This study describes a mouse model of progressive resistance exercise that utilizes a full-body/multi-joint exercise (weight pulling) along with a training protocol that mimics a traditional human paradigm (three training sessions per week, ~8–12 repetitions per set, 2 min of rest between sets, around two maximal-intensity sets per session, last set taken to failure, and a progressive increase in loading that is based on the individual’s performance). We demonstrate that weight pulling can induce an increase in the mass of numerous muscles throughout the body. The relative increase in muscle mass is similar to what has been observed in human studies, and is associated with the same type of long-term adaptations that occur in humans (e.g., fiber hypertrophy, myonuclear accretion, and, in some instances, a fast-to-slow transition in Type II fiber composition). Moreover, we demonstrate that weight pulling can induce the same type of acute responses that are thought to drive these long-term adaptations (e.g., the activation of signaling through mTORC1 and the induction of protein synthesis at 1 h post-exercise). Collectively, the results of this study indicate that weight pulling can serve as a highly translatable mouse model of progressive resistance exercise.

The study of muscle reinnervation has been difficult because of lack of an accurate, reproducible method to monitor return of function. Visual assessment relies on subjective interpretation. Histology provides anatomic, not functional, information. Electromyography and anatomic tracing have been most effective in evaluating physiologic return of muscle function. It has been difficult to assess the timing of functional return electromyographically because measurements are intermittent and electrode placement varies. A method was designed to allow long-term monitoring of electromyographic (EMG) activity in the facial musculature of the rabbit. Sixteen rabbits were monitored for at least 1 month or until return of normal EMG activity was identified. Various levels of injury (nerve crush, transection without repair, and transection with immediate end-to-end anastomosis) were evaluated. EMG evidence of reinnervation was seen in all animals with nerve crush injuries as well as those with anastomoses. Physiologic continuity of the nerves was then evaluated by retrograde transport of horseradish peroxidase. All muscles showing return of EMG activity had uptake of HRP into the appropriate brain stem motor neurons. The denervated muscles showed no HRP uptake. The information gained in this study shows potential for use of this technique in comparing functional return of muscle activity between different reinnervation methods.

This study describes a mouse model of human progressive resistance exercise that utilizes a full-body/multi-joint exercise (weight pulling) along with a training protocol that mimics a traditional human paradigm (3 training sessions per week, ~8-12 repetitions per set, 2 minutes of rest between sets, ~2 maximal-intensity sets per session, last set taken to failure, and a progressive increase in loading that is based on the individual's performance). We demonstrate that weight pulling can induce an increase in the mass of numerous muscles throughout the body. The magnitude of increase in muscle mass is similar to what has been observed in human studies, and it is associated with the same type of long-term adaptations that occur in humans (e.g., fiber hypertrophy, myonuclear accretion, and in some instances a fast-to-slow transition in Type II fiber composition). Moreover, we demonstrate that weight pulling can induce the same type of acute responses that are thought to drive these long-term adaptations (e.g., the activation of signaling through mTORC1 and the induction of protein synthesis at 1 hr post-exercise). Collectively, the results of this study indicate that weight pulling can serve as a highly translatable mouse model of human progressive resistance exercise.

No abstract

Stand-up paddle boarding (SUP) as both a competitive and recreational sport has grown in popularity over the last decade. Better understanding paddling kinematics is beneficial for both injury prevention and informing coaching practices in this growing sport. The purpose of this study was to analyze sagittal plane kinematics during both standing and kneeling paddling postures commonly adopted by injury-free, recreational SUP participants. Eighteen recreational SUP participants (seven males/eleven females) were asked to complete a series of paddling tasks on a SUP ergometer in two postures, during which kinematic data were acquired. Sagittal plane kinematic data were analyzed for joint excursion, or range of motion used, while paddling on both sides of the body in each posture. Analysis of variance was used to compare joint excursions across tasks. There were no significant differences in hip or trunk sagittal plant excursion between postures. However, there was significantly greater sagittal plane excursion at the shoulder in the kneeling as compared to the standing posture with the shoulder opposite the paddling side demonstrating the greatest total excursion. These results help establish the parameters of the paddling technique currently in use among injury-free SUP participants and may be used in the future to inform coaching practices.

