Study with the Sexes: Muscle Growth & Aerobics.. Are They Equal?

Aerobics for Muscles

Advanced Exercise Science & Research

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Does the biologic disparity between the sexes mean they have to train differently? A study recently conducted at the University of Alberta, Edmonton, Canada, suggests that while men and women both benefit from weight training and cardiovascular activity, men may have a distinct advantage over women when it comes to gaining strength during a concurrent training program (weight training plus aerobic exercise, aka cross training).

Thirty-three subjects (20 males and 13 females) who were recruited from a Canadian university and local rowing club were divided into two groups: strength training only and strength training with concurrent endurance exercise. The subjects lifted weights three days a week on a 16-week schedule that made gradual increases in intensity (amount of weight) and decreases in volume (number of sets and reps) over the given period. Typically, the end result in such a periodization schedule is a dramatic increase in muscle strength.

Before beginning the 16-week protocol, subjects underwent upper- and lower-body strength testing on a standard leg press and bench press. Those in the strength- and-endurance group utilized a rowing machine as their form of aerobic activity. Urine and blood samples were collected to measure changes in testosterone and cortisol levels, and results showed that the concurrent endurance and strength- training program didn't affect the strength adaptations in men. Yet differences were seen among female subjects: Their urinary' free cortisol (a catabolic steroid hormone) increased during the last eight weeks of concurrent training. This training appears to create a catabolic state in women and, at least in this investigation, contributed to a decrease in strength gains.


The relationship between testosterone and cortisol plays a major role in muscular hypertrophy and accompanying strength increases. Women produce about 0.3 mg of testosterone per day, compared to the 7 mg produced in men This lower testosterone level combined with an increase in cortisol could negatively affect the performance of female athletes and those involved in intense fitness training.

The gender differences seen in this study support the notion that the individual should consider his or her gender when designing a weight-training! Aerobic-exercise program. Men appear to have a distinct biological advantage over women when it comes to adding muscle and increasing strength.





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