The weight you should lift to build strength: bigger isn’t necessarily better

Whether we train on our own or have a professional to guide us, we must learn to manage the external load we work with ourselves. And depending on what we’re aiming for, more isn’t always better. You can be strong without being overly muscular, and you can be as big as the Hulk yet lift less weight than someone who’s a bit more lanky. This is more or less the conclusion reached by researchers from three universities - two Canadian ones, McMaster and Queen’s, and one British one, John Moores - who have worked side by side to answer the age-old question: how much weight should I put on the bar today?

They recruited 20 healthy, active men who did not do strength training, and placed the weights in front of them. With one arm, they had to use lighter weights, which allowed them to do more repetitions. With the other arm, they used heavier weights, which they lifted fewer times. After 30 sessions spread over 10 weeks, they found that there were hardly any significant differences between the two limbs. In other words, both arms had the same strength and the same muscle mass.

We’re off to the gym now. Shall we use two kilos instead of eight, then? “Every exercise should be a challenge, a stimulus,” replies Álvaro Puche, a personal trainer and rehabilitation specialist, without hesitation. In other words, if we normally work with four kilos and find it hard, but we do it properly, using the correct technique… the two-kilo dumbbell is going to be a bit of a joke. “You’ll get bored,” he predicts. Now, “lifting a weight that exceeds my capacity isn’t an option either” because it will have the opposite effect - it’ll cause injury.

– I’m still not quite sure what weight I should use.

– You need to choose a load that, on the one hand, challenges you, but, on the other, you can handle well: move it properly, whilst adhering to the correct technique for the exercise.

To continue with the example: if I can manage it with eight, then go ahead. But it’s probably better to try with six kilos first. Furthermore, to manage the load, we need to consider two other concepts. The first is ‘intentionality’, which ‘makes the difference between substantial and poor improvement’. For Puche, ‘it’s more valuable to lift less weight with the intention of doing it well and quickly during the concentric phase’. But we mustn’t lose sight of the fact that to build strength, you need to use heavy loads and do shorter sets.

The second factor to bear in mind is ‘mechanical tension, which is the tension generated within our muscles when we perform a series of strength exercises’. It is directly related to muscle hypertrophy: if I’m aiming for big biceps, it’s better to use a slightly lighter load and train to what is known as ‘failure’, without compromising on technique. The leading researcher in this field, Brad Schoenfeld, estimates that the duration of the exercise should be at least 48 seconds.

In the study published in The Journal of Physiology, the participants were able to do 12 repetitions with the heavier weights and up to 25 with the lighter ones. And the results obtained (and measured by the researchers) were virtually identical. This offers hope to those who find strength training a real chore, as they no longer have to push themselves to the limit with the heavier dumbbells.

Puche also points out that the weights we choose will not only weigh the number of kilos stated on the scale, but will also have an additional load ‘known as allostatic load’, which depends on how we are feeling at that moment: how much sleep we’ve had, how our working day has gone, whether we’ve had an argument with our family… “Depending on this, we also need to assess how much weight we’re going to lift. You might be used to lifting 60 kilos in a squat, but one day, due to one of these factors, you might not be able to go beyond 40,” he points out. It’s not that you’ve become lazy; it’s something else. “What’s more, it might actually be better not to go to the gym that day because you’re at greater risk of injury.” Take it from an expert.