Creatine monohydrate is considered the most effective nutritional supplement in terms of increasing lean body mass and improving anaerobic performance [1]. Typical recommended creatine supplementation regimen consists of a loading phase of 20–25 g ∙ d⁻¹ for 2–7 days, followed by a maintenance phase of 2–5 g ∙ d⁻¹ thereafter [1–6]. A meta-analysis of 96 published investigations totaling 1847 subjects revealed that the effect of creatine supplementation is more pronounced in repetitive-bout than in single-bout exercise and in upper-body performance tasks than in lower body exercise [7]. Furthermore, the effect size for improvement in performance in high-intensity exercise lasting ≤ 30 s is greater than for tasks of longer duration, but no significant differences occur in performance effect between males and females or between trained athletes and untrained subjects [7].

In wrestling, repetitive forceful muscle contractions are required during most of sport’s maneuvers and the upper-body anaerobic power of an athlete is considered an important factor influencing competitive success [8, 9]. To this end, the findings of Branch [7] suggest that wrestlers may benefit from creatine supplementation, but surprisingly there are only a few previous studies which have examined the impact of creatine on physical performance indices in competitive wrestlers. Nevertheless, Koçak and Karli [10] demonstrated significant increases in mean power and peak power attained in a 30-s Wingate test after compared to before creatine supplementation in elite male Turkish wrestlers. Ziegenfuss et al. [11] studied elite male and female power athletes, including eight male wrestlers, and demonstrated significant improvement in repeated cycling sprint performance following short-term creatine supplementation. Ööpik et al. [12] found that creatine supplementation during 17-h recovery from rapid body mass loss stimulated the regain of physical working ability in a performance test simulating wrestling match in well-trained wrestlers.

The limitations in the data regarding the impact of creatine supplementation on physical performance in trained wrestlers are due to studies employing non-wrestling-specific test protocols [10, 11] or use extremely limited sample sizes (n = 5) [12]. A wrestling tournament usually lasts for many hours and in order to win a wrestler has to defeat on average four to five opponents. Whether creatine supplementation helps a wrestler to better maintain the ability to perform powerful actions throughout a tournament situation is not known.

Therefore, the aim of this study was to examine the influence of creatine monohydrate loading on upper-body intermittent sprint performance (UBISP) across four consecutive tests mimicking four wrestling matches on the same day. Considering the proved positive impact of creatine on performance in repeated high-intensity upper-body exercise in trained athletes [7], we hypothesized that creatine use compared to placebo would increase upper-body anaerobic power in trained wrestlers.

The main finding of this study was that short-term creatine supplementation had no impact on PP or MP attained by trained wrestlers during consecutive anaerobic tests intended to mimic a typical competition-day in wrestling. Furthermore, creatine did not influence fatigue development substantially relative to the placebo. To the best of our knowledge, this is the first study assessing the potential efficacy of creatine loading in improving upper-body anaerobic performance in combative-type sports under a simulated competition setting. Previous studies focusing on wrestling scenarios have demonstrated ergogenic effects of creatine supplementation in participants, but as noted earlier these studies have limitations [10–12].

Our hypothesis that creatine loading would increase upper-body anaerobic power was based on the outcomes of meta-analytic and systematic literature reviews. These reviews revealed that creatine supplementation has the most pronounced positive effect on performance in multiple bouts of high-intensity, short-duration exercise [2, 4, 7, 21, 22] and that generally the effect of creatine on performance is greater in upper-body exercise than in lower-body exercise [7]. Regarding intermittent sprint performance in exercise tasks loading lower-body musculature, marked improvement following short-term creatine supplementation has been reported by numerous research groups in untrained and moderately trained subjects [23–29] as well as in highly trained athletes [11, 30–35]. Not all of the relevant studies, however, have confirmed the ergogenic effect of creatine loading [36–40]. Furthermore, to the best of our knowledge, only two research groups [41, 42] have assessed the potential impact of short-term creatine supplementation on repeated high-intensity arm-cranking exercise performance in athletes and the findings of these studies were conflicting. Grindstaff et al. [41] reported 7.5 % greater peak power output during the first of three consecutive 20-s arm ergometer maximal-effort sprint tests after compared to before nine days of creatine monohydrate (21 g ∙ d⁻¹) ingestion in trained swimmers. Green et al., however, found that six days of creatine supplementation (20 g ∙ d⁻¹) did not enhance peak power or mean power during three consecutive 30-s arm Wingate tests in recreational athletes [42]. In addition, Jacobs et al. [43], employing incremental peak arm ergometry test consisting of 2-min work stages and 1-min recovery periods, observed a significant increase in peak power output (6.7 %) following seven days of creatine supplementation (20 g · day⁻¹) in men with complete cervical-level spinal cord injury.

Taken together, the limited and inconsistent literature and the current findings are clearly insufficient to draw any definitive conclusions regarding the influence of short-term creatine supplementation on anaerobic performance in arm-cranking exercise. Therefore, further studies are warranted in order to better elucidate the potential impact of creatine on performance in this particular mode of physical activity.

