High Intensity Interval Training in Older Adults

Results of a randomized and controlled trial were recently published in the Scandinavian Journal of Medicine & Science in Sports, reporting on the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness in older adults. It’s worth noting that cardiorespiratory fitness, often assessed as VO2max (oxygen consumption at a maximum workload), has previously been shown to be one of the most predictive variables for mortality that we know of, with a greater influence than smoking, diabetes, etc. Additionally, every reduction (measured in mL/kg/min) is associated with a 14% greater risk of older adults becoming dependent.  

This study was part of the Fitness, Ageing, and Bilingualism (FAB) project, and enrolled 233 healthy older adults (60-84 years) who were randomly assigned either to a control group or to receive home-based HIIT (once-weekly circuit training and twice-weekly interval training) for a 6-month period. The HIIT intensity gradually increased over time, with the first month as a “familiarization period,” reaching a targeted intensity of <80% of peak heart rate (determined from a treadmill VO2max test). It was also designed to be performed at home or outdoors, requiring little or no equipment, with each session ranging between 40 to 60 minutes. 

After 6 months, the HIIT group improved in every outcome measured in comparison to the control group. This included a 1.8 mL/kg/min increase in VO2max in the HIIT group compared to a decrease of 0.4 mL/kg/min in the control group. Other improvements included a mean reduction of 19% in sub-maximal blood lactate levels (vs. 4% in controls), lower % of peak heart rate, and lower % of VO2max at pre-intervention intensity levels. Given these impressive results and their clinical importance, the home-based approach used in this trial may serve as a model for intervention. 

For a deeper discussion into VO2max as a predictor of mortality, please see a previous blog, Cardiorespiratory Fitness & Mitochondrial Function.