Sprints – 30s Versus 60s

Hello!

Today I will be summarizing a recent study that evaluated sprint interval training on rate of perceived exertion on 20 healthy participants, entitled “Exertional Responsese to Sprint Interval Training: A Comparison of 30-sec. and 60-sec. Conditions”

I’m a huge fan of sprints (versus steady state cardio) – you can read more about my experiences with long distance running on my about page. I usually switch up the length of my sprint intervals (anywhere between 30 to 90s), so this article was interesting to me.

Usain Bolt – the sprint master

Methods

20 students (average age 23.4) were recruited from a university in the US. They were all screened for prior/existing health conditions (orthopaedic, cardiovascular or pulmonary). They were instructed to avoid alcohol, caffeine, and tobacco for three hours prior to testing.

Two groups were established, both consisted on 20 minutes (2 min warm up, 16 min intervals, 2 min cool down) on a stationary cycle, one with 60s intervals, one with 30s intervals, with a 1:1 rest period (i.e.60s on, 60s off vs. 30s on, 30s off)

The investigators tested each participant for peak workload capacity by determining the point at which they couldn’t maintain a cadence of 30rpm. They were then given 3-5 minutes of active recovery.

After recovery, each participant began the interval trial. The intensity used for sprint intervals was 90% peak power achieved on the first test.

The outcome of interest was a valid and reliable rate of perceived exertion (RPE) scale,i.e. how hard did the participant think they were working, on a scale of 0-10. This is a standard scale that trainers use to assess how hard they think their clients are working.  (0 is nothing at all, 3 is moderate, 5 is hard, and 10 is very, very hard or maximal.

Results

Both trials showed a significant increase in RPE from before the trial to after the trial. RPE for the 60s trial was significantly higher both after, and during exercise.

Conclusion

Shorter intervals are perceived as less work than longer intervals, even though the participants were sprinting and resting for the exact same time!

Unfortunately the only variable the authors evaluated was the RPE, I would be interested to see the effect of interval duration on VO2 max, heart rate, calorie expenditure etc. There might be a trial out there that already evaluated this though, I’ll have to check!

Citation

Kilpatrick, M.W., Greely, S.J. Exertional responses to sprint interval training: A comparison of 30-sec. and 60-sec. conditions. 2014 Psychological Reports. 144 (3) 854-865.