Oxygen uptake, respiratory exchange ratio, or total distance: a comparison of methods to equalize exercise volume in Wistar rats

This study compared strategies to equalize the volume of aerobic exercise performed with different intensities by Wistar rats, based on the distance covered during exercise bouts and energy expenditure (EE, isocaloric sessions) obtained from oxygen uptake (V̇O2) or respiratory exchange ratio (RER). Thirty-three male rats (270.5±12.8 g) underwent maximal exercise tests to determine V̇O2 reserve (V̇O2R), being randomly assigned to three groups: moderate-intensity continuous exercise at speed corresponding to 50% V̇O2R (MIC; n=11); high-intensity continuous exercise at 80% V̇O2R (HIC; n=11); and high-intensity intermittent exercise (HII; n=11) at 60% V̇O2R (3 min) and 80% V̇O2R (4 min). Exercise duration was calculated individually to elicit EE of 5 kcal in each session. No difference between groups was found for total running distance (MIC: 801±46, HIC: 734±42, HII: 885±64 m; P=0.13). Total EE measured by RER was systematically underestimated compared to values obtained from V̇O2 (HII: 4.5% and MIC: 6.2%, P<0.05). Total EE (calculated from V̇O2), and duration of HIC bouts (2.8 kcal and 30.8±2.2 min) were lower (P<0.0001) than in MIC (4.9 kcal and 64.7±1.8 min) and HII (4.7 kcal and 46.9±2.2 min). Predicted and actual values of total V̇O2, total EE, and duration of isocaloric sessions were similar in MIC and HII (P>0.05), which were both higher than in HIC (P<0.0001). In conclusion, the time to achieve a given EE in exercise bouts with different intensities did not correspond to the total distance. Therefore, the volume of aerobic exercise in protocols involving Wistar rats should be equalized using EE rather than total covered distance.

Estudo morfometrico do musculo soleo denervado de ratos tratados pela associacao de metformina e estimulacao eletrica / Morphometric study os rats denervated soleus muscle treated by association of metformin and electrostimulation

Diversos estudos relatam os efeitos da denervacao sobre a homeostasia energetica do musculo soleo, sendo demonstrado que concomitante ao processo de atrofia ha reducao no metabolismo muscular da glicose e aumento de colageno no endomisio e perimisio, indicando que a atrofia e acompanhada de alteracoes metabolicas e fibrose. O objetivo deste trabalho foi estudar os efeitos da associacao dos tratamentos com metformina(0,1g/kg) e estimulacao eletrica (f=10Hz, fase=3ms, 20 min/dia) sobre a morfologia e reserva de glicogenio do musculo soleo denervado de ratos. Tratamento com PAS (acido periodico de Schift) foi utilizado para evidenciar reservas de glicogenio, e a densidade de areas das fibras foi obtida pela tecnica morfometrica e analisada pela ANOVA com teste F e teste de Tukey para comparacao das medias. Apos 15 dias, a associacao dos tratemntos nao recuperou o peso do musculo soleo (69,33mg), perdido com a denervacao (63,33mg, p>0,05), no entanto, promoveu aumento de granulos de glicogenio, evidenciando melhora nas condicoes metabolicas das fibras