Heavy weights vs Light weights for muscle growth

For decades, there has been a common belief that you can't achieve serious muscle growth unless you lift as heavy as you possibly can and that lighter weights are mostly suitable for better definition and pump. This is not completely true and you are about to find out why.

Muscle fibers

People have two general types of skeletal muscle fibers: slow-twitch (Type I) and fast-twitch (Type II). Type I fibers are mostly stimulated by longer duration sets requiring lower loads and help us enable long-endurance feats such as distance running. On the other hand, Type II fibers require shorter duration sets with heavier loads in order to be activated and are used in powerful bursts of movements like sprinting.

Research

There have been several studies that divide people into 2 groups. The group A lifting heavy weights for less repetitions and group B lifting light weights for more repetitions. All of them came out with pretty close results concluding that heavy weights and light weights lead to similar muscle growth when volume is equated for and sets are taken close to failure.

Facts

So according to research, heavy weight training provides similar or equal results to light weight training. Before you think that the load weight is irrelevant keep in mind that these studies required pushing to near failure regardless of the weight used.

Training to failure in a higher rep range is much harder than doing so with lower reps due to the increased metabolic stress. It actually feels a lot more uncomfortable trying to get to failure with light weights that you will probably quit in the process. Therefore, you will never have the same results as if you were lifting heavy, just like the research indicates.

Whereas, reaching close to failure tends to be more achievable when lifting heavy weights as the metabolic stress you will experience will be for much shorter duration. In order to reach fatigue levels you will need 5-8 reps of heavy lifting compared to 20-25 reps with light weights.

At the end of the day, it is all about the tension you drive into the muscle and the stress you experience trying to lift those weights. If the tension is high enough you will experience muscle growth regardless of the amount of weight you are lifting, but in order to achieve maximum growth you need to use heavy and light loads so that you can activate both types of muscle fibers.

Comparing heavy versus light weights showed that the use of heavy weights tends to be better in terms of strength gains. So if you want to increase your strength in certain exercise you will need to focus on lifting heavy for low reps (max 5).

Advice

All things considered, it is essential to use both heavy and light weights while training. My advice is to go heavy on compound movements (such as bench press, dead-lift, squat etc.) trying to achieve progressive overload and use lighter weights on isolation exercises trying to increase reps or weight if possible. This is proven to be the best way to accomplice maximum muscle growth.

Sources:

https://www.ncbi.nlm.nih.gov/pubmed/25530577

https://www.ncbi.nlm.nih.gov/pubmed/28032435

https://www.ncbi.nlm.nih.gov/pubmed/18978616