A question I get asked a lot, especially this time of year, is about weight lifting routines. Specifically should my athletes (runners, cyclists, and triathletes) lift throughout the winter, and if they do it, when and if they should stop lifting.
Let me start by saying that, as a physical therapist, I do think that weight-lifting is beneficial for most every athlete, but the degree to which an athlete needs to participate can vary greatly.
I think that in the dark of winter, just about every athlete could see some benefit from a few weeks of weight lifting. Will this make them stronger in the short term? Certainly. But they shouldn't expect to really hang on to any of this strength once they stop, and especially as they head into the summer racing season. What's the point then? While I wouldn't expect to see someone really cranking out significantly more watts I think the benefits for injury prevention or resistance are worthwhile. Some of the structural changes that occur at the tendon and bone/tendon junction can help prevent break down of these tissues during hard training phases. I know some people may say, "Well if it helps you during hard efforts, then it must make you stronger/faster". Maybe. It's no guarantee that the athlete who didn't do the weight routine, would definitely get injured; nor is it clear that he athlete who did the weight routine would be able to swim/bike/run faster or harder during their intervals.
I think triathletes have the most chance for gain with the weights -- the more "whole body" nature of the sport and the fact that triathletes tend to be bigger and more muscular than their cycling and running counterparts, makes it a good match for weight-lifting.
The problem with weight-lifting and these types of sports is two-fold:
1. the extra body weight is often not helpful and often becomes a liability -- again triathletes are exempted from this a little
2. sport-specificity is definitely not a strong suit of weight-training
The extra muscle mass is easy to understand, but what is the sport-specificity thing have to do with it?
Put simply, some tasks (specifically pedaling a bike is what I will spend the most time on right now) are too complex biomechanically to have the strength increases transfer over from weight-training. Think about it this way: when you train your quadriceps in the gym what is the most common exercise? The squat or leg press, right? How does the brain "see" this exercise from a motor-plan standpoint? It basically breaks down like this:
distal quads activate (eccentrically of course) first to manage patellar movement -- progressive engagement of the majority of the quad muscles -- deeper into hip flexion the gluteals/hip extensors engage progressively -- then all these muscles work concentrically to reverse the motion
The most important aspect here? BOTH legs are working at the same time in the same direction.
So what about the motor plan of a pedal stroke on the bike:
(starting at the top of the pedal stroke - 12 o'clock)
the gastroc-soleus muscles (calves) progressively engage from 12 until about 3o'clock as does the gluteus max (rear end), but the gluteus is done with it's power phase and on the decline even before 3 o'clock -- in this same time period the quad muscles (specifically the vastus muscles and the rectus femoris) are in the middle of their engagement and declining, and their involvement flatlines around 4 or 5 o'clock -- just before 3 o'clock the hamstrings start to engage and they peak about 4:30 and start their slow decline until about 8 o'clock -- after 6 o'clock nothing much is going on, but ideally the tibialis anterior and the hip flexors would be working powerfully from about 7 o'clock until about 9 or 10 o'clock (this does not happen to a significant degree, however, for all but the most talented of pedalers) -- at 9 o'clock the rectus femoris begins it's phase and the vastus muscles start a bit later at around 10:30 -- and then we're back at the beginning.
What's the most important aspect here? ONE leg is doing this complex sequence while the other is doing the OPPOSITE while positionally opposed 90 degrees.
The second most important aspect? On the back side of the pedal stroke (from 6 until 9 o'clock specifically) our leg can't get out of the way fast enough of the rising pedal (and it's rising because our opposite leg is powerfully pushing it down) so everyone (yes, everyone - even the most efficient pedalers) is exerting a sort of "negative torque on the pedals with their recovering leg.
Back to the weights: If you are training your quads/gluts to push downward with more force, invariably they will be doing so with more speed as well. If you haven't improved your body's ability to get the recovering leg out of the way, that leg will only be exerting more "negative torque" and your net gain of power is roughly zero. Can you train the legs to improve during their recovery phase -- basically training to improve hip flexion? Possibly, but their is a significant limitation of this as well and it has to do with another aspect of sport or task specificity -- cadence. Often we're pedaling at roughly 90 rpms. Do we ever do weights at this frequency? It's not really feasible.
What's the answer? If you're going to work on your strength do it on the bike where you have the specificity of the pedal stroke motor plan and where you can work on training the recovery leg to improve with the power phase.
For my athletes, I have them do specific intervals on the bike to work on strength AND cadence in a bilateral and a unilateral manner.
So if you don't get into the gym this spring after being diligent through the winter, don't sweat it too much. Often there are other, more efficient ways to use your time.