Many expert sporting bodies now support a pragmatic acceptance of the use of performance supplements which have passed a risk:benefit analysis of being safe, effective, and permitted for use, while also being appropriate to the athlete’s age and maturation in their sport. However, gaining evidence of the performance benefits of these supplements is a process challenged by the scarcity of research in relation to the number of available products, and the limitations of the poor quality of some studies. While meta-analyses and systematic reviews can help to provide information about the general use of performance supplements, the controlled scientific trial provides the basis on which these reviews are undertaken, as well as an opportunity to address more specific questions about supplement applications. Guidelines for the design of studies include the choice of well-trained athletes who are familiarized with performance tasks that have been chosen on their basis of their known reliability and validity. Supplement protocols should be chosen to maximize the likely benefits, and researchers should also make efforts to control confounding variables, while keeping conditions similar to real-life practices. Performance changes should be interpreted in light of what is meaningful to the outcomes of sporting competition. Issues that have been poorly addressed to date include the use of several supplements in combination and the use of the same supplement over successive events, both within a single, and across multiple competition days. Strategies to isolate and explain the variability of benefits to individuals are also a topic for future investigation.
Louise M. Burke and Peter Peeling
Daniel Tan, Brian Dawson, and Peter Peeling
This study aimed to quantify the hemolytic responses of elite female football (soccer) players during a typical weekly training session.
Ten elite female football players (7 field players [FPs] and 3 goalkeepers [GKs]) were recruited from the Australian National Women’s Premier League and asked to provide a venous blood sample 30 min before and at the immediate conclusion of a typical weekly training session. During this training session, the players’ movement patterns were monitored via a 5-Hz global positioning system. The blood samples collected during the training session were analyzed for iron status via serum ferritin (SF) analysis, and the hemolytic response to training, via serum free hemoglobin (Hb) and haptoglobin (Hp) measurement.
50% of the participants screened were found to have a compromised iron stores (SF <35 μg/L). Furthermore, the posttraining serum free Hb levels were significantly elevated (P = .011), and the serum Hp levels were significantly decreased (P = .005), with no significant differences recorded between the FPs and GKs. However, the overall distance covered and the movement speed were significantly greater in the FPs.
The increases in free Hb and decreases in Hp levels provide evidence that a typical team-sport training session may result in significant hemolysis. This hemolysis may primarily be a result of running-based movements in FPs and/or the plyometric movements in GKs, such as diving and tackling.
Maddison J. Jones and Peter Peeling
To compare the differences in peak oxygen uptake (VO2peak) and lactate threshold (LT2) between the 7 × 4-min incremental step test (7-ST) and the maximal accumulated oxygen deficit (MAOD) test protocols in sprint kayak athletes.
Nine highly trained kayak athletes performed the 2 laboratory test protocols. The 7-ST involved six 4-min submaximal incremental stages, each separated by a 1-min recovery, before a 4-min all-out effort. The MAOD test involved four 4-min submaximal incremental stages (also with each stage separated by a 1-min recovery), followed by 20-min recovery and a 4-min all-out effort.
No statistically significant differences in VO2peak were recorded between the 2 protocols (P > .05). However, distance covered, power output, stroke rate, and speed were almost certainly greater in the MAOD test (magnitude-based inference: 99–100% positive), while blood lactate (BLa), heart rate (HR), and rating of perceived exertion (RPE) were likely lower (magnitude-based inference: 78–92% negative). The derived measures of LT2 (excluding HR) were not different between the 2 protocols.
The results of this study suggest that both the 7-ST and MAOD test protocols are comparable with regard to the measurement of VO2peak and LT2 in highly trained sprint kayak athletes. However, since differences in the measures of distance traveled, power, stroke rate, HR, BLa, and RPE were reported in the maximal stage of the these 2 test protocols, their interchangeable use in a laboratory setting is not ideal if the data output is to be compared and contrasted over time.
Mohammed Ihsan, Grant Landers, Matthew Brearley, and Peter Peeling
The effect of crushed ice ingestion as a precooling method on 40-km cycling time trial (CTT) performance was investigated.
