Changes in Lean Mass and Serum Myostatin with Habitual Protein Intake and High-Velocity Resistance Training.

OBJECTIVES: Examine the associations between dietary protein intake, lean mass (LM), and serum myostatin (Mstn) levels among community-dwelling older adults participating in a 20-week high-velocity resistance training (HVRT) program. DESIGN, SETTING, AND PARTICIPANTS: This longitudinal study consisted of 33 community-dwelling, older adults (mean age 77.0 years, SD = 6.4); all of which obtained physician clearance prior to study participation. MEASUREMENTS: Twenty-five females and eight males were randomized to a control (CON) or HVRT group. Anthropometric measures were obtained via dual energy x-ray absorptiometry (DXA) and peripheral venous blood draw used for serum myostatin analysis. Exercise was performed twice per week for 20 consecutive weeks. Food intake estimation with a diet history questionnaire (DHQ) was used for protein intake comparison to the recommended dietary allowance (RDA). All measures were recorded both prior to and following study participation. RESULTS: Altogether, protein was consumed in amounts more generous (1.01 ± 0.47 g·kg-1·d-1) than that of the RDA (0.8 g·kg-1·d-1). As a result of significant LM differences among men and women (p < 0.01), additional data were analyzed specific to sex. Serum myostatin was greater among females (6681.8 ± 3155.0 pg·mL-1) than males (5560.0 ± 2946.1 pg·mL-1); however, these values were not significantly different (p = 0.39). Combined, protein consumption and serum myostatin did not significantly influence LM among males (p = 0.09) or females (p = 0.71). Irrespective of training group, significant changes were not exhibited in dietary intake patterns, LM, or serum myostatin. CONCLUSIONS: Contrary to the proposed hypothesis, results suggest protein consumption and circulating serum myostatin levels did not significantly influence LM among older adults. Although HVRT positively impacts LM, neither exercise group displayed significant changes in LM. Therefore, further research is needed examining dietary intake, exercise modality, and myostatin downregulation as non-pharmacological approaches to combating sarcopenia.

The effects of power and strength training on bone mineral density in premenopausal women.

AIM: The purpose of this 48-week exercise intervention was designed to examine the effects of power and resistance training on bone mineral density (BMD). METHODS: Premenopausal women were recruited and randomly assigned to either a power (N.=8) or resistance (N.=11) training group. The power exercises included jumping rope, skipping, hopping, and other power-type exercises. The resistance training group performed 8-10 whole-body strengthening exercises at 70% one-repetition maximum (1RM). Before and after the exercise intervention, BMD was measured via dual energy x-ray absorptiometry (DXA) for the total-body, lumbar spine, left femoral neck, and left greater trochanter. Muscular strength was measured by hand grip dynamometer and 1RM of chest press and leg press. Muscular power was assessed by the Margaria-Kalamen stair climb test. Data were analyzed using repeated measures ANOVA. RESULTS: There were no statistical differences between the two training groups for any of the BMD measurements. Chest press strength was different between the two groups, increasing 6.41 and 1.1kg for the resistance and power groups, respectively over the course of the training period (F[1.15]=9.44, P<0.01). There was a significant time effect for leg press 1RM (F[1.15]=6.04, P=0.03). The participants increased by 12.37kg after the 48-week intervention. Hand grip strength also increased after the study intervention (F[1.16]=46.32, P<0.01). CONCLUSION: The results of this study suggest that power and resistance training are comparable techniques for maintaining bone density.

Relationships among strength, endurance, weight and body fat during three phases of the menstrual cycle.

The purpose of this study was to investigate the relationships among body weight, body fat, and dynamic strength and muscular endurance during different phases of the menstrual cycle. Twenty-one female subjects, ages 18-36, with normal menstrual cycles and no dysfunction were tested for strength and endurance of the knee flexors and extensors on a Cybex II isokinetic dynamometer. Body weight and percent body fat were also assessed. Each subject was tested at three speeds (60 degrees, 180 degrees, and 240 degrees/sec) during three phases of the menstrual cycle: mensus (within 24 hours of onset); ovulation (13-14 days from onset); and luteal (10 days from ovulation). The data were analyzed descriptively and by Pearson Product-Moment Correlations with each phase of the cycle and between cycle phases. Results indicated high correlations among most strength measures at the three test speeds for each phase during the cycle and between the cycle phases. Overall, the different phases of the menstrual cycle had little or no effect upon the relationships among body weight, percent body fat, knee extension and flexion strength or endurance.

The relationship of maternal exercise on labor, delivery and health of the newborn.

Thirty women were interviewed and divided into active and sedentary groups. Pre-delivery data, information regarding labor and delivery, Apgar scores of the newborn and perceived exertion during labor were recorded and statistically analyzed. Neonates of active women showed slightly higher one-minute Apgars and no difference in fetal weight or five-minute Apgars. Active women indicated lower perceived exertion during labor, longer delivery times and no differences in gestational length, maternal weight gain and time during the first stage of labor. Maternal weight gain in both groups correlated positively with fetal weight. A higher fetal weight indicated a slightly higher five-minute Apgar. Primaparas showed no difference in the first stage of labor although longer delivery time was noted. No differences in levels of medication during labor were revealed although the youngest and oldest subjects required cesarean delivery. Obese women labored longer, indicated higher perceived exertion and higher fetal weights.

Dynamic strength and work variations during three stages of the menstrual cycle.

The purpose of this article was to investigate the effects of three different phases of the menstrual cycle on dynamic strength and work performance of the knee flexors and extensors. Twenty-one women (18-36 years of age) were tested for dynamic strength and endurance on a Cybex II isokinetic dynamometer at speeds of 60, 180, and 240 degrees /sec. Each subject was tested within 24 hours from the onset of the menses, at the time of ovulation, and during the luteal phase. Strength was determined by peak torque values of knee flexion and extension at the three speeds. Flexion and extension endurance ratios and a work ratio was determined at a speed of 240 degrees /sec. ANOVA failed to show any significant differences among the strength variables during the three phases of the menstrual cycle. The endurance ratios indicated that peak torque values were less than two-thirds of original strength at the end of 20 repetitions. Flexors fatigued slightly less than extensors. There were no significant differences in work ratios among the three phases. Thus it was concluded that the active woman with a normal cycle should experience no discernible change in strength and work performance as a result of cycle changes.J Orthop Sports Phys Ther 1988;10(4):113-116.