Key Points

A recent study investigated if sprinting 30 seconds per day was enough to elicit positive health outcomes
Such low volume of training was not effective in subjects, despite a high intensity
More research is needed to find minimum doses of training

Introduction:

Most everyone wants more for less, especially when it comes to fitness. This may be, in part, why companies like Barry’s Bootcamp, F45, and OrangeTheory have seen success. They implement a strategy of HIIT, or High Intensity Interval Training. HIIT training, in case you don’t know, or need a refresher, is a form of cardio that alternates between short bursts of intense anaerobic exercise and brief recovery periods. The idea behind HIIT is that it aims to improve cardiovascular fitness, while burning calories, and boost metabolism in a shorter amount of time compared to traditional steady-state cardio workouts. Steady state cardio is a cardio where you maintain a steady pace of moderate intensity for an extended period. Think jogging or hopping on a stationary bike for an hour.

While both HIIT and steady state offer similar health benefits, the advantage of HIIT is that it can be done in significantly less time. The tradeoff is that each exercise bout is significantly harder than anything done in steady-state. But if intensity was high enough, could there still be benefit from doing less than 5 minutes of working out per week? That was basically the question Wong and colleagues asked in a new study (1).

STUDY SUMMARY

Here is a brief overview of the 2024 study. It was a 6 week intervention involving 19 healthy, physically active 20-28 year olds, who were split into two groups: an exercise group, and a control group. The exercise group did one set of sprints on a stationary bike five days a week. Sprints were 20 seconds for the first week, and then 30 seconds for the final five weeks. The control group went about their daily routine with no additional exercise intervention. Researchers measured performance through testing VO2 max, max power output, strength of the knee flexors and strength of knee extensors. Researchers measured health markers by testing blood pressure, glycemic control, and blood lipids.

FINDINGS

If you were hoping to get away with working out less per week than the length of your favorite gym song, I have some not-so-good news for you. In terms of performance the results were underwhelming. In fact, the exercise group did not see any significant improvements in any of the tests, other than a small increase in VO2 max.

Results for health markers weren’t better, and in fact maybe worse. Most of the health related tests (blood pressure, glycemic control, blood lipids) did not show improvement for those in the exercise group. There was no significant difference in change between the control and exercise group for body mass , % body fat, blood pressure, and other metrics related to cardiometabolic health. However, there was one worth mentioning for some reason, there was an increase in LDL-cholesterol in the control group while that in the exercise group didn’t change. The authors attributed this to a possible indication that performing at least one sprint-cycle a day may “defer” the individual from raising levels of LDL-cholesterol that could happen from a lack of physical inactivity or poor diet. Of note, physical activity or diet were not assessed, so these explanations were not tested. Of further note, 19 measures of health were measured and the P value of 0.05 was used to define significant differences. This means that there was a 5% chance that you would have gotten a significant result without there being a real effect. That is, a P value of 0.05 means if you have 20 measures, one of the significant findings could have been by chance. Pretty close to 19.

INTERPRETATION

Despite the fact that this intervention was not effective at eliciting positive responses for participants for either performance or health markers, there is interesting information to be derived from the results. While HIIT can definitely be an effective strategy for developing fitness, there is a minimum dosage required to see those benefits, which single 30 second bouts daily does not meet. Where that minimum limit is, both in terms of relative intensity, volume and frequency, remains to be seen. More research is needed in this area.

I should also note that there are many ways to train. A lot of ways to adapt and no single style of training will be a silver bullet for all your fitness needs. My recommendation is to find a style of training that you enjoy, can progress at, and can be easily integrated into your life and becomes a habit. Training should be smart. Hard enough to draw out the adaptation that you want, but not so hard that it causes anxiety or risks injury.

CONCLUSION

While the study results may not have yielded the expected outcomes regarding the efficacy of extremely brief HIIT interventions, they shed light on the complexity of fitness adaptations and the importance of dosage in exercise regimes. While HIIT has shown promise as an efficient training method, it appears that there is a threshold below which its benefits may not be fully realized. Further research is needed to pinpoint the individual’s optimal balance of intensity, volume, and frequency required to elicit meaningful improvements in both performance and health markers.

Sources:

Wong PY, Soh SMM, Chu WM, Lim MXC, Jones LE, Selvaraj S, Chow KMS, Choo HWD, Aziz AR. A single all-out bout of 30-s sprint-cycle performed on 5 consecutive days per week over 6 weeks does not enhance cardiovascular fitness, maximal strength, and clinical health markers in physically active young adults. Eur J Appl Physiol. 2024 Jan 17. doi: 10.1007/s00421-023-05411-0. Epub ahead of print. PMID: 38233706.

DISCLAIMER

The information in this article is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider or medical professional before beginning any new exercise, rehabilitation, or health program, especially if you have existing injuries or medical conditions. The assessments and training strategies discussed are general in nature and may not be appropriate for every individual. At Verro, we strive to provide personalized guidance based on each client’s unique needs and circumstances.