A caloric deficit in conjunction with a strength training program is paramount for weight loss, but how intense should your workouts be to achieve weight loss while maintaining muscle mass?
In this blog post, I’ll see what the science has to say about workout intensity for weight loss and muscle maintenance and share how you can measure your intensity based on heart rate and the rate of perceived exertion scale.
What is workout intensity?
Intensity itself refers to how hard you're working during your workout. It's a crucial factor that can affect the results you see from your workouts. If you're not working hard enough, you may not see the weight loss results you desire. On the other hand, if you're working too hard, you may risk burnout or even injury.
So what should your workout intensity be for weight loss and muscle maintenance?
A 2009 position stand and a 2010 report for the World Health Organization concluded that moderately intense activity is a sufficient baseline for modest weight loss when it is in conjunction with a caloric deficit and you workout 150 to 250 minutes per week (1,2). At 60 minutes per workout, this is equivalent to working out 3-4 times per week.
Measuring workout intensity
There are several ways to measure workout intensity, including heart rate and perceived exertion, which I’ll get into below.
With smartwatches and fitness trackers, measuring your heart rate has become very straightforward. There are three levels of heart rate intensity you should know about:
your maximum rate,
moderate-intensity rate, and
Your maximum heart rate is calculated by subtracting your age from 220, so for someone 30 years of age, we would take 220 and subtract 30 to get 190 beats per minute for our maximum.
Maximum heart rate = 220 - your age
Now that we have our maximum, we can calculate our target heart rate for moderate and vigorous-intensity activity or 55-75% of our max heart rate.
Continuing with my example, the 30-year-old with a 190 maximum heart rate, we take 190 and multiply it by 0.55, and we get 105 beats per minute, then take 109 and multiply it by 0.75, and we get 143 beats per minute.
Vigourous heart rate = your max heart rate x 0.75 Moderate heart rate = your max heart rate x 0.55
This means that moderate to vigorous activity for someone 30 years of age is roughly 105 to 143 beats per minute, respectively.
Now if you’re not a fan of math, then you’ll like this next method.
Rate of perceived exertion (RPE)
Rate of Perceived Exertion, or RPE, is a scale that measures workout intensity on a scale from 0-10, with 0 being no exertion or at rest, 4-5 being moderate or somewhat challenging, and 10 being your maximal effort. The scale itself is based on how you are feeling in the moment and doesn’t require calculation.
For moderately-intense activity, or a 4-6 out of 10, you can see that having a short conversation is possible but as we move up to more vigorous activity or a 7-8 out of 10, you can see that having a conversation becomes more challenging.
Workout intensity does vary from person to person, so it’s important to note that while you may find something challenging, that may look very different to the person working out beside you. Various factors influence the intensity of a workout, like the type of exercise, weight used, training volume and, of course, rest.
Firstly, different exercises require different levels of effort. For example, compound movements like a squat require more effort than single-joint movements like bicep curls. By combining these two, a 2021 position stand discovered you’ll actually amplify muscle development (3).
Secondly, the amount of weight or resistance used during an exercise also affects the intensity. The heavier the weight, the more effort is required. Also, free weights and cable machines offer different levels of resistance, with cable machines creating more resistance throughout the entire exercise.
When it comes to sets, that 2021 study found that each additional set per week produced a small but statistically significant increase of 0.37% in muscle growth (3).
The number of reps performed also plays a role in workout intensity. To focus on endurance, increase your reps. To focus on strength, you'll want to lift heavier with lower reps.
Are you working hard enough?
Overall, your weekly training volume, or the total sets, reps and weight used is incredibly important to consider as a higher weekly training volume does result in greater muscle hypertrophy. I go into further research on structuring exercises and training volume in this video if you’re looking to understand that more.
Next time you’re in the gym, give one of the workout intensity measurements a try to gauge how intense your workout actually is and think about how you can level up your workout intensity with different exercises, equipment or training volume.
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Donnelly, J. E., Blair, S. N., Jakicic, J. M., Manore, M. M., Rankin, J. W., & Smith, B. K. (2009). American College of Sports Medicine Position Stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Medicine and science in sports and exercise, 41(2), 459-471.
World Health Organization, T. (2010). Global recommendations on physical activity for health. World Health Organization.
Schoenfeld, B., Fisher, J., Grgic, J., Haun, C., Helms, E., Phillips, S., ... & Vigotsky, A. (2021). Resistance training recommendations to maximize muscle hypertrophy in an athletic population: Position stand of the IUSCA. International Journal of Strength and Conditioning, 1(1).