Sodium bicarbonate supplementation prevents skilled tennis performance decline after a simulated match

International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance

Based on a comprehensive review and critical analysis of the literature regarding the effects of sodium bicarbonate supplementation on exercise performance, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Supplementation with sodium bicarbonate (doses from 0.2 to 0.5 g/kg) improves performance in muscular endurance activities, various combat sports, including boxing, judo, karate, taekwondo, and wrestling, and in high-intensity cycling, running, swimming, and rowing. The ergogenic effects of sodium bicarbonate are mostly established for exercise tasks of high-intensity that last between 30 s and 12 min. 2. Sodium bicarbonate improves performance in single- and multiple-bout exercise. 3. Sodium bicarbonate improves exercise performance in both men and women. 4. For single-dose supplementation protocols, 0.2 g/kg of sodium bicarbonate seems to be the minimum dose required to experience improvements in exercise performance. The optimal dose of sodium bicarbonate dose for ergogenic effects seems to be 0.3 g/kg. Higher doses (e.g., 0.4 or 0.5 g/kg) may not be required in single-dose supplementation protocols, because they do not provide additional benefits (compared with 0.3 g/kg) and are associated with a higher incidence and severity of adverse side-effects. 5. For single-dose supplementation protocols, the recommended timing of sodium bicarbonate ingestion is between 60 and 180 min before exercise or competition. 6. Multiple-day protocols of sodium bicarbonate supplementation can be effective in improving exercise performance. The duration of these protocols is generally between 3 and 7 days before the exercise test, and a total sodium bicarbonate dose of 0.4 or 0.5 g/kg per day produces ergogenic effects. The total daily dose is commonly divided into smaller doses, ingested at multiple points throughout the day (e.g., 0.1 to 0.2 g/kg of sodium bicarbonate consumed at breakfast, lunch, and dinner). The benefit of multiple-day protocols is that they could help reduce the risk of sodium bicarbonate-induced side-effects on the day of competition. 7. Long-term use of sodium bicarbonate (e.g., before every exercise training session) may enhance training adaptations, such as increased time to fatigue and power output. 8. The most common side-effects of sodium bicarbonate supplementation are bloating, nausea, vomiting, and abdominal pain. The incidence and severity of side-effects vary between and within individuals, but it is generally low. Nonetheless, these side-effects following sodium bicarbonate supplementation may negatively impact exercise performance. Ingesting sodium bicarbonate (i) in smaller doses (e.g., 0.2 g/kg or 0.3 g/kg), (ii) around 180 min before exercise or adjusting the timing according to individual responses to side-effects, (iii) alongside a high-carbohydrate meal, and (iv) in enteric-coated capsules are possible strategies to minimize the likelihood and severity of these side-effects. 9. Combining sodium bicarbonate with creatine or beta-alanine may produce additive effects on exercise performance. It is unclear whether combining sodium bicarbonate with caffeine or nitrates produces additive benefits. 10. Sodium bicarbonate improves exercise performance primarily due to a range of its physiological effects. Still, a portion of the ergogenic effect of sodium bicarbonate seems to be placebo-driven.

Effect of sodium bicarbonate supplementation on two different performance indicators in sports: a systematic review with meta-analysis

[Purpose]

Sodium bicarbonate shows ergogenic potential in physical exercise and sports activities, although there is no strong evidence which performance markers show the greatest benefit from this supplement. This study evaluated the effects of sodium bicarbonate supplementation on time trial performance and time to exhaustion in athletes and sports practitioners.

[Methods]

A systematic review was conducted using three databases, including 17 clinical trials. Among these clinical trials, 11 were considered eligible for the meta-analysis according to the criteria for the assessment of methodological quality using the PEDro Scale. Time to exhaustion was assessed in six studies, while time trial performance was evaluated in five studies.

