Both heavy lifting with few reps and light lifting with many reps cause muscle damage, but neither does it more than the other.

When rats do low-frequency weightlifting, their blood doesn't show signs of muscle soreness or energy stress, meaning this kind of exercise doesn't hurt or tire their muscles.

When rats do resistance exercises less often, their blood doesn't show signs of muscle damage or stress—so this kind of workout seems gentle on their bodies.

If you're a guy who lifts weights regularly, taking a specific supplement called HMB-FA about 30 minutes before a super tough workout might cut down muscle soreness and damage by nearly 70% compared to not taking it.

If you slow down the lowering part of weightlifting, your muscles might get more damaged and your body might release more of the hormones that help build muscle—this is what the claim says about guys who lift weights.

When trained guys do lots of reps, they feel more tired, weaker longer, and more stressed than when they do fewer heavy reps — even though their muscles are damaged about the same.