Cells continuously produce free radicals and reactive oxygen species (ROS) as part of metabolic processes (31). About 5% of the oxygen reduced during oxidative phosphorylation in the respiratory chain is converted into superoxide anion (13). Physical exercise is characterized by an increase in oxygen uptake, particularly by muscle, which can be up to 10 or 15 times higher than in regular conditions (19). The high production of ROS during exhaustive exercise could be responsible for muscular damage (1), leading to a consequent drop in muscular functionality, enzyme release to plasma, histological changes, and muscular soreness (24).
Coenzyme Q10 (CoQ10), known as ubiquinone, CoQ, and vitamin Q10, is a fat-soluble vitamin-like quinone existing in all cells (5,30). Coenzyme Q10 acts as a redox electron carrier in the mitochondria (35). Coenzyme Q10 is an antioxidant, and the limited data that is available has provided a direct link between physical performance and blood and muscle tissue CoQ10 levels (8,16,37). It has been claimed that increased ROS production and metabolic stress attenuate CoQ10 levels in muscle tissue, and this decrease negatively affects exercise performance (16). Coenzyme Q10 supplementation should increase CoQ10 concentration in muscle tissue, thus elevating free radical-scavenging activity period. Therefore, CoQ10 supplementation could normalize and even increase the exercise performance in athletes (8).
In some studies (7,17,33,35), it has been shown that oral CoQ10 supplementation has no effects on physical performance in healthy athletes and/or untrained individuals. On the contrary, some researchers (34,37) suggest that aerobic power, anaerobic threshold, or exercise performance increased after CoQ10 supplementation. Although there are limited studies (8,20,29) about the effects of CoQ10 supplementation on anaerobic exercise performance, we could not find any study about the effects of CoQ10 supplementation on performance during repeated bouts of supramaximal exercise.
Anaerobic exercise, such as 30-second supramaximal Wingate test (WT), can induce oxidative damage to proteins, lipids, and DNA (4). Generally accepted performance indices of WT are peak power (PP), mean power (MP), and fatigue index (FI). Mean power has also been called “anaerobic capacity” (2). It has been assumed that PP is based on the alactic (phosphagen) anaerobic processes and reflects to maximal anaerobic power, and MP shows the anaerobic glycolysis rate in muscles (25,32).
The WTs 30-second duration was chosen for being sufficiently long, not only for eliciting maximal glycolytic power but also for requiring a good measure of “glycolytic/anaerobic endurance” (10). The WT strongly stimulates both the adenosine triphosphate-phosphocreatine and glycolytic systems (26), and thus activates purine catabolism and lactic acid production (12). In addition, supramaximal anaerobic exercise has been associated with major increase in plasma catecholamine levels (36). These factors are the cause of oxidative stress in supramaximal anaerobic exercise.
It has been shown that during WT, performance to be dependent on energy release from both anaerobic and aerobic processes (3,11). It has been suggested that the WT may be used as an exercise task that stimulates both aerobic and anaerobic processes (21). In the previous studies, it has been demonstrated that aerobic contribution in WT is between 19.5 (3) and 27% (28) but during the repeated supramaximal activities aerobic contribution might be increased. Therefore, in this study, we are planning to investigate the effects of CoQ10, which has been known to effects on aerobic performance. The purpose of this study was to determine the effects of oral CoQ10 supplementation on performance during repeated bouts of supramaximal exercise.
Experimental Approach to the Problem
This study was a randomized, double-blind, crossover trial composed of two 8-week periods of supplementation with pills containing either 100 mg·d−1 CoQ10 (GNC, Pittsburgh, PA) or placebo (glucose). In the baseline exercise session, exercise tests were applied to all participants. After the baseline exercise session, the participants were randomly allocated to 2 groups. Seven participants received CoQ10 and 8 participants received placebo for 8 weeks. At the end of 8 weeks, a second exercise session period same as the baseline exercise session was administrated. After a 4-week washout period, the placebo and CoQ10 supplementation was reversed. After 8 weeks of supplementation, a third exercise session was then administrated (Figure 1).
Fifteen healthy, nonsmoker, and sedentary men (aged 19.9 ± 0.9 years, height 178.1 ± 5.0 cm, and body weight 72.1 ± 12.9 kg) participated in the present study. Subjects completed a medical history, diet and supplementation history, and physical activity questionnaire to determine eligibility. No subject was a vegetarian or a smoker, nor did they use anti-inflammatory drugs or any other antioxidant supplements before (for a minimum of 3 months) or during the study period. Individuals did not participate in any regular form of aerobic and/or anaerobic exercise for at least the past year.
The study protocol was approved by the Ethical Committee of Meram Faculty of Medicine, Selcuk University. Written informed consent was obtained from all study participants after they were informed about the purpose, procedures, and possible risks of the study.
