How caffeine affects the body

How caffeine affects the body

Caffeine’s Effect on Skeletal Muscle during Athletic Performance

Introduction: 

90 percent of athletes consume caffeine regularly to improve sport performance1. Caffeine is a stimulant that decreases heart rate but increases blood pressure in adults. Caffeine also affects the physiology of skeletal muscle. Caffeine can be found in coffee, soda drinks, pills, energy drinks, energy bars, and even chocolate.The use of caffeine for stimulant effects has become increasingly more popular among athletes4. The purpose of this paper is to explore the effects of caffeine on adult athletic performance.

 

Results: 

Research studies have consistently shown that caffeine affects psychological performance in athletes. Caffeine can improve an athlete’s alertness, subjective energy level, concentration, and arousal, however it can also cause negative effects like anxiety nausea, and nervousness4. 

 

Caffeine has shown to affect the physiology of skeletal muscle. It has been shown to decrease AKT phosphorylation and to increase AMPk but only under extreme amounts of caffeine concentration in mouse skeletal muscle3,5. Furthermore it enhanced the phosphorylation of S6 immediately after muscle contractions5. Caffeine has also been shown to have an effect on cytokine concentrations post-exercise. In a placebo study, cytokines increased in the placebo group, but did not increase in the caffeinated group11.

 

Athletic performance is increased with caffeine supplementation, but it has been determined that the dosage needed to produce any performance effects is 3-9 mg per kg body weight6,7. Under this dosage, caffeine has been shown to improve short-term endurance exercise, possibly due to muscle glycogen sparing2. Caffeine has also been shown to increase maximal strength, isokinetic strength, torque, power output, and muscular endurance in several studies7,8,10. Finally, caffeine can improve time to exhaustion with anaerobic exercise, but it does not change anaerobic capacity9.

 

Discussion: 

Caffeine decreases AKT phosphorylation, increases AMPk activation and enhances phosphorylation of S6. This is indicative of the possibility of the increase of energy due to increased glucose uptake into the cells and increased fatty acid metabolism from AMPk activation5,12. Increase in muscle force could be due to S6 activation, however, no muscle growth is found with increased caffeine ingestion, which could be due to inhibition of AKT. In light of these discoveries, it is still inconclusive of the implications of these results. Further research is required to confirm the validity of these claims.

 

The decrease in cytokines post-exercise with caffeine ingestion needs further research on the effect of muscle growth and post-exercise hypertrophy.

 

One limitation to these studies is that most researchers used male subjects when collecting data, so, consequently, the difference in performance between male and female subjects is not well known6. Additionally, caffeine performance was tested on mice skeletal muscle. The half-life of caffeine in mice is one hour, whereas in humans the half-life is five hours5. Further research that could be done is testing human muscle biopsies after various doses of caffeine ingestion in both male and female subjects.

 

Conclusion:

Caffeine is a definite ergogenic aid that is widely used by athletes. It is regulated as a controlled substance in professional sports, so recommended dosages are encouraged when supplementing caffeine to improve sports performance. Although caffeine has been proven to be an ergogenic aid, current studies are inconclusive as to why it has physiological benefits. Further research is necessary to determine the effects of caffeine on the human body with sports performance.

 

Citations:

 

1 – Burke, L., 2008. Caffeine and sports performance. Appl. Physiol. Ntr. Metab. 33:1319-1334. doi:10.1139/H08-130

2 – Spriet, L., Graham, T., (2018) Caffeine and Exercise Performance. American College of Sports Medicine. www.acsm.org

3 – Green, J., Olenick, A., Eastep, C., Winchester, Lee., (2016) Caffeine effects on velocity selection and physiological responses during RPE production. Appl. Physiol. Nutr. Metab. 41: 1077-1082  https://doi.org/10.1139/apnm-2016-0098

4 – Temple, J., Dewey, Amber., Briatico, L., 2010. Effects of Acute Caffeine Administration on Adolescents. American Psychological ASsociation 18(6): 510-520 doi: 10.1037/a0081651

5 – Moore, T., Mortensen, X., Ashby, C., Harris, A., et al. (2017) The effect of caffeine on skeletal muscle anabolic signaling and hypertrophy. Appl. Physiol. Nutr. Metab. 42: 621-629 dx.doi.org/10.1139/apnm-2016-0547

6 – Talanian, J., Spriet, L. (2016) Low and moderate doses of caffeine late in exercise improve performance in trained cyclists. Appl. Physiol. Nutr. Metab. 41: 850-855 dx.doi.org/10.1139/apnm-2016-0053

7 – Miyagi, W., Bertuzzi, R., Nakamura, F., de Poli, R. and Zagatto, A. (2018). Effects of Caffeine Ingestion on Anaerobic Capacity in a Single Supramaximal Cycling Test. Frontiers in Nutrition, 5. doi:10.3389/fnut.2018.00086

8 – Grgic, J. and Pickering, C. (2018). The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis. Journal of Science and Medicine in Sport. https://doi.org/10.1016/j.jsams.2018.08.016

