Heavy Weights Vs Light Weights, what does the research say is best for building Strength and Size.
Heavy Weights vs Light Weights, which are better?
Well that is going to depend more specifically on what your own goals are as we will see.
One thing that has be thoroughly proven, regardless of gender or age, resistance training results in muscle growth.
Lifting weights is also called resistance training because you are contracting your muscle fibers against resistance, in this case the resistance is gravity resisting your muscle as you move the weight through space.
Each muscle is made up of thousands of individual muscle fibers.
Resistance training results in this growth thanks to a phenomenon called mechanotransduction, where specific sensors in your individual muscle fibers known as mechanosensors, convert this mechanical energy into chemical signals that mediate myocellular anabolic and catabolic pathways. In other words, once they detect that their fibre is under enough load to trip a certain threshold, they start signaling that the muscle fiber needs to grow.
The idea that you need to go heavy is based on the idea that heavier weights are needed to achieve full recruitment of those higher threshold fibers, the ones that are the most stubborn to sending the growth signal.
In 2016 a Meta Analysis was published in the European Journal of Sport Science, which compiled 9 studies on this topic, and set out to answer this question once and for all.
The meta analysis found studies which compared two groups of participants, where one group was lifting weights that were above 65% of their 1 rep max strength, while the other group was lifting less than 60% of their 1rm strength and both groups lifted the weight until they couldn’t do another rep.
In terms of muscle gained, the high and low weight groups both gained a similar amount.
How can this be?
Well, although a single rep of a heavier weight vs a lighter weight will provide greater activation to the type 2 fibers, the KEY lies in the fact that both groups took their sets to momentary muscle failure.
So although the lightweight group got less activation per set, their sets lasted much longer, and those additional reps, although they were with a lighter weight, continued to activate the muscle, until even the most stubborn fibers activated.
So it looks like both light and heavy weights, as long as taken to momentary failure result in about equal hypertrophy, I say that because although it wasn’t statistically significant, there was still a slight trend in favour of the higher weight.
Strength was a slightly different story, because although strength is highly correlated with muscle hypertrophy. There are also various other elements at play, psychological factors including confidence and fear, your motor control and technique, and CNS adaptations all play a roll. These are better trained by lifting those heavier weights.
Lastly it should be mentioned that muscle size and hypertrophy aren’t one and the same, because of this, people who do high reps with a lighter weight may benefit from the illusion of larger muscles.
This is because your muscles store their energy along with water which can influence how big they look at any given time, despite not being a result of hypertrophy Glycogen content in the muscle can significantly alter the apparent size of the muscle at any given moment.
Glycogen is the primary fuel burned by your muscles after about 10 seconds of activity and continues to be the main mover until about 120 seconds, the advantage of it is that burning it is an anaerobic process, meaning it doesn’t require oxygen so the power output isn’t limited by your ability to breathe in oxygen.