Soldiers in combat undergo catabolic conditions due to prolonged physical activity and hypocaloric states which cause decrements in lean mass and physical performance. We investigated the impact of ...HMB on muscle mass and performance along with transcript factors during catabolic conditions. C57BL/6 male mice (N=61, 6wks) underwent a 4‐wk run‐in‐phase to simulate basic training (1h/d for 3d/wk forced wheel walking). Twenty one mice were sacrificed for baseline and the remaining animals were divided into 4 groups (10/group): AL=ad lib fed+exercise (1h/d for 3d/wk), ALH=AL+HMB (0.5 g/kg BW/day), C=caloric restricted (−30% of ad lib groups)+exercise (2 km/d, 6d/wk) and CH=C+HMB to simulate 6 wks of normal and catabolic condition in soldiers. Grip strength and incline plane were assessed pre‐ and post‐experiment. Gastrocnemius (GAS) and soleus (SOL) were isolated. C demonstrated a decline in grip strength (−10% vs pre) whereas CH showed no decrement. Sensorimotor function declined in CH (−12%) and showed a trend for decline in C (p=0.056). A decrease in GAS MyoD mRNA was shown only in C (−44% vs pre) and an increase in SOL MyoD mRNA expression was shown only in CH (+295% vs pre). GAS myogenin mRNA increased in both C (+73% vs pre) and CH (+69% vs pre) while only C increased SOL myogenin mRNA (+98% vs pre). It is suggested that HMB possibly improves myogenesis and maintains strength during a 6‐wk catabolic condition.
Older women exhibit blunted skeletal muscle hypertrophy following resistance training (RT) compared to other age and gender cohorts that is partially due to an impaired regenerative capacity. In the ...present study, we examined whether beta-hydroxy-beta-methylbutyrate (HMB) provision to aged female rodents would enhance regenerative mechanisms and facilitate RT-induced myofiber growth. Nineteen-month old female Sprague-Dawley rats were randomly divided into three groups: HMB (0.48 g/kg/d; n = 6), non-HMB (n = 6), and control (n = 4). HMB and non-HMB groups underwent RT every third day for 10 weeks using a ladder climbing apparatus. Whole body strength, grip strength, and body composition was evaluated before and after RT. The gastrocnemius and soleus muscles were analyzed using magnetic resonance diffusion tensor imaging, RT-PCR, and immunohistochemistry to determine myofiber dimensions, transcript expression, and satellite cells/myonuclei, respectively. ANOVAs were used with significance set at p < 0.05. There were significant time effects (pre vs. post) for whole body strength (+262%), grip strength (+17%), lean mass (+20%), and fat mass (-19%). Both RT groups exhibited significant increases in the mean myofiber cross-sectional area (CSA) in the gastrocnemius and soleus (+8-22%) compared to control. Moreover, both groups demonstrated significant increases in the numbers of satellite cells (+100-108%) and myonuclei (+32%) in the soleus but not the gastrocnemius. A significant IGF-I mRNA elevation was only observed in soleus of the HMB group (+33%) whereas MGF and myogenin increased significantly in both groups (+32-40%). Our findings suggest that HMB did not further enhance intense RT-mediated myogenic mechanisms and myofiber CSA in aged female rats.PUBLICATION ABSTRACT
Purpose: The purpose of this investigation was to examine the effects of a submaximal running warm-up on running performance in male endurance athletes (n = 16, Mage = 21 ± 2 years, MVO2max = 69.3 ± ...5.1 mL/kg/min). Method: Endurance performance was determined by a 30-min distance trial after control and submaximal running warm-up conditions in a randomized crossover fashion. The warm-up began with 5 min of quiet sitting, followed by 6 min of submaximal running split into 2-min intervals at speeds corresponding to 45%, 55%, and 65% maximal oxygen consumption (VO2max). A 2-min walk at 3.2 km/hr concluded the 13-min warm-up protocol. For the control condition, participants sat quietly for 13 min. VO2 and heart rate (HR) were determined at Minutes 0, 5, and 13 of the pre-exercise protocol in each condition. Results: At the end of 13 min prior to the distance trial, mean VO2 (warm-up = 14.1 ± 2.2 mL/kg/min vs. control = 5.5 ± 1.7 mL/kg/min) and mean HR (warm-up = 105 ± 11 bpm vs. control = 67 ± 11 bpm) were statistically greater (p < .001) in the warm-up condition compared with the control condition. The distance run did not statistically differ (p = .37) between the warm-up (7.8 ± 0.5 km) and control (7.7 ± 0.6 km) conditions; however, effect size calculation revealed a small effect (d = 0.2) in favor of the warm-up condition. Thus, the warm-up employed may have important and practical implications to determine placing among high-level athletes in close races. Conclusions: These findings suggest a submaximal running warm-up may have a small but critical effect on a 30-min distance trial in competitive endurance athletes. Further, the warm-up elicited increases in physiological variables VO2 and HR prior to performance; thus, a submaximal specific warm-up should warrant consideration.
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