Isolated leg drills and potential imbalances? What would you do?

Triathlon Forum
1

Here is data from a rider doing isolated leg drills on a Computrainer in erg mode. The rider was riding in erg mode in a pretty large gear and fairly low wattage (erg at 150, this rider’s threshold power is nearly twice that value), so initial wheel speed was around 26-27 mph or so and cadence over 90. 5 sets of isolated 30 second drills were performed switching from left to right.

Below is the drop in wheel speed (kph), average power, and average torque for each test over the 30 seconds (L# is left, R# is right). These were data collected from a PT wheel which explains the inconsistency between desired erg load and actual.

L1 - -10.9 kph, 119 W, 4 N-m
L2 - -11.9, 122, 4.1
L3 - -8.3, 136, 4.2
L4 - -11.2, 122, 3.88
L5 - -11.2, 117, 3.7
R1 - -8.2, 132, 4.21
R2 - -5.8, 139, 4.24
R3 - -5.4, 141, 4.22
R4 - -4.9, 138, 4
R5 - -4.8, 150, 4.12

Average, deviation of left and right parameters

Left speed – 10.7 kph drop, 1.39 kph deviation
Right speed – 5.82 drop, 1.39 deviation

Left power – 123.2 avg, 7.46 deviation
Right power – 140 avg, 6.52 deviation

Left torque – 3.976 avg, 0.19 deviation
Right torque – 4.158 avg, 0.1 deviation

What, if anything, would you conclude about this rider? Does there appear to be an obvious imbalance in leg strength or muscle composition? What would you recommend to this rider to fix this apparent difference?

2

Isolated leg tests are not a very good indicator of cycling functional capacity since they don’t replicate what is really going on when riding with two legs. The problem is the upstroke. The upstroke has to actually apply substantial force and power to keep the stroke going, when pedaling with just one leg whereas it need simply unweight (and not even fully unweight unless riding with PowerCranks) when riding two legged. So, someone could appear to be very unbalanced when riding one legged (because the unbalance could only be in the hip flexors) but not be so unbalanced when riding two.

Anyhow, if one is substantially unbalanced correcting it is almost impossible, me thinks, without PowerCranks.

3

What if one were to notice such a discrepency while 2 legged pedaling! Is it correctable, and if so, where would one start. How can one diagnose where the issue is…leg length, muscle imbalance, unusual tightness, flexibility, etc…?

4

What if one were to notice such a discrepency while 2 legged pedaling! Is it correctable, and if so, where would one start. How can one diagnose where the issue is…leg length, muscle imbalance, unusual tightness, flexibility, etc…?
It is very difficult to recognize, and when it is recognized it is very difficult to “diagnose”, let alone correct. Here is why I say so. When I go to expo’s we put people on PowerCranks and what do most of them find, one leg is stronger than the other, yet they never knew that. Then, some get on the bike saying they know one leg is stronger than the other and, occasionally, what they find out is the leg they thought was the weak one was really the strong one. They thought it was weak because it was the one that was always getting tired. What they find out is it is the one doing all the work.

PowerCranks is about the only way I know of that can reliably diagnose then correct these lower extremity muscle imbalances because there is no way to compensate for the weaknesses.

5

Thanks, Frank. I notice quite a difference in the spinscan screen between my 2 legs, so wonder where my issue is, as I’m sure my age and lack of flexibility has a lot to do with it. That said, I also wonder if it is worth messing with as sometimes the body compensates for an issue in the way it should. Convoluted thinking?

6

Thanks, Frank. I notice quite a difference in the spinscan screen between my 2 legs, so wonder where my issue is, as I’m sure my age and lack of flexibility has a lot to do with it. That said, I also wonder if it is worth messing with as sometimes the body compensates for an issue in the way it should. Convoluted thinking?
Spinscan can be difficult to interpret because the two legs are tied together. A weakness unweighting on the right can look like a weakness pushing on the left. The body compensates for weaknesses however it can, not how it should. Weaknesses and imbalances are simply injuries waiting to happen (and most, probably, are the result of an earlier injury that was improperly rehabbed) and they should be corrected, if possible.

7

My issue seems to be someone competent in finding those issues, and solving them. After this many years in sport, one thing compensates for another, and down the line and now I’d like to be more efficient. When going for a bike fit, they said…wow, left hip is high, right shoulder drops, this and that, but you’re still fast??? If we could break your hip and start again…

8

My issue seems to be someone competent in finding those issues, and solving them. After this many years in sport, one thing compensates for another, and down the line and now I’d like to be more efficient. When going for a bike fit, they said…wow, left hip is high, right shoulder drops, this and that, but you’re still fast??? If we could break your hip and start again…
You don’t have to find someone competent to diagnose and fix these problems. PowerCranks will probably do it for you. If they don’t you can send them back within 3 months and get your money back.

9

Thanks. With this economy, the only thing I could do was get a loaner set. I bought the new bike before business came to a screeching halt…

10

And now for the punchline. The rider in question is myself. Some 6-7 years ago I fractured my left leg at the femoral head. Ever since then my left leg has been slightly weaker (if I spinscan I’d get like a 54/46 or better split). I can tell that my right leg is stronger with regular cranks. I’ve logged over 170 hours on PCs since August and haven’t noticed any perceptable change in left/right split with either PCs or regular cranks…

So what did this little experiment tell me?

  1. You fatigue a lot faster doing isolated leg drills than using PCs with both legs
  2. There’s not much sense to pedaling one legged
  3. Along the lines of 2) above, you need that proper balancing of forces to pedal effectively (i.e., two-legged pedaling compensates for known issues)
  4. PCs haven’t changed my l/r distribution when doing isolated leg drills (i.e., they haven’t improved my “condition”)
11

And now for the punchline. The rider in question is myself. Some 6-7 years ago I fractured my left leg at the femoral head. Ever since then my left leg has been slightly weaker (if I spinscan I’d get like a 54/46 or better split). I can tell that my right leg is stronger with regular cranks. I’ve logged over 170 hours on PCs since August and haven’t noticed any perceptable change in left/right split with either PCs or regular cranks…

So what did this little experiment tell me?

  1. You fatigue a lot faster doing isolated leg drills than using PCs with both legs
  2. There’s not much sense to pedaling one legged
  3. Along the lines of 2) above, you need that proper balancing of forces to pedal effectively (i.e., two-legged pedaling compensates for known issues)
  4. PCs haven’t changed my l/r distribution when doing isolated leg drills (i.e., they haven’t improved my “condition”)
    Some people are not capable of attaining 50-50 l/r balance because of structural/mechanical issues. A femoral head fracture could change the mechanical advantage of the muscles if it didn’t heal exactly as it was before. So, perhaps that is the case with you as a result of your fracture. Or, do you know you were balanced before the injury? Perhaps this is just you. (edit: some people are missing muscles, one side vs the other - this is seen fairly commonly in the anatomy lab in medical school so it may be impossible for some to ever achieve complete 50-50 balance).

To me, what is important is whether one is as balanced as possible when doing the core activity, not when doing some drill. It is hard to imagine that the PC’s do not get the rider as close to that goal as is possible with enough time.

12

Got a funny story:

I started with my “powercranking” in the middle of my racing season (I’m a road cyclist) So most days I just did 15-20 mins. inside on a trainer before my regular training outside. After the first interval of the day I remember myself standing at the side of the road with a VERY “dead” left leg, while my right leg was fine: guess I used to pedal more with the right leg :slight_smile: