There seem to be two polar opposites when it comes to exercise: yoga vs. weight training. Weightlifters are bulky and tight, while yoga fans are lithe and limber. Is this generalization supported by a science based difference in the effects of different exercise on muscles? A new study suggests it might.
Our muscles can be active in one of three ways: concentric, isometric, eccentric. Concentric is when the muscle shortens against resistance while the opposite lengthening against resistance is called eccentric. Most weightlifters focus on concentric contractions when they “pump iron”. On the other hand, many forms of exercise including yoga focus on isometric (when the muscle just tightens but nothing moves) or slow lengthening type movements (eccentric). We can certainly tell by just looking at a weightlifter and and a yogi that they get fit in different ways. The weightlifter is bigger and how he or she moves also seems different. They tend to be “musclebound” and tight, versus a yogi who has smaller sinewy muscles that are very flexible. Does the different effect of these two types of training produce different results?
The new study looked at 28 people who were randomized such that half did 6 weeks of concentric and half eccentric exercise weight training for their hamstrings muscles. After that time period, the researchers assessed the architecture of the biceps femoris hamstrings muscle using ultrasound imaging to look for differences at various times and then after a detraining period. Amazingly, the muscle was significantly shorter in the concentric training group and longer in the eccentric group! After the detraining period, the eccentric group’s muscles returned to normal length while the concentric training group’s muscles never returned to their normal length! How much was the effect? A little less than 3/4 of an inch! That’s a huge amount given muscles are tuned to millimeter precision.
The upshot? Being a weightlifter, this study is enough to make me want to change my training routine! With the explosion of male testosterone supplementation, I’ve seen countless guys for neck problems after they’ve hit the gym to develop new found muscles by pumping some iron. While they generally look good, their muscles in their chest are so tight that they end of developing neck problems as their chest pulls their neck forward. Now it seems like there’s a scientific reason this is happening outside of just bigger muscles -tighter muscles! So I know I’ll begin mixing in some eccentric exercise (called “negatives” where you begin contracted and then release a weight slowly) or maybe even a little yoga! Maybe I need to warn some of my age management patients of what Billie Crystal once said, “It’s better to look good than to feel good”!