Recent studies have found that both heavy and light weight training can increase muscle growth, both can equally stimulate muscle protein synthesis when reps are taken close to failure.
HEAVY WEIGHT VS LIGHT WEIGHT TRAINING: WHICH IS THE BEST WAY TO INCREASE MUSCLE PROTEIN SYNTHESIS? SUMMARY
- Both heavy and light weights can stimulate muscle protein synthesis equally. However, while you don’t need to lift heavy weights (>60% of a 1-RM) to failure to boost protein synthesis, you should lift light weights (~30% of a 1-RM) to failure to achieve the same effect.
- Both heavy and light weight can equally produce hypertrophy.
- Acute increases in muscle protein synthesis don’t always result in long-term muscle growth.
IS HEAVIER WEIGHT LINKED TO HIGHER MUSCLE PROTEIN SYNTHESIS?
After resistance training and taking in all essential amino acids post-exercise, protein synthesis increases, but protein breakdown stays the same. This consistent tension overload and the subsequent rise in muscle protein synthesis drive the body’s adaptations to exercise, leading to muscle enlargement. People once thought that you needed to exercise at intensities above 60% to get the best increases in muscle protein synthesis. Yet, it’s important to note that the weight lifted (from about 30-90% of a 1RM) doesn’t directly correlate with muscle growth when exercises are done to complete failure.
DOES THE INCREASE IN PROTEIN SYNTHESIS CORRELATE DIRECTLY WITH THE WEIGHT LIFTED?
Resistance exercises using light weight and high volume (24 reps at 30% of a 1 RM to failure) prove more effective in enhancing muscle protein synthesis than those using heavy weight and low volume (5 reps at 90% of a 1 RM to failure). Notably, the protocol using 30% of a 1 RM to failure showed similar muscle protein synthesis increases to the 90% of a 1 RM to failure protocol 4 hours post-exercise. However, only the 30% of a 1RM to failure group maintained this response at 24 hours post-exercise.
It’s essential not to misinterpret this study as advocating for consistent light weight training. The research indicates that one can achieve comparable muscle protein synthesis increases across a broad range of exercise intensities, as long as they push to failure. On the other hand, heavier weights can trigger significant protein synthesis increases without reaching failure.
AT WHAT % OF A 1-RM DOES PROTEIN SYNTHESIS MAX OUT?
Researchers had subjects exercise at different exercise intensities that ranged from 20% to 90% of a 1RM. The study was designed to make the total exercise volume as close as possible between exercise intensities. Exercise intensity, sets, and reps for the groups were: 20% of 1-RM (3 sets × 27 reps), 40% (3 sets × 14 reps), 60% (3 sets × 9 reps), 75% (3 sets × 8 reps), and 90% (6 sets × 3 reps).
Keep in mind that this study did not have subjects train to complete failure. At the end of the study, protein synthesis maxed out at approximately 60% of a 1RM; adding higher amounts of weight did not result in additional increases in protein synthesis. There was no difference in protein synthesis rates between 60%-90% of a 1RM. Despite the subjects not training to failure, heavier weights (>60% of a 1RM) can still maximally increase protein synthesis rates.
The research indicates that for lighter weights (around 30% of a 1RM), sets should reach complete muscular failure to optimize protein synthesis. In contrast, with heavier weights (ranging from 60-90% of a 1RM), you don’t need to push to complete failure to achieve peak increases in protein synthesis.
DOES ACUTE PROTEIN SYNTHESIS RESULT IN MUSCLE GROWTH LONG TREM?
Protein synthesis and its relation to muscle growth are complex biochemical processes that take place over time. Be cautious when extrapolating acute protein synthesis studies to increases in muscle growth. One might logically think that immediate spikes in protein synthesis would align with muscle growth. Yet, research shows that short-term protein synthesis rates don’t necessarily correlate with muscle development.
A study by Mitchell et al. had men follow a linear periodized resistance training program consisting of 3 sets of 12 repetitions to 4 sets of 6 repetitions for 16 weeks. At the end of the study, despite increased muscle protein synthesis post-exercise and 6-hour post-exercise, the increases in muscle protein synthesis were not predictive of muscle hypertrophy. It’s likely that the protein synthesis responses are highly variable among lifters, and long-term changes in muscle protein synthesis may change over a training program.
Keep this study in mind when you read a study that finds a particular exercise or supplement results in acute increases in protein synthesis; this does not mean it will translate into greater muscle growth. This is similar to the article on believing that increased muscle activation will always result in muscle growth.
In sum, you can get optimal increases in protein synthesis from an extensive range of exercise intensities (i.e., 30-90%) provided the repetitions are close to failure; however, going heavier than 60% of a 1-RM will not elevate protein synthesis further based on the research. Recent studies have found that both heavy and light weight training can increase muscle growth when reps are taken close to failure.
- Both heavy and light weights can stimulate protein synthesis equally. However, while heavier weights (>60% of a 1-RM) don’t need to reach failure to boost protein synthesis, lighter weights (~30% of a 1-RM) should be taken to failure.
- Both heavy and light weight can equally produce hypertrophy.
1. Brad J. Schoenfeld et al., “Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-Analysis,” Journal of Strength and Conditioning Research 31, no. 12 (December 2017): 3508–23.
2. Nicholas A. Burd et al., “Low-Load High Volume Resistance Exercise Stimulates Muscle Protein Synthesis More than High-Load Low Volume Resistance Exercise in Young Men.,” PloS One 5, no. 8 (August 9, 2010): e12033.
3. Vinod Kumar et al., “Age-Related Differences in the Dose-Response Relationship of Muscle Protein Synthesis to Resistance Exercise in Young and Old Men,” The Journal of Physiology 587, no. 1 (January 15, 2009): 211–17.
4. Cameron J. Mitchell et al., “Acute Post-Exercise Myofibrillar Protein Synthesis Is Not Correlated with Resistance Training-Induced Muscle Hypertrophy in Young Men,” PLOS ONE 9, no. 2 (February 24, 2014): e89431.