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Effect of caffeine supplementation on exercise performance, power, markers of muscle damage, and perceived exertion in trained CrossFit men: a randomized, double-blind, placebo-controlled crossover trial
Abstract
Background:
Caffeine is a popular nutritional supplement among athletes. It is frequently used as an ergogenic aid to improve physical performance, delay fatigue, and increase muscle power. However, these effects have not been tested in CrossFit athletes. The aim of this study was to evaluate the effects of acute caffeine supplementation on workout performance, power, markers of muscle damage, and soreness in trained CrossFit men.
Methods:
Nine men (28 ± 2 years) with experience in CrossFit (2 ± 0.3 years) were investigated in a randomized, double-blind, placebo-controlled crossover trial, with a 7-day washout between treatment periods. The athletes received anhydrous caffeine (CAF: 6 mg / kg body mass) or placebo (PLA) 60 minutes before a CrossFit workout with tasks that involved muscle strength, power, gymnastic movements, and metabolic conditioning. Blood samples were collected for creatine kinase (CK), C-reactive protein, and glucose determination. Workout performance, rating of perceived exertion (RPE), delayed-onset muscle soreness (DOMS), muscle strength (handgrip strength) and power (bench throw, jump squat and countermovement jump) were also evaluated.
Results:
CAF resulted in higher glucose concentration after workout compared to PLA (+3.2 mmol/L, 95%CI: 2.1 to 4.3 vs +1.5, 95%CI: -0.1 to 3.0 mmol/L, p = 0.01). No differences were found between treatments in workout performance, CK, DOMS, RPE, muscle power and strength.
Conclusions:
Acute CAF supplementation did not alter performance, markers of muscle damage, power, and RPE in trained CrossFit men.
... Dietary interventions included a 9-day training protocol alongside a carbohydrate (CHO)-rich or control diet (for the last 3 days) on Benchmark Rahoi performance (Escobar et al., 2016) and a 6- (Gregory et al., 2017) and 12-week (Kephart et al., 2018) ketogenic diet (KD) or control diet throughout CrossFit ® training with performance assessed via a battery of anaerobic performance tests (Table 3). Supplementation studies included caffeine (Fogaça et al., 2020;Stein et al., 2020), sodium bicarbonate (SB; Durkalec-Michalski et al., 2018), nitrate (Kramer et al., 2016), and betaine (Moro et al., 2020) interventions as well as CHO (Rountree et al., 2017), epicatechin (Schwarz et al., 2020), and Zea Mays juice (Ahmad et al., 2019). Six weeks of green tea extract (GTE) supplementation alongside structured CrossFit ® training (Sadowska-Krepa et al., 2019) and 6 weeks of preworkout and postworkout protein-CHO supplementation alongside routine CrossFit ® training (Outlaw et al., 2014) were also investigated. ...
... The SB improved the total number of repetitions performed during FGB (Durkalec-Michalski et al., 2018), whereas potassium nitrate supplementation improved peak power output during a 30-s Wingate but did not affect 2,000-m rowing, isokinetic and isometric extension, or Benchmark Grace performance (Kramer et al., 2016; Table 3). Two studies that supplemented 5-6 mg/kg BM caffeine did not show performance improvements in CrossFit ® exercise (Fogaça et al., 2020;Stein et al., 2020). A Zea Mays juice drink improved performance during CrossFit ® Benchmark Cindy compared with a CHO-electrolyte solution (Ahmad et al., 2019; Table 3). ...
... Caffeine has been shown to be effective for both aerobic and anaerobic exercise (Grgic et al., 2019), making it a compound of interest for CrossFit ® athletes. However, 5 and 6 mg/kg acute caffeine supplementation did not improve CrossFit ® performance (Fogaça et al., 2020;Stein et al., 2020). Neither study familiarized their participants to the exercise protocol, and, in fact, Stein et al. (2020) showed a significant learning effect from the first to the second session, which undermines any conclusions taken from this study. ...
CrossFit ® is a high-intensity functional training method consisting of daily workouts called “workouts of the day.” No nutritional recommendations exist for CrossFit ® that are supported by scientific evidence regarding the energetic demands of this type of activity or dietary and supplement interventions. This systematic review performed in accordance with PRISMA guidelines aimed to identify studies that determined (a) the physiological and metabolic demands of CrossFit ® and (b) the effects of nutritional strategies on CrossFit ® performance to guide nutritional recommendations for optimal recovery, adaptations, and performance for CrossFit ® athletes and direct future research in this emerging area. Three databases were searched for studies that investigated physiological responses to CrossFit ® and dietary or supplementation interventions on CrossFit ® performance. Various physiological measures revealed the intense nature of all CrossFit ® workouts of the day, reflected in substantial muscle fatigue and damage. Dietary and supplementation studies provided an unclear insight into effective strategies to improve performance and enhance adaptations and recovery due to methodological shortcomings across studies. This systematic review showed that CrossFit ® is a high-intensity sport with fairly homogenous anaerobic and aerobic characteristics, resulting in substantial metabolic stress, leading to metabolite accumulation (e.g., lactate and hydrogen ions) and increased markers of muscle damage and muscle fatigue. Limited interventional data exist on dietary and supplementation strategies to optimize CrossFit ® performance, and most are moderate to very low quality with some critical methodological limitations, precluding solid conclusions on their efficacy. High-quality work is needed to confirm the ideal dietary and supplemental strategies for optimal performance and recovery for CrossFit ® athletes and is an exciting avenue for further research.
... Fogaça et al. [12] and Stein et al. [13] evaluated the effect of caffeine supplementation on performance parameters. Five studies (Escobar et al. [14]; Gregory et al. [15]; Rountree et al. [16]; Kephart et al. [6], and Durkalec-Michalski et al. [17]) assessed the effects of CHO intake on different parameters. ...
... Fogaça et al. [12] evaluated the effects of acute caffeine supplementation (6 mg/kg body mass) on workout performance, power, markers of muscle damage, and soreness in trained CF men. Caffeine supplementation had no influence on CF workout performance compared with the placebo group (PLA Studies included in quantitative synthesis (meta-analysis) (n = 0) Day 1: "Rahoi" CF workout (12 min: AMRAP of 12 box jumps, 6 thrusters, 6 bar-facing burpees) Day 5: "Rahoi" CF workout Day 9: "Rahoi" CF workout Training: Day 6: "120107" CF workout (fixed workload; 10 rounds of 15 deadlift, 15 push-ups) Day 7: "Sean" CF workout (fixed workload; 10 rounds of 11 chest-to-bar pull-ups, 22 front squats) Days 2, 3, 4, and 8: rest days ! ...
... Studies of caffeine supplementation on CF [12,13] have not shown positive results. Several studies discuss genotypic limitations that prevent caffeine from exerting its ergogenic effects [37], and it is also believed that the effects (when positive) are higher in men than in women [38]. ...
CrossFit (CF) is characterized as a constantly varied high-intensity functional movement training program, performed with little or no rest between bouts, combining strength and endurance exercises, such as running, cycling, rowing, Olympic weightlifting, power weightlifting, and gymnastic-type exercises. Several nutritional strategies are used to improve sports performance of CF practitioners; however, most of them are empirical and lack scientific evidence. Thus, the aim of this review was to determine the effect of diet intervention, dietary supplements, and performance-enhancing substances in exercise-performance parameters of CF practitioners. MEDLINE/PubMed, Web of Science, LILACS, SciELO, and Scopus databases were searched using specific Medical Subject Headings and keywords for clinical studies which enrolled CF athletes in a diet, dietary supplements, or performance-enhancing substances intervention. Athletic performance was considered as the primary outcome. No other filters were applied. Including grey literature search, a total of 217 studies and 2 abstracts were identified, however only 14 studies met the eligibility criteria. Two studies evaluated the effect of caffeine supplementation on exercise performance and performance parameters; five studies evaluated high or low carbohydrate effect on performance and other parameters. One study verified the effect of multi-ingredient supplementation on CF-specific performance and body composition. One study compared protein supplements intake on performance and body composition. Two studies assessed the effect of green tea and (-)-epicatechin on performance and other parameters. One study evaluated the effects of nitrate supplementation on exercise performance. One study investigated the effect of betaine supplementation on body composition and muscle performance. Finally, one study examined the effects of sodium bicarbonate (SB) ingestion on exercise performance and aerobic capacity. Only sodium bicarbonate (SB) supplementation improved CF performance. These outcomes may have been obtained due to methodological limitations such as small sample size, lack of control over influencing variables, short period of exercise intervention. Despite the popularity and growing evidence about the CF, little is known about the relationship between performance-enhancing substances or dietary interventions and CF performance. Given the lack of scientific evidence, new studies with potential ergogenic supplements, good methodological model, and practical application are required.
... The current evidence examining the effects of dietary supplementation on CrossFit ® performance is limited, with only one investigation examining the effect of acute caffeine supplementation on CrossFit ® performance [30]. The recent investigation by Fogaca and colleagues found no significant effect of acute caffeine supplementation on CrossFit ® performance; however, their investigation may be limited by the small sample size (n = 9), CrossFit ® performance that included power-based exercises (snatches and double-unders), and short duration of the CrossFit ® workout (10 min). ...
... In the current study, caffeine supplementation (5 mg·kg −1 body mass) did not significantly increase the mean CrossFit ® performance. These results echo the findings of Fogaca and colleagues, who found no effect of a 6 mg·kg −1 body mass dose of caffeine on CrossFit ® performance prior to a CrossFit ® bout including as many rounds as possible of double-unders and power snatches in 10 min [30]. Caffeine's ergogenic effect has been reported to improve performance by 5.5-8.5% during other repeated-high-intensity efforts in team sports athletes, and by 6-7% during muscular endurance exercise [4,17,43]. ...
... This investigation utilized a 10-point Likert scale for RPE and may not be sensitive enough to capture perceptual changes during CrossFit ® protocols. These results also reflect the findings of Fogaca and colleagues who reported no difference in post-workout RPE between the caffeine and placebo conditions using the CR10 Borg Scale [30]. Although mixed results exist for 10-point and 15-point scales for RPE during caffeine supplementation utilizing resistance-and endurance-based protocols, a recent publication by Crawford and colleagues highlights that a 15-point scale may be more appropriate in CrossFit ® athletes [5,47,55]. ...
