Skeletal muscle phosphocreatine recovery after submaximal exercise in children and young and middle-aged adults.

CONTEXT

Elderly subjects have reduced mitochondrial function. However, it remains unclear whether the decline in mitochondrial function begins earlier in the life span.

OBJECTIVE

The objective of the study was to determine skeletal muscle mitochondrial oxidative phosphorylation by (31)phosphorous-magnetic resonance spectroscopy (MRS) across a variety of age groups.

DESIGN

This was a cross-sectional study of 121 healthy normal-weight and overweight individuals from age 8 to 55 yr.

SETTING

The study was conducted at a single university medical center in Boston, MA.

PARTICIPANTS

Participants included 68 children and 53 adults from the Boston community.

INTERVENTIONS AND MAIN OUTCOME MEASURES

Phosphocreatine (PCr) recovery was evaluated by (31)phosphorous-MRS after submaximal exercise. Subjects were also evaluated with anthropometric measurements, metabolic profiles, and measures of physical activity.

RESULTS

PCr recovery determined by (31)phosphorous-MRS is positively associated with age in univariate analysis in a cohort of individuals aged 8-55 yr (r = +0.55, P < 0.0001). Stratification of subjects into four age groups (prepubertal and early pubertal children, pubertal and postpubertal children < 18 yr, young adults aged 18-39 yr, and middle aged adults aged 40-55 yr) demonstrates prolongation of PCr recovery with increasing age across the four groups (P < 0.0001 by ANOVA). The relationship between PCr recovery and age remains strong when controlling for gender; race; ethnicity; body mass index; measures of physical activity and inactivity; and anthropometric, nutritional, and metabolic parameters (P < 0.004).

CONCLUSIONS

Skeletal muscle PCr recovery measured by (31)phosphorous-MRS is prolonged with age, even in children and young adults.