Group and Supplementation
The study was conducted between November and April. Coenzyme Q10 and placebo were given orally in capsule form and they were taken after breakfast. Coenzyme Q10 and placebo capsules were of same size, shape, and color. Given the long supplementation period, the adherence to treatment was evaluated using patient's self reports daily. Capsules were given weekly during the 16 weeks of supplementation period. During the 20 weeks of study period, subjects were not undertaking any dietary restriction.
Each exercise session started same hours (between 9am and 10 am), 2 hours after a carbohydrate-rich light breakfast, and consisted of five 30-second WT with 2-minute rest between consecutive exercise bouts. Before the tests, each participant's body weight and height were measured. The WT was performed on an Ergometric 894E Peak Bike (Monark Exercise AB, Varberg, Sweden) against a resistance of 75 g·kg−1 body weight (4.41 J·pedal revolution−1·kg−1 body weight). The participants were allowed to pedal unloaded and instructed to reach a pedaling rate of 100 revolutions per minute. The predetermined load was applied to the flywheel automatically by the Monark Anaerobic Test Software and the participants were verbally encouraged to maintain as high a pedaling rate as possible throughout the 30-seond test duration.
Mean power performed during the 30-second duration and the highest power (PP) obtained in any seconds were determined by Monark Anaerobic Test Software 2.0. According to this software, PP is the highest power achieved at any given 5-second period. Mean power is the average power of the entire test. Fatigue index was defined by the following formula:
Distribution of variables was evaluated using Shapiro-Wilk test. Statistical evaluation was made by means of nonparametric ranking tests. Changes occurring with time were evaluated with Friedman test, and overall differences between experimental curves were tested with Wilcoxon test with the Bonferroni correction for comparisons within groups. A p value of ≤0.05 was considered to indicate statistical significance. Data are reported as mean ± SD.
At WT1 and WT2, PP decreased with CoQ10 supplementation from 881.7 ± 292.5 W to 686.5 ± 161.5 W and from 708.6 ± 189.8 W to 621.4 ± 137.9 W, respectively, compared with the baseline exercise session (p < 0.05). At WT2, PP decreased with placebo (p < 0.05). No changes were observed in PP at WT3, WT4, and WT5 with neither CoQ10 nor placebo supplementation compared with the baseline exercise session. Peak power output in WT4 and WT5 was significantly decreased with CoQ10 supplementation and baseline exercise, respectively, compared with WT1 (p < 0.05) (Figure 2).
Mean power at the WT5 increased with CoQ10 supplementation from 285.6 ± 47.7 W to 331.5 ± 84.3 W compared with the baseline exercise session (p < 0.05). There were no changes in MP values at other WTs. Mean power in baseline exercise session significantly decreased in WT3 and WT5 compared with WT2, WT2 and WT3 (p < 0.05). In WT3 and WT4, MP in the CoQ10 trial was significantly decreased compared with WT1 and WT2, and in WT5, MP was decreased compared with WT1. In WT4, MP in the placebo trial was significantly decreased compared with WT1 (p < 0.05, Figure 3).
At WT2, FI decreased with CoQ10 supplementation compared with the baseline exercise session. Fatigue index decreased significantly at WT3 with both CoQ10 and placebo supplementation compared with the baseline exercise session. At WT4, FI decreased only with placebo supplementation compared with the baseline exercise session (Figure 4). Fatigue index in baseline exercise session significantly greater in WT2 compared with WT1 and the FI was significantly higher in WT3, WT4, and WT5 compared with WT1 and WT2. In CoQ10 trial, FI increased in WT3 compared with WT1 and WT2. In the same trail, FI increased in WT4 and WT5 compared with WT3, WT4, and WT5. In placebo trial, FI increased in WT4 compared with WT1 and WT2. In the same trail, FI increased in WT5 compared with WT1, WT2, WT3, and WT4 (p < 0.05, Figure 4).
Anaerobic performance is important, and oxidative stress increases in short-term maximal and supramaximal exercises. Repeated supramaximal exercise-induced oxidative stress may lead to muscle damage and decrease anaerobic performance (4). Contradictory results have been found regarding the effects of CoQ10 supplementation on aerobic performance (8,17,34,35). Laaksonen et al. (17,18) found that CoQ10 supplementation of 120 mg·d−1 for 6 weeks did not affect muscle CoQ10 concentration and aerobic performance. In placebo-controlled studies, it was shown that CoQ10 supplementation alone (7,33) or combined with vitamins C and E (22,27) had no significant effect on respiratory capacity, performed work, or muscle metabolism. In untrained subjects, Porter et al. (23) did not find any changes in VO2max, lactate threshold, heart rate, and maximal workload during maximal cycle ergometer test after supplementation with CoQ10 for 2 months. Bonetti et al. (6) found that CoQ10 supplementation of 100 mg·d−1 for 8 weeks increased plasma CoQ10 concentration but did not affect aerobic power. Similarly, Zhou et al. (35) demonstrated that CoQ10 supplementation of 150 mg·day−1 for 4 weeks did not affect maximal oxygen consumption and ventilatory threshold in healthy sedentary males. In contrast to these results, Ylikoski et al. (34) demonstrated that CoQ10 supplementation of 90 mg·d−1 for 12 weeks caused small but significant increase in VO2max in cross-country skiers compared with the placebo control group.
