Mouse Chromosome 11

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46996/1/335_2004_Article_BF00648429.pd

Age effect on myocellular remodeling: Response to exercise and nutrition in humans

Aging is associated with decline in muscle mass and muscle functions. Muscle strength declines disproportionate to the decline in muscle mass indicating that muscle quality or protein quality also declines with age. Human studies have shown a progressive decline in muscle protein synthesis including proteins in the contractile apparatus and mitochondria with age. However, the decline in muscle protein synthesis is disproportionate to the decline in muscle mass that occurs with age prompting to hypothesize that muscle protein degradation also declines with age. A decline in mitochondrial capacity to synthesize ATP is likely a limiting factor of both synthesis and degradation, which are ATP dependent processes. In support of the above hypothesis, several studies have shown a decline in whole body protein turnover (synthesis and degradation). The timely and efficient degradation of irreversibly damaged or modified proteins is critical to maintain the quality of protein. It is proposed that a failure to degrade the damaged proteins and replacing them with newly synthesized proteins contribute to age related decline in muscle mass and quality of muscle proteins. The underlying molecular mechanism of these age related changes in human muscle needs further investigation

Differences emerge in visceral adipose tissue accumulation after selection for innate cardiovascular fitness

Cardiorespiratory fitness (CRF) has been reported to be inversely associated with visceral adipose tissue (VAT) accumulation, independent of body weight. However, the confounding effect of physical activity on the association between CRF and VAT remains inadequately addressed. Based on VO(2max), 143 sedentary, overweight women were dichotomized into high-fit (HF) and low-fit (LF) groups. Body composition and VAT were measured using DEXA and CT, respectively, and activity-related energy expenditure (AEE) was calculated using the doubly-labeled water technique. No differences were observed between HF and LF for BMI (HF: 28.2 ± 1.3; LF: 28.3 ± 1.31 kg/m(2)), total body weight (HF: 77.5 ± 6.8; LF: 77.9 ± 7.3 kg), total fat mass (HF: 33.5 ± 5.1; LF: 33.9 ± 4.4 kg), or AEE (HF: 439.9 ± 375.4; LF: 517.9 ± 298.7 kcal/day). Significant differences in visceral adiposity (HF: 68.5 ± 30.4; LF: 91.2 ± 31.8 cm(2); P < 0.001) and insulin sensitivity (HF: 5.1 ± 1.8; LF: 3.1 ± 2.4 S(I) ×10(−4)min(−1)/μIU/ml; P < 0.01) were observed between the high- and low-fitness groups, independent of age, race, and AEE. This study affirms previous findings that CRF is an important determinant of the accumulation of VAT, and this relationship is independent of physical activity

Reliability of the VmaxST portable metabolic measurement system

The purpose of this study was to evaluate the reliability of the VmaxST portable metabolic measurement system. Forty-five healthy adults (age = 25.7 ± 5.9 yr; height = 171.8 ± 9.1 cm; weight = 69.6 ± 12.8 kg; VO(2)peak = 40.7 ml/kg/min; percent fat = 21.7 ± 11.0) performed two separate and identical exercise routines on different days consisting of treadmill walking at 2.0 mph (53.6 m/min), 3.0 mph (80.5 m/min), and 4.0 mph (107.3 m/min) and running at 6.0 mph (160.9 m/min). V(E) and gas exchange were measured continuously breath-to-breath. A random effects model on log-transformed data yielded coefficients of variation (CV) and intraclass correlation coefficients (ICC) for VO(2) and V(E) of 5.2–7.6%, and 0.77–0.92, respectively, for all walking and running trials. For VCO(2), CVs were higher (10–12%) and ICCs lower (0.70–0.81). Ordinary least squares regression between the individual difference scores and the individual mean scores for V(E), VO(2) and VCO(2), respectively, indicated no systematic bias (all p > 0.05). Bland-Altman analysis also illustrated no systematic bias between repeated measurements. The VmaxST provides reliable measurements of VO(2) and V(E) duringduring walking and running eliciting V(E) and VO(2) at least up to ~56 and 2.2 l/min, respectively. The system appears to be less reliable for measuring VCO(2)