Unilateral training (single-arm and single-leg)
Single-limb exercises build strength well and are better for single-leg jumping, while two-limb lifts are better for two-limb strength: each mainly improves what it trains. Training one limb also makes the untrained one somewhat stronger.
What the science says
- Each mode best improves its own tasks Moderate evidence
Liao et al.'s 2022 meta-analysis of 14 studies (392 people aged 16–26) found unilateral training improved single-leg jumping more, while bilateral training improved bilateral strength more. Differences for sprinting, change of direction and bilateral jumping were not significant.
- Training one limb strengthens the other Moderate evidence
Manca et al.'s 2017 meta-analysis of 31 randomized trials found unilateral training raised strength in the untrained limb by about 12% on average, although risk of bias was high across studies.
How to apply it
Use bilateral lifts as the base for strength and add unilateral work to cover each side and sport-specific needs.
Who should be careful
Single-leg exercises demand balance; use support or a lighter load at first. For training around an injured limb, ask a physician or physical therapist rather than relying on cross-education.
Frequently asked questions
Are single-leg exercises better than squats?
Neither is better overall: a meta-analysis found unilateral training improved single-leg jumping more and bilateral training improved two-leg strength more.
Does training one arm make the other stronger?
Yes, somewhat: a meta-analysis of 31 trials found about a 12% strength gain in the untrained limb, although the studies had a high risk of bias.
Which side should I start with?
Start with the weaker side and match its reps on the stronger side, so both get the same work.
Scientific references
More training variables
- Training volume (sets per muscle per week) Strong evidence
Weekly volume, counted as hard sets per muscle, is one of the best-supported drivers of muscle growth: more sets bring more growth, with diminishing returns.
- Training frequency (sessions per muscle per week) Moderate evidence
When weekly volume is the same, how many days you split it across makes little difference to muscle growth.
- Rest intervals between sets Moderate evidence
Very short rests (under about a minute) tend to cost you reps and slightly blunt growth; past about 90 seconds, extra rest brings little added hypertrophy.
- Load and rep range (heavy vs light) Strong evidence
Muscle grows similarly across a wide range of loads, from heavy sets of 5 to light sets of 30, as long as sets are taken close to failure.
- Proximity to failure (reps in reserve) Moderate evidence
Sets need to be hard to drive growth, and hypertrophy tends to rise the closer you get to failure.
- Repetition tempo (time under tension) Limited evidence
Deliberately slowing your reps to maximize 'time under tension' does not build more muscle.