Caffeine’s ergogenic effects persist during various exercise modalities; however, information establishing its efficacy during CrossFit® protocols is limited. This study aimed to determine the effects of caffeine supplementation on CrossFit® performance. Twenty CrossFit®-trained men (age = 26.7 ± 6.2 years, experience = 3.7 ± 2.9 years) were randomized in a double-blind, crossover design. Participants completed two sessions separated by a seven-day washout period, 60 min after consuming 5 mg/kg body mass of caffeine or a placebo. In each session, participants completed as many rounds as possible in 20 min of five pull-ups, 10 push-ups, and 15 air squats. CrossFit® performance was the total number of repetitions completed in 20 min. Paired-samples t-tests were used to compare CrossFit® performance between caffeine and placebo conditions and to test for a potential learning effect between the first and second sessions. CrossFit® performance was not significantly different during the caffeine condition compared to the placebo (468.6 ± 114.7 vs. 466.7 ± 94.3 repetitions, p = 0.861). A significant learning effect was identified between the first and second sessions (452.4 ± 101 vs. 483.8 ± 106.5 repetitions, p = 0.001), with no significant effect of treatment order (p = 0.438). Caffeine’s ergogenic effect were not present during the CrossFit® workout “Cindy”; however, future research should include familiarization sessions and examine other CrossFit® workouts in novice and women participants.
... Several studies reported that caffeine is able to reduce and attenuate delayed-onset muscle soreness (Caldwell et al. 2017;Nobahar 2013;Maridakis et al. 2007). However, others have reported that caffeine is unable to affect DOMS (Chen et al. 2019;Hurley et al. 2013;Al-Nawaiseh et al. 2020;Fogaça et al. 2020). No meta-analysis related to this topic has been published yet. ...
... This can result in decreased levels of muscle soreness (Hurley et al. 2013). In previous RCT studies, reduced feelings of pain and fatigue resulting from the adenosine antagonist action of caffeine have been demonstrated (Caldwell et al. 2017;Maridakis et al. 2007;Hurley et al. 2013;Fogaça et al. 2020). This is the first study that describes the reduced perception of soreness at 24-48 h post-exercise, without a difference in the CK level. ...
Background
There are multiple strategies that have been suggested to attenuate delayed-onset muscle soreness (DOMS). Caffeine has been shown to assist with blocking pain associated with DOMS. However, currently there is still controversy over the effects of caffeine use.
Main body
We conducted a meta-analysis to compare pain associated with muscle soreness by both the VAS and indirect markers by CK of caffeine and placebo after exercise. The meta-analysis was carried out in accordance with the PRISMA guidelines. Relevant studies from Medline and Scopus published up to May 20, 2021, were included, which resulted in a total of 477 and 132 studies being retrieved from Scopus and Medline, respectively. Seven studies met the inclusion criteria, and in these, there were 68 persons in the caffeine group and 74 persons in the placebo group. A visual analog score of muscle soreness was recorded pre-exercise, immediately post-exercise, and at one to four days post-exercise; the scores at these time points in the caffeine group as compared to those in the placebo group progressed from 0.00 (95% CI − 0.51, 0.50) to − 0.20 (− 1.09, 0.69), − 0.92 (− 2.20, 0.36), − 1.02 (− 1.86, − 0.19), 0.00 (− 0.36, 0.36), and 0.18 (− 0.56, 0.92), respectively. No statistically significant differences were noted for CK between the two groups at 24 h post-exercise.
Short conclusion
Our meta-analysis results indicate that caffeine supplements reduce delayed-onset muscle soreness when compared to a placebo 48 h after exercise. However, at 24 h post-exercise, caffeine can reduce DOMS only in people who worked on resistant exercise. The CK used in this meta-analysis did not show any differences.
Trial registration : PROSPERO CRD42021260248.
Level of evidence I.
... One possible mechanism of CAF is its ability to act as an adenosine antagonist. When CAF binds to adenosine receptors, it can increase alertness [15] and reduce the CNS's perception of pain, fatigue, and effort [16]. In addition, CAF stimulates the release of beta-endorphins, which helps increase pain and stress tolerance [11]. ...
Background: CrossFit includes weightlifting, powerlifting, and gymnastics in various combinations of overloads and repetitions with limited rest periods or no rest between training sets. Due to the novelty of CrossFit, there are few studies on the effect of nutritional strategies on the acute response to this type of sports activity. This study examined the effect of caffeine (CAF) and sodium bicarbonate (NaHCO3) ingestion separately and in combination on the performance and rate of perceived exertion (RPE) during the Cindy CrossFit workout (Cindy) in CrossFit participants.
Method: In a double-blind, crossover, randomized, placebo-controlled trial, 20 CrossFit participants underwent five experimental conditions, including control (CON), placebo (PLA), CAF, NaHCO3, and CAF + NaHCO3 (7 days to wash-out between assessment sessions) before completing the Cindy protocol (age: 22.30 ± 2.88 years, body mass index: 25.22 ± 2.51 kg/m2). Capsules containing 6 mg/kg body weight (BW) CAF were consumed 50 min before the Cindy workout while 0.3 g/kg BW NaHCO3 was consumed for 3 days, leading to 120, 90, and 60 min before the Cindy workout. Performance, RPE, muscular power (MP), handgrip strength (HGS), and maximum heart rate (MHR) were measured before and shortly after the Cindy.
Results: The performance of CrossFit participants during the Cindy protocol was not significantly improved following CAF, NaHCO3, and CAF + NaHCO3 (P > 0.05). In contrast, RPE during and at the end of the Cindy was significantly decreased following CAF + NaHCO3 consumption compared to PLA and CON (P = 0.001, P = 0.02). However, MP (P = 0.82) and HGS (P = 0.52) were not significantly different between conditions. Also, MHR was significantly greater following CAF, NaHCO3, and CAF + NaHCO3 consumption than CON (P = 0.01).
Conclusion: CAF + NaHCO3 supplementation decreased RPE despite significantly increased MHR, but with no significant effect on performance, HGS, or MP. Therefore, CrossFit participants may benefit from the ergogenic effects of CAF and NaHCO3 when consumed separately or together.
... The effects of ED, or of its isolated ingredients, on performance during high-volume muscular endurance workouts that tax multiple muscle groups with limited recovery (e.g., CrossFit®) remains unknown. However, the caffeine, one of the main ingredients in ED, with "good evidence" establishing its ergogenicity across a variety of exercise protocols and muscle groups, was analyzed in two randomized, double-blind, crossover studies 24,25 , but caffeine's ergogenic effect were not present during the CrossFit® workout, performanced by CrossFit®-trained men CrossFit®. Fundamentally, the limited evidence from the sports nutrition community exists regarding the utility of dietary supplementation for CrossFit® performance. ...
The aim of this study was to analyze the acute effects of energy drink (ED) ingestion on CrossFit® performance in a randomized, double-blind, cross-over study, with 8 CrossFit®-trained (26.5 ± 2.7 years; 70.2 ± 13.0 kg; 1.7 ± 0.09 m; 23.0 ± 3.2 kg/m2; ∑ skinfold thickness: 34.1 ± 6.9 mm; body fat: 13.3 ± 3.0 %), that were randomly allocated to 2 groups and underwent 2 trials separated by a 7-day washout period. Participants ingested either a dose of 300 mL of ED or Placebo (soda), 30 minutes before the start of tests of muscular strength (MS), 10 and 12 maximum repetitions (MRs) in barbell bench press (BBP) and barbell squat (BS), respectively and localized muscular endurance (LME) using Workout of the Day (WOD) selected. The rating of perceived exertion (RPE) and the rating of perceived pain (RPP) were evaluated immediately after the tests. The total volume of repetitions (TVR) was evaluated to each test. The TVR was significantly higher after consuming the ED (p = 0.012) and of the Placebo (p = 0.027). There was a reduction in the rate of RPE after the consumption of both drinks (p = 0.023 and p = 0.024). The consumption of ED significantly reduced the rate of RPP (p = 0.017). Acute ED ingestion improved CrossFit® performance by increased the TVR and the pain tolerance.
https://www.revistas.usp.br/rbefe/article/view/172340
... De los artículos que fueron descartados los temas con mayor relevancia en el CrossFit es referente a lesiones provocadas por el entrenamiento (Moya et al., 2017;Summitt et al., 2016;Minghelli, 2019;Gardiner et al., 2020;Weisenthal et al., 2014;Mehrab et al., 2017;Tafuri et al., 2019), los autores manifiestan la importancia de la incidencia de lesiones en el entrenamiento de CrossFit, así como identificar cuando fue la lesión y su causa. Por otro lado, el área de nutrición y suplementación tiene un papel importante para los atletas de CrossFit algunos autores (Jaramillo et al., 2017;Gogojewicz et al., 2020;Fogaça et al., 2020;Kramer et al., 2016;Stein et al., 2019) hacen énfasis en planes nutricionales y suplementación para mejorar el rendimiento de los atletas. En el área de psicología autores señalan algunas pruebas de evaluación para individuos que practican CrossFit, (Elks et al., 2020;Cadegiani et al., 2019;Cataldi et al., 2021). ...
