FATIGUE

 

 

Fatigue is commonly associated with a reduction of force production in athletic performance either on the playing field or during training sessions (Hooper et al., 2013). An athlete becomes fatigued by being placed under a stress inducing stimulus and then not being capable to adequately recover from it (Johnston et al., 2013). These stressors are either external stressors (training sessions, workouts, gameplay etc) situations that can be in the coach’s control to change or internal stressors (psychological stress, lack of proper nutrition and sleep etc) that perhaps the coach can’t control (Sapolsky, 2004).

 

The concept of fatigue is considered to be either short term or long term fatigue. Short term fatigue can be seen through a drop in performance during a match or in training sessions (hours to a few days). This can be noticed by reduced energy levels and unable to continually repeat high power outputs (Hester, Conchola, Thiele & DeFreitas, 2014; Bishop, 2012; Laurent, Fullenkamp, Morgan & Fischer, 2014). This can be easily reversed with the right prescription of rest and a well-managed recovery system. Yet when an athlete experiences long term fatigue (a few weeks to many months) athletes struggle to handle excess stress on their nervous systems which result in the constant feeling of being tired and changes in mood and personality can be seen (Lehmann et al., 1997).

 

To explain how the two different situations can occur, short term fatigue happens through the peripheral nervous system. The central nervous system operates by sending signals from the brain, down through the spinal cord and branching out into the peripheral nervous system (Allen, Lamb & Westerblad, 2008). The peripheral nervous system controls everything on a muscular cell level. The muscle is able contract by the process of possible three different energy systems. The first energy system is active by releasing a stored energy source called adenosine triphosphate (ATP).

 

For explosive, powerful muscle contractions, like the ones that happen in rugby, this can last up to around 10 seconds (Katch, McArdle & Katch, 2011). This is called the phosphocreatine energy system and is predominantly expressed in a rugby game during a tackle, scrummaging and during very short explosive change of direction. ATP can be fully restored within the muscle with between 2 to 5 minutes passive rest. Obviously, due to the nature of the sport, rugby players can’t rest for that time to be able to rely on natural ATP stores.

 

However, when muscle contractions lasting longer than 10 seconds and natural ATP stores start to deplete, than the muscles start converting stored glycogen or take ready available glucose from the blood stream to make ATP (Green, 1997). This energy system is called anaerobic glycolysis and through this system lactate and hydrogen ions are produced and can start accumulating in the muscle. This system is really being worked when players need to keep repeating bouts of tackling and multiple changes of direction. Yet, when rest time is minimal and oxygen becomes present within the muscle, the aerobic system helps out to regenerate ATP stores to allow for a forceful muscle contraction (McLellan & Lovell, 2012).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Together, all three energy systems work simultaneously throughout a game of rugby. However, players can suffer short term fatigue at the peripheral nervous system level by muscles being unable to contract forcefully when trying to make rapid decisions (Behm, Baker, Kelland & Lomond, 2001; Davis & Bailey, 1997). Researchers have found that the release of cytokines when muscles contract can affect functions in the brain amongst other areas (Ament & Verkerke, 2009). With an added combination of depletion in ATP, not enough sufficient glycogen available, change to a negative pH level within the muscle, not being able to transport oxygen to muscles quickly and overall muscle damage, a player will become exhausted (Granatelli et al., 2014). This highlights the importance of training a player’s strength and conditionings levels as a player with a lower level will become fatigued faster in a game compared against a player with a higher level.

 

With short term fatigue affecting muscle function, long term fatigue can affect the hormonal balance between sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). When this balance is disrupted for a long period of time, it is argued to be an important component in becoming overtrained (Hackney, 2006). These two systems are known as the autonomic nervous system because of the way they both automatically respond to a stimulus within the body. It happens by the release of hormones adrenaline, nor-adrenaline and cortisol from the adrenal glands as the SNS is otherwise known as the ‘fight or flight’. When stressed, the system automatically releases adrenaline, which in turn increases heart rate, releases stored glycogen for instant energy supply and constricts and diverts blood flow from the digestion system towards working muscles (Sluiter, Frings-Dresen, Meijman & Van der Beek, 2000). This same hormonal response process is activated in the same way from either an external stimulus (weight training, during competition) or an internal stimulus (psychological feelings of stress or anxiety).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference List

 

Allen, D. G., Lamb, G. D. and Westerblad, H. (2008) Skeletal muscle fatigue: cellular mechanisms. Physiological Reviews, 88, 287-332.

