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This study aimed to determine whether high-intensity dumbbell exercise involving both concentric and eccentric contractions would provide a temporary alleviation of delayed-onset muscle soreness (DOMS). It also examined the effect of alleviated muscle soreness on dynamic muscle performance using a stretch-shortening cycle (SSC; peak angular acceleration and velocity of the elbow during both lowering and concentric phases) to provide indirect evidence that DOMS contributes to the dynamic performance decrement after eccentric injury. Thirteen untrained adults performed 30 maximal isokinetic eccentric contractions of the elbow flexors to induce eccentric damage. Five sets of arm curls using a dumbbell (equivalent to 70% of isometric maximal voluntary contraction) were then performed until failure on days 1, 2, 3, and 5 of recovery. Muscle soreness significantly decreased after each session of dumbbell exercise (p = 0.001). Isometric strength further decreased immediately after dumbbell exercise, indicating muscle fatigue (p < 0.001). Dynamic performance variables were less affected by fatigue, however, with performance being reduced only for peak lowering velocity (p < 0.001). Other measures of dynamic performance were relatively constant after dumbbell exercise, particularly on days 2 and 3 when soreness was greatest. It was concluded that high-intensity concentric/eccentric dumbbell exercise was able to temporarily alleviate DOMS and that this reduction in soreness served to counter the effect of peripheral muscle fatigue during dynamic activities. Practical applications of this study are that after eccentric damage, alleviation of muscle soreness through an optimal warm-up may be helpful to temporarily recover dynamic muscle performance. Free-weight loading is one suggested technique to temporarily manage DOMS. KEY WORDS exercise-induced analgesia, DOMS, isometric strength, stretch-shortening cycle

This study examined the recovery of static and dynamic muscle performance after eccentric damage with and without repeated exercise, using different exercise modes between the initial and subsequent exercise bouts. Twelve nonweight-trained adults performed both control and repeated exercise conditions. Soreness, limb circumference, static joint angles, creatine kinase (CK), isometric strength, and dynamic muscle performance involving a stretch-shortening cycle (SSC) were monitored for 7 days to evaluate the recovery. After baseline measures, subjects performed 30 maximal isokinetic eccentric contractions (90 degrees/second) of the elbow flexors in each experiment. For the control condition, no treatment was applied. For the repeated exercise condition, 5 sets of arm curls using dumbbells (70% isometric maximal voluntary contraction of each testing day) were performed until failure on days 1, 2, 3, and 5 of recovery. Significant condition vs. time interactions existed in circumference (p = 0.012), static relaxed angle (p = 0.013), isometric strength (p = 0.039), and dynamic extension angle (p = 0.039), suggesting a slightly delayed onset of recovery with the repeated exercise. SSC performance changed more in parallel with soreness after eccentric exercise than did the other measures. It was concluded that the repeated bout effect was present, although slightly reduced, when subsequent exercise performed before recovery was intense and differed in mode from the initial eccentric exercise. Practical applications of this research are that resistance training may be continued after eccentric damage; however, a minor delay in the onset of recovery may occur depending on training modes. Muscle soreness is a good indicator of performance decrement during dynamic movements following eccentric damage. KEY WORDS DOMS, strength, stretch-shortening cycle, repeated bout effect

The present study was performed to investigate the involvement of SNARK in physical activity levels in mice. To examine the acute effect of SNARK deficiency on voluntary running, Snark-deficient mice ([Snark.sup.+/-] : n = 16) and their wild-type counterparts ([Snark.sup.+/+] : n = 16) were assigned to sedentary or exercise (1 wk voluntary wheel running) groups. In addition, to clarify the differences in voluntary running activity and its effect between genotypes, mice ([Snark.sup.+/+] : n = 16; [Snark.sup.+/-] : n = 16) were also kept in individual cages with/without a running wheel for 5 mo. Unexpectedly, in both voluntary running experiments, running distances were increased in [Snark.sup.+/-] mice compared with [Snark.sup.+/+] mice. Under sedentary conditions, body and white adipose tissue weights were increased significantly in [Snark.sup.+/-] mice. However, no significant differences were observed between the two genotypes under exercise conditions, and the values were significantly less than those under sedentary conditions in the long-term experiment. In the short-term experiment, serum interleukin-6 level in exercised [Snark.sup.+/+] mice was the same as that in sedentary [Snark.sup.+/+] mice, whereas that in sedentary [Snark.sup.+/-] mice was significantly lower than in the other groups. In contrast, serum leptin level was reduced significantly in exercised [Snark.sup.+/-] mice compared with sedentary [Snark.sup.+/-] mice. The results of this study demonstrated that exposure to an environment that allows voluntary exercise promotes increased running activity and prevents obesity in Snark-deficient mice. SNARK; adenosine 5'-monophosphate-activated protein kinase; voluntary running activity; adipose tissue; adipokine

This study aimed to assess (1) blood pressure between young, current athletes, and non‐athletes early in life; (2) hypertension prevalence between former athletes and the general population later in life; and (3) understand the mechanisms between exercise training and hypertension risks in the form of DNA methylation. Study 1: A total of 354 young male participants, including current athletes, underwent blood pressure assessment. Study 2: The prevalence of hypertension in 1269 male former athletes was compared with that in the Japanese general population. Current and former athletes were divided into three groups: endurance‐, mixed‐, and sprint/power‐group. Study 3: We analyzed the effect of aerobic‐ or resistance‐training on DNA methylation patterns using publicly available datasets to explore the possible underlying mechanisms. In young, current athletes, the mixed‐ and sprint/power‐group exhibited higher systolic blood pressure, and all groups exhibited higher pulse pressure than non‐athletes. In contrast, the prevalence of hypertension in former athletes was significantly lower in all groups than in the general population. Compared to endurance‐group (reference), adjusted‐hazard ratios for the incidence of hypertension among mixed‐ and sprint/power‐group were 1.24 (0.87–1.84) and 1.50 (1.04–2.23), respectively. Moreover, aerobic‐ and resistance‐training commonly modified over 3000 DNA methylation sites in skeletal muscle, and these were suggested to be associated with cardiovascular function‐related pathways. These findings suggest that the high blood pressure induced by exercise training at a young age does not influence the development of future hypertension. Furthermore, previous exercise training experiences at a young age could decrease the risk of future hypertension. [ABSTRACT FROM AUTHOR]