El CrossFit es un entrenamiento sumamente practicado por diversos atletas alrededor del mundo, los cuales se preparan cada año para ser mejores y ser seleccionados para competir en los CrossFit Games. Actualmente se conoce muy poco acerca de las pruebas que valoran la fatiga muscular en atletas que practique este tipo de entrenamiento. La fatiga muscular tiene un papel fundamental en el rendimiento de los atletas para su preparación y competición. El propósito de este estudio fue comparar las diferentes pruebas que se utilizan para medir la fatiga muscular en atletas hombre de CrossFit. Por ellos se realizó una búsqueda sistemática siguiendo las pautas de PRISMA y en los artículos se incluyeron los siguientes criterios de inclusión: artículos originales, atletas hombres de CrossFit y evaluación de la fatiga muscular. Estudios publicados en los últimos 10 años (desde el año 2011 hasta el 31 de marzo del 2021), los artículos no se limitaron a un idioma en específico, encontrando en su mayoría inglés y español. La selección principal fue por medio del título, después por medio del resumen y lectura del documento completo en estudios potenciales. Finalmente, se encontraron cinco artículos en los cuales se identificaron diversas pruebas para medir la fatiga muscular en los atletas de CrossFit. Como conclusión dada la amplia variedad de entrenamientos (WOD), tipos de ejercicios e intensidades en CrossFit es necesario valorar pruebas físicas y marcadores bioquímicos. Abstract. CrossFit is training highly practiced by various athletes around the world, who prepare each year to be better and be selected to compete in the CrossFit Games. Currently very little known about the tests that assess muscle fatigue in athletes who practice this type of training. Muscle fatigue plays a fundamental role in the performance of athletes for their preparation and competition. The purpose of this study was to compare the different tests used to measure muscle fatigue in male CrossFit athletes. For them, a systematic search was carried out following the PRISMA guidelines, and the following inclusion criteria were included in the articles: original articles, CrossFit male athletes, and evaluation of muscle fatigue. Studies published in the last 10 years (from 2011 to March 31, 2021) the articles were not limited to a specific language, finding mostly English and Spanish. The main selection was by title, then by abstracting and reading the entire document in potential studies. Finally, five articles were found in which various tests were found to measure muscle fatigue in CrossFit athletes. In conclusion, given the wide variety of workouts (WOD) types of exercises and intensities in CrossFit, it is necessary to assess physical tests and biochemical markers.
Background
Systematic reviews and meta-analyses related to high-intensity functional training (HIFT) have been conducted. However, due to a restricted pool of available research, these investigations are often limited in scope. As such, a scoping review investigating the present literature surrounding the acute physiological response to HIFT-based exercise was chosen as a more appropriate structured review.
Methodology
A scoping review was conducted following Arksey and O’Malley’s framework. Three large scale databases were searched to reveal any article pertaining to HIFT and related exercise terminology.
Results
A total of 2,241 articles were found during the initial search. Following this, titles, then abstracts, and full-texts were reviewed to determine inclusion eligibility. A total of 60 articles which investigated a combined total of 35 unique HIFT workouts were included within this review.
Conclusions
A variety of physiological parameters and HIFT workouts have been examined. Markers of intensity ( e.g ., blood lactate concentrations, heart rate) have been most consistently assessed across all studies, and these support the idea that HIFT workouts are typically performed at high-intensity. In contrast, the inclusion of most other measures ( e.g ., hormonal, markers of inflammation and damage, energy expenditure, performance) has been inconsistent and has thus, limited the possibility for making generalized conclusions. Differences in study methodologies have further impacted conclusions, as different studies have varied in sample population characteristics, workouts assessed, and time points. Though it may be impossible to comprehensively research all possible HIFT workouts, consistent adoption of population definitions and workload quantification may overcome this challenge and assist with future comparisons.
Purpose
The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes.
Methods
Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low = ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high = ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes.
Results
The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between −0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine.
Conclusion
In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.
Despite the demonstrated evidence of the importance of eccentric contractions in sports performance, no research has evaluated the ergogenic effects of caffeine on this type of contraction means during flywheel exercises. Therefore, the aims of the present study were to compare the power outcomes, using different inertial loads, between caffeine and placebo conditions. Twenty-four young, healthy, and active men (age: 22.5 ± 4.8 years) took part in the study. A crossed, randomised double-blind design was used to analyse the effects of caffeine on lower limb power outcomes during a flywheel half-squat exercise. Participants completed four sets of eight all-out repetitions with a fixed three-minutes rest interval, and each set was performed using different inertial loads (i.e., 0.025, 0.050, 0.075 and 0.100 kg·m −2). Both the mean power (MP) and peak power (PP) in concentric (CON) and eccentric (ECC) movement phases at each inertial load were recorded after participants were administered either a caffeine supplement (6 mg·kg −1) or placebo (sucrose). Participants receiving a caffeine supplementation demonstrated improvements versus the placebo in total MP (MP total), as well as MP in CON phase (MP con) and in ECC phase (MP ecc) at each inertial load (22.68 to 26.53%; p < 0.01, effect size (ES) = 0.89-1.40). In addition, greater improvements with caffeine ingestion were obtained with respect to the placebo condition (18.79 to 24.98%; p < 0.01, ES = 1.03-1.40) in total PP (PP total), as well as PP in CON phase (PP con) and in ECC phase (PP ecc) at each inertial load. Thus, the supplementation of 6 mg·kg −1 caffeine may be considered to maximise on-field physical performance in those sports characterised by high demands of resistance.
Abstract Background CrossFit® practitioners commonly track progress by monitoring their ability to complete a variety of standardized benchmark workouts within a typical class setting. However, objective assessment of progress is challenging because normative data does not currently exist for any of these benchmark workouts. Therefore, the purpose of this study was to develop normative values for five common benchmark workouts (i.e., Fran, Grace, Helen, Filthy-50 [F50], and Fight-Gone-Bad [FGB]). Methods Performance data from 133,857 male (M) and female (F) profiles located on a publicly available website were collected and sorted by sex (i.e., male [M] and female [F]) and competitive age classification (i.e., teen [T], individual [I], or masters [M]) and screened for errors. Subsequently, 10,000 valid profiles were randomly selected for analysis. Results Means and standard deviations were calculated for each category for Fran (IM 250 ± 106 s; IF 331 ± 181 s; MM 311 ± 138 s; MF 368 ± 138 s; TM 316 ± 136 s; and TF 334 ± 120 s), Grace (IM 180 ± 90 s; IF 213 ± 96 s; MM 213 ± 93 s; MF 238 ± 100 s; TM 228 ± 63 s; and TF 223 ± 69 s), Helen (IM 9.5 ± 1.9 min; IF 11.1 ± 2.4 min; MM 10.2 ± 2.0 min; MF 11.5 ± 2.3 min; TM 9.4 ± 1.6 min; and TF 12.7 ± 1.9 min), F50 (IM 24.4 ± 5.9 min; IF 27.3 ± 6.9 min; MM 26.7 ± 6.1 min; MF 28.2 ± 6.0 min; TM 25.9 ± 7.9 min; and TF 28.3 ± 8.1 min), and FGB (IM 335 ± 65 repetitions; IF 292 ± 62 repetitions; MM 311 ± 59 repetitions; MF 280 ± 54 repetitions; TM 279 ± 44 repetitions; and TF 238 ± 35 repetitions). These values were then used to calculate normative percentile (in deciles) values for each category within each workout. Separate, one-way analyses of variance revealed significant (p
High-intensity functional training (HIFT) is an exercise modality that emphasizes functional, multi-joint movements that can be modified to any fitness level and elicit greater muscle recruitment than more traditional exercise. As a relatively new training modality, HIFT is often compared to high-intensity interval training (HIIT), yet the two are distinct. HIIT exercise is characterized by relatively short bursts of repeated vigorous activity, interspersed by periods of rest or low-intensity exercise for recovery, while HIFT utilizes constantly varied functional exercises and various activity durations that may or may not incorporate rest. Over the last decade, studies evaluating the effectiveness of HIIT programs have documented improvements in metabolic and cardiorespiratory adaptations; however, less is known about the effects of HIFT. The purpose of this manuscript is to provide a working definition of HIFT and review the available literature regarding its use to improve metabolic and cardiorespiratory adaptations in strength and conditioning programs among various populations. Additionally, we aim to create a definition that is used in future publications to evaluate more effectively the future impact of this type of training on health and fitness outcomes.
Background:
Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise.
Objectives:
To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance.
Methods:
A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance.
Results:
Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial.
Conclusion:
Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.
Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete’s health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete’s health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.
Background
Caffeine is commonly used as an ergogenic aid. Literature about the effects of caffeine ingestion on muscle strength and power is equivocal. The aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power.
Methods
A search through eight databases was performed to find studies on the effects of caffeine on: (i) maximal muscle strength measured using 1 repetition maximum tests; and (ii) muscle power assessed by tests of vertical jump. Meta-analyses of standardized mean differences (SMD) between placebo and caffeine trials from individual studies were conducted using the random effects model.
Results
Ten studies on the strength outcome and ten studies on the power outcome met the inclusion criteria for the meta-analyses. Caffeine ingestion improved both strength (SMD = 0.20; 95% confidence interval [CI]: 0.03, 0.36; p = 0.023) and power (SMD = 0.17; 95% CI: 0.00, 0.34; p = 0.047). A subgroup analysis indicated that caffeine significantly improves upper (SMD = 0.21; 95% CI: 0.02, 0.39; p = 0.026) but not lower body strength (SMD = 0.15; 95% CI: -0.05, 0.34; p = 0.147).
Conclusion
The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power. Future studies should more rigorously control the effectiveness of blinding. Due to the paucity of evidence, additional findings are needed in the female population and using different forms of caffeine, such as gum and gel.
A strong foundation in physical conditioning and sport-specific experience, in addition to a bespoke and periodized training and nutrition program, are essential for athlete development. Once these underpinning factors are accounted for, and the athlete reaches a training maturity and competition level where marginal gains determine success, a role may exist for the use of evidence-based performance supplements. However, it is important that any decisions surrounding performance supplements are made in consideration of robust information that suggests the use of a product is safe, legal, and effective. The following review focuses on the current evidence-base for a number of common (and emerging) performance supplements used in sport. The supplements discussed here are separated into three categories based on the level of evidence supporting their use for enhancing sports performance: (1) established (caffeine, creatine, nitrate, beta-alanine, bicarbonate); (2) equivocal (citrate, phosphate, carnitine); and (3) developing. Within each section, the relevant performance type, the potential mechanisms of action, and the most common protocols used in the supplement dosing schedule are summarized.
