Pain Tolerance and Threshold in Athletes

Literature Review

The purpose of this study is to investigate how trained and untrained athletes tolerate pain and their ability to tolerate pain threshold. Hence the study will provide information on an athlete’s perception of pain and the way in which they respond to exercise induced pain. Studies have shown the way in which athletes perceive pain as “part of the game” (Deroche et al., 2011). It has now widely been an interest for researchers in observing the psychological and physiological basis of pain (Scott and Gijsbers, 1981). This approach is claimed to generate more pressure on athletes to continue pushing through despite them being in pain.

This study can therefore help in identifying athletes coping mechanisms towards pain management, therefore maintaining involvement in physical activity. Recent Studies have attempted to find a correlation between fitness levels, sporting achievements and pain sensitivity using anecdotal observations (Jones et al., 2014). The findings from several cross-sectional studies have shown that they are equivocal and vary depending on the sport, standard and phase of competition (Ryan and Kovacic, 1966). There are many different factors as to why particular athletes may experience “more” or “less” pain tolerance and threshold. These factors include; gender, age, race and a decline in blood lactate and fitness levels all of which can have an effect on the threshold and tolerance levels of an athlete.

In the recent years, there has been tremendous research which has focused on understanding pain experience in sport (Hall and Davies, 1991). They have demonstrated differences in pain tolerance and threshold which can emerge depending on whether it is an individual or team sport. There are a number of considerable variables that may determine whether an athlete has a higher tolerance or threshold in sport due to stress levels, coping strategies, anxiety levels and perception (Sanderson, 1978).

https://medicalsciences.med.unsw.edu.au/sites/default/files/soms/page/SOMSAdmin/Matt%20Jones_Ex%20Phys.pdf

The hypoalgesic effect, in healthy individuals, of acute exercise is subject to well refined documentation (Naugle et al., 2012). There is also demonstration of the chronic exercise training in reducing the patients’ pain activity who are suffering from persistent pain (Hoffman et al., 2004) and in accordance to that, exercise training has turned out to be one of the key aspects of these patients’ treatments. However, in spite of increasing effect of chronic disease populations’ pain relieving effect, the aerobic training’s effect on pain sensitivity is not known much in healthy individuals. Therefore, there is little knowledge as to how exercise training can do modulation to the pain independently of disease.

There have been a study conducted that examined the chronic aerobic exercise effect in healthy participants on pain sensitivity (Anshel and Russell, 1994). Examination carried out by Anshel and Russell (1994) related to the 12 week resistance or aerobic or combined resistance and aerobic exercise and their effect in 48 unfit males on pressure pain tolerance. The group having completed cycling which was a part of aerobic exercise training could tolerate the application of the greater degree of mechanical pressure to the upper limb. A similar change pattern for the lower limb was apparent, although the findings were statistically significant.

Moreover, in spite of the fact that aerobic exercise group tolerates mechanical pressure of higher intensities; a subjective appraisal of more severe nature related to pain has been reported following the training period. The resistance training ceases to have any influence on pain tolerance. The study provides weak, but preliminary evidence that aerobic exercise training can pave the way for augment in pain tolerance, although it has many limitations. The exercise training’s effect on pain threshold and the painful stimuli’s duration that can be tolerated have not been quantified. The intensity and volume of exercise that the participants perform have been varied highly across the period of 12 weeks that makes it difficult in identifying the intensity and volume of the needed exercise in eliciting the hypoalgesic response. Finally, there was no measurement of the maximal aerobic capacity which makes it impossible to determine the endurance performance and V˙ O2max, pain sensitivity’s exercise training and its influence.

There are many other studies that wanted to obtain a relationship between the pain sensitivity and the sporting or fitness achievement on the basis of the anecdotal observation about which there is more stoic for the athletes. The cross sectional studies have found that there is equivocal and varied dependence on the sport and even the competitive season’s phase or the competition standard that have been studied by the athletes (Scott and Gijsbers, 1981) and along with it the coping strategies usable by various individuals (Manning and Fillingim, 2002). The duration, the intensity, the volume, and the exercise training type that the athletes perform have been poorly quantified or controlled. Moreover, the findings heavily depend on the protocol and modality to evoke pain, and especially when the pain tolerance or the pain threshold has been measured (Ord and Gijsbers, 2003). Generally speaking, the cross-sectional investigation has the provision of evidence that pain tolerance is increased by the chronic exercise, although not pain threshold. Anshel and Russell (1994) supports this notion and have demonstrated that after exercise training, there is an augment of pain tolerance. However, this study has been only examining the exercise training’s effect on pain sensitivity in non-athlete and healthy individuals. Thus, it remains unclear whether pain sensitivity can be influenced by the chronic exercise independently of the status of an athlete.

This research will be used to determine whether untrained or trained athletes have different levels of tolerance and threshold due to their experience. It could potentially lead to new theoretical models that will influence athletes in training to increase their pain tolerance and threshold. This study shows how pain is an integral part of athletic training which is how trained athletes are able to withstand pain in comparison to untrained athletes. As a sports therapist I am able to conduct research methods to determine whether untrained or trained athletes have any difference in pain.

