Senchyna: Work out one limb at a time or two?

Go into any gym and you will see people doing weight training using two arms at the same time and others using one arm.

Likewise, some do two-legged exercises while some use one leg only.

Are there advantages to using one limb in isolation or is it better to use both at the same time?

Although there is no definitive single answer to this question yet, there is more research accumulating, which is helping to refine our understanding of these questions.

The crux of the debate arises because of an experimentally measured phenomenon called the bilateral force deficit.

The result of some research shows that if you measure the force you can produce with each limb separately and add these results together, you end up with a larger total force than if you use both limbs at the same time.

The exact reason for this phenomenon is not completely known, but there is speculation.

This has led people to think that it is more beneficial to exercise arms and legs in isolation, doing unilateral exercise rather than bilateral exercise.

Conversely, there are also those who would advocate doing bilateral for various reasons.

The research that indicates a bilateral exercise contains some subtle nuances that are important.

It turns out that the bilateral difference is greater in untrained, novice weight lifters compared to elite athletes or strength trainers.

The greater your strength and experience with weight lifting, the less this issue matters.

Elite athletes get less advantage doing unilateral exercises compared with beginners.

Another qualification in the research is that the advantage of using unilateral decreases with time, even over a period of a few months.

So what are the advantages of using one limb really?

Doing unilateral will necessitate the greater use of stabilizing muscles that surround the joint because the second limb is not contributing to assist in providing stability.

This is especially true for the legs.

Unilateral can also provide better sports-specific training. For example, sports like basketball that require one leg jumping are better served by training each leg in isolation in order to generate more force and stability.

The same can be argued for throwing sports.

Another advantage for unilateral is for rehabilitative or monitoring purposes.

When a limb is injured and in the process of being rehabilitated, using unilateral at low, safe loads will enhance the proprioception and balance of the injured limb, which is crucial, especially in the earlier stages of recovery.

Unilateral also serves as a marker of progress and comparison between limbs, which can sometimes be masked when doing bilateral.

There are advantages of doing bilateral over unilateral, however.

Bilateral is inherently safer at higher loads so there is less risk of injury. This is especially important with novice lifters who reach beyond their abilities, and with heavy weight lifters who are pushing into maximum ranges of force production.

Some have argued that by doing more stable bilateral exercises, you allow greater loads to be attempted and can make better progress as a result.

Another more practical advantage of doing bilateral exercise is that the sessions are shorter (by 50 per cent), and more effective than working each limb in isolation. This can be an advantage for beginners or those who have limited time to commit to the sessions.

In practice, elite athletic programs use both bilateral and unilateral exercises, depending on the particular sport and the time of the competitive season the athlete is in.

In the final analysis, there are merits for both methods.

And when it comes to starting a weight training program, or any other exercise program, it doesn’t matter if you do bilateral or unilateral.

Starting to exercise is the most important thing.

Kerry Senchyna holds a bachelor of science degree in kinesiology and is owner of West Coast Kinesiology in Maple Ridge.


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