[Results]

A significant beneficial effect of supplementation on time to exhaustion was found in a random effects model (1.48; 95% confidence interval [CI], 0.49 to 2.48). There was no significant effect of supplementation on time trial performance in a fixed effects model (slope = −0.75; 95% CI, −2.04 to 0.55) relative to a placebo group.

[Conclusion]

Sodium bicarbonate has the potential to improve sports performance in general, especially in terms of time to exhaustion.

Effect of sodium bicarbonate contribution on energy metabolism during exercise: a systematic review and meta-analysis

Background

The effects of sodium bicarbonate (NaHCO₃) on anaerobic and aerobic capacity are commonly acknowledged as unclear due to the contrasting evidence thus, the present study analyzes the contribution of NaHCO₃ to energy metabolism during exercise.

Methods

Following a search through five databases, 17 studies were found to meet the inclusion criteria. Meta-analyses of standardized mean differences (SMDs) were performed using a random-effects model to determine the effects of NaHCO₃ supplementation on energy metabolism. Subgroup meta-analyses were conducted for the anaerobic-based exercise (assessed by changes in pH, bicarbonate ion [HCO₃⁻], base excess [BE] and blood lactate [BLa]) vs. aerobic-based exercise (assessed by changes in oxygen uptake [VO₂], carbon dioxide production [VCO₂], partial pressure of oxygen [PO₂] and partial pressure of carbon dioxide [PCO₂]).

Results

The meta-analysis indicated that NaHCO₃ ingestion improves pH (SMD = 1.38, 95% CI: 0.97 to 1.79, P < 0.001; I² = 69%), HCO₃⁻ (SMD = 1.63, 95% CI: 1.10 to 2.17, P < 0.001; I² = 80%), BE (SMD = 1.67, 95% CI: 1.16 to 2.19, P < 0.001, I² = 77%), BLa (SMD = 0.72, 95% CI: 0.34 to 1.11, P < 0.001, I² = 68%) and PCO₂ (SMD = 0.51, 95% CI: 0.13 to 0.90, P = 0.009, I² = 0%) but there were no differences between VO₂, VCO₂ and PO₂ compared with the placebo condition.

Conclusions

This meta-analysis has found that the anaerobic metabolism system (AnMS), especially the glycolytic but not the oxidative system during exercise is affected by ingestion of NaHCO₃. The ideal way is to ingest it is in a gelatin capsule in the acute mode and to use a dose of 0.3 g•kg^− 1 body mass of NaHCO₃ 90 min before the exercise in which energy is supplied by the glycolytic system.

Nutritional Ergogenic Aids in Racquet Sports: A Systematic Review

A nutritional ergogenic aid (NEA) can help athletes optimize performance, but an evidence-based analysis is required in order to support training outcomes or competition performance in specific events. Racquet sports players are regularly exposed to a high-intensity workload throughout the tournament season. The activity during a match is characterized by variable durations (2–4 h) of repeated high-intensity bouts interspersed with standardized rest periods. Medline/PubMed, Scopus, and EBSCO were searched from their inception until February 2020 for randomized controlled trials (RCTs). Two independent reviewers extracted data, after which they assessed the risk of bias and the quality of trials. Out of 439 articles found, 21 met the predefined criteria: tennis (15 trials), badminton (three trials), paddle (one trial), and squash (two trials). Among all the studied NEAs, acute dosages of caffeine (3–6 mg/kg) 30–60 min before a match have been proven to improve specific skills and accuracy but may not contribute to improve perceived exertion. Currently, creatine, sodium bicarbonate, sodium citrate, beetroot juice, citrulline, and glycerol need more studies to strengthen the evidence regarding improved performance in racquet sports.

