Analysis of power output time series in response to supramaximal exercise: an approach through dynamic factor analysis.

The responses to supramaximal exercise testing have been traditionally analyzed by means of standard parametric and nonparametric statistics. Unfortunately, these statistical approaches do not allow insight into the pattern of variation of a given parameter over time. The purpose of this study was to determine if the application of dynamic factor analysis (DFA) allowed discriminating different patterns of power output (PO), during supramaximal exercise, in two groups of children engaged in competitive sports: swimmers and soccer players. Data derived from Wingate testing were used in this study. Analyses were performed on epochs (30 s) of upper and lower body PO obtained from twenty two healthy boys (11 swimmers and 11 soccer players) age 11-12 years old. DFA revealed two distinct patterns of PO during Wingate. Swimmers tended to attain their peak PO (upper and lower body) earlier than soccer players. As importantly, DFA showed that children with a given pattern of upper body PO tend to perform similarly during lower body exercise.

Influence of long-term exercise training on submaximal and peak aerobic capacity and locomotor economy in adult males with Down's syndrome.

BACKGROUND: The effect of exercise training on submaximal aerobic capacity and locomotor economy (LE) of Down's syndrome (DS) individuals has never been analyzed and their peak physiological adaptability to long-term physical conditioning is poorly understood. Thus the purpose of the present study was to determine whether DS males could improve their submaximal and peak aerobic capacity and LE after a 28-week training program. MATERIALS/METHODS: Twelve Caucasian DS males aged 34.5+/-7.0 years (range: 21-49) underwent a 28-week aerobic exercise intervention consisting of two 40-min sessions of ergometer conditioning per week. Body composition was assessed by anthropometric and bioelectrical impedance spectroscopic measurements. Pre- and post-training submaximal physiological response was determined by means of a 2.5-km/h treadmill flat-walk. Graded maximal exercise tests were performed to investigate the participants' peak exercise capacity. Multivariate analyses of variance were performed to explore the influence of training on the subjects' body composition and submaximal and peak aerobic capacity not. RESULTS: After training, the participants decreased their fat mass from 27.3+/-11.2 to 23.5+/-11.1% (p<0.01) and increased their absolute fat-free mass from 48.4+/-8.6 to 50.8+/-9.3 kg (p<0.01). There were no differences between pre- and post-training locomotor economy (LE). However, the subjects decreased their respiratory exchange ratio from 0.91+/-0.11 to 0.83+/-0.05 (p<0.05) while exercising at the same submaximal workload. Peak exercise capacity improved 27.8% following training (p<0.01). CONCLUSIONS: Despite improving body composition and peak cardiovascular fitness and lipidic oxidation during submaximal exercise, DS males were unable to modify their LE after 28 weeks of exercise intervention.

Between-day variability of net and gross oxygen uptake during graded treadmill walking: effects of different walking intensities on the reliability of locomotion economy.

There have been few studies of clinical relevance conducted on the reliability of walking economy. This study was designed to determine if walking economy reproducibility increases as a function of walking intensity, and if there is any advantage in expressing walking economy as net oxygen uptake (VO2) rather than gross VO2 for reproducibility purposes. Sixteen participants (9 males, 7 females; mean age, 22.3 +/- 4.3 years) performed resting, submaximal, and maximal protocols on 2 different days, under identical circumstances, within a 7 day period. The submaximal protocol consisted of five 5 min walks (4 km.h-1) at treadmill grades of 0%, 2.5%, 5.0%, 7.5%, and 10%. Findings indicate that increments of 2.5% in treadmill grade effectively increased gross and net VO2 during walks. The reliability of net and gross measures increased as a function of walking relative intensity, reporting intraclass correlation coefficients ranging from 0.89-0.94 and 0.87-0.91, respectively, and mean coefficients of variation (CV) from 7.3%-3.6% and 8.8%-4.4%, respectively. There were no significant differences between the CV for gross and for net VO2 across the spectrum of walking relative intensities. In conclusion, there is no advantage of expressing walking economy as net VO2 instead of gross VO2 for reproducibility purposes, and a single treadmill testing session at a constant speed of 4 km.h-1 is reliable for estimating group and individual walking economy, particularly at higher percent grades.