Who doesn’t love efficient workouts? And if efficiency is your goal, you can’t beat the benefits of high-intensity interval training or HIIT. High-intensity interval training is short and sweet and one of the most efficient ways to improve your cardiovascular fitness, burn calories, and build lean muscle mass in short order. But as any HIIT devotee knows, these workouts are intense! That’s why you need proper recovery to reap the full benefits without overtraining or getting injured.
Why Is HIIT Training So Demanding?
HIIT is challenging because of its intensity and the way it boosts your heart rate and makes your muscles burn. With high-intensity intervals, you do short bursts of near-maximum effort followed by periods of rest or lower-intensity exercise to allow your body partial recovery. The intensity of HIIT is more challenging to your cardiovascular system and to your muscles than moderate-intensity exercise.
And there’s a lot going on at the cellular level too. High-intensity intervals deplete your muscles’ supply of ATP, glycogen, and phosphocreatine and boost the buildup of metabolic byproducts like lactate. Your body must work harder to return to baseline homeostasis after an intense workout. You also get more muscle damage than you do with a moderate-intensity workout. Therefore, your cells must work harder to repair the damage and you get a more pronounced inflammatory response.
Of course, this is all short-term. In the longer term, these adaptations are what help your body get fit in a more efficient manner. The intensity of this style of workout boosts aerobic capacity, enhances fat burning, and you get muscle adaptations, like increased muscle strength and endurance. HIIT training places substantial metabolic and mechanical stress on your body.
The Importance of Optimized Rest Intervals
First, ensure your rest intervals are long enough when you do a HIIT workout. It’s common for avid HIIT enthusiasts to shortchange their rest intervals, so they can pack more exercise into less time. But you won’t maximize the work you do during the active intervals unless your rest is long enough.
So, what’s the ideal rest interval? It will vary with your fitness level and goal. A general rule of thumb is to use a work-to-rest ratio between 1:1 and 1:2. For example if you choose the 1:2 structure, you would do a 20 second sprint (or another exercise with intensity) followed by 40 seconds of rest and keep repeating. This is an ideal work-to-rest interval when you’re starting out. As you get fitter, you can switch to 1:1. An interval timer makes it easier to track the timing of your intervals.
Active vs Passive Recovery
Another aspect of HIIT is whether your rest intervals are active or passive. If you go the active route, you do low-intensity exercise during a rest interval. You wouldn’t stop moving altogether. But with passive rest intervals, you stop exercising entirely until it’s time for the next active interval.
Although there is debate over which approach is best, research shows passive rest helps best maximize your output and performance for the following active interval. So, you may be able to exercise more intensely and do more total work if you take a passive rest. On the other hand, research shows active rest intervals are better for reducing the perception of how hard you’re working, despite raising your heart rate more.
Another consideration is the impact each type of rest has on the hormonal response to a HIIT session. A study found that active rest had more pronounced effects on anabolic hormones that promote muscle growth and repair, like testosterone and human growth hormone.
Which should you choose? You don’t have to do only one or the other. You could include both in your routine or select one based on the length and intensity of the work sessions you’re doing.
Refueling and Rehydrating After HIIT
HIIT training is intense, so prioritize hydration during your post-workout recovery. Depending on the environment you’re working out in, you could lose a significant amount of fluid and electrolytes. If you feel exhausted after a HIIT workout, you’re either working too hard or not hydrating and fueling up adequately beforehand. Your body can’t perform its best when it’s deprived of fluid and key nutrients!
One strategy for optimizing hydration is to weigh yourself before a HIIT session. Afterward, reweight yourself again and drink 16 to 24 ounces of fluid for every pound you’re down. In most cases, you won’t need an electrolyte beverage, as HIIT sessions are usually under an hour. If you’ll be exercising longer, sip an electrolyte-rich beverage.
After a HIIT session, your muscles are primed for taking up carbohydrates to replenish the glycogen you lost. Your muscles are also begging for protein to help with muscle repair. Refuel with a snack with a ratio of 3-4:1 carbohydrate to protein, optimally within an hour of your workout.
Don’t forget about sleep! It’s during sleep that your body releases growth hormones and goes into muscle repair mode. If you don’t get adequate sleep for recovery and repair, your cortisol level may shoot up and jeopardize your muscle gains and adaptations to HIIT training. Poor quality sleep can also reduce the ability of your muscles to repair. Aim for 7-9 hours of quality sleep per night, and don’t be afraid to take a short nap on intense training days.
Incorporating Other Recovery Modalities
Optimizing your rest intervals, nutrition, and high-quality sleep are the basics of recovery, but science shows that other strategies can give you an edge too. Why not grab a foam roller and massage the muscles you worked? Doing so could help alleviate soreness and help with recovery. Some people use contrast water therapy where they alternate hot and icy water to boost recovery and there’s evidence to support this.
The key is to choose a recovery approach that works for your body and lifestyle. But one thing is universal – shortchanging recovery will shortchange your HIIT results overall. Embrace rest as an integral part of your training, and you’ll enjoy better performance, faster progress, and a healthier body. Hit it hard but recover harder!
References:
- Abderraouf Ben Abderrahman, Hassane ZOUHAL, Karim Chamari, and Jacques Prioux. “Effects of Recovery Mode (Active vs. Passive) on Performance during a Short High-Intensity Interval…” ResearchGate. Springer Nature, December 11, 2012. https://www.researchgate.net/publication/233892435_Effects_of_recovery_mode_active_vs_passive_on_performance_during_a_short_high-intensity_interval_training_program_A_longitudinal_study.
- Davey, K.D.A, C.J Pastorino, E.L Kass, C.W Carroll, and M.M Lockard. “ACTIVE RECOVERY during HIIT INDUCES HIGHER HR but LOWER PERCEIVED EXERTION than PASSIVE RECOVERY.” TopSCHOLAR®, 2024. https://digitalcommons.wku.edu/ijesab/vol8/iss1/4/.
- Hassane Zouhal, Abderraouf Ben Abderrahman, Ayyappan Jayavel, Anthony C Hackney, Ismail Laher, Ayoub Saeidi, Fatma Rhibi, and Urs Granacher. “Effects of Passive or Active Recovery Regimes Applied during Long-Term Interval Training on Physical Fitness in Healthy Trained and Untrained Individuals: A Systematic Review.” Sports Medicine – Open/Sports Medicine – Open 10, no. 1 (March 5, 2024). https://doi.org/10.1186/s40798-024-00673-0.
- Wahl P, Mathes S, Achtzehn S, Bloch W, Mester J. Active vs. passive recovery during high-intensity training influences hormonal response. Int J Sports Med. 2014 Jun;35(7):583-9. doi: 10.1055/s-0033-1358474. Epub 2013 Nov 20. PMID: 24258473.
- Bieuzen F, Bleakley CM, Costello JT. Contrast water therapy and exercise induced muscle damage: a systematic review and meta-analysis. PLoS One. 2013 Apr 23;8(4):e62356. doi: 10.1371/journal.pone.0062356. PMID: 23626806; PMCID: PMC3633882.
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