Effects of Beetroot Juice Ingestion on Physical Performance in Highly Competitive Tennis Players

Beetroot juice (BJ) contains high levels of inorganic nitrate (NO₃⁻) and its intake has good evidence in increasing blood nitrate/nitrite concentrations. The ingestion of BJ has been associated with improvements in physical performance of endurance sports, however the literature in intermittent sports is scarce. The aim of this study was to investigate whether BJ could improve physical performance in tennis players. Thirteen well-trained tennis players (25.4 ± 5.1 years) participated in the study during their preparatory period for the tennis season. Subjects were randomly divided into two groups and performed a neuromuscular test battery after either BJ or placebo (PLA) consumption. Both trials were executed on two separate days, in randomized order, with one week of wash out period. The test battery consisted of serve velocity test (SVT), countermovement jump (CMJ), isometric handgrip strength (IHS), 5-0-5 agility test (5-0-5), and 10 m sprint (10-m). No significant differences were found in SVT (1.19%; p = 0.536), CMJ (0.96%; p = 0.327), IHS (4.06%; p = 0.069), 5-0-5 dominant and nondominant side (1.11–2.02%; p = 0.071–0.191) and 10-m (1.05%; p = 0.277) when comparing BJ and PLA ingestion. Thus, our data suggest that low doses of BJ (70 mL) consumption do not enhance tennis physical performance.

Sodium citrate supplementation enhances tennis skill performance: a crossover, placebo-controlled, double blind study

Background

The efficacy of sodium citrate supplementation (SC) in exercise performance is unclear. Therefore, the aim of this study was to investigate the effect of SC on skilled tennis performance.

Methods

Ten Brazilian nationally-ranked young male tennis players (age: 17 ± 1 yrs.; stature: 176.7 ± 5.2 cm; body mass: 68.4 ± 7.9 kg) participated in this crossover, placebo-controlled, double-blind study. Upon arrival, at baseline, in both experimental sessions blood was collected, then subjects ingested either sodium citrate (SC - 0.5 g^.kg⁻¹BM in capsules of 500 mg) or a placebo (PLA). Two hours later, pre-match blood was collected then skills tests (skill tennis performance test - STPT, repeated-sprint ability shuttle test - RSA) were performed followed by a 1-h simulated match. Immediately following the match, blood was again collected, and STPT, and RSA were administered.

Results

All metabolic parameters (i.e. base excess, pH, bicarbonate, and blood lactate) increased (p < 0.001) from baseline to pre-match and post-match in SC condition. Each metabolic parameter was greater (p < 0.001) in SC compared to PLA condition at both pre- and post-match. The SC condition elicited a greater (p < 0.01) shot consistency at post-match in the STPT vs. PLA condition (SC: 58.5 ± 14.8% vs. PLA: 40.4 ± 10.4%). A greater (p < 0.001) amount of games won was observed in the simulated match for SC condition vs. PLA condition (SC: 8.0 ± 1.6 vs. PLA: 6.0 ± 1.7). Additionally, the games won during the simulated match in SC condition was positively correlated with percentage shot consistency (r = 0.67, p < 0.001).

Conclusions

The current findings suggest that SC supplementation is an effective ergogenic aid to enhance skilled tennis performance.

The Impact of Sodium Bicarbonate on Performance in Response to Exercise Duration in Athletes: A Systematic Review

According to recent literature sodium bicarbonate (NaHCO₃) has been proposed as a performance enhancing aid by reducing acidosis during exercise. The aim of the current review is to investigate if the duration of exercise is an essential factor for the effect of NaHCO₃. To collect the latest studies from electronic database of PubMed, study publication time was restricted from December 2006 to December 2016. The search was updated in July 2018. The studies were divided into exercise durations of > 4 or ≤ 4 minutes for easier comparability of their effects in different exercises. Only randomized controlled trials were included in this review. Of the 775 studies, 35 met the inclusion criteria. Study design, subjects, effects as well as outcome criteria were inconsistent throughout the studies. Seventeen of these studies reported performance enhancing effects after supplementing NaHCO₃. Eleven of twenty studies with exercise duration of ≤ 4 minutes showed positive and four diverse results after supplementing NaHCO₃. On the other hand six of fifteen studies with an exercise duration of >4 minutes showed performance enhancing and two studies showed diverse results. Consequently, the duration of exercise might be influential for inducing a performance enhancing effect when supplementing NaHCO₃, but to which extent, remains unclear due to the inconsistencies in the study results.