Cooke et al. (8) showed that both acute CoQ10 supplementation (200 mg) 60 minutes before exercise test and chronic CoQ10 supplementation of 200 mg·d−1 for 14 days did not effect aerobic exercise time to exhaustion. In contrast, Cowie and Mendez (9) demonstrated that CoQ10 supplementation increased 6-minute walk distance from 269 to 382 m in patients with chronic heart failure and suggested that CoQ10 supplementation increased performance improving the time to exhaustion. It has been demonstrated that the CoQ10 redox shuttle was a rate-limiting step in the oxidative phosphorylation pathway. Hence, an increase in CoQ10 content within the mitochondria would potentially enhance the oxidative phosphorylation process and subsequently prolong exercise performance (35). Oral CoQ10 supplementation at different doses increased plasma CoQ10 concentrations (8,15,35) but had no significant effects on exercise performance. In the current study, plasma CoQ10 status of the subjects was not measured before and after supplementation period, but the effectiveness of our supplementation protocol is supported by prior research (6,15). In addition, ingestion of CoQ10 at “fast-melt” or capsule form could affect plasma availability of CoQ10. It has been suggested that fast-melt CoQ10 formulations enhanced absorption kinetics into the blood stream compared with previous commercially available formulations (14), the increased bioavailability may enhance greater uptake into the muscle. This can explain the differences between the studies on muscle CoQ10 concentrations.
Studies investigating the effects of CoQ10 supplementation on anaerobic exercise performance are limited (8,20). Malm et al. (20) demonstrated that CoQ10 or placebo supplementation of 2 × 60 mg·d−1 for 22 days had no significant effects on 4 anaerobic cycling tests performed during the supplementation period. Similarly, Cooke et al. (8) showed that CoQ10 supplementation of 200 mg·d−1 for 14 days caused no significant changes on anaerobic power measured by PP, MP, and FI compared with placebo. In the present study, although some changes were observed in PP and FI, similar changes were seen also with placebo supplementation and these data support the study of Malm et al. (20) and Cooke et al. (8). However, the present study was different from the study of Cooke et al. (8) because we repeated WT test 5 times. This could be explained by either a psychological familiarization affect of the exercise test. Power peak values significantly decreased WT1 and WT2 with CoQ10 and WT2 with placebo compared with baseline; unfortunately, we could not explain this decrease but it could be depending on the familiarization of the WT.
Increase of the MP during WT5 is important for the contribution of aerobic metabolism and prevention of muscular damage, and this may be depending on the key role of the CoQ10 in energy metabolism. However, Bonetti et al. (6) suggested that increase in muscle performance might be due to the antioxidant effect of CoQ10 supplementation and/or its probable action on the central nervous system. There is a direct relationship between the PP and MP: PP is based on the alactic (phosphagen) anaerobic processes and reflects to maximal anaerobic power and MP shows the anaerobic glycolysis rate in muscles (25,32).
In the present study, limited changes were observed in FI following CoQ10 or placebo supplementation; this could be due to the chronic supplementation of CoQ10 because it has been demonstrated that chronic CoQ10 supplementation had no significant effect on muscle CoQ10 concentration (17,29). Fatigue index levels were lowered with CoQ10 and placebo supplementation compared with baseline. This could be explained by the familiarization effect to the WT. During the 5 WTs, PP and MP tended to decrease and FI tended to increase in all groups. This decrease in PP and MP related with the decline in anaerobic power and as a result of this decline, FI increased.
In conclusion, the most important effect of CoQ10 supplementation is an increase in MP during the WT5. Increase of the MP during WT5 suggested that contribution of aerobic metabolism was increased during the repeated supramaximal exercises and CoQ10 supplementation increased performance in this type of exercises. Therefore, we concluded that CoQ10 supplementation increases exercise performance, especially anaerobic capacity during repeated bouts of supramaximal exercises. This is the first study investigating the effects of CoQ10 on supramaximal exercises.
This study suggests that the effects of 8 weeks of CoQ10 supplementation on PP and FI during the 5 WTs were limited. Of primary importance, our results demonstrate that CoQ10 supplementation increased MP during the repeated bouts of supramaximal exercise. This increase in MP might be due to antioxidant effect of CoQ10 or contribution of CoQ10 to the aerobic metabolism and increasing of the aerobic contribution caused to amelioration of performance during the repeated bouts of the supramaximal exercises. It means that CoQ10 might be used as an ergogenic aid to increase anaerobic power after its effect clearly exhibited with the further research. In addition, during the further research, familiarization session must be applied to all participants before the baseline exercise session and values of this session should not be used in the study.
Scientific Research and Project Coordinator of Selçuk University supported this study (Fund number: SABE 06202030). We thank Professor Said Bodur for statistical assistance and Çiğdem Dölek, Safiye Sayar, and Emrah Uğur for technical assistance.
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