9 – Ferreira GA, Felippe LC, Bertuzzi R, Bishop DJ, Barreto E, De-Oliveira FR and Lima-Silva AE (2018) The Effects of Acute and Chronic Sprint-Interval Training on Cytokine Responses Are Independent of Prior Caffeine Intake. Front. Physiol. 9:671. doi: 10.3389/fphys.2018.00671

10 – Glaister, M., Towey, C., Jeffries, O., Muniz-Pumares, D., Foley, P. and McInnes, G. (2018). Caffeine and Sprint Cycling Performance: Effects of Torque Factor and Sprint Duration. International Journal of Sports Physiology and Performance, pp.1-19. https://doi.org/10.1123/ijspp.2018-0458

11 – Grgic, J., Mikulic, P., Schoenfeld, B., Bishop, D. and Pedisic, Z. (2018). The Influence of Caffeine Supplementation on Resistance Exercise: A Review. Sports Medicine. https://doi.org/10.1007/s40279-018-0997-y

12 – Marabita, M., Baraldo, M., Solagna, F., Ceelen, JJM., et al., (2016) S6K1 is Required for Increasing Skeletal Muscle Force during Hypertrophy. Cell Rep. 17(2):501-513 doi: 10.1016/j.celrep.2016.09.020

 

RPE (Green)

• 16 recreationally fit volunteers
• All were physically examined
  • Par-Q
  • Hieght
  • Body fight (skin fold)
  • Body weight
  • VO2max
• 24 hours after assessment
  • 2 groups were made: control (consumed PLA), (consumed CAF)
  • Made to run on a treadmill
  • Required to run at a constant RPE (Determined by VO2). Velocity was adjusted to maintain RPE

 

Muscle signaling and hypertrophy (Moore)

• Used muscle cells for test. Separated them into groups and exposed them in varying amounts of caffeine.
• Also took mice and used STI to test muscle contraction. After collection of  data they injected varying amounts of caffeine into their muscle. Later they tested the muscles again through STIM and later dissected them for testing.

Influence of caffeine supplementation on resistance exercise review

• Caffeine increases maximum strength and muscular endurance
• Caffeine may decrease perceived DOMS
• Caffeine may increase testosterone and cortisol, but more likely due to exercise, not caffeine
• Dosage that produces effect = 3-9 mg/kg 60 min before exercise
• Most caffeine studies use only male participants, so it is less known how caffeine affects women during exercise

Caffeine and sprint cycling performance: effects of torque factor and sprint duration

• When torque factor and sprint duration are at optimal level for athlete to achieve peak power output, the effect of caffeine supplementation on sprint cycling is statistically significant

Effects of caffeine ingestion on anaerobic capacity in cycling

• Caffeine improves time to exhaustion with anaerobic exercise, but it does not affect anaerobic capacity

Effects of caffeine ingestion on isokinetic muscular strength meta-analysis

• Caffeine ingestion increases isokinetic strength
• Effects of caffeine on strength are seen in knee extensor muscles and at higher angular velocities

Effects of sprint interval training on cytokine responses with and without caffeine

• CK (cytokines) increased 24-48 hrs post-exercise after first training session for placebo group, but did not change post-exercise for caffeine group

 

Results

RPE (Green)

• No in RPE4 or RPE7 between CAF and PLA. Overall CAF vel increased

Muscle signaling and hypertrophy (Moore)

• Caffeine did not cause the hypertrophy, it did eliminate the increase in AKt phosphorlation. 
• It led to a decrease in food consumption, and retroperitoneal fat pad weight.

 

Discussion/Conclusion]

RPE (Green)

• Potential ergogenic aide is fiber recruitment at a given intensity, augmented pain or enhanced substrate FFA availability. 
• Positives: increased attention, alertness, and metabolic rate. Enhance acute performance through CNS.
• Negatives: Blocks insulin signaling through protein kinase B and activation of rapamycin (for protein synthesis)
• Activates AMPK which could be why rapamycin is inhibited.
• These results occured in supraphysiological conditions.

 

Muscle signaling and hypertrophy (Moore)

• Caffeine is one of the most widely consumed drug in the world. 10% of America ingests 100mg or more per day. 
• In this study of concentrations of 0-.3uM it did not have any significant effect on AMPK phosphorylation in cells, but it did at 2.5mM. 
• In humans blood concentration ranges from 15-80uM
• Although concentrations are different, the half life of caffeine in mice is 1 hr whereas in humans it is around 5 hours. They hypothesize this could make a difference in AMPK signaling.
• We found that while caffeine injection did not significantly affect Akt phosphorylation in resting or contracted mouse muscles, or in cultured mouse C2C12 myotubes, caffeine completely blocked the increase in Akt phosphorylation in hypertrophying plantaris muscles, but this did not significantly affect signaling through the mTOR pathway to 4EBP1 or muscle growth.
• Two weeks of caffeine treatment did, on the other hand, reduce the size of the retroperitoneal fat pad without impacting muscle hypertrophy. This suggests that caffeine has the ability to mobilize fat stores, which is consistent with previous research where caffeine prevented adipose accretion with a high-fat diet (but the rats did eat less)
• AMPK, is an important negative regulator of muscle cell size and hypertrophy
• In conclusion, we observed that caffeine at physiological concentrations did not generally impair AMPK or anabolic signaling (except for blocking overload-induced Akt phosphorylation) or skeletal muscle hypertrophy after OVLD or STIM in rats and mice respectively. Indeed, although it did not affect protein synthesis or hypertrophy, caffeine enhanced the phosphorylation of S6 immediately after muscle contractions. Though inconclusive, this suggests that if anything, caffeine may provide some anabolic benefit.

