Strength vs. Size - How Many Reps Are Really Best?

Just the other day, a client named Tim came into my office because he was struggling to add lean muscle. He was eating right and training at a CrossFit box 4-5x per week (and getting stronger), but couldn’t seem to pack on the 10 pounds of lean muscle he was looking for. He was stumped. This is a classic case of really having clarity in your goals. Are training to get stronger so that you can perform better in your sport? Or is your primary goal to get bigger and add size to your frame? 

This is an age-old question and some new research is helping to shed some light on the best repetition range for promoting hypertrophy gains (aka – getting bigger!).

A new study in the Journal of Sports Science and Medicine investigated the muscular adaptations to heavy and moderately heavy loads in the gym. In short, they wanted to nail down what the ideal rep ranges for increasing your strength and hypertrophy. Are the same loads enough to produce gains in both? Or do you need to tailor your training to your specific goals?

Nineteen young men were recruited and divided into two groups; the heavy group trained in the 2-4 repetitions range per set and the moderate group trained at 8-12 repetitions per set. They trained three days per week for two months, performing three sets of seven total exercises per session.

The results reinforced something all great strength coaches likely already know… rep scheme really matters.

While both groups showed increases in 1-repetition maximum (RM) squat, the group training with the heaviest loads (2-4 reps) had much greater increases than the moderate group.(1) On the other hand, muscle thickness in the thighs were notably higher in the group training at 8-12 reps versus the heavy group.(1) This reinforces the notion that moderate loads are crucial for adding size and increasing hypertrophy. The researchers concluded that heavy loads are best for maximal strength goals, while moderate loads of 8-12 reps are best suited for hypertrophy goals when performing the same number of sets.

So, how does this impact Tim’s hypertrophy roadblock?

Many CrossFit-style training centers focus on heavy Olympic lifts (5 reps or less) at the start of sessions, and metabolic conditioning at the end of sessions (i.e. 15 reps or higher). While this is great for improving strength and work capacity, it’s not a lot of time spent in the loading range that support the greatest gains in hypertrophy and size.

Make no mistake, you can get achieve hypertrophy doing CrossFit workouts. However, if you’re an ectomorph body-type (i.e. tall and skinny) you’ll likely need to add more training sessions in the hypertrophy rep range of 8-12 to achieve your goals. (Oh yeah, and don’t forget to eat 6 meals a day too!)

Dr. Marc Bubbs ND, CISSN, CSCS


Check out more articles in the HYPERTROPHY SERIES...


1) Schoenfeld B., et al. Differential Effects of Heavy Versus Moderate Loads on Measures of Strength and Hypertrophy in Resistance-Trained Men. Journal of Sports Science and Medicine (2016) 15, 715 – 722.