Chronic Ingestion of Sodium and Potassium Bicarbonate, with Potassium, Magnesium and Calcium Citrate Improves Anaerobic Performance in Elite Soccer Players

Anaerobic power and anaerobic capacity significantly influence performance in many sport disciplines. These include prolonged sprints in athletics, swimming, or cycling, and other high intensity intermittent sports, such as soccer or basketball. Considering the association of exercise-induced acidosis and fatigue, the ingestion of potential buffering agents such as sodium bicarbonate, has been suggested to attenuate metabolic acidosis and improve anaerobic performance. Since elite soccer players cover from 200 to 350 m while sprinting, performing 40–60 all out sprints during a game, it seems that repeated sprint ability in soccer players is among the key components of success. In our experiment, we evaluated the effectiveness of chronic supplementation with sodium and potassium bicarbonate, fortified with minerals, on speed and speed endurance in elite soccer players. Twenty-six soccer players participated in the study. The subjects were randomly divided into two groups. The experimental group was supplemented with sodium bi-carbonate and potassium di-carbonate fortified with minerals, while the control group received a placebo. The athletes were tested at baseline and after nine days of supplementation. Anaerobic performance was evaluated by the Repeated Anaerobic Sprint Test (RAST) protocol which involved 6 × 30 m max sprints, separated by 10 s of active recovery. Resting, post ingestion and post exercise concentrations of HCO₃⁻ and blood pH were measured as well as lactate concentration. The current investigation demonstrated a significant increase in RAST performance of elite soccer players supplemented with sodium and potassium bicarbonate along with calcium phosphate, potassium citrate, and magnesium citrate ingested twice a day over a nine-day training period. The improvements in anaerobic performance were caused by increased resting blood pH and bicarbonate levels.

Analysis of Nutritional Supplements Consumption by Squash Players

The aim of the present study is to analyse nutritional supplements (NS) consumption by squash players of different levels (international vs. national). A total of 14 international players and 28 national ones answered a NS consumption frequency questionnaire that had been previously validated. A T-Student test was used for independent samples and a χ² test was used in the comparative analysis among athletes of different levels. International level players consume NS in greater proportion vs. national level players (100% vs. 67.9% p = 0.017), with differences in the consumption of bicarbonate of soda, glutamine, branched-chain amino acids, and flaxseed oil (p < 0.05). Even though international level athletes show a greater total number of NS, as well as of the total of NS of each of the categories based on scientific evidence level (sports food, medical supplements, and ergogenic aids of groups A, B, C, and D) in relation to the national level athletes, no statistically significant differences were detected (p > 0.05). With regard to nutritional advice, there are also differences among performance levels (p = 0.003), being personal trainers (28.6%) and dietitians-nutritionists (21.4%) the greatest prescribers when it comes to international-level players, whereas 55.6% of the national-level players do not receive nutritional advice. The pattern of NS consumption, based on evidence level, is unbalanced and its performance could be favored if the dietitian-nutritionist were included as a nutritional advisor for these athletes.

Sodium bicarbonate supplementation does not improve elite women's team sport running or field hockey skill performance

