Research presented recently at the 2018 American College of Sports Medicine Annual Meeting recommends an upper limit of high-intensity interval training (HIIT) at 30 to 40 minutes about 90% of the maximum heart rate per week.

During the meeting, Penn State Associate Professor Jinger Gottschall presented findings from a recent study suggesting that more than 30 to 40 minutes of HIIT in a maximum training zone per week may reduce performance and potentially result in a greater risk of injury.

According to Gottschall in a media release, the research findings highlight the urgent need for evidence-based guidelines around HIIT.

“Currently there are no guidelines concerning the greatest amount of HIIT people should do in a week for the optimal training effect,” she says. “Given the extreme intensity involved in this kind of exercise, it’s imperative that maximum guidelines are provided in the same way that minimum guidelines have been in the past.  We hope this study will be instrumental in helping make these recommendations official.”

In the study, 35 active individuals (28 women and 7 men) who exercise more than 8 hours per week recorded their heart rate during every training session and answered surveys regarding their mood for 3 weeks, the release explains.

Then on an experimental day, at the end of their typical 3-week training period, participants did two high-intensity workouts—in the form of LES MILLS GRIT—4 hours apart.

Saliva samples were collected 30 minutes prior to each exercise session, immediately following, and 30 minutes post-exercise to assess cortisol and testosterone concentrations. This process enabled the team to track the individual’s stress response.

Heart rate was also monitored throughout the experimental day using Polar A370 devices with the H10 chest straps to determine exercise and recovery values.

“In scientific terms, what we’ve observed by measuring the stress response in the saliva of our study participants is that those who do more than 30-40 minutes of HIIT per week are unable to produce a positive stress response,” says Gottschall.

“If you want to get the best possible results from HIIT, our recommendation, based on these findings, is to balance your weekly HIIT sessions with other, less intense cardiovascular and strength workouts. It’s also imperative that you let your body recover properly after a HIIT session.  This way, you’re likely to perform better when you do your HIIT workouts and benefit from the positive results.”

Publication of this study in a journal is currently pending, according to the release.

[Source(s): Les Mills, Newswise]