Ask The Trainer #93 – Lighter Weight & More Reps?

Ask The Trainer #93 - Lighter Weight & More Reps?


I am 56. My orthopedic doctor told me after looking at recent knee x-rays that I should not go heavy on leg exercises (leg press 1,000 lb for reps) She said maybe do lighter weights and higher reps. I was wondering in doing so, won’t I end up doing as much or more total weight pushed. I wanted to know if one method is better than the other, or does it come down to personal preference?



Hi, Kevin. This somewhat of a tricky question to answer, simply because I don’t know exactly what your diagnosis is.

Your knee is made up of many important structures, any of which can be injured. The more common knee injuries include fractures around the knee, dislocation, and sprains and tears of soft tissues, like ligaments. In many cases, injuries involve more than one structure within the knee. The safest, and most advantageous approach will depend on the exact injury, or injuries, you have sustained.

Since your doctor instructed you to lighten up on the weights and perform higher reps, I’m guessing there’s an existing injury that could be exacerbated by using too heavy of a workload.

The risk of working with heavy, high impact workloads in low reps ranges is that some really bad things can happen instantaneously without warning. If you’re using a lighter workload, you have time to detect potential catastrophes before they occur.

For example, let’s say you were recovering from a sprained medial collateral ligament in one of your knees, and you decided to go do a leg workout. Bear in mind that a component of your knee has already been compromised, and it’s not at full strength yet. Let’s say you go hit the leg press machine, throw on 1,000 pounds and crank out a heavy set.

Initially, when you engage in a very heavy weight, there is so much shock to your central nervous system, you can lose awareness regarding any potential threats to the tissues in your body. Instead of thinking about your knee, you feel like you’re going to throw up from the extreme effort and strain on your nervous system.

Furthermore, let’s also say that the sudden impact of 1,000 pounds happens to present the exact amount of stress that exceeds the structural integrity of the sprained ligament in your knee. Without any warning, there’s a gut-wrenching SNAP! You didn’t see this coming! Your MCL ruptures, causing your knee to suddenly give way, and you lose control of the weight.

I won’t explain the rest of this story in any great detail. But, let’s just say that if this actually did happen, it’s a pretty sure bet the results would be extremely unpleasant!

Okay, now let’s consider a more pleasant scenario. Let’s assume you decided to put only 500 lbs. on the leg press machine. It’s not nearly as much of a shock to your nervous system, and you don’t feel like throwing up, so you’re more in tune with the tissues in your body. Your knee in particular.

Nothing is numb. You go ahead and do 20 reps. You can feel the muscles in your legs burning, but you’re still well aware of how your knee is holding up. It feels good. No issues. No problems since 500 lbs. did NOT exceed the threshold of that ligament. Even though you did 20 reps, there simply wasn’t enough immediate overall force to cause that ligament to rupture.

Do keep in mind, however, there is still a chance you could still cause further damage to the weakened ligament. The impact of 500 pounds may not be enough force to cause that ligament to completely rupture, but it could still be enough to increase stretching and micro-tearing, which would worsen your injury.

Fortunately, when that begins to happen, you’ll be able to feel something is wrong before you do any serious damage. Maybe your knee will burn, or suddenly feel unstable. But, you will be in a better position to sense possible injury so you can immediately terminate your set. Make sense?

With all of that said, I’d advise you to heed the instructions of your doctor. Of course, it’s your right to get a second opinion from another doctor or orthopedic specialist who has an extensive background in treating knee injuries.

The Bottom Line: When in doubt, always err on the side of caution.

Good luck with your knee issues, and your training!

Prove ‘Em Wrong,
Chad Shaw

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