The study design the scientists used is quite awkward, but clever. They had 9 (unfortunately) untrained subjects perform 4 workouts per week. On two of the occasions the subjects trained legs + one arm (L + A) on the other two occasions they only trained the other arm. Thus, Ronnestad et al. made sure that "both conditions have the same nutritional and genetic environment".
|Figure 1: Plasma testosterone and growth hormone measured before the strength training session (T-0), immediately after the leg exercises in the L ? A session (T-1), immediately after the arm exercises for both the L + A and A session (T-2), and 30 min after the arm exercises in both L + A and A session (T-3). (Ronnestad. 2011)|
only L + A increased the elbow ﬂexors’ CSA at the two middle sections where the CSA of elbow ﬂexors was largest.In other words, the peak of your biceps, this hallmark, every bodybuilder is looking for, comes from training your legs (prior to your biceps).