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Squat vs. Leg Press: Effects on Testosterone, Growth Hormone and Cortisol

(Originally posted on 22-04-2014) WhetherSquat vs leg press training with free weights is more effective than training on machines has been an ongoing debate and both methods have their advantages and disadvantages. To see which has the largest effects on our hormones scientists of the University of North Texas started a study on the effects of two of the most popular leg exercises: the squat vs leg press.

When are you training too much?

Exercise normally stimulates the body to recover and through this process improve endurance, strength or other variables through super compensation. Well performed fitness training will increase growth hormone secretion, which stimulates recovery and rejuvenates tissue. A higher training frequency and training intensity normally results in better results. This is true up to a point. While it does not happen too often, it is possible to break down the body instead of improving performance by training too much.

This can occur when someone for example performs resistance exercise two times a day targeting the same muscle groups. This is rare however, since resistance exercise stimulates anabolic hormone production, such as growth hormone and testosterone, which stimulate recovery.

In addition the intensity of resistance exercise, when performed right, is too high to sustain for longer periods or very often because of muscle soreness. When performing cardiovascular exercise, one runs a greater risk of overtraining, because the total exercise duration is often longer and relative intensity is lower than resistance training. The longer duration increases cortisol production, a stress hormone which breaks down muscle for energy and inhibits testosterone production. The lower intensity does not stimulate growth hormone and testosterone production as much as resistance exercise.

So on the one hand, cardiovascular exercise can break down the body and inhibits recovery and on the other hand, not much growth hormone and testosterone is produced to stimulate recovery. As a result, people get weaker by training too much. In addition, the immune system is suppressed, increasing the risk of infection. This does not mean that cardiovascular exercise should be avoided altogether, it merely means that one should be wary of performing too much exercise without adequate rest. The negative effects of too much training can already occur by training 8-10 hours per week, which is normal for quite a few endurance athletes.

How does strength training increase muscle mass?

The increase in muscle mass due to resistance exercise is a result of several hormone mechanisms. High intensity resistance training increases hormone concentrations of testosterone, growth hormone and IGF-1. These hormones stimulate protein synthesis and therefore increase muscle mass.

Men naturally produce more testosterone and growth hormone and these levels rise more strongly than in women as a result of resistance exercise. In men testosterone seems to be the most important regulator hypertrophy in muscle mass, in women, who produce much less testosterone, this role is reserved for growth hormone.

The amount of these hormones produced depends on several factors, the amount of muscle mass active during training, training intensity and rest periods between series. When more muscles are activated during training, anabolic hormone levels rise. The same applies to higher training intensity and shorter rest durations.

References:

-Heyward, V.H. (2010). Designing Resistance Training Programs. Advanced Fitness Assessment and Exercise Prescription Sixth Edition. USA. Human Kinetics

Growth Hormone

Growth hormone is produced in the anterior pituitary gland. The best known function of growth hormone is stimulating cell growth in almost all tissues, hence the name. Growth in children is regulated by growth hormone. In adults it still has many important functions, not the least of which are inducing muscle growth or hypertrophy, stimulating bone mineralization and increasing lipolysis or fat metabolism.