The positive effects of caffeine ingestion on aerobic performance are well-established; however, recent findings are suggesting that caffeine ingestion might also enhance anaerobic performance. A commonly used test of anaerobic performance and power output is the 30-second Wingate test. Several studies explored the effects of caffeine ingestion on Wingate performance, with equivocal findings. To elucidate this topic, this paper aims to determine the effects of caffeine ingestion on Wingate performance using meta-analytic statistical techniques. Following a search through PubMed/MEDLINE, Scopus, and SportDiscus®, 16 studies were found meeting the inclusion criteria (pooled number of participants = 246). Random-effects meta-analysis of standardized mean differences (SMD) for peak power output and mean power output was performed. Study quality was assessed using the modified version of the PEDro checklist. Results of the meta-analysis indicated a significant difference (p = 0.005) between the placebo and caffeine trials on mean power output with SMD values of small magnitude (0.18; 95% confidence interval: 0.05, 0.31; +3%). The meta-analysis performed for peak power output indicated a significant difference (p = 0.006) between the placebo and caffeine trials (SMD = 0.27; 95% confidence interval: 0.08, 0.47 [moderate magnitude]; +4%). The results from the PEDro checklist indicated that, in general, studies are of good and excellent methodological quality. This meta-analysis adds on to the current body of evidence showing that caffeine ingestion can also enhance components of anaerobic performance. The results presented herein may be helpful for developing more efficient evidence-based recommendations regarding caffeine supplementation.
Background: CrossFit is a new strength and conditioning regimen involving short intense daily workouts called workouts of the day (WOD). This study assesses muscular fatigue levels induced by the three modalities of CrossFit WOD; gymnastics (G), metabolic conditioning (M) and weightlifting (W).
Material and methods: 34 healthy subjects undertook three WOD (one per week): a G WOD consisting of completing the highest number of sets of 5 pull-ups, 10 push-ups and 15 air squats in 20 min; an M WOD, in which the maximum number of double skipping rope jumps was executed in 8 sets (20 s), resting (10 s) between sets; and finally, a W WOD in which the maximum number of power cleans was executed in 5 min, lifting a load equivalent to 40% of the individual’s 1RM. Before and after each WOD, blood lactate concentrations were measured. Also, before, during, and after each WOD, muscular fatigue was assessed in a countermovement jump test (CMJ).
Results: Significant reductions were produced in the mechanical variables jump height, average power and maximum velocity in response to G; and in jump height, mean and peak power, maximum velocity and maximum force in response to W (P<0.01). However, in M, significant reductions in mechanical variables were observed between pre- and mid session (after sets 2, 4, 6 and 8), but not between pre- and post session.
Conclusions: Muscular fatigue, reflected by reduced CMJ variables, was produced following the G and W sessions, while recovery of this fatigue was observed at the end of M, likely attributable to rest intervals allowing for the recovery of phosphocreatine stores. Our findings also suggest that the high intensity and volume of exercise in G and W WODs could lead to reduced
Background
The aim of this study was to compare the effects of the ingestion of either the caffeine (CAF) or the placebo (PLA) on performance of repeated modified agility test (RMAT), some cardiovascular factors, metabolic and notes of perceived exertion (RPE) in young males and females.
Methods
In a randomized double-blind study, we enrolled 18 active students (10 males and 8 females) in Sport Sciences pursuing degrees in Exercise Science and Physical Education at the University of Sports of Kef (Tunisia), during the academic year 2013–2014. All participants were ingested CAF (5 mg.kg⁻¹) or PLA 60 min before performing an RMAT. Total times (TT), peak time (PT) and fatigue index (FI) were identified as the RMAT indices. Heart rate (HR), arterial pressures (PA), blood glucose (BG) and RPE were assessed before, during and after the RMAT.
Results
Taking caffeine had been improved the performance by the significant decreased of TT on male gender better than female gender and the entire group. In addition, there was a significant improvement on HR during and after RMAT in both genders and the whole group, except after RMAT among male gender. However, the repeated measurement results had demonstrated no effect of caffeine on PA, BG and RPE.
Conclusion
Caffeine supplement had a beneficial effect on agility performance and HR in male better than in female, although, there was no improvement in PA, BG and RPE.
The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE), and pain perception (PP) in resistance-trained men. Seventeen volunteers (mean ± SD: age = 26 ± 6 years, stature = 182 ± 9 cm, body mass = 84 ± 9 kg, resistance training experience = 7 ± 3 years) consumed placebo or 6 mg kg −1 of anhydrous caffeine 1 h before testing. Muscular power was assessed with seated medicine ball throw and vertical jump exercises, muscular strength with one-repetition maximum (1RM) barbell back squat and bench press exercises, and muscular endurance with repetitions of back squat and bench press exercises (load corresponding to 60% of 1RM) to momentary muscular failure. RPE and PP were assessed immediately after the completion of the back squat and bench press exercises. Compared to placebo, caffeine intake enhanced 1RM back squat performance (+2.8%; effect size [ES] = 0.19; p = .016), which was accompanied by a reduced RPE (+7%; ES = 0.53; p = .037), and seated medicine ball throw performance (+4.3%, ES = 0.32; p = .009). Improvements in 1RM bench press were not noted although there were significant (p = .029) decreases in PP related to this exercise when participants ingested caffeine. The results point to an acute benefit of caffeine intake in enhancing lower-body strength, likely due to a decrease in RPE; upper-, but not lower-body power; and no effects on muscular endurance, in resistance-trained men. Individuals competing in events in which strength and power are important performance-related factors may consider taking 6 mg kg −1 of caffeine pre-training/competition for performance enhancement.
Objective:
To investigate the influence of habitual caffeine intake on exercise performance to acute caffeine supplementation.
Methods:
A double-blind, crossover, counterbalanced study was performed. Forty endurance-trained cyclists were allocated into tertiles according to their daily caffeine intake: low (58 ± 29 mg(.)d(-1)), moderate (143 ± 25 mg(.)d(-1)), and high consumers (351 ± 139 mg(.)d(-1)). Participants completed three trials in which they performed simulated cycling time-trials in the fastest time possible following ingestion of: caffeine (CAF: 6 mg(.)kg(-1) BM), placebo (PLA), and no supplement (CON).
Results:
Mixed-model analysis revealed time-trial performance was significantly improved in CAF compared to PLA and CON (29.92±2.18 min vs 30.81±2.67 and 31.14±2.71 min; P = <0.0002). ANCOVA revealed no influence of habitual caffeine intake as a covariate on exercise performance (P=0.47). Time-trial performance was not significantly different between tertiles (P=0.75). No correlation was observed between habitual caffeine intake and absolute changes (CAF - CON) in time-trial performance with caffeine (P=0.524). Individual analysis showed that eight, seven and five individuals improved above the variation of the test in CAF in the low, moderate and high tertiles. A Fisher's Exact Test did not show any significant differences in the number of individuals who improved in CAF between the tertiles (P>0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles (P>0.05).
Conclusion:
Performance effects of acute caffeine supplementation during a ~30 min cycling TT performance were not influenced by the level of habitual caffeine consumption.
Background
While it is well established that dietary nitrate reduces the metabolic cost of exercise, recent evidence suggests this effect is maintained 24 h following the final nitrate dose when plasma nitrite levels have returned to baseline. In addition, acute dietary nitrate was recently reported to enhance peak power production. Our purpose was to examine whether chronic dietary nitrate supplementation enhanced peak power 24 h following the final dose and if this impacted performance in a heavily power-dependent sport.
Methods
In a double-blind, randomized, crossover design, maximal aerobic capacity, body composition, strength, maximal power (30 s Wingate), endurance (2 km rowing time trial), and CrossFit performance (Grace protocol) were assessed before and after six days of supplementation with nitrate (NO) (8 mmol·potassium nitrate·d⁻¹) or a non-caloric placebo (PL). A 10-day washout period divided treatment conditions. Paired t-tests were utilized to assess changes over time and to compare changes between treatments.
Results
Peak Wingate power increased significantly over time with NO (889.17 ± 179.69 W to 948.08 ± 186.80 W; p = 0.01) but not PL (898.08 ± 183.24 W to 905.00 ± 157.23 W; p = 0.75). However, CrossFit performance was unchanged, and there were no changes in any other performance parameters.
Conclusion
Consuming dietary nitrate in the potassium nitrate salt form improved peak power during a Wingate test, but did not improve elements of strength or endurance in male CrossFit athletes.
CrossFit is a metabolically demanding strength and conditioning method which performance may benefit from a carbohydrate (CHO)-rich diet. This study investigated the effect of three consecutive days of high CHO intake on CrossFit performance and corresponding metabolically -related variables in strength trained individuals. Eighteen subjects with a CHO intake of <6 g/kg/day were randomly assigned into a CHO (n = 9) or control (C) group (n =9) and underwent a 9-day training protocol. During days 1, 5, and 9, performance was measured as repetitions completed during a 12 minute CrossFit workout. Oxygen consumption (VO2), respiratory exchange ratio (RER), and blood lactate (BL) were also measured. Days 6–8, the CHO group increased CHO intake from <6 g/kg/day to 6–8 g/kg/day; the C group maintained their current intake of <6 g/kg/day. On days 6 and 7 both groups performed CrossFit workouts followed by a day of rest prior to day 9. There was a significant increase in repetitions completed in both groups in day 9 (vs. means score of day 1 + 5) (p = 0.002), but no differences between C and CHO groups (p = 0.111). However, the CHO group displayed a 15.2 repetition increase (+10.9%) in day 9, compared to 5.7 (+4.2%) by the C group. VO2, RER, and BL were not influenced by the experimental intervention. Our results suggest that the CrossFit-embraced practice of moderately-low CHO diets may be adequate in CHO during short periods of training, however, given the noted trend, extended training periods may be effected.
