Effects Of Caffeine Containing Sports Gel On Muscular Force Production During Isokinetic Exercise
Caffeine containing sports supplements are widely used ergogenic aids due to their perceived potential to enhance muscular work and improve performance. Although many studies have found significant improvements in muscular endurance with acute ingestion of caffeine, there is limited research comparing the effect of acute ingestion of sports gels containing caffeine on muscular strength performance.Therefore, the purpose of this study was to examine quadriceps and hamstring muscle strength including peak torque and hamstring to quadricep ratio (H:Q) during an isokinetic strength test. Knee flexion and extension will be measured with the use of an electromechanical device, the Cybex, after ingesting a High 5 Energy Gel Plus supplement containing 23g of CHO and 30mg of caffeine. We hypothesise an increase in peak torque of both knee flexion and extension and an increase in the H:Q ratio. Explain why you expect to see this outcome (you must incorporate the underlying physiological mechanisms in your answer).(15 marks)
Caffeine is a popular ergogenic aid and has become increasingly available in many forms of supplementation, such as sports drinks and gels since being validated as a Group A by the Australian Institute of Sport (AIS, 2018). It is a 1, 3, 7 trimethylxanthine and can be found in non prescription medications, coffee, tea, soft drink, chocolate and many other consumables.It is metabolized in the liver to dimethyxanthines (paraxanthine, theobromine, theophylline) and is suggested to have an affect on numerous central and peripheral tissues throughout the body (Davis & Green, 2009). The exact mechanisms by which caffeine exerts its ergogenic effects are still undetermined, however caffeine ingestion has been shown to reduce the sensation of pain induced by exercise, enhance excitation contraction coupling, and stimulate the central nervous system via antagonism of the adenosine receptor (Astorino, Rohmann & Firth, 2008). Caffeine stimulates the central nervous system acting as a competitive antagonist to the inhibitory effects of adenosine. It has shown to counteract the inhibitory effects of adenosine such as the enhanced perception of pain, induced sleep, reduced arousal, and depression of spontaneous locomotor activity. Therefore, it is proposed that caffeine ingestion will lead to modified pain perception whilst sustaining motor unit firing rates and neuro-excitability (Davis & Green, 2009) all of which will increase muscle force production. Studies examining the response of catecholamines to high intensity exercise have shown an increased secretion of adrenaline with caffeine ingestion when compared to placebo. Furthermore, the increased level of adrenaline is proposed to enhance performance due to an increased heart rate and increased glycolytic flux. An increase in heart rate will result in a higher blood flow to working muscles and glycolytic flux will provide energy to the working muscle (Davis & Green, 2009), both factors will contribute to an increase in muscle force production. Caffeine is suggested to enhance excitation – contraction coupling via caffeine facilitating Na+/K+ ATPhase activity. Maintaining an electrochemical gradient of Na+ and K+ is critical for a forceful muscle contraction to occur. Strenuous muscle activity requires high frequencies of action potentials, which leads to extracellular accumulation of K+, the prevention of a rise in K+ by enhancing Na+/K+ ATPhase activity could promote an optimal environment for excitation – contraction as it will potentially delay fatigue and avoid the reduction in muscle force caused by high concentrations of extracellular K+ (Davis & Green, 2009). Additionally caffeine has shown to increase Ca2+ release from the sarcoplasmic retinaculum, further increasing excitation – contraction coupling and increasing muscle force (Davis & Green, 2009). It is expected that the experimental condition with caffeine ingestion prior to the isokinetic strength test will result in an increase in muscle force production. This may be due to the direct effect on muscle via enhancements of the Na+/K+ pump and increased calcium release from the sarcoplasmic retinaculum and/ or by an effect on the central nervous system with the increase in motor unit recruitment. Describe two studies that have investigated this area and help you explain your hypothesis and explain how they relate to your study (10 marks).
