Single Leg Versus Double Leg Training

L leg bigger

We see many cases where patients have one limb bigger than the other in our clinics. There is an imbalance or deficit between limbs e.g. healthy versus injured, left versus right or dominant versus non dominant. This is also known as interlimb asymmetry in research. 

Strength, power, reactive strength have been shown to be affected when there were interlimb asymetries, especially in sporting performances. I have seen differences of 10-15 percent in deficits for patients even 5 years after they had surgery. Hence, I often suggest that patients work on single limb exercises to reduce this deficit/ asymmetry.

Single leg and double leg strength exercises, plyometrics, balance and even core training have been investigated in a wide variety of athletic populations to understand the effects of interlimb asymmetry. The following systematic analysis was to examine if training interventions are effective in reducing interlimb asymmetries and which types of interventions were more effective in the athletic population.

The single leg counter movement jump (SLCMJ), single leg broad jump (SLBJ), single leg lateral jump (SLLJ) and change of direction (COD) speed were the most commonly used test to check for sprint performance, jump height and COD speed.

Ready for the results? The review suggested that all training interventions have a small to moderate effects on the reduction of asymetry in SLBJ, SLCMJ and COD speed from pre to post training, although no statistically significant differences were reported. This was found in the intervention groups versus the control groups.      

The researchers suggested both unilateral and bilateral training should be considered to decrease interlimb asymmetries. If you're an athlete and have any limb asymmetries and no pain, then definitely do both single and double leg exercises to reduce the asymmetry. 

Please note that the above study was done on athletic populations. I will definitely avoid single leg exercises in the recently injured/ immediate post surgery patients and get them to do bilateral leg exercises first.

What about patients who are not loading equally a year (or longer) after a knee replacement or ACL reconstruction? I always see patients who tend to compensate too much with the non injured/ painful leg. By doing single leg exercises (pictured above), I can make their weaker side work harder.

Reference

Bettariga F,Turner A, Maloney S et al (2021). The Effects Of Training Interventions On Interlimb Asymmetries: A Systematic Review With Meta-Analysis. Strength Cond J. DOI: 10.1519/SSC.0000000000000701