Nakagata, T, Yamada, Y, and Naito, H. Estimating energy cost of body weight resistance exercise using a multistage exercise test. J Strength Cond Res 36(5): 1290–1296, 2022—The purpose of this study was to examine energy cost of body weight resistance exercises with slow movement in young men using a multistage exercise test. Fifteen men aged 21–29 years performed 3 exercises (heel-raise, squat, and push-up) at different frequencies (1, 2, 3, 4, 5, and 6 repetitions·min−1). Oxygen consumption was measured using indirect calorimetry; we then computed a simple linear regression between aerobic energy expenditure (EE) and repetition frequency. The slope coefficient in the regression represents the energy cost of those exercises; we compared the extrapolated EE for a frequency of 10 repetitions·min−1. Gross EE increased linearly with repetition frequency in all subjects (y = a x + b). Energy cost was significantly greater in the case of the push-up than in the case of the squat {squat: 0.50 ± 0.14 (95% confidence interval [CI], 0.42–0.58); push-up: 0.77 ± 0.20 kcal (95% CI, 0.66–0.88); and the heel-raise elicited the lowest energy cost: 0.13 ± 0.04 kcal (95% CI, 0.11–0.15)}. Extrapolated EE at 10 repetitions·min−1 was 2.7 ± 0.5 kcal (2.3 metabolic equivalents [METs]), 6.3 ± 1.4 kcal (5.4 METs), and 9.2 ± 2.1 kcal (7.8 METs), respectively, according to the regression based on aerobic EE. These results will be useful for health professionals in prescribing resistance exercise programs improving muscle fitness and considering for weight management. [ABSTRACT FROM AUTHOR]

This study examined whether the exercise-increased extracellular heat shock protein 72 (eHsp72) levels in rats was associated with body temperature elevation during exercise. In all, 26 female Sprague-Dawley rats (3 mo old) were assigned randomly to control (CON; n = 8), exercise under warm temperature (WEx; n = 9), or exercise under cold temperature (CEx; n = 9). The WEx and CEx were trained at 25[degrees]C or 4[degrees]C, respectively, for nine days using a treadmill. Before and immediately after the final exercise bout, the colonic temperatures were measured as an index of body temperature. The animals were subsequently anesthetized, and blood samples were collected and centrifuged. Plasma samples were obtained to assess their eHsp72 levels. Only the colonic temperature in WEx was increased significantly (P < 0.05) by exercise. The eHsp72 level in WEx was significantly higher (P < 0.05) than that of either the CON or CEx. However, no significant difference was found between CON and CEx. Regression analyses revealed that the eHsp72 level increased as a function of the body temperature. In another experiment, the eHsp72 level of animals with body temperature that was passively elevated through similar kinetics to those of the exercise was studied. Results of this experiment showed that mere body temperature elevation was insufficient to induce eHsp72 responses. Collectively, our results suggest that body temperature elevation during exercise is important for induction of exercise-increased eHsp72. In addition, the possible role of body temperature elevation is displayed when the exercise stressor is combined with it. running exercise; warm; cold; ELISA; stress proteins

Protein kinase B [PKB, also known as Akt (PKB/Akt)] and calcineurin (CAN) are postulated to play important roles in integrating intracellular signaling in skeletal muscle in response to disuse and increased muscle loading. These experiments investigated changes in signal transduction of the downstream pathways of PKB/Akt and CaN during recovery following disuse-induced muscle atrophy. A 10-day period of hindlimb unloading (HLU) via tail suspension (male rats) was used to produce soleus muscle atrophy. Muscle recovery was achieved by returning animals to normal ambulation for 3-10 days. HLU resulted in significant muscle atrophy and a slow-to-fast fiber transition as revealed by appearance of type IId/x and IIb myosin heavy chain (MHC) isoforms. Muscle mass in HLU animals recovered to control (Con) levels after 10 days of reloading, but the fast-to-slow shift in muscle MHC was incomplete, as indicated by the continued presence of type IId/x MHC. Ten days of HLU resulted in a significant decrease (-43%) in muscle levels of phosphorylated PKB/Akt. In contrast, muscle levels of phosphorylated PKB/Akt were greater (+56%) in HLU than in Con animals early after the onset of reloading (3 days). Soleus levels of phosphorylated [p70.sup.S6K] were significantly higher (+26%) in HLU animals after 3 days of muscle reloading. Muscle levels of phosphorylated PKB/Akt and phosphorylated [p70.sup.S6K] returned to Con levels by day 10 of recovery. Moreover, muscle CaN levels were significantly higher than Con levels after 10 days of muscle reloading. These findings are consistent with the hypothesis that PKB/Akt and its downstream mediators are active in the regrowth of muscle mass during the early periods of recovery from muscle atrophy. Our data support the concept that CaN is involved in muscle remodeling during the later phases of recovery from disuse muscle atrophy. regrowth; skeletal muscle; hindlimb unloading