5. Discussion
±, irritation, gastrointestinal distress
ADVERSE EFFECTS, FIRE, FLUID RETENTION
The primary aim of the current study was to examine the effects of adding creatine to protein and carbohydrate supplementation over a period of 3 weeks on changes in occupational performance in firefighters. The study’s main findings were that providing a daily protein and carbohydrate supplement to the diet over a three week period improved select measures of occupational performance in firefighters. Specifically, improvements in completion times for rescue, stair climb, overall time to completion for all tasks, and time trial performance were observed post testing. Further, the addition of creatine led to greater improvements in time to completion for the rescue and forcible entry tasks, compared to protein and carbohydrate supplementation alone. This study is the first of its kind to report on the ergogenic benefits of providing firefighters with dietary ingredients purported to enhance occupational-specific performance outcomes.Because of the physical demands of their occupation, it is recommended that tactical populations adhere to specialized dietary recommendations designed to meet their activity levels and fitness-related training goals [The addition of creatine was found to further improve select measures of performance for the firefighters included in the current study. Several of the occupational tasks completed in the current study can be characterized as short-duration bouts of maximal effort. Specifically, average completion times for the tasks completed in the current study were 9–30 s in duration, with the exception of the time trial which lasted ~340 s in duration. We previously reported that this type of firefighter circuit elicits mean heart rate values of 86.8 ± 6.3% of age-predicted max heart rates, with peak values reaching 98.9 ± 5.6% of maximum heart rate [It is unknown why improvements in some performance parameters have been observed while others have reported null findings within the same population across the literature, including what was found in the current study. Variations in training age, physical fitness status, and familiarity with performance tasks may influence outcomes following creatine supplementation. Furthermore, despite the term tactical population being used to characterize military personnel, firefighters, police, and first responders, the heterogeneity of the individuals across these sub-groups, along with the differences in job activities or daily physical activity levels, may preclude the generalizability of findings across all tactical populations. Therefore, it is important for future research to isolate each sub-group to examine the efficacy of various dietary interventions on performance outcomes that are specific to that population and, subsequently, the occupational demands. Even within the fire service, there are well-known differences in the occupational demands of wildland versus structural firefighting because of the contrast in how fire suppression is handled, along with the environmental demands.Importantly, with the exception of an increase in body mass, which can commonly be attributed to increased fluid retention and increases in fat-free mass, none of the studies reported adverse effects, which is an important indication of the safety of creatine supplementation for this population. In the current study, two participants from the creatine group and one from the ProCarb group reported mild gastrointestinal distress during the supplementation period that resolved on its own, even with continuation of the assigned supplement. It is possible the artificial flavoring agents used in the manufacturing of the supplement caused mild irritation; however, it is difficult to definitively identify the primary causality. This study is not without limitations. For example, this study did not include a true control group in the current design. Additionally, due to the field-based nature of this study, there were no intramuscular measurements of metabolites, so changes in phosphocreatine and total creatine content were not assessed. Lastly, due to the varying schedules of the firefighters, a standardized diet and training program were not imposed throughout the duration of this study. Thus, future research involving firefighters should consider strategies to minimize the potentially confounding factors.