The aim of this study was to investigate the effects of two consecutive Crossfit® training sessions (24 hours apart) designed to enhance work-capacity that involved both cardiovascular and muscular exercises on cytokines, muscle power, blood lactate and glucose. Nine male members of the CrossFit® community (age 26.7 ± 6.6 years; body mass 78.8 ± 13.2 kg; body fat 13.5 ± 6.2 %; training experience 2.5 ± 1.2 years) completed two experimental protocols (24 hours apart): 1) strength and power exercises 2) gymnastic movements and 3) metabolic conditioning as follows: 10 min of as many rounds as possible (AMRAP) of 30 double-unders and 15 power snatches (34kg). The same sequence as repeated on session 2 with the following metabolic conditioning: 12 min AMRAP of: row 250m and 25 target burpees. Serum interleukin-6 (IL-6), IL-10 and osteoprotegerin were measured before, immediately post and 24 h after workout of the day (WOD) 1, immediately post, 24 h and 48 h after WOD 2. Peak and mean power were obtained for each repetition (back squat with 50% of 1 repetition maximum) using a linear position transducer measured before, immediately post and 24 h after WOD 1, immediately post and 24 h after WOD 2. Blood lactate and glucose were measured pre and immediately post WOD 1 and 2. Although both sessions of exercise elicited an significant increase in blood lactate (1.20 ± 0.41 to 11.84 ± 1.34 vs 0.94 ± 0.34 to 9.05 ± 2.56 mmol/l) and glucose concentration (81.59 ± 10.27 to 114.99 ± 12.52 vs 69.47 ± 6.97 to 89.95 ± 19.26 mg/dL), WOD 1 induced a significantly greater increase than WOD 2 (p ≤ 0.05). The training sessions elicited significant changes (p ≤ 0.05) in IL-6, IL-10 and osteoprotegerin concentration over time. IL-6 displayed an increase immediately after training WOD 1 [197 ± 109%] (p = 0.009) and 2 [99 ± 58%] (p = 0.045). IL-10 displayed an increase immediately after only WOD 1 [44 ± 52%] (p = 0.046), and decreased 24 and 48 h following WOD 2 (~40%; p = 0.018) as compared to pre-exercise values. Osteoprotegerin displayed a decrease 48 h following WOD 2 (~25%; p = 0.018) as compared with pre intervention. In conclusion, two consecutive Crossfit® training sessions increase pro/anti-inflammatory cytokines with no interference on muscle performance in the recovery period.
It is the position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine that the performance of, and recovery from, sporting activities are enhanced by well-chosen nutrition strategies. These organizations provide guidelines for the appropriate type, amount, and timing of intake of food, fluids, and supplements to promote optimal health and performance across different scenarios of training and competitive sport. This position paper was prepared for members of the Academy of Nutrition and Dietetics, Dietitians of Canada (DC), and American College of Sports Medicine (ACSM), other professional associations, government agencies, industry, and the public. It outlines the Academy’s, DC’s and ACSM’s stance on nutrition factors that have been determined to influence athletic performance and emerging trends in the field of sports nutrition. Athletes should be referred to a registered dietitian/nutritionist for a personalized nutrition plan. In the United States and in Canada, the Certified Specialist in Sports Dietetics (CSSD) is a registered dietitian/nutritionist and a credentialed sports nutrition expert.
Caffeine ingestion has been shown to be an effective ergogenic aid in several sports. Caffeine administration may increase exercise capacity, which could lead to a greater degree of muscle damage after exercise. This was a randomized, double-blind, placebo-controlled crossover study. Six male handball athletes ingested placebo (PLA) or caffeine (CAF; 6 mg.kg body mass) capsules on two different occasions. 60 min after the ingestion the capsules, was to evaluate serum caffeine levels. Thereafter, all participants performed a protocol of vertical jumps. The protocol consisted of four sets of 30 sec of continuous vertical jumps with 60 sec of recovery between sets. Blood lactate (LAC) and creatine kinase (CK) were determined before and after the protocol. We found significant differences in serum caffeine levels between PLA 0.09±0.18 µg/mL vs. CAF 6.59±4.44 µg/ mL (p<0.001). CAF elicited a 5.23% (p<0.05) improvement in the leg power compared to PLA. The CAF trial displayed higher (LAC) (p<0.05) compared to PLA (6.26±2.01 vs. 4.39±2.42 mmol.L, respectively) after protocol of vertical jumps', while no difference in CK was observed between trials (p>0.05). These results indicate that acute ingestion of caffeine (6 mg.kg body weight) can reduce the level of muscle fatigue and preserved leg power during the test, possibly resulting in increase in blood lactate levels. There was no increase in muscle damage, leading to believe that acute administration of (6 mg.kg body weight) caffeine is safe. Thus, nutritional interventions with caffeine could help athletes in supporting a greater physiological overload during high intensity training sessions. Sports and activities that require repetitive leg power would be applicable to the results of the study.
Caffeine and coffee are widely used among active individuals to enhance performance. The purpose of the current study was to compare the effects of acute coffee (COF) and caffeine anhydrous (CAF) intake on strength and sprint performance. Fifty-four resistance-trained males completed strength testing, consisting of one-rep max (1RM) and repetitions to fatigue (RTF) at 80% of 1RM for leg press (LP) and bench press (BP). Participants then completed five, 10-second cycle ergometer sprints separated by one minute of rest. Peak power (PP) and total work (TW) were recorded for each sprint. At least 48 hours later, participants returned and ingested a beverage containing CAF (300 mg flat dose; yielding 3-5 mg/kg bodyweight), COF (8.9 g; 303 mg caffeine), or placebo (PLA; 3.8 g non-caloric flavouring) 30 minutes before testing. LP 1RM was improved more by COF than CAF (p = .04), but not PLA (p = .99). Significant interactions were not observed for BP 1RM, BP RTF, or LP RTF (p > .05). There were no sprint × treatment interactions for PP or TW (p > .05). 95% confidence intervals revealed a significant improvement in sprint 1 TW for CAF, but not COF or PLA. For PLA, significant reductions were observed in sprint 4 PP, sprint 2 TW, sprint 4 TW, and average TW; significant reductions were not observed with CAF or COF. Neither COF nor CAF improved strength outcomes more than PLA, while both groups attenuated sprint power reductions to a similar degree. Coffee and caffeine anhydrous may be considered suitable pre-exercise caffeine sources for high-intensity exercise.
CrossFit(®) is a new but extremely popular method of exercise training and competition that involves constantly varied functional movements performed at high intensity. Despite the popularity of this training method, the physiological determinants of CrossFit performance have not yet been reported. The purpose of this study was to determine whether physiological and/or muscle strength measures could predict performance on three common CrossFit "Workouts of the Day" (WODs).
Fourteen CrossFit Open or Regional athletes completed, on separate days, the WODs "Grace" (30 clean and jerks for time), "Fran" (three rounds of thrusters and pull-ups for 21, 15, and nine repetitions), and "Cindy" (20 minutes of rounds of five pull-ups, ten push-ups, and 15 bodyweight squats), as well as the "CrossFit Total" (1 repetition max [1RM] back squat, overhead press, and deadlift), maximal oxygen consumption (VO2max), and Wingate anaerobic power/capacity testing.
Performance of Grace and Fran was related to whole-body strength (CrossFit Total) (r=-0.88 and -0.65, respectively) and anaerobic threshold (r=-0.61 and -0.53, respectively); however, whole-body strength was the only variable to survive the prediction regression for both of these WODs (R (2)=0.77 and 0.42, respectively). There were no significant associations or predictors for Cindy.
CrossFit benchmark WOD performance cannot be predicted by VO2max, Wingate power/capacity, or either respiratory compensation or anaerobic thresholds. Of the data measured, only whole-body strength can partially explain performance on Grace and Fran, although anaerobic threshold also exhibited association with performance. Along with their typical training, CrossFit athletes should likely ensure an adequate level of strength and aerobic endurance to optimize performance on at least some benchmark WODs.
Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also ben shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.
Purpose
The purpose was to assess effects of a pre- and a post-workout protein-carbohydrate supplement on CrossFit-specific performance and body composition.
Methods
In an open label randomized study, 13 male and 16 female trained Crossfit participants (mean ± SD; age: 31.87 ± 7.61 yrs, weight: 78.68 ± 16.45 kg, percent body fat: 21.97 ± 9.02) were assessed at 0 and 6 weeks for body composition, VO2max, Wingate peak (WPP) and mean power (WMP), in addition to sport-specific workouts (WOD1: 500 m row, 40 wall balls, 30 push-ups, 20 box jumps, 10 thrusters for time; WOD2: 15 minutes to complete an 800 m run "buy in", followed by as many rounds as possible (AMRAP) of 5 burpees, 10 Kettlebell swings, 15 air squats). The supplement (SUP) group consisted of 19 g of a pre-workout drink (extracts of pomegranate, tart cherry, green and black tea) taken 30 minutes before and a post-workout protein (females: 20 g; males: 40 g) and carbohydrate (females: 40 g; males: 80 g) supplement consumed immediately after each workout. The control (CTL) group consumed only water one hour before or after workouts. Participants completed three (minimum) varied workouts per week at a CrossFit gym as typical to habitual training throughout the six week study. Data were analyzed by repeated measures ANOVA (p <0 .05), 95% Confidence Intervals, and Magnitude Inferences.
Results
There were no time × group interactions for body composition, WMP, or WOD1 based on ANOVA statistics. VO2MAX, WPP, and WOD2 results revealed that the pre/post supplements were likely beneficial after 95% Confidence Intervals and Magnitude Inferences analysis.
Conclusion
The combination of proprietary supplements taken for 6 weeks may provide benefits during certain sport-specific performance in trained CrossFit athletes but not others.
To determine whether the ergogenic effects of caffeine ingestion on neuromuscular performance are similar when ingestion takes place in the morning and in the afternoon.
Double blind, cross-over, randomized, placebo controlled design.
Thirteen resistance-trained males carried out bench press and full squat exercises against four incremental loads (25%, 50%, 75% and 90% 1RM), at maximal velocity. Trials took place 60min after ingesting either 6mgkg(-1) of caffeine or placebo. Two trials took place in the morning (AMPLAC and AMCAFF) and two in the afternoon (PMPLAC and PMCAFF), all separated by 36-48h. Tympanic temperature, plasma caffeine concentration and side-effects were measured.
Plasma caffeine increased similarly during AMCAFF and PMCAFF. Tympanic temperature was lower in the mornings without caffeine effects (36.7±0.4 vs. 37.0±0.5°C for AM vs. PM; p<0.05). AMCAFF increased propulsive velocity above AMPLAC to levels similar to those found in the PM trials for the 25%, 50%, 75% 1RM loads in the SQ exercise (5.4-8.1%; p<0.05). However, in the PM trials, caffeine ingestion did not improve propulsive velocity at any load during BP or SQ. The negative side effects of caffeine were more prevalent in the afternoon trials (13 vs. 26%).
The ingestion of a moderate dose of caffeine counteracts the muscle contraction velocity declines observed in the morning against a wide range of loads. Caffeine effects are more evident in the lower body musculature. Evening caffeine ingestion not only has little effect on neuromuscular performance, but increases the rate of negative side-effects reported.
