Muscles: Associations with Physical Function

Introduction It is not known whether the age‐related increase in fatigability of fast dynamic contractions in lower limb muscles also occurs in upper limb muscles. We compared age‐related fatigability and variability of maximal‐effort repeated dynamic contractions in the knee extensor and elbow flexor muscles; and determined associations between fatigability, variability of velocity between contractions and functional performance. Methods 35 young (16 males; 21.0 ± 2.6 years) and 32 old (18 males; 71.3 ± 6.2 years) adults performed a dynamic fatiguing task involving 90 maximal‐effort, fast, concentric, isotonic contractions (1 contraction/3 s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the elbow flexor and knee extensor muscles on separate days. Old adults also performed tests of balance and walking endurance. Results Old adults had greater fatigue‐related reductions in peak velocity compared with young adults for both the elbow flexor and knee extensor muscles (P < 0.05) with no sex differences (P > 0.05). Old adults had greater variability of peak velocity during the knee extensor, but not during the elbow flexor fatiguing task. The age difference in fatigability was greater for the knee extensor muscles (35.9%) compared with elbow flexor muscles (9.7%, P < 0.05). Less fatigability of the knee extensor muscles was associated with greater walking endurance (r = − 0.34, P = 0.048) and balance (r = − 0.41, P = 0.014) among old adults. Conclusions An age‐related increase in fatigability of a dynamic fatiguing task was greater for the knee extensor compared with the elbow flexor muscles in males and females, and greater fatigability was associated with lesser walking endurance and balance. HighlightsOld adults were more fatigable than young during a high velocity task.Age differences in fatigability were greater for knee extensors than elbow flexors.Old were more variable in peak velocity than young during the knee extensor task.Fatigability of knee extensors was associated with walking endurance and balance.

Sex Differences in Participation, Performance, and Age of Ultramarathon Runners.

The sex difference in marathon running is increased with lower participation of women than men, but whether this occurs for ultramarathon running is not known. The study purpose was to determine whether the sex difference in performance widens among lower-placed runners and the association between the sex difference in running speed and participation rates. The top-10 ultramarathon running times, age at performance date, and the number of men and women finishers were analyzed from 20 races (45-160 km) in the US Track and Field Ultra Running Grand Prix. Men were faster than women for all events (18.7% ± 5.8%, P < .001). The sex difference in speed was the least for 100 km (14.9% ± 4.2%) and greatest for 45-50 km (19.3% ± 5.8%). The top-10 men were younger than the top-10 women (37.7 ± 3.2 and 39.0 ± 3.1 y, respectively, P < .001). The sex difference in speed increased with finishing place (1st place 15.6% ± 6.6% vs 10th 20.8% ± 5.6%, P < .001). Association analysis showed that the sex difference in speed was largest when there were fewer women than men finishers in a race; the strength of the association was greatest for the 80-km distance and least for the 160-km. Lower participation rates of women than men in the lower-distance ultramarathons and less depth among lower-placed women runners inflate the sex difference in ultramarathon performance.

Molecular underpinnings of diabetic polyneuropathy

to the editor: Allen and colleagues ([2][1]) provided an in-depth review of the pathophysiology and functional outcomes of diabetic polyneuropathy (DPN) among patients with diabetes mellitus (DM). As explained ([2][1]), DPN often manifests in a symmetrical and length-dependent pattern affecting

Girls in the Boat: Sex Differences in Rowing Performance and Participation

Men outperform women in many athletic endeavors due to physiological and anatomical differences (e.g. larger and faster muscle); however, the observed sex differences in elite athletic performance are typically larger than expected, and may reflect sex-related differences in opportunity or incentives. As collegiate rowing in the United States has been largely incentivized for women over the last 20 years, but not men, the purpose of this study was to examine sex differences in elite rowing performance over that timeframe. Finishing times from grand finale races for collegiate championship on-water performances (n = 480) and junior indoor performances (n = 1,280) were compared between men and women across 20 years (1997–2016), weight classes (heavy vs. lightweight) and finishing place. Participation of the numbers of men and women rowers were also quantified across years. Men were faster than women across all finishing places, weight classes and years of competition and performance declined across finishing place for both men and women (P<0.001). Interestingly, the reduction in performance time across finishing place was greater (P<0.001) for collegiate men compared to women in the heavyweight division. This result is opposite to other sports (e.g. running and swimming), and to lightweight rowing in this study, which provides women fewer incentives than in heavyweight rowing. Correspondingly, participation in collegiate rowing has increased by ~113 women per year (P<0.001), with no change (P = 0.899) for collegiate men. These results indicate that increased participation and incentives within collegiate rowing for women vs. men contribute to sex differences in athletic performance.

Mechanisms for the Increased Fatigability of the Lower Limb in People with Type 2 Diabetes

Fatiguing exercise is the basis of exercise training and a cornerstone of management of type 2 diabetes mellitus (T2D); however, little is known about the fatigability of limb muscles and the involved mechanisms in people with T2D. The purpose of this study was to compare fatigability of knee extensor muscles between people with T2D and controls without diabetes and determine the neural and muscular mechanisms for a dynamic fatiguing task. Seventeen people with T2D [ten men and seven women: 59.6 (9.0) yr] and twenty-one age-, body mass index-, and physical activity-matched controls [eleven men and ten women: 59.5 (9.6) yr] performed one hundred twenty high-velocity concentric contractions (one contraction/3 s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the knee extensors. Transcranial magnetic stimulation (TMS) and electrical stimulation of the quadriceps were used to assess voluntary activation and contractile properties. People with T2D had larger reductions than controls in power during the fatiguing task [42.8 (24.2) vs. 26.4 (15.0)%; P < 0.001] and MVIC torque after the fatiguing task [37.6 (18.2) vs. 26.4 (12.1)%; P = 0.04]. People with T2D had greater reductions than controls in the electrically evoked twitch amplitude after the fatiguing task [44.0 (20.4) vs. 35.4 (12.1)%, respectively; P = 0.01]. However, the decrease in voluntary activation was similar between groups when assessed with electrical stimulation [12.1 (2.6) vs. 12.4 (4.4)% decrease; P = 0.84] and TMS ( P = 0.995). A greater decline in MVIC torque was associated with larger reductions of twitch amplitude ( r2 = 0.364, P = 0.002). Although neural mechanisms contributed to fatigability, contractile mechanisms were responsible for the greater knee extensor fatigability in men and women with T2D compared with healthy controls. NEW & NOTEWORTHY Transcranial magnetic stimulation and percutaneous muscle stimulation were used to determine the contributions of neural and contractile mechanisms of fatigability of the knee extensor muscles after a dynamic fatiguing task in men and women with type 2 diabetes (T2D) and healthy age-, body mass index-, and physical activity-matched controls. Although neural and contractile mechanisms contributed to greater fatigability of people with T2D, fatigability was primarily associated with impaired contractile mechanisms and glycemic control.

Predicting human ageing with Masters athletics: ‘one size doesn't fit all’

Scientific understanding of human ageing is confounded by lifelong differences in physical activity, exercise training, disease, nutrition and a myriad of other environmental and physiological factors. This article is protected by copyright. All rights reserved