Q & A: How do I prove unilateral training is harder?

“I read your short piece on mountain bike training using unilateral training methods.I am not a biker but am interested in unilateral training.

I like your point about recruiting more muscles.

But . . . if you curl 100 lbs for 10 reps bilaterally, you’ve done 1000 lbs. If it takes 40 seconds, then you’ve put 25 lbs/sec of stress on your heart, lungs, Central Nervous System, spine, etc.

Now let’s say you’re stronger unilaterally and can curl 60 lbs, each arm.

60 lbs x 10 reps + 60 lbs x 10 reps = 1200 lbs . . . ostensibly more work.

But if it took you 40 seconds + 40 seconds = 80 seconds . . . that’s 15 lbs/sec worth of stress.

In other words . . . even though I “know” that unilateral is more work I’m stuck on how to show it.”


While I understand where you are coming from I first have to say that the “proof” of any training program lies in the results in produces. Using math equations can help us understand training better but it never “proves” anything.

To your point, though, bilateral training will allow you to expose the body to higher levels of stress. This is one of the main reasons that you still need it in your program. However, one method that allows you to accomplish a specific thing does not address everything you need as an athlete.

In my opinion, unilateral work should represent up to 50-80% of an athletes strength training volume because it is more specific to creating athletic movement, it does recruit muscles that do not activated during bilateral exercises and it allows you to expose your body to difficult exercises without excessive loads. In my experience this approach works best for long term development.

Hope this answers your question, let me know if you have any more…

Ride Strong,

James Wilson

MTB Strength Training Systems

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  1. Eric says:

    Effectively what you’re doing is calculating average power, where the units would be something like lbf*ft/sec. To do this you’d want to take the total work done and divide by the amount of time that it took to do it…you’re leaving out the distance that the weight was moved in your calculation, which is ok for comparison since it’s the same for both cases. A (somewhat) more rigorous derivation would look like:

    distance=reps/(distance per rep)

    Using your numbers and a “distance per rep” of 3ft (just picking something) you wind up with 75 lbf*ft/s for the first case and 45 lbf*ft/s for the second case…the same ratio that you came up with.

    What we’re looking at by doing this is the average power of the course of your workout, which is nice but only part of the picture. If this were really a good way of quantifying the “difficulty” of a workout, simply hoisting a 100lb weight quickly to your waist and then dropping it would give you an average power several times what we just calculated. Another problem with this is that you could do planks for an hour straight (good times!) and wind up with an average power of 0 because, although a force was clearly applied, there wasn’t any motion.

    Another way of looking at the problem would be the total force exerted by your muscles multiplied by the amount of time they were under that stress. This would be an impulse-based approach. The problem, obviously is that getting a total force summation for all of the muscles in your body isn’t exactly practical. As a complete guess I’d offer that the total force that your body produces for a unilateral 60lb dumbell curl is similar to that of a 100lb bilateral dumbell curl, due to the stabilization required. And the amount of time that you’re applying that force is roughly doubled, as you noted…therefore our total impulse for the unilateral case would be on the order of double the bilateral case…or something. I’m no expert.

    It’s an interesting question and obviously a lot goes into determining the answer. I’d be curious to know how the fitness professionals deal with these issues. Ok, time for a beer.

    Reply • January 18 at 1:47 pm
    • bikejames says:

      Thanks for the insight. Two quick points, though…

      First, the equation mentioned in the post was one the guy that contacted me was using. It is a bit simplistic but it does give you an idea of the different overall stress levels a bilateral vs. unilateral exercise puts on the body.

      Second, I’d like to consider myself a “fitness professional” and I model my training philosophy off of other highly successful fitness professionals so my response is how a certain segment of our profession approaches these problems. To be honest, over reliance on math equations and “scientifically proven” methods is the first sign of an amatuer in my book. When you actually work with real people in the real world you quickly find that training is just as much of an art as it is a science, requiring a broader view of program design than simply analyzing numbers.

      Thanks again for the insight, though, I hope you enjoyed your beer…

      James Wilson

      Reply • January 19 at 11:36 am
  2. Eric says:

    Yeah, I don’t disagree really with the equation. I mainly wanted to point out that there’s more to the effectiveness of a workout than how much weight you move and how far, so quantifying it that way will never tell the full story.

    Also didn’t mean to imply that you’re not a “fitness professional” by any means. I know next to nothing about training, but I feel like I’m pretty good at picking up on technical BS and it’s clear that you know what you’re talking about and I can trust what you’re writing without question. I guess it’s just the engineer in me that likes to describe certain things in terms of math…but any equation is only as good as the person doing the interpreting, and if it can’t be related/understood with respect to the problem it’s pretty worthless. Seems like the fitness industry is full of that pseudo-science. Heck, so is the medical field.

    Either way, thanks for the insight and keep up the good work…really enjoy the blog updates.

    Reply • January 21 at 5:49 pm

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