Impact of COVID-19 lockdown on physical activity behaviours of older adults who participated in a community-based exercise program prior to the lockdown

This study investigated the impact of the 2020 COVID-19 lockdown on community-dwelling older adults attending a community-based exercise program to seek strategies to keep them active during self-isolated situations. A two-phase mixed methods approach included a survey followed by in-person focus groups. Forty-eight participants, with 32 starting a community-based exercise program before the lockdown and 16 joining the program after the lockdown, completed a questionnaire survey about physical activities before and during the lockdown. This was followed by three focus groups (26 participants in total) to identify factors influencing physical activity behaviours found in the survey. The survey found that the COVID-19 lockdown had varied impact on exercise adherence of the older adults: 43 % of the participants exercised less during the lockdown than pre-lockdown, but 26 % exercised more. Interestingly, among the participants approximately 80 % still achieved the recommended physical activity level by the WHO during the lockdown. The focus groups revealed that exercise behaviours before the lockdown directly affected the behaviours during the lockdown. Participants’ recognition of the support from trustworthy people also influenced their motivation to perform exercises in an isolated environment. Remote exercise programs, such as digital and printed exercise materials, were found beneficial for the participants only when they came from the people the older adults trusted through their previous experience (i.e., the program). A sense of belonging to the exercise group was also essential for the participants to achieve self-managed exercise. It was concluded that older adults need connections to an exercise group and a trustworthy exercise instructor who could continuously support them to be physically active in isolated situations such as lockdowns, in addition to exercise knowledge and a better understanding of the benefits of exercise

Measurement of biceps brachii muscle cross-sectional area by extended-field-of-view ultrasound imaging technique

This study investigated the reliability of the extended-field-of-view (EFOV) ultrasonography technique and its validity against magnetic resonance imaging (MRI) for biceps brachii muscle cross-sectional area (CSA) assessment, and applied the method to examine changes in CSA following 10 sets of 3 maximal eccentric contractions of the elbow flexors. Bicep brachii CSA was assessed using both EFOV and MRI techniques at the mid-point of the upper arm. A Pearson product moment analysis showed a high correlation (r = 0.99) between the EFOV and MRI measures; however, the CSA obtained from the EFOV (12.5 ± 6.3 cm² ) was smaller (P=0.004) than that of MRI (12.9 ± 6.1 cm²). The reliability of the EFOV technique was assessed using the same scan image tracing twice (between-traces) and two images scanned from the same site (between-scans), and using the images taken from the same site one hour apart (between-measures). An Intra-class correlation (ICC) analysis showed good reliability (R=1.0) for both between-traces and between-scans, and coefficient of variation (CV) was less than 0.1 %. The reliability was also high for the measurements taken one hour apart (R=0.99, CV=0.7 %). These results show that EFOV is a valid and reliable method to assess biceps brachii CSA, but EFOV could give a smaller (~1 %) CSA than MRI. However, brachial is CSA was difficult to assess in this method, because of the limitation of the scanning technique. Biceps brachii CSA was increased (P\u3c0.05) immediately (8.7 ± 5.8 %) and 4 days (7.7 ± 6.0 %) following eccentric exercise of the elbow flexors, illustrating muscle swelling

Could titin have a role in strain-induced injuries?

It has been known for some time that strain injuries occur through the excessive lengthening of a muscle. However, the precise mechanism for strain injury remains elusive and has been the subject of recent debate in the Journal of Sport and Health Science, but it seems sensible to consider mechanisms at the level of the muscle fiber. It was previously believed that damage was the result of non-uniform stretching of sarcomeres on the descending limb of the length–tension curve, with the weakest sarcomeres undergoing the greatest deformation and ultimately damaging the myofibril. This non-uniform lengthening was also believed to explain the residual force enhancement observed during lengthening contractions, as the rapid lengthening of some sarcomeres gives rise to passive tension whilst allowing the remaining sarcomeres to operate closer to their optimal length. While it has been shown sarcomeres do lengthen non-uniformly, it does not appear to be dependent on the strength of the sarcomere. Furthermore, the increase in sarcomere length non-uniformity after active stretching is not correlated to the residual increase in force (r = −0.309). Although this does not disprove the notion that sarcomere lengthening is responsible for muscle damage and injury, it does contradict the idea that the weakest sarcomeres lengthen first as suggested by the sarcomere popping theory

Comparison of velocity-based and traditional 1RM-percent-based prescription on acute kinetic and kinematic variables

Purpose: This study compared kinetic and kinematic data from three different velocity-based training (VBT) sessions and a 1-repetition maximum (1RM) percent-based training (PBT) session using full-depth, free-weight back squats with maximal concentric effort. Methods: Fifteen strength-trained men performed four randomized resistance-training sessions 96-hours apart: PBT session involved five sets of five repetitions using 80%1RM; load-velocity profile (LVP) session contained five sets of five repetitions with a load that could be adjusted to achieve a target velocity established from an individualized LVP equation at 80%1RM; fixed sets 20% velocity loss threshold (FSVL20) session that consisted of five sets at 80%1RM but sets were terminated once the mean velocity (MV) dropped below 20% of the threshold velocity or when five repetitions were completed per set; variable sets 20% velocity loss threshold (VSVL20) session comprised 25-repetitions in total, but participants performed as many repetitions in a set as possible until the 20% velocity loss threshold was exceeded. Results: When averaged across all repetitions, MV and peak velocity (PV) were significantly (p<0.05) faster during the LVP (MV: ES=1.05; PV: ES=1.12) and FSVL20 (MV: ES=0.81; PV: ES=0.98) sessions compared to PBT. Mean time under tension (TUT) and concentric TUT were significantly less during the LVP session compared to PBT. FSVL20 session had significantly less repetitions, total TUT and concentric TUT than PBT. No significant differences were found for all other measurements between any of the sessions. Conclusions: VBT permits faster velocities, avoids additional unnecessary mechanical stress but maintains similar measures of force and power output compared to strength-oriented PBT

Water intake after dehydration makes muscles more susceptible to cramp but electrolytes reverse that effect

Objective No previous study has compared water and oral rehydration solution (ORS) intake after dehydration induced by exercise in the heat for the effect on muscle cramps. The present study tested the hypothesis that water ingestion after dehydration would increase muscle cramp susceptibility, but this would be prevented by ORS ingestion. Methods Ten men performed two bouts of downhill running (DHR; -5%) in the heat (35°C-36 °C) until their body mass was reduced by 2%. Ten minutes after DHR, either spring water or electrolyte water similar to ORS (OS-1 ®) was ingested in a counter-balanced order on two different days separated by a week. Muscle cramp susceptibility was assessed by a threshold frequency (TF) of electrical train stimulation to induce cramp before, immediately after (0), and 30 and 60 min after the ingestion. Blood samples were taken before, immediately and 80 min after DHR to measure serum electrolyte concentrations. Results Muscle cramp susceptibility assessed by TF did not change from baseline to immediately after DHR for both conditions (water: 24.6 ± 2.1 Hz, OS-1 ®: 24.7 ± 1.4 Hz). TF decreased after water intake by 4.3 Hz (30 min) and 5.1 Hz (60 min post-ingestion), but increased after OS-1 ® intake by 3.7 and 5.4 Hz, respectively. Serum sodium and chloride concentrations decreased after water intake but maintained after OS-1 ® intake. Conclusion These results suggest that water intake after dehydration makes muscles more susceptible to electrical simulation-induced muscle cramp, probably due to dilution of electrolytes, and when OS-1 ® is consumed, the susceptibility to muscle cramp decreases. © Author(s) (or their employer(s)) 2019