Lift Heavy or Lift Light?

“If you’re really trying to put on size, then you have to lift heavy – you need to start doing 1RMs[1] or 3RMs if you really wanna get big”

Sound familiar? The common paradigm surrounding light and heavy weightlifting is that “light weights get you toned, and heavy weights get you big”. It’s also the biggest misconception that novice weightlifters still fall for – and even some advanced lifters.

Let’s explore the benefits both versions of training can bring, as well as the science behind both styles – and learn why you have to include both in your training.

The Mitchell CJ Untrained Study

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If we’re going prove why both lifting light and lifting heavy are necessary to your overall training, we have to first look at the results both bring. In a study done by Mitchell CJ and colleagues[2], 18 untrained men were brought together to train their quadriceps via leg extensions. Out of the four groups, two are noteworthy:

·       Group A trained at 30% of 1RM for 3 sets (undisclosed rep range – estimated 25+)

·       Group B trained at 80% of 1RM for 3 sets (undisclosed rep range – estimated 8-12)

What does this mean? Group A trained at a lower weight, for more reps, while Group B trained with higher weights, for less reps. They both trained for 10 weeks, 3 times a week.

The key takeaway from this study is that both groups experienced similar muscular growth in their quadriceps at the end of the 10 weeks – virtually little-to-no difference was found in muscle size between the two groups.

Unfortunately, since the study used untrained men as their subjects, the reliability of this study was called into question. Luckily, we can look at similar study that utilised trained individuals.

The Morton RW study

Morton and his colleagues gathered 49 resistance-trained men to perform a variety of exercises for 12 weeks[3]. Two groups stand out in their study:

·       Group A lifted 30-50% of their 1RM for 20-25 reps

·       Group B lifted 75-90% of their 1RM for 8-12 reps

The result? Strength and muscle volume increased for all exercises used in both groups by statistically identical amounts. Only one minor area experienced a statistical difference – bench press strength increase was slightly lower in the Group A than Group B.

Why bother doing both?

You’re probably thinking “well if both styles get me the same result, then why should I bother even doing both”. Here’s where we delve into the unique benefits both lifting forms can bring.

The Principle of Specificity implies that to become better at something, you have to do that something – and it’s heavily used in sports, training, bodybuilding, and arguably all competitive activities. So in order to achieve maximum growth, we’re going to split the repetition motion into two phases – the concentric action, and the eccentric action. We’ll use the standing bicep curl as an example.

The concentric action occurs at the positive portion of the rep – when the muscles shorten. During a bicep curl, when you bring your hand to your shoulder, your biceps tense up and shorten. The eccentric action occurs at the negative portion of the rep – when the muscles lengthen. When you bring the weight back down to your hip it pulls and lengthens the muscles.

The principle of specificity can be applied using light and heavy lifting to achieve maximum growth by pairing each lifting style with the portion of the rep they best overload. For heavy lifts, overloading the eccentric action is much easier. It’s much easier to bring the weight down and with gravity, than up and against gravity – therefore we need heavier dumbbells to challenge us during the eccentric portion. Don’t be afraid of using a little momentum during your lifts – as long as you keep it under control. Lifting light allows yours muscles to spend more time under tension during the concentric portion.  It’s imperative to slow down the reps – doing so will accommodate for the lighter weight you’ll be lifting so you can achieve concentric overload effectively.

Training becomes a different activity when you understand the science and physicality behind each exercise – you’ll learn to train smarter and harder. You’ll stop seeing it as “moving weight from point A to B” and instead understand the numerable contractions and changes your body makes throughout each movement. As much as it’s impossible to experience injury from training, it’s can an entirely safe and  rewarding passion for those who take the time to learn how the body works.

Keep the training safe, smart, and hard.



[1] Rep Max – The maximum amount of weight an individual can lift for an X amount of reps (3 Rep Max, or 3RM etc)



Ryan ModyComment