Acute Caffeine administration on adolescents (temple)

• children ages 12 to 17 are among the fastest-growing segment of the population for caffeine use
• moderate doses of caffeine (200 –350 mg) decrease heart rate and increase blood pressure in adults (Bender, Donnerstein, Samson, Zhu, & Goldberg, 1997; Lane & Williams, 1987; Sung et al., 1994; Waring, Goudsmit, Marwick, Webb, & Maxwell, 2003). In addition, these same doses of caffeine produce enhanced feelings of well-being, improve concentration, and increase arousal and energy
• however, lead to feelings of anxiety, nausea, jitteriness, and nervousness

Burke

• A criticism on studies.
• Caffeine is an ergogenic aid, but to what level is unknown
• Regulations on caffeine in sports
• Education on the adverse effects of caffeine is lacking.

Talanian

• Increasing caffeine intake from a low (<2.5 mg·kg bm−1) to a moderate dose (3–6 mg·kg bm−1) can increase the ergogenic effect when caffeine is ingested just prior (<60 min) to the endurance performances. (ii) The timing of intake may significantly affect the efficacy of caffeine on endurance performance. (iii) Mixed results between studies may suggest inter-individual differences in the optimal timing and minimal dose required to maximize performance benefits from caffeine during endurance performance.
• More ergogenic effects from caffeine the closer to the exercise bout it was taken (within 40-60 minutes)

 

Citations

Burke, L., 2008. Caffeine and sports performance. Appl. Physiol. Ntr. Metab. 33:1319-1334. doi:10.1139/H08-130

Spriet, L., Graham, T., (2018) Caffeine and Exercise Performance. American College of Sports Medicine. www.acsm.org

Green, J., Olenick, A., Eastep, C., Winchester, Lee., (2016) Caffeine effects on velocity selection and physiological responses during RPE production. Appl. Physiol. Nutr. Metab. 41: 1077-1082  https://doi.org/10.1139/apnm-2016-0098

Temple, J., Dewey, Amber., Briatico, L., 2010. Effects of Acute Caffeine Administration on Adolescents. American Psychological ASsociation 18(6): 510-520 doi: 10.1037/a0081651

Moore, T., Mortensen, X., Ashby, C., Harris, A., et al. (2017) The effect of caffeine on skeletal muscle anabolic signaling and hypertrophy. Appl. Physiol. Nutr. Metab. 42: 621-629 dx.doi.org/10.1139/apnm-2016-0547

Talanian, J., Spriet, L. (2016) Low and moderate doses of caffeine late in exercise improve performance in trained cyclists. Appl. Physiol. Nutr. Metab. 41: 850-855 dx.doi.org/10.1139/apnm-2016-0053

Miyagi, W., Bertuzzi, R., Nakamura, F., de Poli, R. and Zagatto, A. (2018). Effects of Caffeine Ingestion on Anaerobic Capacity in a Single Supramaximal Cycling Test. Frontiers in Nutrition, 5. doi:10.3389/fnut.2018.00086

Grgic, J. and Pickering, C. (2018). The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis. Journal of Science and Medicine in Sport. https://doi.org/10.1016/j.jsams.2018.08.016

 Ferreira GA, Felippe LC, Bertuzzi R, Bishop DJ, Barreto E, De-Oliveira FR and Lima-Silva AE (2018) The Effects of Acute and Chronic Sprint-Interval Training on Cytokine Responses Are Independent of Prior Caffeine Intake. Front. Physiol. 9:671. doi: 10.3389/fphys.2018.00671

Glaister, M., Towey, C., Jeffries, O., Muniz-Pumares, D., Foley, P. and McInnes, G. (2018). Caffeine and Sprint Cycling Performance: Effects of Torque Factor and Sprint Duration. International Journal of Sports Physiology and Performance, pp.1-19. https://doi.org/10.1123/ijspp.2018-0458

Grgic, J., Mikulic, P., Schoenfeld, B., Bishop, D. and Pedisic, Z. (2018). The Influence of Caffeine Supplementation on Resistance Exercise: A Review. Sports Medicine. https://doi.org/10.1007/s40279-018-0997-y

Marabita, M., Baraldo, M., Solagna, F., Ceelen, JJM., et al., (2016) S6K1 is Required for Increasing Skeletal Muscle Force during Hypertrophy. Cell Rep. 17(2):501-513 doi: 10.1016/j.celrep.2016.09.020