Long-term Effects Of Supervised Endurance Exercise On Peak Oxygen Uptake In Older Adults

Cardiorespiratory fitness (CRF) is a strong predictor of future health; however, it progressively declines with age, and the role of exercise in mitigating this decline is unclear. Controlled studies have shown high-intensity interval training (HIIT) to produce more pronounced effects on CRF compared to moderate-intensity continuous training (MICT). Nonetheless, evidence on the long-term effects of HIIT and MICT on directly measured CRF remains limited. PURPOSE: To evaluate changes in CRF during and after a five-year aerobic exercise intervention in older adults. METHODS: A total of 324 subjects (50% females) with a mean age of 71.6 ± 1.6 years at baseline, from Trondheim, Norway, were randomized to five years of either twice-weekly sessions of HIIT at ∼90% of peak heart rate, MICT at ∼70% peak heart rate, or controls instructed to follow the national guidelines for physical activity. CRF was measured objectively as peak oxygen uptake (VO2peak) at five timepoints. Longitudinal change in VO2peak and between-group differences were assessed using a linear mixed model adjusted for age, gender and cohabitation status. RESULTS: After five years, VO2peak declined by -2.6% (p < 0.05) and -3.8% (p < 0.05) in controls and MICT, respectively, with no significant change in HIIT. Although no between-group differences were observed, there was a strong tendency towards higher VO2peak in HIIT compared to controls (0.98 mL/kg/min, CI: -0.17 to 2.09) and MICT (1.11 mL/kg/min, CI: -0.14 to 2.37). After ten years, VO2peak declined by -17.9% (p < 0.05), -20,5% (p < 0.05), and -15.3% (p < 0.05) in controls, MICT and HIIT, respectively. The decline in VO2peak was smaller in HIIT compared to both controls (1.13 mL/kg/min, CI: 0.01 to 2.21) and MICT (1.65 mL/kg/min, CI: 0.41 to 2.29). No difference was observed in MICT compared to controls after ten years (0.52 mL/kg/min, CI: -1.71 to 0.91). CONCLUSION: The age-related change in VO2peak over a decade is lower in subjects randomized to five years of HIIT compared to MICT and controls. These findings reveal that the beneficial effects of supervised endurance training — at least with HIIT — on CRF remain evident even five years after the intervention ended.