high-intensity exercise and recovery during short-term supplementation with creatine plus a protein-carbohydrate formula

Objective. To determine the effect of short-term creatine supplementation plus a protein-carbohydrate formula on high-intensity exercise performance and recovery. Design. A repeated-measures, experimental study, employing a randomised, double-blind, placebo-controlled, group comparison design was used. Interventions. Thirty active but not sprint-trained male subjects were randomly assigned to 1 of 3 groups: creatine plus protein-carbohydrate formula (CRF); creatine only (CRE); and control (CON). All groups were exposed to the same high-intensity sprint exercise programme, 3 times per week for 30 days. Main outcome measures. Dependant variables included total repeat sprint distance, fatigue index, perceived muscle pain, and blood lactate, urea, creatine kinase, and cortisol concentrations. Results. All groups significantly (p ≤ 0.05) increased total sprint distance and decreased blood urea concentrations. There were no significant changes in blood lactate or cortisol concentrations in any group. CRF showed significant decreases (p ≤ 0.05) in fatigue index, muscle pain, and creatine kinase concentration. However, no significant differences were found between groups. Conclusion. Short-term creatine supplementation with or without protein-carbohydrate supplementation does not appear to enhance performance or recovery significantly over high-intensity exercise training alone in non-sprinttrained individuals. A longer trial period may be required to evaluate effect on recovery more conclusively. In addition, the prime importance of physical conditioning, and in particular task-specific exercise training, in stimulating performance and recovery adaptations is highlighted.


Introduction
[17][18]27,36 It is frequently recommended to power athletes and other individuals wishing to improve performance in high-intensity training or competition, or seeking gains in strength and muscle mass.
and repetitive maximal exercise tasks lasting less than 30 seconds. 1,2,4,36In repeated bouts of high-intensity exercise, creatine supplementation attenuated fatigue 17 and resulted in better sustained power output over the duration of an exercise set. 1,36Since ATP and PC stores are limited, it seems reasonable to hypothesise that increasing the concentration of free creatine and PC within skeletal muscle may improve performance in maximal work demanding these substrates for rapid ATP resynthesis.Greater levels of intracellular creatine may also result in improved PC resynthesis during the recovery period, maximising power output in subsequent efforts. 1,36It has also been hypothesised to act as a buffer to muscle cell acidity during high intensity work. 2 For athletes, a notable reported benefit of creatine supplementation is enhanced recovery from high-intensity work.1,14,21,27,36   Carbohydrate replenishment following exercise is widely recommended as a means to enhance the recovery process. 2,4,5,21Combined carbohydrate and protein supplementation has been shown to enhance recovery following endurance exercise, with more rapid replenishment of muscle glycogen, 12 reduced muscle soreness, 23 and improved performance in subsequent bouts of exercise.

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More specifically, addition of protein seems less beneficial when sufficient carbohydrate is ingested, 3,13 although addition of even small amounts of essential amino acids to carbohydrate may enhance recovery. 6It is unclear whether combined protein-carbohydrate supplementation enhances recovery from high-intensity sprint exercise, although the coingestion of carbohydrate and amino acids has been shown to stimulate net muscle protein synthesis following resistance exercise. 24Combining creatine supplementation with protein and carbohydrate supplementation is sometimes promoted by dietary supplement manufacturers as maximising work performance while improving recovery following exercise training.This supplementation strategy is claimed to enhance the training effect.However, scientific investigations are required to validate such claims.Therefore, the purpose of this pilot trial was to investigate the effect of creatine supplementation versus creatine combined with a proteincarbohydrate formula on high-intensity exercise performance and recovery.

Subjects
Thirty male subjects volunteered for the study.On day 1, subjects completed a high-intensity sprint running performance test.Day 2 involved blood sampling and evaluation of perceived muscle pain.Running performance measures involved analysis of repeat sprint performance, while recovery measures assessed perceived muscle pain and blood markers of muscle damage the day after highintensity running exercise.A time line for events in the study is outlined in Fig. 1.

