Without trying to stereotype an entire sporting population, many individuals who attend the gym and undertake resistance training do so to enhance their lean muscle mass percentages and achieve hypertrophic (muscle) gains.

Furthermore, there is a commonly held notion amongst gym users that the heavier you load the resistance, the greater the hypertrophic changes you achieve. The load selected is often represented as a portion of that individual’s single repetition maximum, or 1RM for short. Despite this, there is actually very little evidence to support this theory (ACSM, 2009).

One of the primary reasons for this lack of evidence to support the gains of lifting heavy is that the mechanisms by which this additional resistance would result in greater hypertrophic alterations are still unclear. It becomes even less transparent when you move to the other end of the spectrum and lift a light resistance to the point of fatigue.

Which method is more successful at bringing about hypertrophic advantages? Both training methods would result in close to maximal muscular fibre recruitment (Burd et al, 2010).

Training To Failure

Previous research by Burd et al. (2010) that considered these two very different training methods concluded that a single bout of exercise at 30% of an individual’s 1RM was just as successful as performing the exercise at 90% of an individual’s 1RM, when both were completed to muscular fatigue.

Both methods produced similar results when protein synthesis rates post exercise became the measured variable. This research boldly stated that training at a lighter load to exhaustion over a prolonged period of time had the potential to be just as, if not more so, effective as training with heavier loads.

Could this really be the case? Could you achieve similar or even enhanced muscular hypertrophy in any given muscle by simply dropping the resistance and working to failure? Within the health and fitness world, there has been support for this theory, however, this has not been unanimous and has not escaped without its criticism.

As is the case for many other research investigations, the critique often focuses around the control of the investigation and the ability to transfer results into real life settings. Have all other extraneous variables which could potentially impact upon the research findings been controlled? Can controlled measurements taken from the quadriceps muscle in a laboratory be applied to gyms nationwide and other key target muscle groups?

Often the findings create more questions than they do answers…

Research Investigation: Lifting Heavy Versus Lifting Light

With all this in mind, Mitchell et al. (2012) attempted to bring about some clarity to this key area of interest through their investigation, aptly titled: ‘Resistance exercise load does not determine training mediated hypertrophic gains in young men’.

For this research investigation, 18 healthy, male individuals were selected who were physically fit and active but who did not have any previous weightlifting experience. Participants were required to complete a 10 week unilateral knee extension resistance training programme in which each leg was randomly assigned to one of three training conditions.

These training conditions were as follows:

  • One set of knee extensions to failure at 80% 1RM.
  • Three sets of knee extensions to failure at 80% 1RM.
  • Three sets of knee extensions to failure at 30% 1RM.

All other variables, including pre and post exercise dietary consumption, were regulated throughout. Various standardised measurement and evaluation procedures were utilised to gather a collection of information data that could be accurately compared and allowed for conclusions to be drawn.

The Results

Following the 10 week research investigation, various findings were highlighted through the data collected. In terms of muscular hypertrophy, the quadriceps muscle, which was utilised as the target muscle in this unilateral knee extension test, demonstrated a significant increase in volume in all three testing conditions. However, there were no significant differences between each of the testing groups.

In terms of muscle function, this was assessed through measurements of the participants’ 1RM strength – the maximal resistance they could move for one repetition. Although all three groups demonstrated significant strength increments, this was greater in each of the 80% 1RM groups when compared to the 30% 1RM group.

Final Word

All participants during the 10 week training period developed significantly in both strength and size. These findings were to be expected as none of the participants had previously undertaken resistance training and so any weightlifting stimulus was likely to invoke positive alterations.

One potentially surprising finding was that there were no significant differences when considering hypertrophic alterations between groups. In fact, the group that performed three sets of knee extensions to failure at 80% 1RM recorded equivocal scores to the group that performed three sets of knee extensions to failure at 30% 1RM.

So why is this? Previous research suggests that when sub maximal contractions are sustained, all motor units that were initially recruited will eventually fatigue and in order to continue you require further recruitment of additional motor units. Ultimately, training to the point of failure with lower resistance brings about a state of near maximal motor unit recruitment (Fuglevand et al, 1993).

It appears then, that the key to training at lower resistance is to ensure a state of muscular fatigue. If you don’t exercise to exhaustion then your ability to bring about hypertrophic changes will diminish. This is supported by Holm et al. (2008), who demonstrated that when using lower resistance but not reaching the point of exhaustion, the hypertrophic results are reduced when compared to that of heavier resistance loads.

The only significant difference between the 80% 1RM group and the 30% 1RM group was observed when comparing repetition maximums. 1RM’s were stronger in the 80% group compared to that of the 30% group. Again this finding is to be expected as the 80% group were trained to lift close to their maximum throughout the 10 week testing period. This would have resulted in neural adaptations within the target muscle that would not have been developed at lighter loads.

Putting It Into Practise

So what does this mean to you? From a training point of view, if the only outcome you are looking to achieve from resistance training is hypertrophy then it doesn’t appear to matter what resistance you choose to lift, as long as you lift to a point of exhaustion.

This offers several training benefits, which you might have previously not contemplated. For example, if you train alone and have no one to act as a spotter then you would be far safer opting for a lighter load and performing further repetitions than you would struggling with a heavier weight.

Furthermore, if you are currently struggling with an injury that is worsened through the resistance applied, then why not drop the weight and work to failure? If your bench press 1RM is 100kg, then the stresses and strains of 30kg to exhaustion is much more appealing than 80kg, especially when struggling with an elbow or shoulder injury.

However, if you are looking to develop strength through your resistance training then there’s no substitute to lifting heavy. At a lower resistance, you simply won’t achieve the neural stimulation you require to develop.

So there you have your answer. If nothing else, the findings in this article provide real food for thought and equip you with the necessary knowledge to alter your training regime without fear of losing that all important muscle mass.