HIIT Sprints & Adults Over-50: The Minimum-Effective Dose

As you get older, it’s more difficult to maintain lean muscle mass. Muscle is not only a crucial factor in physical performance but also a key marker of healthy ageing.(1) After the age of 50 muscular power starts to decline, more rapidly than strength qualities, making it an important factor to focus on during training. Power isn’t just for dynamic sports efforts, your fast-twitch muscles are essential for “catching yourself” as you fall and hip fractures are significant risk factor in older populations.(2) The good news is maintaining muscular power predicts a reduction in future falls, so not only is focusing on power qualities during exercise important for performance, but overall health as well.(3)

High-intensity interval training (HIIT) is a fantastic tool to improve aerobic fitness, body composition, strength and power.(4) HIIT involves brief, intermittent bursts of training at high-intensity with low-intensity rest periods sprinkled in between. However, in older adults it typically takes much longer to recover after HIIT sessions. Therefore, the question is how little HIIT does an older person need to reap the benefits, while mitigating the excessive muscular damage and inflammation. In short, what is the minimum-effective dose of HIIT training in older adults over 50? A recent study attempts to answer the question.

In this study, 36 healthy but sedentary men between the ages of 56-65 were divided into two groups; one performing the HIIT intervals while the other did remained inactive. Researchers wanted to assess their power output, body composition, and effects on balance post-training. Furthermore, since there is not a lot of research on HIIT in older men, it’s important to note they added 6 weeks of “pre-conditioning” before the study to ensure all the participants had the fitness to take part in the study (i.e. they didn’t want to break anyone!).

For six weeks, the men performed 6 sets of 30-second sprints every 5 days on a cycle ergometer with three-minute rest periods in between bouts. Researchers found the sprint group had a 26.5% increase in peak power output following the six week training protocol.(5) While this sounds very impressive, it’s likely exaggerated due to their age and the fact the men were sedentary. Remember, normal ageing is associated with a steady decline in power.

The sprint group also got much leaner performing HIIT sessions, compared to the 6-week preparatory phase were little improvement was seen. While the research isn’t clear on why this occurs, the study authors believe improved fat oxidation during exercise and at rest, as well as appetite suppression were the likely causes. There was no effect in this study on balance from the HIIT sprint sessions.

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The Bottom Line: Low frequency HIIT training (every 5 days) is an effective and efficient training intervention for adults over 50 to improve power output and body composition.

HIIT training provides a variety of benefits to clients. In older populations, it appears you can adjust the training frequency and still reap tremendous benefit, making time-efficient HIIT exercise even more appealing in older adults and seniors.

Dr. Marc Bubbs ND, CISSN CSCS