An Introduction to Acute Fatigue within Sport

Definition

Muscle fatigue most often occurs during strenuous dynamic physical activity (James, Scheurmann & Smith, 2010) and within sport, can be explained as a reduction of maximal force or power that is associated with sustained exercise, or the inability to produce or maintain a required force or power output (Celine et al., 2011).


Causes/Classifications

Neuromuscular fatigue is a vast topic of research and though many of the causes are still obscure, it is agreed to be the result of a combination of central and peripheral factors (Allen, Lamb, & Westerblad, 2008; Enoka & Duchateau, 2008; Fitts, 1994; Waldron & Highton, 2014).

Vaguely put, central fatigue is related to the brain and central nervous system while peripheral fatigue is to do with the muscles themselves and the substances related to contracting them.

In a few more words, central fatigue is related to reduced central motor drive of the central nervous system (CNS) due to changes in the synaptic concentration of neurotransmitters and therefore its ability to recruit available motor units (Davis and Bailey, 1997).

Peripheral fatigue on the other hand, relates to limitations of muscle capacity through biochemical changes (Waldron & Highton, 2014), such as an increase in blood lactate concentration and hydrogen ion accumulation (Mohr, Krustup & Bangsbo, 2003). It occurs at, or distal to, the neuromuscular junction and is thought to be linked to several mechanisms such as failure of excitation-contraction coupling, a disruption in neuromuscular transmission and the inhibition of muscle contraction through either the build-up or depletion of metabolites (Kent-Braun, 1999).

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Lactate and hydrogen ions (H+) production is the result of glucose breakdown. If a sufficient amount of oxygen is not available to the working muscles then hydrogen ion concentrations begin to rise and the muscles, including blood flow to the muscles, become acidic. This acidic environment blocks neuromuscular transmission (signal to and from the brain and muscle), slowing down the individual in order to allow more oxygen to get to the working muscles.

Decreased work rate within sports has been affiliated with reduction in muscle glycogen content (Saltin, 1991) while other factors such as physiological changes within the muscle cell, dehydration and a reduction of recruitable muscle fibres for force production have also been suggested (Saltin, 1973; Jacobs et al., 1982; Bangsbo, 1994). Sjersted and Sjoogard (2000) hypothesized that the sarcolemma was one of the sites of fatigue due to its inability of maintaining sodium and potassium concentrations during repeated stimulation. As a result of inefficiency of the sodium/potassium pump, potassium concentrations increase outside the membrane, in turn decreasing the amount within the membrane. This leads to depolarization of the cell, thus reducing action potential amplitude.

Recovery from peripheral fatigue where it relates to metabolic factors and impairments in neuromuscular transmission is known as high frequency fatigue and has been shown to occur within shorts periods of time following exhaustive exercise (Bruton, Lannergren, & Westerblad, 1998; Saltin, Radegran, Koskolou, & Roach, 1998). Low frequency fatigue on the other hand, is related to peripheral fatigue due to impairments within the excitation-contraction coupling process, and occurs as a result of repeated short intervals of repeated muscle stimulation. This type of fatigue is more prominent following eccentric exercise and is likely the cause of a longer lasting neuromuscular fatigue (Keeton & Binder-Macleod, 2006).


Effects/Presentation/Monitoring

Fatigue within sports is primarily identified through a decline in performance (Reilly, 1994). A fatigue effect has been reported to be noticeable in soccer, particularly within the second half due to an observation of decreased work rate (Reilly and Thomas, 1976). Bangsbo et al (1991) reported a 5% greater distance covered within the first half by professional soccer players,

Fatigue been shown to impair sprinting mechanics and joint stability. Such a combination of factors is likely to predispose players to injury during tasks that have high mechanical demands. (Greig, 2009). Fatigue leads to altered movement patterns of athletes into more stressful positions (Borotikar et al., 2008), and has been reported to be a direct contributor towards injuries such anterior cruciate ligament (ACL) injury via promotion of high risk biomechanics (McLean & Samorezov, 2009)

With advancements in team sports performance analysis such as player tracking technology, fatigue is a popular topic of interest and has usually been associated with variables such as running performance, distance covered from baseline, along with reported changes in neuromuscular force or sprinting ability (Rampinini et al., 2011). Basic physiological measures such as heart rate and blood lactate provide a useful index of overall physiological strain and anaerobic energy yield in response to high intensity situations respectively (Reilly & Thomas, 1997; Reilly, 1997). Thus, combining these variables with a measurement in decrease of muscular force overtime within match play may help indicate acute neuromuscular fatigue.

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Other ways include monitoring training load through session RPE’s (rate of perceived exertion) or/and RSI (Reactive strength index). These are easily obtained through a set of numbers based on session time and perceived exertion or using a jump mat and monitoring jump performance which is custom for most professional athletes particularly within team sports. An example and some uses for these two methods are summarised in the below picture.

