Abstract 057: Towards an Optimal Exercise Strategy for Reversing Low Cardiorespiratory Fitness: Distinct Effects of Exercise Volume and Intensity

Abstract

Although a majority of adults increase cardiorespiratory fitness (CRF; VO2 peak) in response to an increase in daily physical activity, the optimal exercise strategy for reversing low CRF is unknown. We performed a randomized, controlled trial designed to study the separate effects of habitual exercise differing in dose (energy expenditure, kcal/session) and intensity (relative to VO2max) on CRF. We randomly assigned sedentary, abdominally obese men and women to one of the following 4 conditions: 1) No-exercise control (C), 2) Low volume, low intensity exercise (LVLI: 180 [[female symbol]] and 300 [[male symbol]] kcal @ 50% VO2 peak), 3) High volume, low intensity exercise (HVLI: 360 [[female symbol]] and 600 [[male symbol]] kcal @ 50% VO2 peak), 4) High volume, high intensity (HVHI: 360 [[female symbol]] and 600 [[male symbol]] kcal @ 75% VO2 peak). All participants were required to exercise under supervision 5 times per week for 24 weeks. Adherence to exercise averaged 95% across groups. Exercise dose and intensity achieved was not different from that prescribed regardless of group. The minutes exercised per session were 30±7 in LVLI, 51±16 in HVLI and 36±11 in HVHI. A marked variability in CRF response to exercise was observed independent of group (Figure). Compared to controls, CRF increased within all exercise conditions (P<0.05). However, the CRF increase within the HVHI group (0.61±0.30L/min) was greater than both the HVLI (0.42±0.32L/min) and LVLI (0.26±0.28L/min) groups (P<0.05). Thus, despite matching exercise volume within the HVHI and HVLI groups, exercise at 75% of VO2peak was associated with a marked increase in CRF by compared to exercise at 50%. Given that the time required to achieve the energy expenditure within the HVHI group was 30% less than the HVLI group (36 vs 51 min), these findings have important implications for allied health professionals seeking options for prescribing exercise to improve a major risk factor for morbidity and mortality, cardiorespiratory fitness.