Team sports, such as field hockey, incorporate high-intensity repeated sprints, interspersed with low-intensity running, which can result in acidosis. The aim of the present study was to examine the effect of acute sodium bicarbonate (SB) supplementation on team sport running and skill performance. Eight elite female field hockey players (age 23 ± 5 years, body mass 62.6 ± 8.4 kg, height 1.66 ± 0.05 m) completed three Field Hockey Skill Tests (FHST) interspersed with four sets of the Loughborough Intermittent Shuttle Test (LIST). Prior to exercise, participants were supplemented with capsules equivalent to 0.2 g·kg-1 body mass (BM) of a placebo (maltodextrin) or 0.3 g·kg-1 BM SB. Field hockey skill performance incorporated overall performance time (PFT), movement time (MT), decision-making time (DMT), and penalty time (PT). Sprint time (ST), rating of perceived exertion (RPE), blood lactate concentration, bicarbonate anion ( HCO 3 - ) concentration, pH, and base excess were measured at various time points. Data (mean ± SD) were analyzed using a two-way analysis of variance (ANOVA) with repeated measures, with Hedges g effect sizes used to interpret the magnitude of differences. Bicarbonate anion concentration (+5.4 ± 2.6 mmol·L-1 ) and pH (+0.06 ± 0.03) were greater during the bicarbonate trial compared with the placebo (P < 0.001). Bicarbonate did not alter PFT (placebo: 87.9 ± 6.9 sec; bicarbonate: 89.0 ± 7.8 sec, P = 0.544, g = 0.14), MT, DMT, PT (all P > 0.30) or ST (placebo: 2.87 ± 0.12 sec; bicarbonate: 2.86 ± 0.12 sec, P = 0.893, g = -0.08). RPE was lower during the SB condition (placebo: 13 ± 2; bicarbonate: 12 ± 2, P = 0.021, g = -0.41). Acute ingestion of bicarbonate did not improve sprint or sport-specific skill performance. Bicarbonate ingestion did result in a lower perception of effort during team-sport running, which may have performance implications in a competitive match situation.

Mechanistic Insights into the Efficacy of Sodium Bicarbonate Supplementation to Improve Athletic Performance

A large proportion of empirical research and reviews investigating the ergogenic potential of sodium bicarbonate (NaHCO₃) supplementation have focused predominately on performance outcomes and only speculate about underlying mechanisms responsible for any benefit. The aim of this review was to critically evaluate the influence of NaHCO₃ supplementation on mechanisms associated with skeletal muscle fatigue as it translates directly to exercise performance. Mechanistic links between skeletal muscle fatigue, proton accumulation (or metabolic acidosis) and NaHCO₃ supplementation have been identified to provide a more targeted, evidence-based approach to direct future research, as well as provide practitioners with a contemporary perspective on the potential applications and limitations of this supplement. The mechanisms identified have been broadly categorised under the sections ‘Whole-body Metabolism’, ‘Muscle Physiology’ and ‘Motor Pathways’, and when possible, the performance outcomes of these studies contextualized within an integrative framework of whole-body exercise where other factors such as task demand (e.g. large vs. small muscle groups), cardio-pulmonary and neural control mechanisms may outweigh any localised influence of NaHCO₃. Finally, the ‘Performance Applications’ section provides further interpretation for the practitioner founded on the mechanistic evidence provided in this review and other relevant, applied NaHCO₃ performance-related studies.

Analysis of the distances covered and technical actions performed by professional tennis players during official matches

The purpose of this study was to analyse the physical and technical performances of professional tennis players during official matches. The trajectories of eight players were obtained during matches, using an automatic tracking method. The distances covered and technical performances were analysed for the first and second sets. The athletes covered (mean ± standard deviation) a total of 1702.4 ± 448.2 m in the first set, 1457.6 ± 678.1 m in the second set and 3160.0 ± 880.1 in the entire match. No differences were found between the sets for the physical variables (lateral and forward displacements, distance covered per rally, per game and per set, and the percentage of time spent in each range of velocity). However, the distances covered by the athletes during the rallies in which they were serving (median = 5.2; interquartile range (IQR) = 6.7 m) were statistically smaller than when they were returning (median = 6.2; IQR = 7.7 m). Forehand ground stroke proficiency decreased from the first (mean ± standard deviation: 75.2 ± 4.11%) to the second set (mean ± standard deviation = 65.5 ± 14.3%). In conclusion, tennis players did not present reduced physical performance from the first to the second set.