Abstract The efficacy of caffeine ingestion in enhancing aerobic performance is well established. However, despite suggestions that caffeine may enhance resistance exercise performance, research is equivocal on the effect of acute caffeine ingestion on resistance exercise performance. It has also been suggested that dampened perception of perceived exertion and pain perception might be an explanation for any possible enhancement of resistance exercise performance due to caffeine ingestion. Therefore, the aim of this study was to examine the acute effect of caffeine ingestion on repetitions to failure, rating of perceived exertion (RPE) and muscle pain perception during resistance exercise to failure. Eleven resistance trained individuals (9 males, 2 females, mean age±SD=26.4±6.4 years), took part in this double-blind, randomised cross-over experimental study whereby they ingested a caffeinated (5 mg kg(-1)) or placebo solution 60 minutes before completing a bout of resistance exercise. Experimental conditions were separated by at least 48 hours. Resistance exercise sessions consisted of bench press, deadlift, prone row and back squat exercise to failure at an intensity of 60% 1 repetition maximum. Results indicated that participants completed significantly greater repetitions to failure, irrespective of exercise, in the presence of caffeine (p=0.0001). Mean±S.D of repetitions to failure was 19.6±3.7 and 18.5±4.1 in caffeine and placebo conditions, respectively. There were no differences in peak heart rate or peak blood lactate values across conditions (both p >0.05). RPE was significantly lower in the caffeine compared to the placebo condition (p=0.03) and was significantly higher during lower body exercises compared to upper body exercises irrespective of substance ingested (p=0.0001). For muscle pain perception, a significant condition by exercise interaction (p=0.027) revealed that muscle pain perception was lower in the caffeine condition, irrespective of exercise. With caffeine, pain perception was significantly higher in the deadlift and back squat compared to the bench press. However, with placebo, pain perception was significantly higher for the deadlift and back squat compared to the prone row only. Therefore, acute caffeine ingestion not only enhances resistance exercise performance to failure but also reduces perception of exertion and muscle pain.
Purpose:
The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements.
Methods:
Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mg · kg(-1) body weight (CAFF 3mg), (c) 6 mg · kg(-1) (CAFF 6mg), and (d) 9 mg · kg(-1) (CAFF 9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free-weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maximum [1RM]). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later.
Results:
Mean propulsive velocity at light loads (25%-50% 1RM) increased significantly above PLAC for all caffeine doses (5.4%-8.5%, P = 0.039-0.003). At the medium load (75% 1RM), CAFF 3mg did not improve SQ or BP muscle power or BP velocity. CAFF 9mg was needed to enhance BP velocity and SQ power at the heaviest load (90% 1RM) and cycling peak power output (6.8%-11.7%, P = 0.03-0.05). The CAFF 9mg trial drastically increased the frequency of the adverse side effects (15%-62%).
Conclusions:
The ergogenic dose of caffeine required to enhance neuromuscular performance during a single all-out contraction depends on the magnitude of load used. A dose of 3 mg · kg(-1) is enough to improve high-velocity muscle actions against low loads, whereas a higher caffeine dose (9 mg · kg(-1)) is necessary against high loads, despite the appearance of adverse side effects.
There is consistent evidence supporting the ergogenic effects of caffeine for endurance based exercise. However, whether caffeine ingested through coffee has the same effects is still subject to debate. The primary aim of the study was to investigate the performance enhancing effects of caffeine and coffee using a time trial performance test, while also investigating the metabolic effects of caffeine and coffee. In a single-blind, crossover, randomised counter-balanced study design, eight trained male cyclists/triathletes (Mean±SD: Age 41±7y, Height 1.80±0.04 m, Weight 78.9±4.1 kg, VO2 max 58±3 ml•kg(-1)•min(-1)) completed 30 min of steady-state (SS) cycling at approximately 55% VO2max followed by a 45 min energy based target time trial (TT). One hour prior to exercise each athlete consumed drinks consisting of caffeine (5 mg CAF/kg BW), instant coffee (5 mg CAF/kg BW), instant decaffeinated coffee or placebo. The set workloads produced similar relative exercise intensities during the SS for all drinks, with no observed difference in carbohydrate or fat oxidation. Performance times during the TT were significantly faster (∼5.0%) for both caffeine and coffee when compared to placebo and decaf (38.35±1.53, 38.27±1.80, 40.23±1.98, 40.31±1.22 min respectively, p<0.05). The significantly faster performance times were similar for both caffeine and coffee. Average power for caffeine and coffee during the TT was significantly greater when compared to placebo and decaf (294±21 W, 291±22 W, 277±14 W, 276±23 W respectively, p<0.05). No significant differences were observed between placebo and decaf during the TT. The present study illustrates that both caffeine (5 mg/kg/BW) and coffee (5 mg/kg/BW) consumed 1 h prior to exercise can improve endurance exercise performance.
The purpose of the present study was to investigate the effects of different methods to calculate vertical jump height in men and women. Fifty men and 50 women performed three countermovement vertical jumps for maximal height on a force platform, the highest of which was used in the statistical analyses. The peak displacement attained by the center of mass (COM) during flight was obtained from three different calculations: (1) using the time in the air (TIA), (2) using the vertical velocity of the COM at take-off (TOV), and (3) adding the positive vertical displacement of the COM prior to take-off to the height calculated using TOV (TOV+s). With all calculations, men produced significantly greater jump heights than women (p < 0.05). TIA produced significantly greater jump heights than TOV in men and women, while TOV+s produced significantly greater jump heights than both TIA and TOV in men and women (p < 0.05). Despite these differences, the methods produced consistent results for both men and women. All calculation methods have logical validity, depending upon the definition of jump height used. Therefore, the method used to calculate jump height should be determined by the equipment available to the practitioner while giving consideration to the sources of error inherent in each method. Based upon the present findings, when using a force platform to calculate vertical jump height, practitioners are encouraged to use the TOV method.
Rationale
Despite 100 years of psychopharmacological research, the extent to which caffeine consumption benefits human functioning remains unclear.
Objectives
To measure the effects of overnight caffeine abstinence and caffeine administration as a function of level of habitual caffeine consumption.
Methods
Medium-high (n = 212) and non-low (n = 157) caffeine consumers completed self-report measures and computer-based tasks before (starting at 10:30 AM) and after double-blind treatment with either caffeine (100 mg, then 150 mg) or placebo. The first treatment was given at 11:15 AM and the second at 12:45 PM, with post-treatment measures repeated twice between 1:45 PM and 3:30 PM.
Results
Caffeine withdrawal was associated with some detrimental effects at 10:30 AM, and more severe effects, including greater sleepiness, lower mental alertness, and poorer performance on simple reaction time, choice reaction time and recognition memory tasks, later in the afternoon. Caffeine improved these measures in medium-high consumers but, apart from decreasing sleepiness, had little effect on them in non-low consumers. The failure of caffeine to increase mental alertness and improve mental performance in non-low consumers was related to a substantial caffeine-induced increase in anxiety/jitteriness that offset the benefit of decreased sleepiness. Caffeine enhanced physical performance (faster tapping speed and faster simple and choice reaction times) in both medium-high and non-low consumers.
Conclusions
While caffeine benefits motor performance and tolerance develops to its tendency to increase anxiety/jitteriness, tolerance to its effects on sleepiness means that frequent consumption fails to enhance mental alertness and mental performance.
The aim of this work was to evaluate the effect of caffeine supplementation and intermittent exercise on the muscle injury markers in soccer players. 15 male professional soccer players completed a placebo controlled double blind test protocol. 45 minutes before exercise, participants ingested 5.5 mg.kg-1 body mass of caffeine (EXP, n=8) or placebo (CONT, n=7). The exercise was 12 sets of 10 sprints (20 m each) with 10 sec recovery time between sprints and 2 min between sets. Blood samples were collected before (PRE) and 48h after exercise (POST). Serum activity of CK, LDH, AST, and ALT were quantified. Serum enzyme activity was enhanced by exercise in both groups, without a synergistic effect of caffeine. The findings suggest muscle injury markers concentration increases after physical activities, but caffeine supplementation (as used in this study) has no influence upon muscle cellular integrity.
Exercise-induced muscle damage (EIMD) occurs primarily from the performance of unaccustomed exercise, and its severity is modulated by the type, intensity, and duration of training. Although concentric and isometric actions contribute to EIMD, the greatest damage to muscle tissue is seen with eccentric exercise, where muscles are forcibly lengthened. Damage can be specific to just a few macromolecules of tissue or result in large tears in the sarcolemma, basal lamina, and supportive connective tissue, and inducing injury to contractile elements and the cytoskeleton. Although EIMD can have detrimental short-term effects on markers of performance and pain, it has been hypothesized that the associated skeletal muscle inflammation and increased protein turnover are necessary for long-term hypertrophic adaptations. A theoretical basis for this belief has been proposed, whereby the structural changes associated with EIMD influence gene expression, resulting in a strengthening of the tissue and thus protection of the muscle against further injury. Other researchers, however, have questioned this hypothesis, noting that hypertrophy can occur in the relative absence of muscle damage. Therefore, the purpose of this article will be twofold: (a) to extensively review the literature and attempt to determine what, if any, role EIMD plays in promoting skeletal muscle hypertrophy and (b) to make applicable recommendations for resistance training program design.
