2009 Studies & Research Blog

If you have the goal of fat loss, one form of cardio that you’re definitely going to want to be doing is sprint interval training.  Sprint intervals have been known to be one of the best forms of cardio for helping to strip body fat off since they cause a larger metabolic increase both during and after the session is completed compared with more steady state type of training.

But, what about the hormonal changes that take place in the body after a good hard interval session?  That’s something many people overlook when deciding how to structure their cardio training into their program and exactly what the researchers of this study set out to assess.

They wanted to look at the effects a brief sprint interval session would have on the balance between anabolic (growth hormone) and catabolic hormones in the body as well as inflammatory cytokines such as interleukin.

They had twelve subjects participate in the study, which consisted of them running 250 m treadmill sprints at 80% max speed, each interval separated by 3 minutes of rest.

Blood samples were taken immediately after each run was completed, as well as one hour after the lat run ended.

The results of the study indicated that testosterone, growth hormone, and IGF binding protein all increased, and remained elevated after the one hour period after the exercise had taken place. The exercise had no significant effect on cortisol levels, however.

Therefore, from this study, we can also conclude that sprinting also has an advantage when it comes to releasing hormones in the body that prime you for muscle tissue growth without altering cortisol levels, further making this mode of cardio a good selection over moderate intensity, long duration cardio sessions.

Reference:

Cooper, DM. et al. (2009) The effect of a brief sprint interval exercise on growth factors and inflammatory mediators. J Strength Cond Res. Jan;23(1):225-30.