Ergogenic effects of caffeine and sodium bicarbonate supplementation on intermittent exercise performance preceded by intense arm cranking exercise

BACKGROUND

Caffeine and sodium bicarbonate ingestion have been suggested to improve high-intensity intermittent exercise, but it is unclear if these ergogenic substances affect performance under provoked metabolic acidification. To study the effects of caffeine and sodium bicarbonate on intense intermittent exercise performance and metabolic markers under exercise-induced acidification, intense arm-cranking exercise was performed prior to intense intermittent running after intake of placebo, caffeine and sodium bicarbonate.

METHODS

Male team-sports athletes (n = 12) ingested sodium bicarbonate (NaHCO3; 0.4 g.kg(-1) b.w.), caffeine (CAF; 6 mg.kg(-1) b.w.) or placebo (PLA) on three different occasions. Thereafter, participants engaged in intense arm exercise prior to the Yo-Yo intermittent recovery test level-2 (Yo-Yo IR2). Heart rate, blood lactate and glucose as well as rating of perceived exertion (RPE) were determined during the protocol.

RESULTS

CAF and NaHCO3 elicited a 14 and 23% improvement (P < 0.05), respectively, in Yo-Yo IR2 performance, post arm exercise compared to PLA. The NaHCO3 trial displayed higher [blood lactate] (P < 0.05) compared to CAF and PLA (10.5 ± 1.9 vs. 8.8 ± 1.7 and 7.7 ± 2.0 mmol.L(-1), respectively) after the Yo-Yo IR2. At exhaustion CAF demonstrated higher (P < 0.05) [blood glucose] compared to PLA and NaHCO3 (5.5 ± 0.7 vs. 4.2 ± 0.9 vs. 4.1 ± 0.9 mmol.L(-1), respectively). RPE was lower (P < 0.05) during the Yo-Yo IR2 test in the NaHCO3 trial in comparison to CAF and PLA, while no difference in heart rate was observed between trials.

CONCLUSIONS

Caffeine and sodium bicarbonate administration improved Yo-Yo IR2 performance and lowered perceived exertion after intense arm cranking exercise, with greater overall effects of sodium bicarbonate intake.

Effects of sports drinks on the maintenance of physical performance during 3 tennis matches: a randomized controlled study

Background

Tennis tournaments often involve playing several consecutive matches interspersed with short periods of recovery.

Objective

The objective of this study was firstly to assess the impact of several successive tennis matches on the physical performance of competitive players and secondly to evaluate the potential of sports drinks to minimize the fatigue induced by repeated matches.

Methods

This was a crossover, randomized controlled study. Eight male regionally-ranked tennis players participated in this study. Players underwent a series of physical tests to assess their strength, speed, power and endurance following the completion of three tennis matches each of two hours duration played over three consecutive half-days (1.5 day period for each condition). In the first condition the players consumed a sports drink before, during and after each match; in the second, they drank an identical volume of placebo water. The results obtained were compared with the third ‘rest’ condition in which the subjects did not play any tennis. Main outcomes measured were maximal isometric strength and fatigability of knee and elbow extensors, 20-m sprint speed, jumping height, specific repeated sprint ability test and hand grip strength.

Results

The physical test results for the lower limbs showed no significant differences between the three conditions. Conversely, on the upper limbs the EMG data showed greater fatigue of the triceps brachii in the placebo condition compared to the rest condition, while the ingestion of sports drinks attenuated this fatigue.

Conclusions

This study has demonstrated for the first time that, when tennis players are adequately hydrated and ingest balanced meals between matches, then no large drop in physical performance is observed even during consecutive competitive matches.

Trial registration

ClinicalTrials.gov: NCT01353872.

