Exercise as a new physiological stimulus for brown adipose tissue activity.

BACKGROUND AND AIM: Brown adipose tissue (BAT) plays a major role in body energy expenditure counteracting obesity and obesity-associated morbidities. BAT activity is sustained by the sympathetic nervous system (SNS). Since a massive activation of the SNS was described during physical activity, we investigated the effect of endurance running training on BAT of young rats to clarify the role of exercise training on the activity and recruitment state of brown cells. METHODS AND RESULTS: Male, 10-week-old Sprague Dawley rats were trained on a motor treadmill (approximately 60% of VO2max), 5 days/week, both for 1 and 6 weeks. The effect of endurance training was valuated using morphological and molecular approaches. Running training affected on the morphology, sympathetic tone and vascularization of BAT, independently of the duration of the stimulus. Functionally, the weak increase in the thermogenesis (no difference in UCP-1), the increased expression of PGC-1α and the membrane localization of MCT-1 suggest a new function of BAT. Visceral fat increased the expression of the FOXC2, 48 h after last training session and some clusters of UCP-1 paucilocular and multilocular adipocytes appeared. CONCLUSION: Exercise seemed a weakly effective stimulus for BAT thermogenesis, but surprisingly, without the supposed metabolically hypoactive effects. The observed browning of the visceral fat, by a supposed white-to-brown transdifferentiation phenomena suggested that exercise could be a new physiological stimulus to counteract obesity by an adrenergic-regulated brown recruitment of adipocytes.

The cardiovascular response to underwater pedaling at different intensities: a comparison of 4 different water stationary bikes.

AIM: Among the fitness activities, cycling in water immersion performed with water stationary bikes (WSB) has become very popular. However, there is a lack of information concerning their physiological demand. The aim of the present study was to assess the cardiovascular responses to four WSBs. METHODS: Twenty-two healthy participants underwent a graded exercise test on a cycle ergometer. Sixteen of them, 8 males (age 31.5 + or - 8.2 years) and 8 females (age 31.9 + or - 5.8 years) with the same level of peak oxygen consumption (VO(2peak)) were chosen and submitted, in random order, to four incremental testing sessions performed with four different models of WSB, one with no resistance (WSB1), two with resistance added to the bottom bracket axle (WSB2 and WSB3), one with resistance added to the pedals (WSB4). The VO(2peak) and heart rate peak (HR(peak)) were measured in all five conditions. RESULTS: Since no significant main effect for gender was detected, the data were grouped and analyzed all together. No significant differences were found in VO(2peak) and HR(peak) within the five testing conditions, whilst time to exhaustion (P<0.01) and pedaling frequency (RPM) at volitional exhaustion (P<0.01) were both significantly different across the four WSBs. When pedaling at 70 RPM, the oxygen consumption and heart rate response (as % of VO(2peak) and HR(peak)) were approximately 45% and 60% for WSB1, 60% and 70% for WSB3, 90% and 90% for WSB2 and WSB4, respectively. CONCLUSIONS: The present results provide useful information for instructors and practitioners because they demonstrate that different models of WSBs could elicit very different cardiovascular responses.