Myriam Guerra

Age-Related Changes in Aerobic Capacity in Individuals with Mental Retardation: A 20-yr Review

INTRODUCTION Persons with mental retardation (MR), particularly individuals with Down syndrome (DS), have been found to have attenuated peak exercise responses in previous research. However, it is unknown if the pattern of age-associated changes in HR or aerobic capacity (VO2peak) is similar to individuals without disabilities. PURPOSE To investigate age-related changes in aerobic capacity in persons with MR, with and without DS, using a retrospective analysis. METHODS Data were collected in university research laboratories, using 180 persons with MR without DS, 133 persons with MR with DS, and 322 persons without disabilities in four age categories: 9-15, 16-21, 22-29, and 30-45 yr. Subjects underwent treadmill testing with peak HR and VO2peak measurements. RESULTS Relative VO2peak was lowest for persons with DS across all age groups. VO2peak did not change after 16 yr in the individuals with DS, whereas the other groups exhibited a slight decline (approximately 10 mL x kg(-1) x min(-1)) with age. Peak HR was overall different between all three groups (P < 0.001), and the youngest age group had the highest peak HR versus the other three age groups (P < 0.0001). CONCLUSIONS Persons with MR without DS exhibit similar age-related changes in VO2peak and peak HR as individuals without disabilities. Similar age-related changes were also observed for peak HR in individuals with DS, despite overall lower levels. However, relative VO2peak did not decline with age in persons with DS, suggesting that aerobic capacity exhibits a different age-related response in individuals with DS.

Sex differences in linear and nonlinear heart rate variability during early recovery from supramaximal exercise.

Women demonstrate greater RR interval variability than men of similar age. Enhanced parasympathetic input into cardiac regulation appears to be not only greater in women, but also protective during periods of cardiac stress. Even though women may have a more favorable autonomic profile after exercise, little research has been conducted on this issue. This study was designed to examine the cardiac autonomic response, in both male and female participants, during the early recovery from supramaximal exercise. Twenty-five individuals, aged 20 to 33 years (13 males and 12 females), performed a 30-s Wingate test. Beat-to-beat RR series were recorded before and 5 min after exercise, with the participants in the supine position and under paced breathing. Linear (spectral analysis) and nonlinear analyses (detrended fluctuation analysis (DFA)) were performed on the same RR series. At rest, women presented lower raw low frequency (LF) power and higher normalized high frequency (HF) power. Under these conditions, the LF/HF ratio of women was also lower than that of men (p<0.05), but there were no differences in the short-term scaling exponent (α1). Even though both sexes showed a significant modification in linear and nonlinear measures of heart rate variability (HRV) (p<0.05), women had a greater change in LF/HF ratio and α1 than men from rest to recovery. This study demonstrates that the cardiac autonomic function of women is more affected by supramaximal exercise than that of men. Additionally, DFA did not provide additional information about sexual dimorphisms, compared with conventional spectral HRV techniques.