The development of fatigue during match-play tennis

Data describing the activity profile and physiological characteristics of tennis match-play are extensive. However, these data have generally provided descriptive accounts of the one-off match-play of amateur or lowly ranked professional players lasting <3 h. Accordingly, these research efforts have likely failed to fully capture the demands of Grand Slam tennis match-play, particularly in the men's game where matches can last >5 h. Furthermore, there is a distinct lack of evidence-based insight regarding the manifestation of fatigue within and between tennis matches, notwithstanding that skeletal muscle function has been reported to reduce following prolonged match-play. Moreover, it is evident that match-play evokes pronounced and prolonged physiological, neuromuscular and psychological perturbations that may be exacerbated with consecutive days of match-play. Separate to these internal load responses, a collection of non-uniform movement and technical performance changes are reported, though rarely from match-play data. Consequently, direct or causal links between altered physiological or muscle contractile function and subsequent match-play outcomes are lacking. Indeed, emerging evidence seems to infer that players adjust their game strategy, and the resultant execution of stroke play, to accommodate any such deterioration in physiological function. The purpose of this review was to discuss the available literature in terms of the physiological, mechanical and psychological responses that occur during prolonged match-play in the context of their likely effect on match-play performance.

Influence of fatigue on upper limb muscle activity and performance in tennis

The study examined the fatigue effect on tennis performance and upper limb muscle activity. Ten players were tested before and after a strenuous tennis exercise. Velocity and accuracy of serve and forehand drives, as well as corresponding surface electromyographic (EMG) activity of eight upper limb muscles were measured. EMG and force were also evaluated during isometric maximal voluntary contractions (IMVC). Significant decreases were observed after exercise in serve accuracy (-11.7%) and velocity (-4.5%), forehand accuracy (-25.6%) and consistency (-15.6%), as well as pectoralis major (PM) and flexor carpi radialis (FCR) IMVC strength (-13.0% and -8.2%, respectively). EMG amplitude decreased for PM and FCR in serve, forehand and IMVC, and for extensor carpi radialis in forehand. No modification was observed in EMG activation timing during strokes or in EMG frequency content during IMVC. Several hypotheses can be put forward to explain these results. First, muscle fatigue may induce a reduction in activation level of PM and forearm muscles, which could decrease performance. Second, conscious or subconscious strategies could lead to a redistribution of muscle activity to non-fatigued muscles in order to protect the organism and/or limit performance losses. Otherwise, the modifications of EMG activity could also illustrate the strategies adopted to manage the speed-accuracy trade-off in such a complex task.

The effect of moderate and high-intensity fatigue on groundstroke accuracy in expert and non-expert tennis players

Exploring the effects of fatigue on skilled performance in tennis presents a significant challenge to the researcher with respect to ecological validity. This study examined the effects of moderate and high-intensity fatigue on groundstroke accuracy in expert and non-expert tennis players. The research also explored whether the effects of fatigue are the same regardless of gender and player's achievement motivation characteristics. 13 expert (7 male, 6 female) and 17 non-expert (13 male, 4 female) tennis players participated in the study. Groundstroke accuracy was assessed using the modified Loughborough Tennis Skills Test. Fatigue was induced using the Loughborough Intermittent Tennis Test with moderate (70%) and high-intensities (90%) set as a percentage of peak heart rate (attained during a tennis-specific maximal hitting sprint test). Ratings of perceived exertion were used as an adjunct to the monitoring of heart rate. Achievement goal indicators for each player were assessed using the 2 x 2 Achievement Goals Questionnaire for Sport in an effort to examine if this personality characteristic provides insight into how players perform under moderate and high-intensity fatigue conditions. A series of mixed ANOVA's revealed significant fatigue effects on groundstroke accuracy regardless of expertise. The expert players however, maintained better groundstroke accuracy across all conditions compared to the novice players. Nevertheless, in both groups, performance following high-intensity fatigue deteriorated compared to performance at rest and performance while moderately fatigued. Groundstroke accuracy under moderate levels of fatigue was equivalent to that at rest. Fatigue effects were also similar regardless of gender. No fatigue by expertise, or fatigue by gender interactions were found. Fatigue effects were also equivalent regardless of player's achievement goal indicators. Future research is required to explore the effects of fatigue on performance in tennis using ecologically valid designs that mimic more closely the demands of match play. Key PointsGroundstroke accuracy under moderate-intensity fatigue is equivalent to performance at rest.Groundstroke accuracy declines significantly in both expert (40.3% decline) and non-expert (49.6%) tennis players following high-intensity fatigue.Expert players are more consistent, hit more accurate shots and fewer out shots across all fatigue intensities.The effects of fatigue on groundstroke accuracy are the same regardless of gender and player's achievement goal indicators.