This study investigated the influence of age, body composition, physical fitness, training volume and intensity, and underlying systemic inflammation on exercise-induced inflammation and innate immune function in a heterogeneous group of cyclists. Subjects included 31 male cyclists (mean ± standard deviation, age 38.8 ± 10.6 years, body fat 17.8%± 5.6%, VO(2max) 55.8 ± 8.4 mL kg(-1) min(-1)) who cycled for 1.75 h at 60% watts(max) followed by a 10-km time trial (18.3 ± 0.3 min). Blood samples were collected pre-, post-, and 1-h-postexercise, and analyzed for WBCs, 9 cytokines [interleukin (IL)-6, tumor necrosis factor-alpha, granulocyte-macrophage colony-stimulating factor, interferon-γ, IL-1β, IL-2, IL-8, IL-10, and IL-12p70], and granulocyte and monocyte phagocytosis (GR-PHAG and MO-PHAG) and oxidative burst activity (GR-OBA and MO-OBA). Exercise-induced changes varied widely, with significant increases measured for 8 of 9 cytokines, GR-PHAG (mean change 99%) (95% confidence limits, 69%, 128%) and MO-PHAG (43%) (28%, 58%), and WBC (160%) (133%, 187%), and decreases for GR-OBA (-30%) (-43%,-16%) and MO-OBA (-23%) (-36%,-10%). Correlation and stepwise regression analysis revealed that changes in these variables were not related to age, body fat percentage, VO(2max), training volume, or pre-exercise C-reactive protein. Performance measures, specifically the average heart rate and rating of perceived exertion, were correlated with changes in several variables, including IL-8 (r=0.68 and 0.67, respectively, P<0.001) and IL-6 (r=0.51, P=0.004, and r=0.46, P=0.011, respectively). In summary, variance in exercise-induced inflammation and innate immunity in male cyclists in response to 2 h of endurance exercise is best explained by exercise intensity.
Caffeine has been shown to reduce leg-muscle pain during submaximal cycle ergometry, as well as in response to eccentric exercise. However, less is known about its analgesic properties during non-steady-state, high-intensity exercise. The primary aim of this study was to examine the effect of 2 doses of caffeine on leg pain and rating of perceived exertion (RPE) during repeated bouts of high-intensity exercise. Fifteen active men (age 26.4 ± 3.9 yr) completed 2 bouts of 40 repetitions of "all-out" knee extension and flexion of the dominant leg at a contraction velocity equal to 180°/s. Before each trial, subjects abstained from caffeine intake and intense exercise for 48 hr. Over 3 days separated by 48 hr, subjects ingested 1 of 3 treatments (5 mg/kg or 2 mg/kg of anhydrous caffeine or placebo) in a randomized, single-blind, counterbalanced, crossover design. Leg-muscle pain and RPE were assessed during and after exercise using established categorical scales. Across all treatments, pain perception was significantly increased (p < .05) during exercise, as well as from Bout 1 to 2, yet there was no effect (p > .05) of caffeine on pain perception or RPE. Various measures of muscle function were improved (p < .05) with a 5-mg/kg caffeine dose vs. the other treatments. In the 5-mg/kg trial, it is plausible that subjects were able to perform better with similar levels of pain perception and exertion.
Caffeine and creatine are 2 of the most widely available and used compounds in sport. Although the use of either is not considered a doping infraction, the evidence does suggest ergogenic potential in certain sports. The purpose of this paper is to review the pharmacology and potential mechanism(s) of action of caffeine and creatine as they pertain to possible use as an ergogenic aid in sport.
Previous review articles on caffeine and creatine use in sport were screened for relevant information and references, and studies for review and recent articles (2007 onwards) were obtained and reviewed using a PUBMED search with the terms 'caffeine AND exercise', 'creatine and creatine monohydrate AND exercise', and appropriate linked articles were evaluated.
Caffeine taken before (3-6 mg/kg) or during (1-2 mg/kg) endurance exercise enhances performance, through central nervous system and direct muscle effects. Creatine monohydrate supplementation at higher (approx. 20 g/day × 3-5 days) or lower (approx. 5 g/day × 30 days) doses increases skeletal muscle total and phosphocreatine by 10-20%. Creatine supplementation appears to minimally but significantly enhance high-intensity sport performance and the mass and possibly strength gains made during resistance exercise training over the first few months.
Although caffeine and creatine appear to be ergogenic aids, they do so in a sport-specific context and there is no rationale for their simultaneous use in sport. Higher doses of caffeine can be toxic and appear to be ergolytic. There is no rationale for creatine doses in excess of the recommendations, and some athletes can get stomach upset, especially at higher creatine doses.
The purpose of this study was to evaluate the effects of caffeine ingestion before a resistance exercise session on markers of muscle damage (CK, LDH, ALT, AST) and leukocyte levels.
Fifteen soccer athletes completed two resistance exercise sessions that differed only in the ingestion of caffeine or a placebo preworkout.
CK concentration increased significantly following the caffeine session (415.8+/-62.8 to 542.0+/-73.5) and the placebo session (411.5+/-43.3 to 545.8+/-59.9), with no significant differences between sessions. Similarly, LDH concentration increased significantly following the caffeine session (377.5+/-18.0 to 580.5+/-36.1) and the placebo session (384.8+/-13.9 to 570.4+/-36.1), with no significant differences between sessions. Both sessions resulted in significant increases in the total leukocyte count (caffeine=6.24+/-2.08 to 8.84+/-3.41; placebo=6.36+/-2.34 to 8.77+/-3.20), neutrophils (caffeine=3.37+/-0.13 to 5.15+/-0.28; placebo=3.46+/-0.17 to 5.12+/-0.24), lymphocytes (caffeine=2.19+/-0.091 to 2.78+/-0.10; placebo=2.17+/-0.100 to 2.75+/-0.11), and monocytes (caffeine=0.53+/-0.02 to 0.72+/-0.06; placebo=0.56+/-0.03 to 0.69+/-0.04), with no significant differences between sessions.
Ingestion of caffeine at 4.5 mg/kg(-1) did not augment markers of muscle damage or leukocyte levels above that which occurs through resistance exercise alone.
The prevalence of diabetes is growing globally, and with no current cure for the disease, management is focused on optimizing blood glucose control to limit complications. The purpose of this review was to examine the effect of caffeine intake on blood glucose levels in people with diabetes. Electronic searches were completed using Pub Med, CINAHL, and Web of Science using the search terms “coffee and insulin,” “caffeine and insulin,” “caffeine and diabetes,” “caffeine and type 1 diabetes,” “caffeine and type 2 diabetes,” and “caffeine and glycemia.” Seven trials were found to meet the search criteria. Five of the 7 studies suggest caffeine intake increases blood glucose levels, and prolongs the period of high blood glucose levels. Future research should focus on larger clinical trials to confirm the relationship and mechanism of action related to caffeine intake and glycemic control in individuals with diabetes.
With the increase in popularity of the CrossFit exercise program, occupational health nurses may be asked questions about the appropriateness of CrossFit training for workers. This systematic literature review was conducted to analyze the current research on CrossFit, and assess the benefits and risks of this exercise strategy. Thirteen studies ( N = 2,326 participants) examined the use of CrossFit training among adults; CrossFit is comparable to other exercise programs with similar injury rates and health outcomes. Occupational health nurses should assess previous injuries prior to recommending this form of exercise. Ideal candidates for CrossFit are adults who seek high-intensity exercise with a wide variety of exercise components.
Background
Extreme conditioning programs (ECPs) are fitness training regimens relying on aerobic, plyometric, and resistance training exercises, often with high levels of intensity for a short duration of time. These programs have grown rapidly in popularity in recent years, but science describing the safety profile of these programs is lacking.
Hypothesis
The rate of injury in the extreme conditioning program is greater than the injury rate of weightlifting and the majority of injuries occur to the shoulder and back.
Study Design
Cross-sectional study.
Level of Evidence
Level 4.
Methods
This is a retrospective survey of injuries reported by athletes participating in an ECP. An injury survey was sent to 1100 members of Iron Tribe Fitness, a gym franchise with 5 locations across Birmingham, Alabama, that employs exercises consistent with an ECP in this study. An injury was defined as a physical condition resulting from ECP participation that caused the athlete to either seek medical treatment, take time off from exercising, or make modifications to his or her technique to continue.
Results
A total of 247 athletes (22%) completed the survey. The majority (57%) of athletes were male (n = 139), and 94% of athletes were white (n = 227). The mean age of athletes was 38.9 years (±8.9 years). Athletes reported participation in the ECP for, on average, 3.6 hours per week (± 1.2 hours). Eighty-five athletes (34%) reported that they had sustained an injury while participating in the ECP. A total of 132 injuries were recorded, yielding an estimated incidence of 2.71 per 1000 hours. The shoulder or upper arm was the most commonly injured body site, accounting for 38 injuries (15% of athletes). Athletes with a previous shoulder injury were 8.1 times as likely to injure their shoulder in the ECP compared with athletes with healthy shoulders. The trunk, back, head, or neck (n = 29, 12%) and the leg or knee (n = 29, 12%) were the second most commonly injured sites. The injury incidence rate among athletes with <6 months of experience in the ECP was 2.5 times greater than that of more experienced athletes (≥6 months of experience). Of the 132 injuries, 23 (17%) required surgical intervention. Squat cleans, ring dips, overhead squats, and push presses were more likely to cause injury. Athletes reported that 35% of injuries were due to overexertion and 20% were due to improper technique.
Conclusion
The estimated injury rate among athletes participating in this ECP was similar to the rate of injury in weightlifting and most other recreational activities. The shoulder or upper arm was the most commonly injured area, and previous shoulder injury predisposed to new shoulder injury. New athletes are at considerable risk of injury compared with more experienced athletes.
Clinical Relevance
Extreme conditioning programs are growing in popularity, and there is disagreement between science and anecdotal reports from athletes, coaches, and physicians about their relative safety. This study estimates the incidence of injury in extreme conditioning programs, which appears to be similar to other weight-training programs.
Background:
CrossFit® is considered an intense and extreme conditioning program (ECP) that can cause overtraining and injury. Exertional Rhabdomyolysis (ER) - breakdown of muscle tissue - after ECP has been reported in CrossFit® and might be linked to comparatively high rates of subjectively perceived exertion levels. Therefore, the present study aimed at (a) recording symptoms of post-exercise physical dysfunction (e.g., excessive muscle soreness, shortness of breath) following CrossFit® and (b) ratings of perceived exertion (RPE) during CrossFit® compared with training according to the American College of Sports Medicine (ACSM) guidelines.
Methods:
A validated questionnaire was completed by 101 CrossFit® (age: 35±8 years; weight: 79±16 kg) and 56 ACSM (age: 35±10 years; weight: 75±27 kg) participants.