A practice session is common prior to strength testing. However, the benefits of practice have not been previously reported. The purpose of this study was to determine the effect of a practice session on peak torque, mean torque and between trial variability across three test days. We hypothesized that peak and mean torque would be higher and less variable the second and third test days than the first. Twenty-five healthy, young participants completed 3 maximal voluntary isometric and isokinetic knee extensions on three separate days. No difference in isometric torque was found between days 1 and 2, but there was a significant decrease in isokinetic torque (8.45 Nm). There was a significant decrease in both mean isometric and isokinetic torque from day 1 to day 3 (12.67 and 13.59 Nm). Contrary to our hypothesis, no benefit from a practice session was found. Healthy, young adults are able to produce peak knee extensor torques on the first day of testing and do not demonstrate any benefit from additional testing. Thus, a practice day preceding isometric and isokinetic knee extensor strength testing may not be necessary when testing healthy, young participants, and may, in fact, negatively impact subsequent strength measurements.

Introduction: It has been shown that older adults have an attenuated hypertrophic response to exercise as compared to young adults. One possible explanation for this response is decreased mechanotransduction into the myocytes due to stiffening of the extracellular matrix with the aging process; thus muscle cells will experience less strain and therefore less mechanical signaling for any applied force. We hypothesize that muscle stiffness decreases response to exercise, and that there is an inverse relationship between strength and muscle stiffness. This would indicate that muscle stiffening plays a role in the development of sarcopenia. Objective: The purpose of this study is to determine the relationship between muscle stiffness and strength in older adults. Methods: Data on muscle stiffness and strength were collected for 19 healthy women (age 70‐80). Stiffness measurements were taken of the Vastus Lateralis using ultrasound elastography (SuperSonic Imagine). Maximal strength was measured using a HUMAC isokinetic dynamometer. Results: Two subjects were excluded for lack of effort during strength testing. There was a moderate correlation (r=‐0.36) between strength and muscle stiffness. There was no relationship (r=‐0.2) between strength and age. Conclusions: This supports the hypothesis that muscle stiffness contributes to decreased response to exercise and the development of sarcopenia.

Hibbert, JE, Klawiter, DP, Schubert, MM, Nessler, JA, and Asakawa, DS. Strength, cardiovascular fitness, and blood lipid measures in law enforcement personnel after a 12-week health promotion program. J Strength Cond Res 36(11): 3105–3112, 2022—Law enforcement personnel often have high rates of cardiovascular disease and injury. Health promotion programs have been found to successfully encourage behavior change among law enforcement personnel, but these programs can often be intensive and expensive. Thus, the purpose of this study was to examine the efficacy of a health promotion program on body composition, metabolic health, muscle strength, and cardiovascular endurance in law enforcement personnel. Active duty officers from a local law enforcement agency were invited to participate in a 12-week health promotion program that included activity tracking and exercise and nutrition education. Eighteen subjects underwent measurements of body composition, V̇o2max through treadmill test, knee extensor strength, and blood lipids. An a priori alpha level for significance was set at 0.05, and comparisons were assessed using paired t-tests. Overall, subjects improved blood lipid levels evidenced by movement of mean values toward established healthy ranges. Although 8 subjects improved their V̇o2max (range: 1.3–30% change), there was large variability and no statistically significant differences in measures of V̇o2max (pre: 38.48 ± 5.86 ml·kg·min−1; post: 39.27 ± 5.26 ml·kg·min−1), body composition (pre: 26.52 ± 8.02% body fat; post: 26.44 ± 7.45% body fat), and strength normalized to body mass (isometric pre: 1.45 ± 0.45; post: 1.08 ± 0.36). Although no significant changes were noted, promising trends in these data suggest that health promotion programs with a modified focus may lead to positive changes in overall health.