Along with achieving a flat stomach and defined arms, getting thinner thighs is a common goal among many women. The leg press can be a highly effective exercise for building muscle and strength in your quads, hamstrings and calves, though it won't necessarily burn fat directly from your thighs and make them smaller. It's still important, however, to pay attention to how much weight you use.
The Myth of Spot Reduction
Although it may make sense that working a muscle will help burn fat from it, this is not true. This concept is known as spot reduction and is one of the biggest myths in the fitness industry. Muscle and fat are disconnected. Although training and using the leg press will help to burn calories, which in turn will burn fat and make you thinner, you can't dictate where you lose this fat from.
Weight and Reps
The weight you use on the leg press depends on the number of reps you perform. To calculate how much weight you need to use, perform a single repetition maximum test, where you keep increasing the weight each set until you can't perform a single rep. The heaviest weight you can use is your one rep max. Use 75 to 100 percent of your maximum when performing one to six reps per set, 60 to 75 percent for sets of eight to 12 and less than 60 percent if you're performing high rep sets of 15 reps or more. If you're new to training, you may wish to skip the one rep max test for safety reasons and perform a five-rep max test instead, then estimate your one rep max from there. Always have a qualified trainer present to assist with safety when performing a rep test.
Rep ranges all relate to different goals. Heavy training is best for strength gains, moderate rep training for muscle growth and high rep training for muscular endurance. Although it's commonly thought that high reps will help tone a muscle and make it thinner and more defined, this isn't the case, according to strength coach Nia Shanks. High reps are no more likely to tone than low reps and won't challenge you nearly as much or burn as many calories as a heavy set. Shanks recommends sticking to sets of five to 10 reps using a weight you find challenging.
The weight you use on the leg press depends on a number of factors, including your strength levels, how long you've been training and what type of leg press machine you're using. What might feel light on one machine may be impossible to move on another, and one person's warm-up weight could be another person's maximum. Diet is key, too. The only way to reduce the size of a body part is to burn more calories than you consume. Do this by increasing calorie expenditure through training harder and challenging yourself on the leg press and by reducing your caloric intake slightly.
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