Evidence from HIIT studies conducted under controlled laboratory conditions has provided proof-of-concept of efficacy . However, it has been argued that HIIT has high efficacy but low effectiveness , and long-term exercise interventions carried out under free-living conditions have been asked for to investigate whether HIIT is feasible as a public health initiative among older adults [9, 16]. Our data showed that both training groups reported on average more than two exercise sessions per week throughout the year. Approximately 60% of the sessions in the HIIT group were performed with a self-reported high-intensity (≥15 Borg scale), indicating that older adults are able to perform HIIT over a long time-period without strict supervision. However, women had a lower proportion of sessions with high-intensity exercise compared to men. This result is in line with previous findings that women (aged 60–67 years) are less likely than men to prefer vigorous physical activity .
The aim of this study was to assess the effects of vigorous exercise on functional abilities by means of a Senior Fitness Test (SFT) in a group of elderly adults. Twenty healthy and inactive people performed vigorous exercise (VE: 12 men and 8 women, aged 69.6 ± 3.9 years). At the beginning of the study (T0) and after 3 months (T1), each subject's functional ability was tested for muscular strength, agility, cardiovascular fitness, flexibility, and balance. The VE was designed with continuous and interval exercise involving large muscle activities. Functional exercises were performed between 60% and 84% of heart rate reserve (HRR) for a duration of 65 minutes. Five out of the 6 SFTs performed were found significantly improved: Chair Stand (T0 12.4 ± 2.4, T1 13.5 ± 2.6, p < 0.01), Arm Curl (T0 14.2 ± 3.6, T1 16.6 ± 3.6, p < 0.01), 2 min step (T0 98.2 ± 15.7, T1 108.9 ± 16.2, p < 0.01), Chair Sit-and-Reach (T0 −9.9 ± 7.7 cm, T1 1.7 ± 6.3 cm, p < 0.01), and Back Scratch (T0 −15.8 ± 10.9 cm, T1 −8.4 ± 13.1 cm, p < 0.01). Our results suggest that a high intensity protocol and functional exercises can improve functional mobility and muscle endurance in those over 65 years of age. SFTs are an effective method for assessing improvements in the functional capacity of elderly adults.