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Why Doing 'As Many Reps As Possible' Is Most Effective

Updated: Aug 4, 2020

It’s likely this short and adaptable form of exercise can provide similar health benefits, says an observer.

HUDDERSFIELD, England: Though it’s recommended that we get a daily average of 60 minutes of physical activity, many of us struggle to find that much time.

This might be one of the reasons high-intensity interval training (HIIT) workouts – which take just 15 to 30 minutes to complete – have become so popular.

Though HIIT workouts might be short, a growing body of research shows they’re just as effective as longer endurance workouts for our health and fitness.

There are many different versions of high-intensity workouts, including CrossFit and Tabata. But the latest trend is AMRAP, which stand for “as many reps (or rounds) as possible”.

Based on what research shows about the effects of HIIT, it’s likely this short but adaptable form of exercise can provide similar health benefits.

AMRAP training is based on time. You work to complete as many repetitions or rounds of exercises as possible within a set time.

For example, you could do ten press-ups, ten crunches and ten jump squats, repeated in that order for as many rounds as possible until time expires.

Or to make things simpler, you could perform a single exercise (such as burpees) for as many repetitions as possible for 60 seconds before taking a rest and repeating.

There’s no specific time requirement, and workouts can be adjusted according to fitness levels. However, most AMRAP workouts tend to be between five and 30 minutes long, with no rest period after each exercise.

Some Tabata workouts – which usually involve a person performing 20 seconds of intense exercise, followed by ten seconds of rest, repeated eight times – take as little as four minutes, but remarkably have been shown to improve a person’s aerobic fitness by as much as 18 per cent following 24 exercise sessions over an eight-week training period.

This is important because our level of fitness has a powerful protective effect against cardiovascular disease. In these studies, fitness is typically defined as the maximum amount of oxygen you can use during intense exercise – known as VO2max.

Though it’s seen a recent spike in popularity, AMRAP training isn’t new. This form of training has been used in high-intensity circuit training for decades – most recently popularised by CrossFit. Although relatively little research has investigated the effects of AMRAP training specifically, strong evidence shows HIIT can improve blood pressure, blood sugar control and lower body fat.

Also, improvements in aerobic fitness following HIIT exercise are similar – or even greater than – those seen after typical endurance training, such as running or cycling, despite a significantly lower exercise volume.

Aerobic fitness is important for our health and might even be more important than the total amount of exercise that we do.


The key reason HIIT seems to be so effective is because it rapidly uses muscle glycogen (stored carbohydrates) through a process known as glycogenolysis.

Research shows that during HIIT performed on a cycling machine, it’s the rate of glycogenolysis that acts as a “signal” to the body to increase fitness, which in turn leads to improvements in health and performance. In short, the intensity of exercise is important.

Although it’s uncertain if a similar mechanism happens following AMRAP workouts, it’s reasonable to assume they might be similar, especially if the activity is performed at a high intensity.

Indeed, CrossFit has been shown to improve aerobic fitness, anaerobic capacity and body composition (lowering body fat and increasing muscle) in people with varying fitness levels.

However, there are