Research by Astorino, Terzi, Roberson, & Burnett (2010) invested the effects of muscular function during isokinetic exercise in response to caffeine intake. The participants included 15 physically active men who were familiarised with the isokinetic dynamometer, followed by three trials with at least 48 hours between trials. The isokinetic test consisted of two bouts of 40 repetitions of maximal knee extension and flexion of the dominant leg at a contraction velocity equal to 180-Isj1. Before testing the all groups refrained from caffeine intake for 48 hours prior to exercise testing. Before testing 3 groups were randomly allocated using a single-blind, randomized, counterbalanced, crossover design. The groups included two caffeine groups 5 and 2 mg/kg respectfully and a placebo group. A 3 (treatment) 2 (sets) ANOVA with repeated measures was used to analyse performance differences regarding peak torque, average torque, total work, work fatigue, power output, and RPE. The results indicated placebo, and caffeine significantly (P G 0. 05) enhanced peak knee flexion torque, knee extension/flexion total work, and knee extension/flexion power in bout 1 with no effect in bout 2. Only the 5-mg/kg dose of caffeine improved performance, with the magnitude of performance improvement ranging from 5% to 8%. Therefore, Astorino et al. (2010) conclude suggesting relatively high (5-mg/kg per body weight) but not low (2-mg/kg per body weight) doses of caffeine can be considered ergogenic for maximal knee extension/ flexion exercise. During our research we also investigated the effects of muscular function during isokinetic exercise in response to caffeine intake. The participants included 10 physically active females, and males 6 and 4 respectfully. All participants were familiarised with the cybex followed by two trials held one week apart. The Isokinetic test was then performed with 5 repetitions (not 40) of maximum knee flexion and extension at 60o per second. Additionally, our study design differed as we implemented a repeated measure design where each participant was their own control and completing bot the control and caffeine conditions. Furthermore, the caffeine condition ingested 2 mg/kg of body weight like the research by Astorino et al. (2010) although the higher dose was not implemented. Therefore, instead of a 3 treatment 2 sets ANOVA a paired t-test was used to determine significance for peak knee extension/flexion, extension/flexion %BW, and H:Q ratio. Our results support Astorino et al. (2010) as no significant results were identified regarding peak knee extension/flexion, extension/flexion %BW, and H:Q ratio. Although our results indicate, peak knee flexion torque increased by 8. 9%, flexion % BW increased by 11. 1% H:Q ratio increased by 11. 2%, peak knee extension decreased by 5. 8%, and knee extension % BW decreased by 4. 6%. Research by Timmins and Saunders (2014) investigated the effects of caffeine ingestion on maximal voluntary contraction (MVC) strength in upper- and lower- body muscle groups. Our research also investigated variable associated with MVC although only regarding lower body muscle groups. Furthermore, Timmins et al. (2014) implemented a randomized, subject-blind crossover protocol consisting of, 16 resistance-trained men who received either 6 mg/kg/BW of caffeine or a placebo. This was similar to our research although both females (6) and males (4) were participants in our research and also the dose of caffeine was lower at 2mg/kg/BW. Although, a repeated measure design where each participant was their own control and completing both the control and caffeine conditions was implemented in our study. Additionally, Timmins et al. (2014) investigated isokinetic peak torque of the knee extensors, ankle plantar flexors, elbow flexors and wrist flexors were measured at an angular velocity of 60o per second. Our protocol used the same isokinetic angular velocity, although investigated peak knee extension/flexion, extension/flexion %BW, and H:Q ratio. Timmins et al. (2014) applied a 2×4 ANOVA to identify a significant finding and reported an increase in isokinetic peak torque from plantar flexor to caffeine ingestion (p = 0. 011) and a significant difference in isokinetic peak torque between muscle groups (p = 0. 001). However, there was no significant treatment 3 muscle group interaction (p = 0. 056). Nonetheless, the % improvement in isokinetic peak torque with caffeine increased with muscle group size. Our results applied a paired t-test to identify significant results. Although, all of our results were determined non-significant. However, our results also indicate the % improvement for isokinetic peak torque with caffeine increases with muscle group size as knee flexors are a larger muscle group than knee extensor muscles respectfully. Describe your participants (2 marks)
10 healthy participants were randomly selected consisting of 6 women and 4 men from an undergraduate university population. The average age was 24 years ± 5. 86 years, average weight of 70. 67kg ± 15. 89kg and average height of 173 ± SD. What are the independent and dependent variables in your study? (3 marks)
Independent Variable: High 5 plus energy gel containing 23g of CHO and 30mg of caffeine. Dependant Variable: Hamstring peak torque, Quadricep peak torque and H:Q ratio. Describe what you did in your study and explain why you chose that specific approach.Points to consider: exercise modality, duration and intensity, outcome variables measured (e. g. heart rate, oxygen consumption) (10 marks).
Isokinetic assessments are used to measure torque values at several joints in the body; with the knee being the most frequently tested (Rosene, Fogarty & Mahaffey, 2001). The study was a repeated measure design in which each participant was required to serve as their own control and each completed the control and experimental conditions seven days apart. Both conditions measured isokinetic knee strength on the participants chosen dominant knee, the control condition consisted of no prior supplementation whilst the experimental condition consisted of ingestion of a single serve of high 5 plus gel 30 minutes prior to performing the test.The participant was restrained in the chair with two straps over the torso and a strap over the thigh, the leg attachment was secured to the anterior lower leg above the medial malleolus. Once the participant was secured in the chair the range of motion limits were set with starting position at 90 degrees knee flexion and the end point as 0 degrees full knee extension. The participant then performed 5 warm up repetitions at 60 degrees/ second followed by a 10 second rest. The Isokinetic test was then performed with 5 repetitions of maximum knee flexion and extension at 60 degrees per second. Isokinetic testing using the cybex provides a quantitative measurement from the agonist and antagonist muscles surrounding the knee joint, specifically measuring peak quadricep and hamstring torque and providing a H:Q ratio (Rosene, Fogarty & Mahaffey, 2001). What risks, if any, are involved in the tests you selected to use?How did you mitigate these risks? (5 marks).
Pre-Screening: All selected participants were pre-screened using the ESSA screening tool to identify any predisposing risk factors before beginning the test. All participants were considered low risk and could therefore perform the test safely. Inclusion Criteria: Participating in at least 4 h·wk-1 of exercise, including recreational sports, aerobic, and/or resistance training for at least 1 yr; nonsmoker; current caffeine intake >100 mg·d-1; 4) absence of existing knee pain; and body mass index (BMI)
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