Knee extensor strength differences in obese and healthy-weight 10-to 13-year-olds.

The purpose of this study was to investigate if obese children have reduced knee extensor (KE) strength and to explore the relationship between adiposity and KE strength. An observational case-control study was conducted in three Australian states, recruiting obese [N = 107 (51 female, 56 male)] and healthy-weight [N = 132 (56 female, 76 male)] 10- to 13-year-old children. Body mass index, body composition (dual energy X-ray absorptiometry), isokinetic/isometric peak KE torques (dynamometry) and physical activity (accelerometry) were assessed. Results revealed that compared with their healthy-weight peers, obese children had higher absolute KE torques (P ≤ 0.005), equivocal KE torques when allometrically normalized for fat-free mass (FFM) (P ≥ 0.448) but lower relative KE torques when allometrically normalized for body mass (P ≤ 0.008). Adjustments for maternal education, income and accelerometry had little impact on group differences, except for isometric KE torques relative to body mass which were no longer significantly lower in obese children (P ≥ 0.013, not significant after controlling for multiple comparisons). Percent body fat was inversely related to KE torques relative to body mass (r = -0.22 to -0.35, P ≤ 0.002), irrespective of maternal education, income or accelerometry. In conclusion, while obese children have higher absolute KE strength and FFM, they have less functional KE strength (relative to mass) available for weight-bearing activities than healthy-weight children. The finding that FFM-normalized KE torques did not differ suggests that the intrinsic contractile properties of the KE muscles are unaffected by obesity. Future research is needed to see if deficits in KE strength relative to mass translate into functional limitations in weight-bearing activities.

Cardiovascular data acquisition in a dynamic motion environment.

INTRODUCTION: One of the challenges in physiological research is the acquisition of good quality, reliable data, especially in the real-world environment. Motor sports provide a unique and challenging environment in which to test the operation and utility of equipment used for physiological data acquisition. Impedance cardiography (IC) is a noninvasive technique for determining stroke volume (SV) and cardiac output (Q). The aim of this feasibility study was to determine if IC could be used to acquire reliable, good quality cardiovascular data in a dynamic motion environment such as in a racing car. This summary overviews the use of a mobile physiological testing apparatus in dynamic real world setting. As reviewed, many physiological indicators have been assessed in the motor racing setting. However cardiovascular outputs including SV and Q have not been measured in such a volatile environment. METHODS: Six professional race car drivers had cardiovascular data (heart rate and SV) acquired via IC while driving their cars under full race-speed conditions. RESULTS: The subjects all completed their driving tasks with no detriment. Despite multiple external influences on cardiovascular function under driving conditions, the data acquired via IC were free from interference, consistent, and within the expected physiological range. DISCUSSION: The results of this study demonstrate that useful cardiovascular data can be successfully acquired via IC in a dynamic motion environment. The potential applications of IC technology in the dynamic motion environments of aviation, space, and motor sports are numerous and diverse. Further research and development will no doubt lead to improved and more widespread applications of IC in the future.