Six weeks of high intensity interval training (HIIT) facilitates a four year preservation of aerobic capacity in sedentary older males: a reunion study

Long-term implications of acutely increased cardiorespiratory fitness following short-term exercise interventions in older adults are unknown. In this study, we examined peak oxygen uptake (VO2peak) four ‘free-living’ after a high intensity interval training (HIIT) intervention. Seventeen lifelong exercisers (LEX) and 17 previously sedentary (SED) males (55–74 years of age in 2012) were tested four years (phase D) after our previous experiment which included 6-weeks of aerobic moderate intensity exercise (phase B), followed by 6-weeks of HIIT (phase C). At all stages, a standard incremental exercise protocol on a cycle ergometer was completed to determine VO2peak. SED (P = 1.000, Cohen's d = 0.01) and LEX (P = 1.000, Cohen's d = 0.11) VO2peak at phase D was not different from phase A (enrolment). SED experienced a large decrease in VO2peak from phase C to phase D (32 ± 6 ml·kg·min−1 to 27 ± 6 ml·kg·min−1 [P < 0.001, Cohen's d = 0.81]). LEX experienced a small decrease in VO2peak from phase C to phase D (42 ± 7 ml·kg·min−1 to 39 ± 9 ml·kg·min−1 [P < 0.001, Cohen's d = 0.46]). At phase D, LEX had greater VO2peak than SED (P < 0.001, Cohen's d = 1.73). The proportion of subjects who reported discontinuing training, maintaining moderate training, and maintaining HIIT differed between groups (P = 0.023), with LEX self-reporting more HIIT, and SED self-reporting more discontinuation from exercise. Those who continued exercising experienced a reduction in VO2peak over the four years from 39 ± 7 ml·kg·min−1 to 36 ± 9 ml·kg·min−1 (N = 25, P < 0.001, Cohen's d = 0.37), and those who discontinued exercising also experienced a reduction in VO2peak from 30 ± 7 ml·kg·min−1 to 25 ± 9 ml·kg·min−1 (N = 9, P = 0.003, Cohen's d = 0.62). Four years after completing a brief period of aerobic exercise and HIIT, older males demonstrated a preservation of VO2peak, irrespective of training status (LEX or SED). However, LEX exhibited greater VO2peak than SED after 4-years of unsupervised ‘free-living’. Finally, those who discontinued exercising experienced a greater reduction in VO2peak. These findings infer that to maintain aerobic capacity, 6 weeks of HIIT every four year may be sufficient, but to attenuate the decline, exercise should be maintained.