Results:
CrossFit® and ACSM groups, respectively, reported significantly different RPE levels of 7.3±1.7 and 5.5±1.4 (p ≤ 0.001) and amounts of hard days per week of 4.0 ± 1.1 and 3.5 ± 1.4 (p = 0.04). The five most frequent and hardest ECP workouts of the day (WODs) were Fran (47), Murph (27), Fight Gone Bad (10), Helen (9) and Filthy 50 (9). Presence of severe post-exercise symptoms was notably higher in CrossFit® for excessive fatigue (42 vs. 8; p<0.001), muscle soreness (96 vs. 48; p=0.04), muscle swelling (19 vs. 4; p=0.048), shortness of breath (13 vs. 1; p=0.02), muscle pain to touch (31 vs. 4; p=0.001), and limited muscle movement during workout (37 vs. 9; p=0.007).
Conclusion:
CrossFit® leads to "very hard" perceived exertion causing detrimental post-exercise effects on muscle and ventilatory function in experienced athletes. Improved training progression with adequate recovery schedules are needed to prevent severe muscle injury, such as ER.
The aim of the present study was to determine the effect on performance of ingesting caffeine-dose matched anhydrous caffeine, coffee or decaffeinated coffee plus anhydrous caffeine during resistance exercise. Nine resistance trained males (Mean±SD age: 24±2 years, weight: 84±8kg, height: 180±8cm) completed a squat and bench press exercise protocol at 60% 1-RM until failure on five occasions consuming either, 0.15 g·kg caffeinated coffee (COF), 0.15 g·kg decaffeinated coffee (DEC), 0.15 g·kg decaffeinated coffee plus 5 mg·kg anhydrous caffeine (D+C), 5 mg·kg anhydrous caffeine (CAF) or a placebo (PLA). Felt arousal and rating of perceived exertion (RPE) were used to assess perceptual variables and heart rate (HR) to assess physiological responses between trials. There were significant differences in total weight lifted for the squat between conditions (P<0.01; ηP =0.54) with a greater amount lifted during D+C compared with DEC (P<0.01), CAF (P<0.05) and PLA (P<0.05) conditions. Total weight lifted during the COF condition was significantly greater than PLA (P<0.01), although not significantly greater than the amount of weight lifted during the DEC condition (P=0.082). No significant differences were observed in total weight lifted in the bench press protocol between conditions (P=0.186; ηP =0.17). Significant differences in HR (P<0.01; ηP =0.39), but not RPE (squat: P=0.690; ηP =0.07; bench press: P=0.165; ηP =0.18) and felt arousal (P=0.056; ηP =0.24) were observed between conditions. Coffee and decaffeinated coffee plus caffeine have the ability to improve performance during a resistance exercise protocol, although possibly not over multiple bouts.
Endurance athletes commonly ingest caffeine as a means to enhance training intensity and competitive performance. A widely-used source of caffeine is coffee, however conflicting evidence exists regarding the efficacy of coffee in improving endurance performance. In this context, the aims of this evidence-based review were three-fold: 1) to evaluate the effects of pre-exercise coffee on endurance performance, 2) to evaluate the effects of coffee on perceived exertion during endurance performance, and 3) to translate the research into usable information for athletes to make an informed decision regarding the intake of caffeine via coffee as a potential ergogenic aid. Searches of three major databases were performed using terms caffeine, and coffee, or coffee-caffeine, and endurance, or aerobic. Included studies (n=9) evaluated the effects of caffeinated coffee on human subjects, provided the caffeine dose administered, administered caffeine ≥45 minutes before testing, and included a measure of endurance performance (e.g., time trial). Significant improvements in endurance performance were observed in five of nine studies, which were on average 24.2% over controls for time to exhaustion trials, and 3.1% for time to completion trials. Three of six studies found that coffee reduced perceived exertion during performance measures significantly more than control conditions (p<0.05). Based on the reviewed studies there is moderate evidence supporting the use of coffee as an ergogenic aid to improve performance in endurance cycling and running. Coffee providing 3-8.1mg/kg (1.36-3.68mg/lb) of caffeine may be used as a safe alternative to anhydrous caffeine to improve endurance performance.
The aim of this study was to compare the response of IL-10, and also of IL-6 and IL-12 p40, to exercise and caffeine supplementation between plasma and blood mononuclear cells (BMNCs). Participants in the study (n=28) were randomly allocated in a double-blind fashion to either caffeine (n=14) or placebo treatments (n=14). One hour prior to completing a 15-Km run competition, athletes took 6 mg/kg body mass of caffeine or a placebo. Plasma and BMNCs were purified from blood samples taken before and after competition. Concentrations of interleukins (IL-10, IL-6 and IL-12 p40), cyclic adenosine monophosphate (cAMP), caffeine, adrenaline and cortisol were measured in plasma. IL-10, IL-6 and IL-12 p40 and cAMP levels were also determined in BMNCs. Exercise induced significant increases in IL-6 and IL-10 plasma levels, with higher increases in the caffeine supplemented group. After 2-hour recovery these levels had been returned to almost pre-exercise values. However, no effect of caffeine on BMNC cytokines was observed. IL-10, IL-6 and IL-12 p40 levels in BMNCs increased mainly at 2-hours post-exercise. cAMP levels increased post-exercise in plasma and after recovery in BMNCs, but no effects of caffeine were observed. In conclusion, caffeine did not modify cytokine levels in BMNCs in response to exercise. However, higher increases of IL-10 were observed in plasma after exercise in the supplemented participants, which could suppose an enhancement of the anti-inflammatory properties of exercise.
Purpose:
Performance improvements after caffeine (CAF) ingestion are well documented when using a 1-d protocol. In numerous competitions such as the Tour de France, Tour de Ski, world championships, and National College Athletic Association championships, athletes compete for several days in a row. To date, no studies have investigated the effects of CAF when competing for consecutive days in a row. This study aimed to investigate the effects of placebo (PLA) and two different CAF doses (3 and 4.5 mg·kg body mass) on performance in a 10-min all-out, cross-country, double poling ergometer test (C-PT) 2 d in a row.
Method:
Eight highly trained male cross-country skiers (V˙O2max-run, 78.5 ± 1.6 mL·kg·min) participated in the study, which was a randomized, double-blind, PLA-controlled, crossover design. Performance was assessed as distance covered during a 10-min all-out C-PT. Oral ingestion of CAF or PLA was consumed 75 min before the all-out C-PT.
Results:
Poling distance was improved after CAF ingestions compared with that after PLA on both days. The improvements on day 1 were 4.0% (90% confidence limits, ±3.3) and 4.0% ± 2.9% for both CAF doses, respectively (P < 0.05), whereas improvements on day 2 were 5.0% ± 3.6% and 5.1% ± 2.8% for CAF3 and CAF4.5, respectively, compared with those for PLA. Improved performance was associated with increased HR, adrenaline concentration, blood lactate concentration, and V˙O2 consumption after CAF ingestion. Furthermore, performance was elevated despite higher creatine kinase concentration and muscular pain at arrival on day 2 for both CAF doses.
Conclusions:
Both CAF doses improved performance in the 10-min all-out C-PT compared with PLA over two consecutive days. Therefore, CAF seems useful for athletes competing over consecutive days despite higher muscle damage occurring after enhanced performance on the first day.
Hurley, CF, Hatfield, DL, and Riebe, DA. The effect of caffeine ingestion on delayed onset muscle soreness. J Strength Cond Res 27(11): 3101-3109, 2013-The beneficial effects of caffeine on aerobic activity and resistance training performance are well documented. However, less is known concerning caffeine's potential role in reducing perception of pain and soreness during exercise. In addition, there is no information regarding the effects of caffeine on delayed onset muscle soreness (DOMS). The primary purpose of this study was to examine the effect of caffeine ingestion on muscle soreness, blood enzyme activity, and performance after a bout of elbow flexion/extension exercise. Nine low-caffeine-consuming males (body mass: 76.68 ± 8.13 kg; height: 179.18 ± 9.35 cm; age: 20 ± 1 year) were randomly assigned to ingest either caffeine or placebo 1 hour before completing 4 sets of 10 bicep curls on a preacher bench, followed by a fifth set in which subjects completed as many repetitions as possible. Soreness and soreness on palpation intensity were measured using three 0-10 visual analog scales before exercise, and 24, 48, 72, 96, and 120 hours after exercise. After a washout period, subjects crossed over to the other treatment group. Caffeine ingestion resulted in significantly (p ≤ 0.05) lower levels of soreness on day 2 and day 3 compared with placebo. Total repetitions in the final set of exercise increased with caffeine ingestion compared with placebo. This study demonstrates that caffeine ingestion immediately before an upper-body resistance training out enhances performance. A further beneficial effect of sustained caffeine ingestion in the days after the exercise bout is an attenuation of DOMS. This decreased perception of soreness in the days after a strenuous resistance training workout may allow individuals to increase the number of training sessions in a given time period.
Purpose:
The objective of this study is as follows: 1) to determine the effects of caffeine supplementation on the inflammatory response (IL-6 and IL-10 levels and leukocyte numbers) induced by a 15-km run competition and 2) to examine the effect of caffeine supplementation on the energetic metabolites as well as on the exercise-induced oxidative stress.
Methods:
A double-blinded study of supplementation with caffeine was performed. Athletes participating in the study (n = 33) completed a 15-km run competition. Before competition, athletes took 6 mg · kg(-1) body weight of caffeine (caffeine group, n = 17) or a placebo (placebo group, n = 16). Blood samples were taken before and after competition (immediately and after 2-h recovery). Leukocyte numbers were determined in blood. Concentrations of oxidative stress markers, antioxidants, interleukins (IL-6 and IL-10), caffeine, adrenaline, and energetic metabolites were measured in plasma or serum.
Results:
Caffeine supplementation induced higher increases in circulating total leukocytes and neutrophils, with significant differences between groups after recovery. Adrenaline, glucose, and lactate levels increased after exercise, with higher increases in the caffeine group. Exercise induced significant increases in IL-6 and IL-10 plasma levels, with higher increases in the caffeine group. Caffeine supplementation induced higher increases in oxidative stress markers after the competition.
Conclusion:
Caffeine supplementation induced higher levels of IL-6 and IL-10 in response to exercise, enhancing the anti-inflammatory response. The caffeine-induced increase in adrenaline could be responsible for the higher increase in IL-6 levels, as well as for the increased lactate levels. Furthermore, caffeine seems to enhance oxidative stress induced by exercise.