RSI RPE

Sport scientists and S&C coaches may prefer to use other methods of further analysis through a combination of the above mentioned factors or equations such as the Fatigue Index equation (Fitzsimons, Dawson, Ward & Wilkinson, 1993) based on peak running speed/peak force produced and sum of general running speeds or gneral force produced, depending on the athlete being monitored.

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An Introduction to Performance Training.

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“One of the misconceptions in the sports world is that a sports person gets in shape by just playing or taking part in his/her chosen sport. If a stationary level of performance, consistent ability in executing a few limited skills is your goal, then engaging only in your sport will keep you there. However, if you want the utmost efficiency, consistent improvement, and balanced abilities sportsmen and women must participate in year round conditioning programs.The bottom line in sports conditioning and fitness training is stress, not mental stress, but adaptive body stress. Sportsmen and women must put their bodies under a certain amount of stress (overload) to increase physical capabilities.” Tancred, 1995

Many people affiliate the term ‘training’ or ‘fitness’ to just strolling into a gym either loaded with weights or treadmills.
But the truth is, the term has such a broad meaning which people have misunderstood so badly, to the extent that they just have no clue what they do in the gym or on a treadmill, but as long as it makes them slightly tired or sweaty, they feel they have achieved something.

How many times have you come across someone in the gym that attempts to bicep curl or tricep pull-down the whole line of weights on the cable machine and sees that as their ultimate sign of progress? How many times have you seen others scoff at people run for a few miles and stick to the lighter weights for multiple reps and sets? How many times have you come across a guy/girl who dead-lifts a phenomenal amount of weight for the size he/she is?

The truth is, each person should be training for their own goals. And the goals vary depending on the person, their sport, their weaknesses/strengths and much more.

However, while the goals of every person may vary, the components of one’s ‘fitness’ or ‘training’ are of few. This means the goals are generally based around these few components.

These include:

1) Power – Exerting maximum muscular contraction/force within the shortest amount of time (A combination of Strength and Speed)
E.g: Weightlifting (to some degree), Wrestling, Judo

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2) Strength – How much a muscle can exert itself against resistance.
E.g: Maximal Strength sports – Powerlifting

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3) Cardiovascular Endurance – Ability and efficiency of the heart in providing blood and oxygen to the working muscles.
E.g: Marathons

4) Muscular Endurance – Ability and efficiency of a single muscle to contract under a sustained strain.
E.g: Rowing, Boxing

5) Strength Endurance – Ability of a muscle to contract maximally repeatedly.
E.g: Baseball throws, Roundhouse kick

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6) Flexibility – Ability of extending range of motion within the body.
E.g: Splits

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7) Agility – Ability to perform explosive fast movements within opposite  directions.
E.g: 90 or 180 degree turns/cuts in any field based sports

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8) Balance – Ability to control movement of body when either moving or  being still.
E.g: Gymnastics

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9) Coordination – The ability to combine all/most of these components effectively to perform a movement.

NOTE: Most sports contain a combination of many components. It is very rare an athlete only possesses just one!

Notice anything missing? Were you looking for something?  Hypertrophy/mass/size?
Well that’s the thing..

Being muscular or aesthetic or ‘dench’ ISN’T a component of fitness. However it may be a by-product of some of the training done by an athlete, or an aid to helping him/her achieve one of the components.

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Hence many argue, Bodybuilding not being a sport, but more an art. A deep appreciation for the outward look of muscular symmetry but not with much function to do something within a sport which require skill along with any of the above mentioned components. However bodybuilders themselves may vary individually; some will decide to stay more athletic than the others by working on some of the above mentioned components of fitness.

(This is not a rip off on bodybuilding!)

If your goal is to truly stimulate muscle growth or fat breakdown so that you look more aesthetic and ‘bigger’, then there is no problem with sticking to the principles of training for hypertrophy or lipolysis and cracking on with just that! I stress with sticking to the principles due to it allowing you to not be one of those wanderers who just have a vague idea of the concept of training and freestyle as they go along, but instead, is a person with set goals and an understanding mindset towards where their routines will lead them towards.

P.S.

Don’t forget! Being powerful doesn’t necessitate you will be extremely muscular and aesthetic either. It’s very easy to think a huge muscular person is very powerful/strong, but that isn’t always the case! Power is a combination of strength AND speed and they will need BOTH. As for their strength, their are many types; is their relative strength compared to others in their weight class up to standard? Well, that’s another question in itself!

Lu xiaojun CHN 77kg
Incredible attempt with a world record 175kg!!! But what does HE weigh? -77kg!

So..
What are YOU training for?