Daily wisdom: muscle versus strength

How to force your body to recruit more motor units every time you lift a weight.

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Weightlifters know that there’s a difference between building strength (what it takes to lift a heavy suitcase into the overhead bin) and building muscle mass (the sheer size of your muscles). While athletes can get similar muscle-building benefits from lifting heavier weights for fewer reps or lighter weights for more reps, your best bet for gaining strength is the former. A new study from the University of Nebraska-Lincoln explains the mechanism behind this phenomenon.


“The amount of weight you are working with is important because that is what tells the body how many motor units it needs to recruit from the nervous system,” explains Matt Berenc, director of education at the Equinox Fitness Training Institute. “At lighter loads, it won’t recruit as many motor units as it would with heavier loads.” According to Berenc, the more motor units recruited from the nervous system, the stronger you will become. (The way muscle size develops, on the other hand, is due to increasing the size, not the number, of muscle cells.)

“The body inherently looks to preserve energy so it won’t stress itself more than it needs to,” says Berenc. “If only 50 percent recruitment is needed to lift a lighter load, then that is all I will recruit so I don’t waste any energy and calories. But in the same instance, if it is a heavier load it will be forced to up the percentage.” This explains why two people lifting different amounts of weight can potentially have the same size muscles, but different levels of strength.

“If you want to start lifting for strength, the best approach is to focus on slowly lowering the number of reps while increasing the weight of the exercises,” says Berenc. “Most strength training programs will have you working around two to six reps for four to six sets.” Start with a more moderate load, about 60 to 70 percent of your max, he suggests. Multi-joint, compound lifts like deadlifts, squats, pull-ups, overhead press, rows, and bench press tend to involve a greater amount of muscle tissue and lead to larger total body gains in strength, Berenc adds.


To challenge your nervous system and get the most strength gains, try lifting heavier weights for fewer reps. But, Berenc recommends alternating your heavy lifting days with lighter or recovery days. “Heavy lifting can put a lot of stress on your body. By spending time with lower intensity drills (stretching, mobility, bodyweight exercises) in between your training days, you allow repair to happen so you can be ready for the next day of lifting.”