Interesting. I think I am also seeing that the DL benefits just as much from increased body weight as the other lifts.
Research shows there are three factors that optimize Hypertrophy. The primary factor is...
It is elicited with "The Pump". Arterial blood is pumped to the working muscles.
Ventricle blood flow is trapped in the working muscle; the muscle contraction restricting blood flow from the muscle back to the heart.
What you end up with are bigger muscles swollen with blood, "Da Pump".
The Pump produces an anabolic hormonal cascade; increasing the size of the muscles.
Hypertrophy Training Prootocol
1) Moderate to Light Loads
2) Moderate to High Repetitins
3) Short Rest Periods between sets.
Take Home Message
A well written and executed Deadlift Training Program will increase muscle mass with a surplus of calories. Weight gain or loss is all about Diet.
The relative weight that lifters can accomplish in various weight classes is not the same as if you took any ONE lifter and somehow put him sequentially at all the different body weights he reasonably occupy and see how strong he is at each weight.
The majority of lifter have a Weight Class "Sweet Spot"; a body weight where their optimal performance occurs.
A Fundamental Issue of Weight Class Resistance
One of the prime issues for a lifter not moving up into a higher weight class is that it takes time to mature and grow into the new weight class. That meaning the lifter will not be initially as good and efficient in the new class as the lower one.
The only way to find out how well you will perform in a higher weight class is to move up, be patient and give yourself time to mature into the new weight class.
Isn't that what we all really want to know? If I put on some weight, how much stronger can I get?
It's what I want to know. I have experimented with moving up and down the Weight Classes.
I began as a 148, dropped down to a 132, then went up to a 165, 181, 198, then down to 181, down to 165, then up to 198, up to a light 220 (208 lbs) and now a light 198 (190 lbs).
It sound like you'd like to know.
...if I steadfastly refuse to let my weight go up, is it seriously limiting how strong I can get?
Gaining weight increases strength. That is why their are Weight Classes.
The question for Competitive Lifters is, "Which Weight Class am I the most efficient?"
One method that will provide you some feed back on that is to employ one of the Powerlifting Formulas that is used for determining who is "The Best Lifter" of the lifters in the various Weight Classes.
Use the Co-Efficient to determine you present number at a specific body weight. Then as you gain weight, use that body weight Co-Efficient to see how your are progressing.
Most importantly, be patient training at you new body weight. Allow yourself time to mature into it. "Rome wasn't built in a day", trite but true.