NPTI Dallas

Interval training (HIIT) interferes more with muscle growth than steady-state cardio,
new meta-analysis finds

High-intensity interval training was heralded as cardio 2.0, a better and more time-efficient way to burn fat and develop endurance. "Train like a sprinter, look like a sprinter!"

Except you're not training like a sprinter. You're training like a soccer player. Olympic 100 m sprinters train with sprints of around 10 seconds and then often rest several minutes. HIIT is metabolically much closer to low-intensity, steady-state cardio (LISS) than strength training.

All forms of cardio can interfere with muscle growth, as endurance and strength training adaptations are partially acutely mutually exclusive. It's like trying to develop your body into 2 different directions along the strength-endurance continuum at the same time. This new meta-analysis confirmed that endurance training on average in the literature significantly reduced both type I and type II muscle growth from strength training ( the interference effect AKA concurrent training effect), although the effect on the whole-muscle level was not statistically significant.

Some people argue that the interference effect is not a real thing, despite numerous studies over the past decades demonstrating doing cardio and strength work in the same program can reduce muscular gains. The counter-arguments mostly rely on studies in untrained individuals. As I recently posted, some research finds that untrained individuals can gain just as much muscle from endurance as from strength training. They can get newbie gains from anything the first few weeks. So of course there's no interference yet at that point.

The novel finding of this new meta-analysis of the literature was that HIIT reduced muscle growth significantly more than LISS cardio. The reason for this may be that HIIT is always intensive, so it will always evoke significant endurance training adaptations and those can interfere with strength training adaptations. With steady-state cardio it's easier to stay under the threshold of evoking strong endurance adaptations.

For body recomposition and strength development, I've always preferred LISS cardio over HIIT. The vast majority of my clients never have to do any cardio at all though.

For health benefits or endurance training, HIIT can still be great. To minimize the interference effect, schedule HIIT sessions as far away from your strength work as possible, on different days.

Bodybuilding cures type II diabetes. Really. A review paper by Shakoor et al. (2021) concluded that the combination of aggressive cutting with high-frequency exercise is one of the most effective methods to cure type II diabetes, one of the top 10 leading causes of death in the world. Full remission of diabetes has been found in as little as 8 weeks(!)⁣

Note that I'm using the word 'cure' here in the colloquial sense of a permanent remission of symptoms.
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Many doctors are still stuck in the pharmaceutical age and think diabetes is irreversible. Nothing could be further from the truth. Lean, muscular, strength training individuals with normal genetics have almost no chance of becoming diabetic. ⁣
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Many people think bodybuilding is unhealthy, but that's only true for drug users (depending on how medically responsible they are) and maybe the last stages of contest prep. ⁣
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Natural recreational bodybuilding has enormous health benefits. In addition to the vast array of health benefits of exercise itself, being lean and muscular enhances your insulin sensitivity enormously, which in turn lowers chronic inflammation levels. Good glucose, insulin and inflammation levels in turn lower your chances of almost every other health condition.⁣

Weight Lifting in Old Age Does More Than Just Keep Your Muscles Strong New research into weight lifting has revealed two insights: that the practice is able to strengthen the connections between nerves and muscles, and that this strengthening can still happen in the later years of our lives.