The study under review was a double-blind randomized controlled trial assessing the effects of vitamin C and E supplementation on strength training and muscle metabolism.
The participants in this study were 32 young recreational strength trainees, who had been regularly performing strength training exercises, one to four times a week for the past six months. The mean age of the groups was in the mid-twenties. The vitamin group had five women, out of 17 total participants, and the placebo group consisted of six women, out of 15 total participants. Most of the trainees engaged in some sort of endurance training as well, but during the study, that was restricted to once per week at most. The participants were also instructed to stop taking any supplements in the two weeks leading up to the study to ensure that the only supplements they used were the studied vitamin C and E.
The study began with a one to four week phase devoted to training the participants in how to perform the strength tests (various single-joint isolation exercises such as biceps curls and leg extensions, which are standard for performance studies). This phase included three relatively light workouts per week (8-12 reps at the 15-rep max of the participants).
After that, the training protocol included six weeks of three sets at the participants’ 9-11 rep maximum and then three weeks of three to four sets at their 6-8 rep maximum. Each week had four sessions with two upper body sessions and two lower body sessions, using a variety of compound and isolation exercises.
The participants were randomized to receive either placebo pills or a total of 1000 mg vitamin C and 235 mg vitamin E per day. This dosing was split into pre- and post-workout doses on training days, with half taken one to three hours before training and half within an hour after training. Non-training day supplements were split between morning and evening doses. The total daily doses of these antioxidants were substantially higher than the recommended daily intakes for vitamin C (90 mg for men and 75 mg for women) and vitamin E (15 mg for both men and women).
The participants were given advice on diet and post-workout protein intake, in order to help maintain a slightly positive energy balance. They also submitted a four-day weighed food diary at the start and end of the study, and recorded their supplement intake and training logs. This helped keep the study participants on protocol, and also served to signal the researchers to advise any participants who weren’t eating enough protein (defined by the researchers as one gram per kilogram of body weight, minimum). Body weight and composition were studied with DEXA scans and muscle cross-section MRIs, which are widely used in training performance studies.
In addition to these long-term analyses, the researchers conducted acute muscle analyses on a subset of participants. These analyses included blood tests and muscle biopsies before and after a relatively strenuous session of leg presses and leg extensions. For these analyses, the participants ate a standardized breakfast, took either the vitamins or placebo, and then came to the lab to complete the testing. After the training, but before the post-training biopsies and blood work, the trainees took another dose of supplements or placebo.The researchers then performed a variety of molecular and biochemical analyses of the blood and muscle samples with the goal of understanding how vitamin C and E affect muscle metabolism and cell signaling pathways important for hypertrophy and muscle adaptation.
Participants in this RCT were young and mostly male. They were given high doses of vitamins C and E before and after training, as well as in the morning and evening of non-training days. Biopsied muscle was also tested to assess the direct effects of these vitamins on critical signaling pathways and muscle metabolism.