Physical testing
Preliminary testing of subjects involved body mass, stature, and skinfold measurement (Harpenden Caliper, Baty International, British Indicators) which were used to calculate BMI and sum of 7 skinfolds. 26Thereafter, subjects engaged in a standardised 10-minute warm-up consisting of selfpaced easy running, static stretching and dynamic drills.Subjects then performed a maximal-effort, repeated sprint running test, involving 10 x 10-second maximal sprints, with 90 s walk recovery between each sprint.This protocol is similar in intensity, volume, and work-rest ratio to others used to assess efficacy of creatine supplementation in a large number of reported studies. 36Subjects sprinted on a level, even, grass surface, in a straight line, with markers along the length of the run.Strong verbal encouragement was given throughout to motivate maximum performance.The distance run in each 10 s sprint was recorded to the nearest metre, s sprint was recorded to the nearest metre, sprint was recorded to the nearest metre, and the sum of the total sprint distance in the 100 s was s was was calculated.Also, the individual sprint distances were used to calculate a sprint fatigue index (%) as follows: Fatigue index = (max -min) / max x 100, where max is the greatest distance (m), and min is the shortest distance (m) achieved in any single 10 s sprint.Blood lactate concentration ([La]B) was measured directly following completion of the test using a Lactate Pro (Arkray, Inc.Shiga, Japan) portable blood lactate meter, using finger capillary blood obtained using standard methods as described by Maw et al. 20 All physical testing was performed at the same time of day on each test occasion.Subjects were instructed to arrive well rested for the test days, and to avoid physical exercise on the day prior to, and after, physical testing.

Pain assessment and blood analysis
The morning after the day of physical testing subjects reported for pain score assessment and blood sampling.This took place at the same time of day on each occasion, and subjects arrived fasted.Perceived local leg muscle pain was evaluated by means of a visual analogue scale (VAS).VASs have been validated for assessment of pain 28 and their use is widespread. 7,19Subjects were asked to report their perceived muscle soreness experienced during activities of daily living (ADL) following sprint testing.Scores were obtained for perceived leg muscle pain in the last 24 hours prior to the pain assessment (VAS24h) and for pain at that moment of assessment (VASNOW).Blood samples were obtained and analysed for blood urea ([UREA]B), creatine kinase ([CK]B) and cortisol ([CORTISOL]B) concentrations.

Exercise sessions
All 3 groups were exposed to the same physical conditioning programme, consisting of high-intensity repeated sprint running exercise, exactly the same as that used in the physical testing i.e. 10 x 10 s repeated maximal sprints with 90 s recovery between each sprint.These were conducted 3 days per week in supervised sessions to encourage maximal effort in training.

Supplementation
Supplementation commenced after the first set of blood samples were taken on day 2 of the study and continued for 29 days.CRF received creatine plus a commercially available protein-carbohydrate formula; CRE received creatine only; and CON received placebo.Creatine monohydrate was provided, with doses approximating 0.3 g.kg -1 body mass for the first 7 days, and 0.03 g.kg -1 thereafter, as widely reported to maximise skeletal muscle stores. 1,5,36 In addition to the creatine, CRF received a ~30 g serving of a protein-carbohydrate blend (whey protein, calcium caseinate, maltodextrin) twice daily, as recommended by the manufacturers, which approximated 110 kcal per serving, and comprised 60% protein, 20% carbohydrate by volume.
All subjects received instructions on individual dosage, as well as a supplementation log book to mark adherence to the supplementation and to record side-effects.Subjects were instructed to take the first serving in the morning, and the second serving within 30 minutes of completion of their sprint training or in the afternoon on non-training days.Subjects were instructed to maintain their habitual diets.

Data analysis
Data analysis procedures included descriptive and inferential statistics.The latter involved Friedman's rank test for k correlated samples for differences between tests within the same group and the Kruskal-Wallis one-way analysis of variance for differences between groups on the dependant variables at both intervals.

Results
Table I presents the mean variables for all groups.No statistically significant differences were found between the 3 groups with regard to all repeat sprint measures (total distance, fatigue index, or [La]B).Across time, all 3 groups showed significant increases in their total sprint distances.
Even though there was a decrease in fatigue index scores in all 3 groups, CRF was the only group to show a statistically significant decrease (p ≤ 0.05) from pre-test to post-test.
No significant differences were found between groups on all perceived leg muscle pain measures.CRF showed a significant decline in VAS24h from pre-test to post-test.The other groups showed the same trend but with no statistically significant differences.CRE showed a significant decrease in VASNOW.The same tendency was found for the other 2 groups, but without statistical significance.