In our participants, creatine loading had no influence on body mass. According to Branch et al. [7], approximately 64 % of studies which have measured body mass and/or body composition have reported statistically significant increases in body mass or lean body mass due to creatine supplementation. Regarding short-term creatine monohydrate loading in particular, a review conducted by Volek and Kraemer [44] revealed that ingestion of 20–30 g of this substance per day for five to seven days usually induces an increase in body mass in the range of 0.9–1.8 kg. Kilduff et al. [45] reported positive correlation between change in body mass and whole-body creatine uptake. Saab et al. [46] suggested that an increase in intracellular muscle water may occur due to osmotic properties of creatine and this may be responsible for the rapid change in body mass accompanying creatine use. Therefore, some authors [28, 34] have interpreted increase in body mass as an indirect evidence of successful muscle creatine loading.

The absence of any change in body mass or hydration in our subjects during the supplementation period does not necessarily, however, indicate that creatine ingestion failed to increase muscle creatine content. Some reports indicate body mass actually does not correlate with increases in muscle creatine content [18] or in the muscle phosphocreatine/ATP ratio [46]. Furthermore, short-term creatine supplementation has been shown to improve performance in high-intensity arm-cranking exercise [41], cycling sprints [25, 27, 29], maximal unilateral knee extension and maximal deadlift strength [47] and to increase anaerobic running capacity [48] without concomitant changes in body mass.

Creatine ingestion did not influence blood lactate response to the anaerobic tests in our participants. The potential effect of creatine on blood lactate levels in repeated high-intensity arm-cranking exercise has not been reported, but blood lactate response to repeated running or cycling sprints have been shown to be unchanged [25, 34], increased [26, 35], or decreased [23, 31] when compared to before creatine loading.

HR_PEAK and HR_ER were consistently higher in CR than PLC group. The reason for this finding is unclear, but the data clearly reveal that supplements ingested (creatine and placebo) had no impact on HR during the UBISP tests or during recovery periods between the consecutive UBISP tests in our participants. Regarding HR_PEAK, our findings are consistent with that reported by Jacobs et al. [43], who observed similar peak HR values before and after creatine loading in cervical cord injury patients performing incremental peak arm ergometry test. Others have reported no effect of creatine on exercise heart rate in repeated running [32, 33] or cycling [27] sprints or lower average heart rate during repeated running sprints after compared to before creatine loading [31], or during recovery [27].

There was no substantial and consistent effect of creatine or placebo supplementation on the RPF or RPE responses to the UBISP tests. This finding suggests that creatine loading did not strongly influence perception of effort during the tests or subjective feeling of recovery between the consecutive tests. Jacobs et al. examined RPE during arm-cranking exercise and reported similar RPE values in creatine and placebo exercise trials [43]. However, as significantly greater peak power output was attained after creatine loading compared to placebo, the RPE data [43] suggest that creatine actually attenuated the perception of effort in their subjects.

An acknowledged methodological limitation of this study is the absence of direct evidence confirming that creatine loading increased muscle creatine content in our subjects. Considering that the extent of creatine uptake during supplementation period appears to be critical to subsequent performance in repeated bouts of high-intensity exercise [17, 19], failure to increase muscle creatine content would explain the lack of any change in upper body anaerobic power. However, we are confident in the high quality of the creatine product and our subjects complied with supplement use based upon food diary reviews and in direct questioning of them individually. The potential influence of participation in routine wrestling training sessions on muscle creatine content in our subjects is difficult to evaluate, because exercise has been demonstrated to increase [49, 50], have no impact [51] or decrease [52] muscle creatine accumulation during loading period. Nevertheless, we cannot completely exclude the possibility that a longer supplementation period might have been needed for occurrence of an ergogenic effect. Vandenberghe et al. [53] and Francaux et al. [54] administered similar daily dosages of creatine (20 g and 21 g) to their subjects for 4 or 14 days, respectively. While both groups reported significant increases in muscle phosphocreatine content following supplementation period, the extent of the increase was much smaller (approximately 5 %) after 4 days [53] compared to that observed after 14 days (approximately 20 %) [54].

The exercise protocol employed was developed to be in line with a “real world” situation for mimicking wrestling matches during a competition-day and hence practical. On the other hand, the specificity of the exercise protocol may have diminished the potential ergogenic effect of increased muscle creatine content in our subjects. Improved performance in repeated bouts of high-intensity exercise following creatine loading is likely due to an increased pre-exercise creatine phosphate availability and enhanced resynthesis of phosphocreatine during recovery periods [17, 23, 24]. However, it has been demonstrated that the rate of resynthesis of phosphocreatine is practically identical in creatine-loaded and non-loaded muscle during the initial 40 s after intense exercise, whereas the accelerated resynthesis mainly occurs during the 2nd minute of recovery [18]. While phosphocreatine resynthesis depends on muscle oxygen supply and removal of lactate and protons [55], i.e. processes which largely are based on diffusion [56], the 40-s unloaded easy cranking periods (active recovery intervals) between consecutive 15-s maximal exercise bouts may be too short to elicit enhanced phosphocreatine resynthesis in creatine-loaded state. Further, high-intensity upper-body exercise relies much more on the anaerobic lactic energy system than lower-body exercise [57, 58], but the diffusional area is smaller and the diffusional distance longer in the arm than in the leg muscles [59]. Therefore, occurrence of the potential ergogenic effect of creatine loading in repeated bouts of high-intensity arm-cranking exercise may require longer between-bout recovery intervals than those used in the current study or in the other relevant studies [41, 42].

Five days of creatine monohydrate supplementation failed to increase upper-body anaerobic power in anaerobic tests mimicking wrestling matches in trained wrestlers. Considering the great practical importance of upper body muscular performance not only for combat sports athletes but also for disabled people who use wheelchair in their everyday life, further studies in this area of interest are warranted.