Workout Supplements: The Impact on Muscle Strength and Fatigue
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Sports supplements, such as pre-workout and post-workout supplements, are not needed or even helpful for the vast majority of people who work out, several experts said. Only people who are really pushing themselves during a workout are likely to see a benefit from such supplements, experts said.

Many studies have found that caffeine can make a workout more effective, said Keith Baar, an exercise physiologist at the University of California, Davis, who studies the effect of macronutrients on exercise performance.

"Caffeine works in the brain to make you think that exercise is easier than it is," Baar said. "It is the number-one performance-enhancing drug. It works in everyone."

Another supplement with demonstrated effects is creatine. Muscles use this protein during the first 6 seconds of any exercise that requires explosive bursts of effort (such as one dead lift or one intense sprint), said Michael Ormsbee, the interim director for the Institute of Sports Sciences and Medicine at Florida State University, who has done extensive research on the effect of pre-workout supplements and nutrition on exercise performance. More than a dozen studies have shown that creatine may help exercisers put forth maximal exertion during strength training.

However, this effect typically requires a steady level of creatine in the muscle, so people who do this type of exercise should take creatine every day, to maintain adequate levels of the protein, said Jordan Moon, the program director of sports and health sciences and sports management at American Public and American Military University as well as the Chief Science Officer for the body composition and fitness tracking app FitTrace. But because most casual exercisers do not work out to exhaustion, any benefit they perceive from creatine is likely a placebo effect, Moon said.

The protein beta-alanine also appears to increase the levels of a protein called carnosine, which is needed for muscle contraction, according to a 2015 review in the journal Current Opinions in Clinical Nutrition and Metabolic Care. And according to the International Society of Sports Nutrition, beta-alanine supplementation for at least two to four weeks can improve performance in exercises that last 1 to 4 minutes. This can also generally reduce fatigue, particularly in older people, the study found.

But neither creatine nor beta-alanine makes much difference for performance in exercisers who are not working to exhaustion or muscle failure, both Moon and Baar said. Beta-alanine induces a tingly sensation, which makes people think, "oh, it's working," and that along with the placebo effect may spur them to work out harder, both experts said.

However, few workout supplements contain only creatine, caffeine or beta-alanine, but rather, may also contain sweeteners and other mystery substances, Baar said.

"For most people, the supplement is just going to be something that adds more calories," Baar told Live Science.

Original article on Live Science.