Discussion
Lack of statistically significant differences in repeat sprint measures between groups at the post-test is perhaps not surprising, since none of the subjects were sprint trained.Physiological adaptations to the sprint programme alone may explain the large improvement in all groups over the short trial period.These may include improved motor unit recruitment and synchronisation, but also increased intracellular PC and muscle glycogen concentration, and improved activity of the enzymes involved in their degradation and resynthesis. 4,21All groups showed a trend towards lower fatigue index scores.The same adaptations above could explain this reduced fatigue.Interestingly, only CRF showed a significantly lower fatigue index from pre-test to post-test.
No significant changes were found in [La]B within any group over the period of the study.Higher blood lactate concentrations may have been expected given the observed improvement in power output (total distance in 100 s).However, a variety of factors can influence blood lactate, and measures should be interpreted with caution.These include rate of change in exercise intensity, carbohydrate levels, exercise mode, monitoring precision, temperature, overtraining, muscle damage. 32The lack of significant changes in [La]B despite an average ~12% higher total sprint distance across all 3 groups may in itself be significant, with improved lactate oxidation a possible mechanism.
CRF and CRE showed statistically meaningful declines in VAS24h and VASNOW, respectively.Once again though, changes were not sufficient to result in any significant differences between groups.It was theorised that supplementation with creatine and protein-carbohydrate may improve recovery by stimulating net protein synthesis while ensuring available precursors for structural repair and improved fibre integrity.While this may indeed contribute to reduced post-exercise muscle pain and discomfort, the physiological adaptations to sprint exercise discussed above may alone result in reduced exercise-induced tissue damage and perceived pain, through a variety of mechanisms, such as increasing the motor unit pool exposed to the work.
2 Since even CON showed a trend towards far lower leg muscle pain or discomfort as measured by VAS, the latter explanation may be the more important.
Selected blood variables were measured that may reflect injury, recovery, or stress.Since all groups showed lower (p ≤ 0.05) values for [UREA]B at the post-test, this may also be the result of training adaptations, specifically reduced postexercise protein degradation or increased protein synthesis.No differences between groups were observed that could point to a supplementation effect.Differences in levels of urea metabolism are likely due to individual differences in protein turnover.The significantly lower [UREA]B for CRE at both tests may be due to the small sample size.The same can be said for the isolated differences found in [CK]B.No significant differences were found between groups or between tests for [CORTISOL]B, although this might not be surprising considering the complex nature of the hormone's response.

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Intense muscular exercise results in skeletal muscle fibre damage. 2,4,21,30Damage to the sarcolemma may result in the appearance of CK in the extracellular environment.
2 Interestingly, a significant decrease was observed in [CK]B values in CRF, with a similar yet not significant trend appearing in CRE and CON.This may indicate reduced muscle damage from intense exercise following a period of training, a trend which, interestingly, parallels the observation in perceived muscle pain discussed above.

Conclusions
Elite sports performance requires intense training, often on a daily basis, and optimal recovery is vital for performance gains and maintaining training intensity.If the diet is inadequate to meet the athletes' requirements, correct nutritional supplementation use may have an important role to play. 4,5,16,21Whether this involves creatine with or without a protein-carbohydrate formula, optimal strategies need to be elucidated.Although prompting interesting speculation, the present results cannot serve as the basis for concluding a cause-and-effect relationship between short-term creatine  plus protein-carbohydrate formula supplementation and improved high-intensity exercise performance or recovery.Factors which may have contributed to this and which have been proposed in other studies include a placebo effect, the relatively small magnitude of any treatment effect, and the unfamiliarity of the exercise task.
CRE had significantly lower scores than the other 2 groups on all measurements of [UREA]B.No significant differences were found regarding [CORTISOL]B or [CK]B amongst the groups.Over time, there were significant decreases in [UREA]B scores in all 3 groups.No significant changes took place in [CORTISOL]B.Only CRF had significant decreases in [CK]B scores from the pre-test to the post-test.

TABLE I . Repeat sprint performance, perceived muscle pain, and blood concentration measures (mean ± SD) before and after 30 days of supplementation and high-intensity sprint training
Significantly different from pre-test value, p ≤ 0.05. * 1It is suspected that a longer trial period with a larger, sprint-trained sample may more clearly highlight any possible differences.Future work should consider use of alternative study designs, athletic abilities, and other indicators of stress, tissue damage, and recovery.Certainly though, the importance of the training stimulus in adaptations is demonstrated, at least with regard to non-sprint-trained individuals.Athletes and coaches, and those starting training programmes would do well to keep this in mind when considering claims from dietary supplement manufacturers.