Seven trained male subjects underwent a familiarization trial and two experimental CTT which were preceded by 30 min of either crushed ice ingestion (ICE) or tap water (CON) consumption amounting to 6.8 g⋅kg-1 body mass. The CTT required athletes to complete 1200 kJ of work on a wind-braked cycle ergometer. During the CTT, gastrointestinal (Tgi) and skin (Tsk) temperatures, cycling time, power output, heart rate (HR), blood lactate (BLa), ratings of perceived exertion (RPE) and thermal sensation (RPTS) were measured at set intervals of work.
Precooling lowered the Tgi after ICE significantly more than CON (36.74 ± 0.67°C vs 37.27 ± 0.24°C, P < .05). This difference remained evident until 200 kJ of work was completed on the bike (37.43 ± 0.42°C vs 37.64 ± 0.21°C). No significant differences existed between conditions at any time point for Tsk, RPE or HR (P > .05). The CTT completion time was 6.5% faster in ICE when compared with CON (ICE: 5011 ± 810 s, CON: 5359 ± 820 s, P < .05).
Crushed ice ingestion was effective in lowering Tgi and improving subsequent 40-km cycling time trial performance. The mechanisms for this enhanced exercise performance remain to be clarified.
Matthew Finberg, Rebecca Braham, Carmel Goodman, Peter Gregory, and Peter Peeling
To assess the efficacy of a 1-off electrostimulation treatment as a recovery modality from acute teamsport exercise, directly comparing the benefits to contrast water therapy.
Ten moderately trained male athletes completed a simulated team-game circuit (STGC). At the conclusion of exercise, participants then completed a 30-min recovery modality of either electrostimulation therapy (EST), contrast water therapy (CWT), or a passive resting control condition (CON). Twenty-four hours later, participants were required to complete a modified STGC as a measure of next-day performance. Venous blood samples were collected preexercise and 3 and 24 h postexercise. Blood samples were analyzed for circulating levels of interleukin-6 (IL-6) and C-reactive protein (CRP).
The EST trial resulted in significantly faster sprint times during the 24-h postrecovery than with CON (P < .05), with no significant differences recorded between EST and CWT or between CWT and CON (P > .05). There were no differences in IL-6 or CRP across all trials. Finally, the perception of recovery was significantly greater in the EST trial than in the CWT and CON (P < .05).
These results suggest that a 1-off treatment with EST may be beneficial to perceptual recovery, which may enhance next-day performance.
Lindy M. Castell, David C. Nieman, Stéphane Bermon, and Peter Peeling
The main focus of this review is illness among elite athletes, how and why it occurs, and whether any measures can be taken to combat it or to prevent its onset. In particular, there is particular interest in exercise-induced immunodepression, which is a result of the immune system regarding exercise (e.g., prolonged, exhaustive exercise) as a challenge to its function. This promotes the inflammatory response. There is often a high incidence of illness in athletes after undertaking strenuous exercise, particularly among those competing in endurance events, not only mainly in terms of upper respiratory tract illness, but also involving gastrointestinal problems. It may well be that this high incidence is largely due to insufficient recovery time being allowed after, for example, a marathon, a triathlon, or other endurance events. Two examples of the incidence of upper respiratory tract illness in moderate versus endurance exercise are provided. In recent years, increasing numbers of research studies have investigated the origins, symptoms, and incidence of these bouts of illness and have attempted to alleviate the symptoms with supplements, sports foods, or immunonutrition. One aspect of the present review discusses iron deficiency, which has been primarily suggested to have an impact upon cell-mediated immunity. Immunonutrition is also discussed, as are new techniques for investigating links between metabolism and immune function.
Angela L. Spence, Marc Sim, Grant Landers, and Peter Peeling
Both caffeine (CAF) and pseudoephedrine (PSE) are proposed to be central nervous system stimulants. However, during competition, CAF is a permitted substance, whereas PSE is a banned substance at urinary levels >150 μg·ml−1. As a result, this study aimed to compare the effect of CAF versus PSE use on cycling time trial (TT) performance to explore whether the legal stimulant was any less ergogenic than the banned substance. Here, 10 well-trained male cyclists or triathletes were recruited for participation. All athletes were required to attend the laboratory on four separate occasions—including a familiarization trial and three experimental trials, which required participants to complete a simulated 40 km (1,200 kJ) cycling TT after the ingestion of either 200 mg CAF, 180 mg PSE or a nonnutritive placebo (PLA). The results showed that the total time taken and the mean power produced during each TT was not significantly different (p > .05) between trials, despite a 1.3% faster overall time (~57 s) after CAF consumption. Interestingly, the time taken to complete the second half of the TT was significantly faster (p < .05) in CAF as compared with PSE (by 99 s), with magnitude based inferences suggesting a 91% beneficial effect of CAF during the second half of the TT. This investigation further confirms the ergogenic benefits of CAF use during TT performances and further suggests this legal CNS stimulant has a better influence than a supra-therapeutic dose of PSE.
