There is no doubt that Paul Cribb and Alan Hayes' amazing paper, "Effects of Supplement Timing and Resistance Exercise on Skeletal Muscle Hypertrophy,"1 will be quoted for years and probably decades.The questions is: Can others duplicate their results? This brings to mind the Isidori2 paper (low-dose arginine and lysine, ingested orally, increased growth hormone by 700 percent), which is still cited 25 years after its publication, even though numerous researchers have failed to reproduce its effects. Replication of Cribb and Hayes' findings by others is critical since, as with most research on ergogenic aids, it was done using a small sample size.
The research was designed to determine if the time of day at which serious weightlifters ingested nutritional supplements influenced muscle strength and size. There have been studies showing that ingesting protein and carbohydrate either before or following exercise is beneficial compared to placebo in stimulating protein synthesis, muscle strength and muscle mass. In order to test these theories, the subject's normal meal patterns are altered. For example, outside a laboratory, those who lift weights for strength and size do not wait three to five hours after a workout to eat - nor do they train after an overnight fast. To me, these studies simply reinforce the fact that food is required to build muscle. I'm not impressed when those who drink a protein/carb shake after a workout make better gains than those who consume a zero-calorie placebo. Normally, people eat after workouts.
In this case, the subjects' diets were analyzed for eight weeks prior to the study and also monitored during the study. Thus, the authors could ensure that the subjects did not alter their diet or meal patterns during the research period. The diet analysis revealed that all subjects had a high-protein intake of around 2 gm per kilogram of body weight (slightly less than 1 gm per pound, which is 2 ½ times the RDA). In addition to protein and carbohydrate, creatine also was included in this trial.
The supplement was dosed by body weight. For an 80 kg (175 lb) subject, this equated to approximately 270 calories, 32 gm of protein, 34.4 gm of carbohydrate, 0.4 gm of fat, and 5.6 gm of creatine. It was taken twice daily on the four days per week during which the subjects worked out. One group drank the supplement in the morning and the evening, while the other group took the supplement just before and just after their workouts.
The exercise routine was mostly free weights, which emphasized compound movements involving large muscle groups. The three exercises that were measured at the beginning and at the end of the 10-week (40-workout) study were the bench press, squat and deadlift. The study methods included whole-body scans, muscle biopsies, diets (analyzed before and during the trial), workout diaries, and workout supervision with personal trainers who were blinded to the test groupings.
Both study groups experienced strength gains. The authors point out that the creatine used was clearly a factor, and that when subjects engaging in resistance-exercise programs take creatine, most notice accelerated muscle response. Unique about this trial was that it compared the timing of creatine dosing. Prior to this study, the time of day that creatine was ingested was not considered important, as long as the amount consumed raised and then maintained elevated intracellular levels. This is because creatine is not a substance that is felt shortly after ingestion (unlike caffeine). Instead, creatine is not noticed at first and will not work until it builds up. This takes a minimum of three days.
Study participants who took the supplements before and after exercise had greater increases in strength on the bench press, squat and deadlift than those who took the same product in the morning and evening. They accrued more lean mass and muscle hypertrophy (greater increases of type 2A and type 2X muscle fiber diameter, as well as higher levels of intramuscular contractile protein) than the AM/PM users. The pre/post group also had more muscle glycogen, total creatine and phosphocreatine (as measured by muscle biopsy).
In other words, 10 weeks of the same amount of supplemental creatine, protein and carbohydrate yielded greater intracellular levels of total creatine, protein and carbohydrate, when taken a few minutes before and after workouts (compared to AM/PM dosing). And these findings were not due to a postprandial spike, because in week one, the pre/post group did not have higher intracellular levels of creatine glycogen or contractile protein than the AM/PM group.
As I said, people will quote these results for years. It will be very interesting to see if others can replicate the results of this study.
- Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sp Ex, 2006;38:1918-25.
- Isidori A, Lo Monaco A, Cappa M. A study of growth hormone release in men after oral ingestion of amino acids. Curr Med Res Opin, 1981;7:475-80.
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