Physical activity accumulation in bouts and nonbouts and relation to cardio respiratory fitness of obese adults

PURPOSE: Accumulating physical activity (PA) in bouts of at least 10 min seems to be potentially more helpful for health promotion because of its higher relation to obesity markers (Strath, 2008). Moreover, the risk of being obese increased with decreasing PA level obtained in bouts of at least 10 min (Hansen, 2013). In contrast, an association between overall PA and metabolic syndrome has been studied, steeper in individuals with lower cardiorespiratory fitness (V’O2max) level (Franks, 2004), and recent literature also suggests than even PA in nonbouts may be beneficial for health (Loprinzi, 2013). The aim of this study was to compare the effects of PA in bouts (≥10 min) and in nonbouts (<10 min) on V'O2max in a population of obese adults. METHODS: Obesity was defined as a BMI of ≥30 (WHO, 2000). 14 obese adults (mean±SE: age 27.9 ± 1.6 y; BMI 39.3 ± 1.5 kg*m-2; V’O2max 31.33±1.55 mL*kg-1*min-1; V’O2max 3.42±0.15 L*min-1) wore an activity monitor that combined HR and movement signals for 7 consecutive days to obtain time spent in moderate and vigorous physical activity (MVPA). MVPA were analyzed in bouts of at least 10 consecutive min (MVPA10) and in overall minutes (MVPAall). V’O2max, expressed in relative (mL*kg-1*min-1) and absolute values (L*min-1), was determined by indirect calorimetry using a maximal treadmill test. RESULTS: MVPA10 was significantly lower than MVPAall (MVPA10: 44.7±10.0 min*day-1; MVPAall: 175.4±21.0 min*day-1; p<0.0001). Only MVPAall significantly (p<0.0001) exceeded current PA guidelines of accumulating a minimum of 30 min of daily MVPA in bouts of 10 min or more and was positively correlated with V’O2max (r=0.567, p<0.05). The regression analyses revealed that only the level of physical activity of people who accumulated 30 min of MVPA in nonbouts was positively associated with absolute V’O2max (R2=.264; β=5.674, p<0.05). Each 100 min of overall MVPA was associated with an increase of 0.4 L*min-1 of V’O2max. CONCLUSIONS: Our data indicate that nonbouts activity seems to play some role in maintaining an adequate level of cardiorespiratory fitness, at least in obese young adults. These results have to be considered when a tailored intervention in an obese population must be planned, suggesting the use of both a lifestyle model and a structured exercise model for health interventions (Loprinzi, 2013).