Are you strength training at home or the gym but not seeing the strength gains and increase in lean body mass you were expecting? It may be because you’re not training for strength development but for muscle endurance. There are two ways you can train muscles and each will give you a different result. If you use heavy weights and lift until failure, you’ll build strength and mass. If you use lighter weights and do more repetitions, you’ll boost muscle endurance more than strength.
Muscle Strength vs. Muscle Endurance: What’s the Difference?
Muscle strength is the maximal force that a muscle can generate during a contraction. Muscle endurance is the ability to lift a lighter weight multiple times without fatiguing.
To build muscle strength, you would train with a weight that fatigues the muscles after 8 to 12 reps. When lifting the weight, your muscles should feel tired after about the eighth rep, and you would only barely be able to eke out the 12th repetition. During strength training, you’re activating fast-twitch fibers and using anaerobic pathways for energy. When these fibers are forced to sustain forces they’re unaccustomed to, adaptation occurs through a process of breakdown and repair that increases the size of the fast-twitch muscle fibers.
With muscle endurance training you won’t get the same degree of muscle development and strength increases that you will when you train for strength. Muscle endurance training primarily activates slow-twitch muscle fibers that use aerobic energy pathways. They adapt by becoming more efficient at supplying oxygen to the muscles so they fatigue less rapidly. To develop muscle endurance, you would train with a lighter weight that you can lift 15 to 50 times.
It’s not an all or none thing. If you choose a weight for endurance training that you can only lift 15 to 20 times, you’ll still get some fast-twitch muscle activation and strength development. But if you use a weight you can lift 50 or more times, strength gains will be minimal, and you’ll get mostly endurance benefits.
What Are Your Goals?
The problem is some people think they’re doing a strength workout when they’re actually training for muscle endurance. Women who don’t want to “bulk up” often use lighter weights and do lots of reps. If their only goal is to build endurance, they’re on the right track. But if they hope to become stronger or build lean body mass, they need to train for strength using heavier weights and a lower number of repetitions. Women who fear bulking up have little to worry about since they don’t have the hormonal makeup to build large amounts of muscle tissue.
Why Not Do Both?
There’s no reason why you can’t incorporate both strength and muscle endurance training into your workout. Muscle endurance is no less important than muscle strength when it comes to the activities you do every day. When you lift a heavy box, you need the strength to lift it but also the endurance to carry it to the next room. If your primary goal is to build lean body mass, you won’t meet your goals doing a muscle endurance workout. Know what your objectives are, and design your strength training workout accordingly.
Exercise Physiology: Theory and Application to Fitness and Performance. Powers and Howley. 2009.
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