We have all heard the saying, "Heavy weight low reps builds muscle and lightweight high reps burns fat."
But is there any truth to this statement or did someone just think it sounded good and so it spread?
The truth in that statement is in both parts. Yes heavy weight with low rep schemes do build muscle but so can lightweight with high rep schemes. The second part of the statement is a little trickier because when it comes to burning fat our objective is to burn extra calories so we can decrease body fat while maintain all or most of our muscle tissues and both can be achieved through both methods but it must be done in a certain way.
There are fast twitch muscle fibers (Type II) and then there are slow twitch muscle fibers (Type I). Slow twitch muscle fibers fire much slower and do not fatigue as quickly as fast twitch. They are responsible for more endurance type feats. Fast twitch muscle fibers on the other hand generate short bursts of speed and strength but fatigue much quicker than slow twitch. Technically there are two types of fast twitch muscle fibers: Type IIa and Type IIb. Type IIa are a combination of both Type I and Type II muscle fibers. Therefore they can perform both short bursts of strength as well as feats of endurance. Type IIb are the traditional fast twitch muscle fibers that fire rapidly but also fatigue rapidly.
As you can see, certain muscle fibers are responsible for different actions therefore they should be trained in different ways as well. Slow twitch muscle fibers should be trained with higher reps and fast twitch with lower reps. Therefore a training protocol that incorporates all different types of rep schemes based on the muscle fibers being worked is a great approach.
The ultimate factor all boils down to improvement or progression. Are you progressively lifting heavier weights or progressively adding more volume or sets? Whether you are using sets of 15 or sets of 8 on bench press you should be working to add in more sets at that same weight or increasing your weight while still hitting those desired reps. At all times you should be striving to add in more sets or increasing the weight at which you perform your sets at. This is known as Progressive Overload and it should be applied to all exercises. This will stimulate your body to build new muscle if in a caloric surplus and if in a caloric deficit it will help maintain the muscle you have while giving up body fat instead.
EX) week 1 -bench press 3 sets of 10 @ 135
week 2 - bench press 4 sets of 10 @ 135
week 3 - bench press 5 sets of 10 @ 135
week 4 - bench press 3 sets of 10 @145
The numbers are all hypothetical and you will need to adjust them based on how fast or slow you are progressing. You will do this will all of the exercises each workout and try to improve over time. Keeping a journal is very important as you can track your progress and know the changes you must make. Also taking each last set to failure is a great idea as you can track progression week to week from that as well.
Ultimately both high and low rep schemes will build muscle and assist with fat loss but a combination of the two is the best approach paired with progressive overload like we talked about above.
