There is, with each new wave of research, little evidence to justify the use of low-intensity steady-state (LISS) cardio for anyone but the endurance athlete crowd. It used to be that this was the preferred method of slimming down or “tightening up” for many a physique-minded athlete. But over the last decade plus, the lab coats have systematically abandoned this approach in favor of high-intensity interval training, or HIIT, which calls for several near-max effort work segments interspersed with short periods of recovery.
The reasons for this seismic generational shift are legion, but chief among them are HIIT’s ability to burn fat at a faster rate while preserving or increasing muscle mass with far less of a time investment than LISS cardio. The mechanisms behind these perks are many but can be boiled down to a single, fundamental truth: Harder training yields better results.
If you’re going to push it to the redline multiple times in a single session — even if only for a few seconds — it’s important to give yourself every advantage possible.
Here are a few ways to ensure that your HIIT stays hot.
Mind Your Ratios
High-intensity activity, such as a 100-meter sprint or an out-of-the-saddle interval in a Spin class, places a high demand on working muscles as well as the central nervous system. You don’t want to rest too long, but you also don’t want to deprive your body of rest. Remembering that the focus is on max effort, there’s no need to rush recovery.
Many people favor work-to-rest ratios of 1:2 — 30 seconds of high-intensity work followed by 60 seconds of rest, for example. But what’s known about energy systems suggests that it may be more worth your while to aim for a ratio closer to 1:5, or 30 seconds of rest followed by 150 seconds of recovery. Researchers at the University of Western Ontario in Canada found that subjects who performed four to six 30-second sprints with four minutes of rest after each sprint lost twice the fat of a steady-state group — a ratio of 1:8.
HIIT+ Don’t be in a rush to dive into that next interval. Instead, focus on giving a max effort on every single sprint.
Though the majority of the research done has revolved around running or cycling, new research published in the Journal of Strength and Conditioning Research has shown that a tussle with the battling ropes — 15-second work intervals followed by 45 seconds of rest — held benefits similar to the lower-body activities.
HIIT+ With upper-body HIIT, your arms and delts may feel the burn but your lungs won’t be missed, either. Battling ropes, boxing, hand cycling or even combo activities like the Airdyne bike will provide a metabolic boost akin to sprinting.
Short, explosive bouts of activity rely mainly on the phosphagen energy system, which relies on the chemical reactions of adenosine triphosphate (ATP) and creatine phosphate (CP). This produces energy at a very high rate, for anywhere from six to 30 seconds. After that, other energy systems start to take over.
During your bouts of recovery, your phosphagen stores are recuperating. If more creatine is available, this fuel is easier to synthesize, keeping you training faster and harder through each interval. As your intervals progress, your muscles also start to fatigue through other mechanisms, such as the accumulation of lactic acid. This can be buffered through the ingestion of beta-alanine. Caffeine has been shown to acutely increase strength, delay fatigue and blunt the pain associated with high-intensity exercise.
HIIT+ Make sure that you take in 3 to 5 grams of creatine and 2 to 3 grams of beta-alanine 30 minutes before your intervals. Adding a 200- to 300-milligram dose of caffeine anhydrous can help you push through your late intervals.
With low-intensity cardio, a familiar practice is to perform it following your weight work. This is ideal because your body will tap into fat faster in the absence of glycogen (which you left in the weight room). But HIIT, done right, is not the type of training that likes to share space with others. Because it places such a high demand on your body, joints and nervous system, HIIT is best done as an exclusive workout.
HIIT+ If you want to run faster or train harder on every one of your intervals, schedule your HIIT on a day when you are not training weights. Also, allow at least 48 to 72 hours before your next HIIT session.
LISS advocates who use it to shed weight like to do it , at least on occasion, on an empty stomach. The glycogen-depleted state your body is in upon waking makes for a more favorable fat-burning environment. This also can eat away at valuable, hard-earned muscle tissue because fat stores are not easily converted to fuel by the body.
If you’re doing HIIT, however, you’re likely more concerned with preserving and/or building muscle, so going empty is probably not advisable. Also, the absence of nutrients also can result in you hitting the wall faster than you had planned, leaving your max-effort work looking sub-spectacular.
HIIT+ Don’t do HIIT on an empty stomach. Try to get at least one whole-food meal in ahead of your workout or, if you must train early, take down about 10 grams of BCAAs for fuel and to aid in muscle preservation.