Marc Sim, Brian Dawson, Grant Landers, Debbie Trinder, and Peter Peeling
The trace element iron plays a number of crucial physiological roles within the body. Despite its importance, iron deficiency remains a common problem among athletes. As an individual’s iron stores become depleted, it can affect their well-being and athletic capacity. Recently, altered iron metabolism in athletes has been attributed to postexercise increases in the iron regulatory hormone hepcidin, which has been reported to be upregulated by exercise-induced increases in the inflammatory cytokine interleukin-6. As such, when hepcidin levels are elevated, iron absorption and recycling may be compromised. To date, however, most studies have explored the acute postexercise hepcidin response, with limited research seeking to minimize/attenuate these increases. This review summarizes the current knowledge regarding the postexercise hepcidin response under a variety of exercise scenarios and highlights potential areas for future research—such as: a) the use of hormones though the female oral contraceptive pill to manipulate the postexercise hepcidin response, b) comparing the use of different exercise modes (e.g., cycling vs. running) on hepcidin regulation.
Benjamin M. Jackson, Ted Polglaze, Brian Dawson, Trish King, and Peter Peeling
Purpose: To compare data from conventional global positioning system (GPS-) and new global navigation satellite system (GNSS-) enabled tracking devices and to examine the interunit reliability of GNSS devices. Methods: Interdevice differences between 10-Hz GPS and GNSS devices were examined during laps (n = 40) of a simulated game circuit and during elite hockey matches (n = 21); GNSS interunit reliability was also examined during laps of the simulated game circuit. Differences in distance values and measures in 3 velocity categories (low <3 m·s−1; moderate 3–5 m·s−1; and high >5 m·s−1) and acceleration/deceleration counts (>1.46 and <−1.46 m·s−2) were examined using 1-way analysis of variance. Interunit GNSS reliability was examined using the coefficient of variation (CV) and intraclass correlation coefficient. Results: Interdevice differences (P < .05) were found for measures of peak deceleration, low-speed distance, percentage of total distance at low speed, and deceleration count during the simulated game circuit and for all measures except total distance and low-speed distance during hockey matches. Interunit (GNSS) differences (P < .05) were not found. The coefficient of variation was below 5% for total distance, average and peak speeds and distance and percentage of total distance of low-speed running. The GNSS devices had a lower horizontal dilution of precision score than GPS devices in all conditions. Conclusions: These findings suggest that GNSS devices may be more sensitive than GPS devices in quantifying the physical demands of team-sport movements, but further study into the accuracy of GNSS devices is required.
Ted Polglaze, Brian Dawson, Daniel J. Hiscock, and Peter Peeling
To determine the relationship between distance covered and player load (PL: sum of accelerations in all 3 planes of movement) in hockey training and competition.
Elite male hockey players (N = 24) wore player-tracking devices in 7 international matches and 7 training sessions. Players were arranged in 4 positional groups (strikers, attacking midfielders, defensive midfielders, defenders) in competition but had generic roles in training. Relationships between distance and PL were assessed in both absolute (m, AU) and relative (m/min, AU/min) terms and were compared between matches and training and between positions within matches, using the Fisher Z test.
In competition, the absolute distance–PL relationship was very large overall (r = .868), with no differences between positions. The relative distance–PL relationship was moderate overall (r = .486) and weaker in strikers than in defensive midfielders (Z = 1.785, P = .037) and defenders (Z = 1.690, P = .045). In training, the absolute distance–PL relationship was very large (r = .742), and large (r = .633) in relative terms. The relationship was stronger in competition than training for absolute values (Z = 2.824, P = .005) but not different for relative values.
The strong relationship between these variables suggests that PL in hockey is mostly accumulated through running and other locomotor actions, such that PL is not effective in quantifying other activities (evasion, low stance) that contribute to physiological demands, particularly in training.