 

Ament, W. and Verkerke, G. J. (2009) Exercise and fatigue. Sports Medicine, 39, 389-422.

 

Behm, D. G., Baker, K. M., Kelland, R. and Lomond, J. (2001) The effect of muscle damage on strength and fatigue deficits. The Journal of Strength and Conditioning Research, 15, 255-263.

 

Bishop, D, J. (2012) Fatigue during intermittent-sprint exercise. Clinical and Experimental Pharmacology and Physiology, 39, 836-841.

 

Brooks, K. A. and Carter, J. G. (2013) Overtraining, exercise, and adrenal insufficiency. Journal of Novel Physiotherapies, 16, 1-10.  

 

Chen, R., Liang, F. X., Moriya, J., Yamakawa, J., Sumino, H., Kanda, T. and Takahashi, T. (2008) Chronic fatigue syndrome and the central nervous system. Journal of International Medical Research, 36, 867-874.

 

Davis, J. M. and Bailey, S. P. (1997) Possible mechanisms of central nervous system fatigue during exercise. Medicine and Science in Sports and Exercise, 29, 45-57.

 

De Vries, J. M., Hagemans, M. L. C., Bussmann, J. B. J., Van der Ploeg, A. T. and Van Doom, P. A. (2010) Fatigue in neuromuscular disorders: focus on guillian-barre syndrome and pompe disease. Cellular and Molecular Life Sciences, 65, 701-713

 

Fletcher, E., Grantham, N., Hamilton, A., Lawson, T., Marshall, J. and Ruddock, A. (2009) How to avoid overtraining. London: P2P Publishing.

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Granatelli, G., Gabbett, T. J., Briotti, G., Padulo, J., Buglione, A., D’Ottavio, S. and Ruscello, B. (2014) Match analysis and temporal patterns of fatigue in rugby sevens. The Journal of Strength and Condition Research, 28, 728-734.

 

Green, H. J. (1997) Mechanisms of muscle fatigue in intense exercise. Journal of Sport Sciences, 15, 247-256.

 

Hackney, A. C. (2006) Stress and the neuroendocrine system: the role of exercise as a stressor and modifier of stress. Expert Review of Endocrinology and Metabolism, 1, 783-792.

 

Hester, G. M., Conchola, E. C., Thiele, R. M. and DeFreitas, J. M. (2014) Power output during a high-volume power-oriented back squat protocol. The Journal of Strength and Conditioning Research, 28, 2801-2805.

 

Hooper, D. R., Szivak, T. K., DiStefano, L. J., Comstock, B. A., Dunn-Lewis, C., Apicella, J. M., Kelly, N. A., Creighton, B. C., Volek, J. S., Maresh, C. M. and Kraemer, W. J. (2013) Effects of resistance training fatigue on joint biomechanics. The Journal of Strength and Conditioning, 27, 146-153.

 

Johnston, R. D., Gibson, N. V., Twist, C., Gabbett, T. J., MacNay, S. A. and MacFarlane, N. G. (2013) Physiological responses to an intensified period of rugby league competition. The Journal of Strength and Conditioning Research, 27, 643-654

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Katch, F. I., McArdle, W. D. and Katch, V. L. (2011) Essentials of exercise physiology. Baltimore, Philadelphia: Lippincott Williams & Wilkins.

 

Laurent, M. C., Fullenkamp, A. M., Morgan, A. L. and Fischer, D. A. (2014) Power, fatigue and recovery changes in NCAA division I hockey players across a competitive season. The Journal of Strength and Conditioning Research, 28, 3338-3345.

 

Lehmann, M. J., Lormes, W., Opitz-Gress, A., Steinacker, J. M., Netzer, N., Foster, C. and Gastmann, U. (1997) Training and overtraining: an overview and experimental results in endurance sports. Journal of Sports Medicine and Physical

Testing, 37, 7-17.

 

McLellan, C. P. and Lovell, D. I. (2012) Neuromuscular responses to impact and collision during elite rugby league match play. The Journal of Strength and Conditioning Research, 26, 1431-1440. 

 

Sapolsky, R. M. (2004) Why zebras don’t get uclers. New York: Holt Paperbacks.

 

Sluiter, J. K., Frings-Dresen, M. H. W., Meijman, T. F. and Van Der Beek, A. J. (2000) Occupation and Environmental Medicine, 57, 298-315.