We have previously looked at how different types of weight training can affect testosterone so a new study showing how strength training versus a combined strength and endurance program affected testosterone and cortisol caught my eye.
Objective: The researchers from Canada (1) set out to investigate the effect of strength training and combined strength and endurance training on testosterone, cortisol, and strength.
Methods: 11 subjects (6 male, 5 female) performed resistance training exercise 3 times a week for 16 weeks while 22 subjects (14 male, 8 female) did the same, but, in addition, performed endurance training exercise 3 times a week on alternate days. The researchers tested 1RM strength on the leg press and bench press, serum testosterone levels, and urinary free cortisol levels every 4 weeks for 16 weeks.
Results: Both groups significantly increased strength on both exercises with the relative gains in the leg press and bench press similar for men. Women showed lower strength gains in the leg press relative to the bench press though when performing concurrent training. Those women who only performed strength training workouts did not show this pattern. Testosterone levels did not show any significant difference with either program. Cortisol levels were elevated to a significant level in the male subjects performing concurrent strength at week 8 and cortisol levels continued to stay elevated in this group to the end of the experiment. By contrast, although the strength training group of men exhibited a similar rise in cortisol at week 8, their cortisol levels declined to baseline values by the end of the trial. Women performing only strength training showed a decrease in cortisol levels at 8 weeks but increased for women in both groups at 16 weeks.
Conclusion: The authors concluded that strength training and concurrent training caused different strength and hormonal adaptations between men and women.
This study brings home the fact that additional training which strength athletes perform outside of the gym can potentially cause negative adaptations. Although this trial did not lead to strength levels being any different between the groups performing strength only training versus those performing a mixed training regime, it is likely that in more advanced subjects, adding aerobic training would lead to a negative effect on strength levels.
Compared to the article we reviewed previously which explored effects of strongman versus bodybuilding training on testosterone, this study added an important variable into the mix, namely cortisol levels.
If we consider the role that stress has in inducing heightened cortisol release, we could expect to see any time we go through a stressful period of life that cortisol levels would rise. This applies equally to both psychological stressors as well as physical stressors such as adding endurance training on top of three strength training workouts which is what happened in this study.
The fact that cortisol remained elevated throughout the trial from week 8 onwards in those performing concurrent training would make it more difficult to gain strength and muscle mass while impeding recovery from training. Unfortunately, while many a bodybuilder may discount the notion of endurance training completely we shouldn’t forget its many benefits for athletes such as enhance nutrient partitioning, increased insulin sensitivity, enhanced glycogen storage, and positive effects on work capacity, and health.
Before throwing out the baby with the bath water and consigning cardio to the bin we can make a few changes which should lead to a better outcome. The first and most obvious absence in this study would be to perform endurance training on the same day as we perform strength training. By doing this the body gets a full day of recovery after training which could be expected to help with recovery. Secondly, we could employ endurance training which meshes better with our training goals. This is exemplified by those athletes who might perform sled drags, or farmers’ walks at the end of a training routine as a finisher move which helps with both strength and endurance adapatations.
If there was one lesson I could give people whose primary aim is to maximise muscle mass it would be to avoid long, slow, low intensity activity which send the opposite signal to the muscles to what our weight training sessions do. Instead employ cardio carefully and introduce it only very slowly into our routine. One of the reasons why the group performing concurrent training probably saw a sustained rise in cortisol is down to the fact that they went from 0 sessions a week to 6 a week.
By failing to introduce a rise in training volume slowly you are more likely to encounter negative outcomes such as a rise in cortisol which causes you to gain muscle and strength much more slowly than you would do otherwise.
1. Bell, Gordon; Syrotuik, Dan; Socha, Teresa; Maclean, Ian; Quinney, H. Art (1997): Effect of Strength Training and Concurrent Strength and Endurance Training on Strength, Testosterone, and Cortisol
Reggie Johal is a former Great Britain American Football player with a background in strength and fitness coaching with articles published in many leading online and print magazines including Muscle and Fitness. Reggie is the founder of Predator Nutrition.