The results from this study suggest that consuming creatine monohydrate post exercise may be superior to consuming it pre exercise with regards to improving body composition (i.e. gains in FFM, loss of FM). This is the first investigation to demonstrate that the timing of creatine intake affects the adaptive response to exercise. When subjects were pooled together, the gains in fat-free mass and muscular strength in the current investigation were similar to others. Rugby union football players who supplemented daily with creatine monohydrate over an 8-week period decreased fat mass (−1.9 kg) and increased lean tissue (+1.2 kg). They also performed better in bench and leg press tests [15]. Older men (71 yrs) who consumed creatine increased lean tissue mass (+3.3 kg) and improved lower body strength as measured using a 1-RM [32]. Using a single-limb training model, men and women who supplemented with creatine after training of the arms increased their muscle thickness. Interestingly, males had a greater increase in lean tissue mass with creatine supplementation than females [4]. In elite male handball players, creatine supplementation for 32 days resulted in an increase in 1-RM bench press (8.30 vs. 5.29 kg; creatine versus control) [33]. These and other investigations indeed show that creatine supplementation in general has a significant anabolic and performance-enhancing effect [34, 35] which is in agreement with the current investigation. Mechanistically, creatine supplementation has been shown to increase muscle fiber size, enhance myosin heavy chain protein synthesis, activate satellite cells as well as increase the concentrations of intramuscular ATP and PCr [6, 7, 12, 36, 37].

However, whether supplement timing has a role in the adaptive response vis a vis creatine has not been previously investigated. Certainly, the most important aspect of the current investigation is that post workout supplementation of creatine may indeed be superior to pre workout supplementation. Data on protein and amino acid supplementation indicate that indeed the pre, during and post workout window are important times to consume nutrients though some studies demonstrate a neutral effect [20–24, 38]. One study examined the effects of a solution of whey protein consumed either immediately before exercise or immediately following exercise. They found no difference in amino acid uptake between the groups [18]. In six subjects (3 men, 3 women) that randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 hour or 3 hours after a bout of resistance exercise, investigators found no difference in the anabolic response whether the drink was consumed 1 hour or 3 hours post exercise [39]. Indeed, others have found that timed protein supplementation immediately before and after exercise does not further enhance muscle mass or strength in healthy elderly men who habitually consume adequate amounts of dietary protein [40]. Also, timed protein-supplement ingestion in resistance-trained athletes during a 10-week training program does not further enhance strength, power, or body-composition changes [41].

On the other hand, consuming an essential amino acid solution immediately before resistance exercise elevates muscle protein synthesis to a greater extent than when the solution is consumed after exercise. The investigators postulated that this may be due to an increased delivery of amino acids to the leg [29]. Clearly, issues related to blood flow would not be advantageous to the POST-SUPP group in the current study.

Another study investigated the importance of immediate (P0) or delayed (P2: 2 hours post exercise) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. In response to training, the cross-sectional area of the quadriceps femoris muscle and mean fiber area increased in the P0 group, whereas no significant increase was observed in P2. These investigators found no difference in the glucose or insulin response at P0 or P2, thus, it is not likely that differences in the hormonal environment contributed to the difference in muscle mass gain. Thus, the early intake of an oral protein supplement after resistance training is important for skeletal muscle hypertrophy [42].

Perhaps the seminal study vis a vis nutrient timing compared taking a protein-carbohydrate-creatine supplement either immediately pre and post exercise (PRE-POST) or in the morning and evening (MOR-EVE). Indeed the PRE-POST group demonstrated a greater increase in lean body mass and 1-RM strength in two of three assessments. Furthermore, type II muscle fiber cross-sectional area was larger in the PRE-POST group as well as intramuscular concentrations of creatine and glycogen [25]. Data from this investigation showed the intramuscular creatine and glycogen concentrations were greater in the PRE-POST versus MOR-EVE groups. Thus, taking the exact same supplement (but timed pre and post exercise) is significantly better than consuming it in the morning and evening.

Our investigation did not involve the use of protein, carbohydrate or amino acids. Whether creatine uptake is truly sensitive to timed intake is not entirely known despite the superior gains in the POST-SUPP group. Moreover, it is entirely possible that the difference in body composition and muscular strength between the two groups was the result of a small sample size. One individual in the POST-SUPP and three individuals in the PRE-SUPP group experienced a minor reduction in FFM. With regards to 1-RM bench press performance, two subjects in the PRE-SUPP group showed either no change or a decline in strength; on the other hand, only one subject in the POST-SUPP group showed no change in strength. All other subjects experienced an increase in strength.

The use of recreational bodybuilders in the current investigation is advantageous because it is difficult for highly trained individuals to experience an increase in FFM or muscular strength in the time frame allotted for this study. Nonetheless, of the 19 subjects that completed the study, 16-21% were non-responders regarding muscular strength and FFM. It should be noted that the nutrient intake (kcals, carbohydrate, fat and protein) was similar between the groups. In fact, each group consumed a high protein diet (1.9 grams of protein per kg bw daily); thus, it is not likely that dietary factors caused the discrepancy in the adaptive response to creatine supplementation and resistance training. Nevertheless, another consideration to take into account would be that because these recreational bodybuilders were already consuming large quantities of protein, this could have affected the results (i.e. they could already have a high amount of creatine stored intramuscularly and this may have blunted the results).

In conclusion, post workout supplementation with creatine for a period of 4 weeks in recreational bodybuilders may produce superior gains in FFM and strength in comparison to pre workout supplementation. The major limitations of this study include the small sample size as well as the brief treatment duration. Future studies should investigate creatine supplementation using resistance trained individuals for a longer duration.