Multiday acute sodium bicarbonate intake improves endurance capacity and reduces acidosis in men

Background

The purpose was to investigate the effects of one dose of NaHCO₃ per day for five consecutive days on cycling time-to-exhaustion (T_lim) at ‘Critical Power’ (CP) and acid–base parameters in endurance athletes.

Methods

Eight trained male cyclists and triathletes completed two exercise periods in a randomized, placebo-controlled, double-blind interventional crossover investigation. Before each period, CP was determined. Afterwards, participants completed five constant-load cycling trials at CP until volitional exhaustion on five consecutive days, either after a dose of NaHCO₃ (0.3 g·kg^-1 body mass) or placebo (0.045 g·kg^-1 body mass NaCl).

Results

Average T_lim increased by 23.5% with NaHCO₃ supplementation as compared to placebo (826.5 ± 180.1 vs. 669.0 ± 167.2 s; P = 0.001). However, there was no time effect for T_lim (P = 0.375). [HCO₃^-] showed a main effect for condition (NaHCO₃: 32.5 ± 2.2 mmol·l^-1; placebo: 26.2 ± 1.4 mmol·l^-1; P < 0.001) but not for time (P = 0.835). NaHCO₃ supplementation resulted in an expansion of plasma volume relative to placebo (P = 0.003).

Conclusions

The increase in T_lim was accompanied by an increase in [HCO₃^-], suggesting that acidosis might be a limiting factor for exercise at CP. Prolonged NaHCO₃ supplementation did not lead to a further increase in [HCO₃^-] due to the concurrent elevation in plasma volume. This may explain why T_lim remained unaltered despite the prolonged NaHCO₃ supplementation period. Ingestion of one single NaHCO₃ dose per day before the competition during multiday competitions or tournaments might be a valuable strategy for performance enhancement.

Trial registration

Trial registration: ClinicalTrials.gov Identifier NCT01621074

Energy expenditure during tennis play: a preliminary video analysis and metabolic model approach

The aim of this study was to estimate, using video analysis, what proportion of the total energy expenditure during a tennis match is accounted for by aerobic and anaerobic metabolism, respectively. The method proposed involved estimating the metabolic power (MP) of 5 activities, which are inherent to tennis: walking, running, hitting the ball, serving, and sitting down to rest. The energy expenditure concerned was calculated by sequencing the activity by video analysis. A bioenergetic model calculated the aerobic energy expenditure (EEO2mod) in terms of MP, and the anaerobic energy expenditure was calculated by subtracting this (MP - EEO2mod). Eight tennis players took part in the experiment as subjects (mean ± SD: age 25.2 ± 1.9 years, weight 79.3 ± 10.8 kg, VO2max 54.4 ± 5.1 ml·kg(-1)·min(-1)). The players started off by participating in 2 games while wearing the K4b2, with their activity profile measured by the video analysis system, and then by playing a set without equipment but with video analysis. There was no significant difference between calculated and measured oxygen consumptions over the 16 games (p = 0.763), and these data were strongly related (r = 0.93, p < 0.0001). The EEO2mod was quite weak over all the games (49.4 ± 4.8% VO2max), whereas the MP during points was up to 2 or 3 times the VO2max. Anaerobic metabolism reached 32% of the total energy expenditure across all the games 67% for points and 95% for hitting the ball. This method provided a good estimation of aerobic energy expenditure and made it possible to calculate the anaerobic energy expenditure. This could make it possible to estimate the metabolic intensity of training sessions and matches using video analysis.