Hi Dude - Thanks for the question
*Won’t my strenth potential actually be limited then? Muscles get stronger from progressive overload right? I understand how I accomplish that on a leg press machine. How do I accomplish progressive overload otherwise? I think in your article you show lunges as a replacement exercise for the leg press. How would I accomplish progressive overload using just my body weight? *
Since I was directing my article towards triathletes I was mainly speaking of sport specific strength, the kind that will carry over to the swim/bike/run. When we concentrate on local groups of muscles our stabilizers tend to be neglected, as in the leg press or most other machines. So, if I read your post correctly, you are saying that with the leg press you can pile on the weight and therefore create overload, one that surpasses what you could do, for instance, on a squat. And that is true. However, you are creating strong muscles that will produce some great force but without the needed core strength for your body to handle that force. A couple things may happen when you call upon that force on the bike. Either your legs will only produce the amount of force your core can handle or it will produce more force than your body can handle and may cause injury (ever have lower back pain?). So, that is why I prescribe closed-chain exercises that start off with body weight, even one-legged to really challenge stability, then progress to adding additional weight to increase force production. This is coming up in the next article but I will write a bit more about it here.
So, if we take the squat exercise, for instance, which is a closed-chain functional exercise that is most similar to the strength created in a leg press, we can create progressive overload in any way that it would tax the muscle more so then we have before. Now, I believe I said in the article that there are 2 ways to create strength in the muscle. One was through hypertrophy, actually increasing the fiber size (myosin) within the muscle cell the other by increasing the amount of motor units that innervate the muscle cell. So, in performing a squat with just bodyweight, if it’s not that difficult, you are not providing sufficient overload to create more strength, maybe not even enough to maintain. However, if a one legged squat is difficult, you are creating sufficient overload to create additional strength. This is done because your body has to recruit additional motor units to innervate muscle cells that may have never been used before or not used to the extent it is needed with this exercise. Hypertrophy is minimal with bodyweight exercises. Now, let’s say you master the one legged squat, how can you progress? Well, you can add weight or place a balance implement under that one foot to make that squat more difficult. This is a common progression that’s in our Stability phase or AA.
Now, let’s say you have mastered the one-legged squat, are 4 months out from your A race and you want to focus on force production. I would prescribe you to move to the Max Strength phase and take that squat to the weight room. In this phase you could execute that squat with 2 legs, max base (legs spread to about hip distance apart for stability), with as much weight as you can handle 3-5 times for 3-5 sets. Now, these should be done with proper technique and each one done strong, NOT “to failure”. This will help to create maximum force by recruiting the maximum number of motor units AND creating hypertrophy.
Let’s continue. You just finished 4 weeks of max strength without any problems and still want to progress. The next step would be Power Endurance Long. Try to recruit the strength gained from the last phase with the quickness you will need in your sport. Again, using the squat, I would turn it into a jump squat. Start with bodyweight only and accomplish as many reps as you can, with minimal ground contact and proper form. The “long” comes from the amount of reps. Most programs that even recognize this phase will recommend 15-20 reps. So ask yourself, how many revolutions will it take to get up that tough hill? If it’s only 20, you may be ok 
And the last phase, Muscular Endurance Long. Again, using the squat, start with bodyweight only, maybe for 2 minutes straight. One legged or two, you can make both a challenge. Slowly progress to more time.
Now, I generalized, but I think it gives you an idea how a simple exercise that is very specific to the movement of your sport, can be a challenge and provide the overload necessary to stimulate the right strength gains that will transfer over to the bike.
Hope that helps and didn’t give you a headache Let me know if I need to further clarify and keep the questions coming!
maylene