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) after 4-years of 'freeliving' 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'. Notably, participants who discontinued exercising experienced a greater reduction in VO2peak. These data suggest that a 6 weeks of supervised HIIT can facilitate the long term.