Author(s): FOSSTVEIT, S., BERNTSEN, S.1, FERON, J.2, JOYCE, K.E.2, IVARSSON, A.3, SEGAERT, K.2, LUCAS, S.J.E.2, LOHNE-SEILER, H.1, Institution: UNIVERSITY OF AGDER, Country: NORWAY, Abstract-ID: 1313

INTRODUCTION:
Cardiorespiratory fitness (CRF), a strong predictor of overall health and longevity, typically declines with age, increasing the risk of chronic diseases in older adults.1 Home-based high-intensity interval training (HIIT) potentially offers a practical and accessible method to improve CRF. However, objectively measured adherence levels and subsequent effectiveness of home-based HIIT in older populations remain underexplored.2,3 Therefore, this study aimed to investigate adherence to a six-month home-based HIIT intervention in older adults, as well as assessing associations between various adherence metrics and the resultant changes in peak oxygen consumption (V̇O2peak).
METHODS:
233 healthy older adults (60-84 years, 54% female) were randomised to six-month, thrice-weekly home-based HIIT (one circuit and two interval sessions) or a passive control group. Exercise sessions were monitored with a Polar watch and logbook for objective and subjective data, respectively, and guided by a personal coach. Adherence was assessed using frequency, intensity, and duration data, and was quantified using a novel method involving metabolic equivalents (METs).4 For each metric, adherence was expressed as percentage completion relative to what was planned. V̇O2peak was assessed using a modified Balke treadmill protocol to volitional exhaustion. General linear regression models (GLMs) assessed between-group differences in post-intervention V̇O2peak, with baseline V̇O2peak, age, sex, and country as covariates, and group as a fixed factor. For adherence-V̇O2peak associations, GLMs were used with age, sex, and country as covariates.
RESULTS:
The HIIT group achieved an average total of 11116±5455 MET-min (122% of the planned exercise volume). Participants completed 2.6±0.6 sessions per week (86% of planned) and spent 10.3±5.2 min per session at ≥80% of HRpeak (98% of planned), with an average session duration of 39.9±11.8 min (135% of planned). Between-group differences were observed in the pre-to-post intervention change in V̇O2peak (1.8 [1.2;2.3] mL/kg/min; effect size: 0.35). There was a positive association between adherence to frequency and intensity and percentage improvements in V̇O2peak (β=0.1 [0.0;0.2]; β=0.04 [0.00;0.07], respectively), but not duration or total MET-mins.
CONCLUSION:
The findings indicate that older adults can successfully adhere to and benefit from a home-based HIIT program, achieving clinically meaningful improvements in CRF over six months. Notably, while adherence levels are crucial in designing effective exercise interventions for this demographic, the findings indicate that exceeding prescribed exercise volumes does not necessarily lead to superior enhancements in CRF.

References:
1. Kaminsky et al. Progress in cardiovascular diseases. 2019.
2. Gray et al. British Journal of Sports Medicine. 2016.
3. Stork et al. Health psychology review. 2017.
4. Nilsen et al. Medicine and science in sports and exercise. 2018.

(www.fab-study.com)