A trained person is defined as an athlete who plays at a high level in their sport, has great endurance level and has greater variables such as anaerobic threshold or VO2 max levels. Vo2 max is defined as the highest rate of oxygen consumption attainable during maximal or exhaustive exercise (Drews and Wilmore, 2000). In the appendix will be a table displaying normative data for Vo2 max in various population groups. Research was conducted to show the difference between trained runners and untrained runners. The project used VO2 as a measuring base, conclusion of the research showed that there were significant differences between trained and untrained runners (Dijk et al., 2017). Results showed that a trained runner required 5% less mechanical energy, 10% less oxygen consumption and their metabolic efficiency was 4% higher. The study shows how training can lead to these physiological adaptation in an athlete.

This research will also be able to show how pain tolerance and threshold greatly varies between the trained and untrained within the same or different sports. Pain threshold is the minimum intensity that is perceived as painful. Whereas pain tolerance is the maximum intensity of pain inflicted by a stimulus that an individual is able to tolerate (Lautenbacher et al., 2017). In order to record results from the study, a questionnaire was given to the participants to fill out post the test, this will enable both quantitative and qualitative data that can be analysed for descriptive classification. A study was conducted to investigate the ability of an athlete to tolerate pain during extreme physical demand. The study used experimentally induced pain to determine pain perception with threshold and tolerance. The study used a pain questionnaire that was composed of systematic structured verbal categories (Scott and Gijsbers, 1981).

Studies were reported by Bartley and Fillingham (2013) to have shown consistent results between females showing greater pain sensitivity. Some may make an assumption from results such as these that there is a difference in pain findings due to the biological sex of a person. There are other factors involved with gender such as state and trait. Trait refers to characteristics, gender-related personality, whereas state gender refers more towards the manipulation of gender-related thought processes of instructions given to a person (Martin, 2019). Pain threshold refers to when a stimulus is first recognised by an individual as pain. Pain tolerance however alludes to the amount of pain that a person is able to endure.

Pain gate theory, this allows the therapist to gain an in depth understanding on how to decrease pain the client may have. (Melzack and Wall, 1996) The theory proposes variety of specific pain receptors in body tissue then projects to a pain centre within the brain. The pain then generates impulses that are carried by A delta fibers and C fibers within the peripheral nerves. A-beta neurons are stimulated to close the gate to a delta and C neurons; in turn this will decrease pain.

Gate control theory of pain

The skin stimulation evokes nerve impulses transmittable to systems of three spinal cords as shown in the figure below. These are, in the dorsal horn, first central T (transmission) cells; dorsal-column fibers projecting towards the brain; and in the dorsal horn, substantia gelatinosa. It has been proposed that (a) the functions of substantia gelatinosa as a gate control system does modulation to the afferent patterns prior to the T cells getting influenced by them; (b) in the system act of the dorsal column, the afferent pattern, at least in part, trigger as a central control activating the processes of selective brain which in turn influences the gate control system’s modulating properties; and (c) the neural mechanism are activated by the T cells comprising the action system responsible for perception and response.

The substantia gelatinosa is comprised of densely packed and small cells forming the functional unit that extends the length of the spinal cord. The connection of the cells are with the long Sbers of Lissauer’s tract and shorter fibers (Moayedi and Davis, 2012), although they refrain from projecting substantia Ejelatinosa’s outside. The evidence found recently (Mander, 2010) is suggestive that gate control system is acted by the substantia gelatinosa modulating the nerve impulses’ synaptic transmission to central cells from the peripheral fibers.

The figure below has shown the involved factors in the impulses’ transmission that has been from the peripheral nerve in the cord to the T cells. The studies conducted recently (Melzack and Katz, 2014) indicates that in the large fibers, the volleys of nerve impulses have high level of effectiveness initially to activate the T cells, although their later effect is subject to reduction by a mechanism of negative feedback. Contrastingly, the activation of the volleys of small fibers has been with a mechanism of positive feedback, exaggerating the arriving impulses’ effect. Experiments (Kandel et al., 2000) conducted have indicated that cells in substantia gelatinosa mediate these feedback effects. These cells’ activity does modulation of the afferent fiber terminals’ membrane potential and thus determines the arriving impulses’ excitatory effect. Despite evidences, there can be postsynaptic control mechanisms which are undetected, for presynaptic control only, contributing to the input output functions observed.

There have been a couple of reasons to believe that resultant pain after afferent input’s prolonged monitoring takes place by the central cells. Firstly, on one arm, the threshold for shock is risible by a delivery of shock so long later 100 milliseconds are applied to the other arm (Lorenzo et al., 2014). Secondly, pain sensation delays, in pathological pain states, as long as 35 seconds following the stimulation is not attributable to slow afferent pathways conduction (Craig, 2003). It is suggestive that there is spatial or temporal integration or summation by the T cells of the arriving barrage. The signal triggering the action system has the responsibility for pain response and experience occurring when the T cells output exceeds or reaches a critical level. This firing’s critical level has been subject to determination by the afferent barrage that impinges on the T cells and modulated by substantia gelatinosa activity.

It can be presumed that there is requirement for the action system with regards to a definitive time period to integrate from the T cells with the total input. Fast and small temporal pattern variations that the T cells produce can be ineffective, and frequency impulses’ smoothed envelop of the impulses’ frequency containing the information of the rise and fall rate, the amplitude and the duration of the firing will be effective stimulus initiating the activities of appropriate sequence in the cells comprising the action system.

Pain itself is a sensation that involves components such as sensory and cognitive (Atlas and Wager, 2012). Pain is not limited to not only one factor but rather it is characterised by individuals themselves and group variability (Fillingim, 2005). Pain responses are said to vary in accordance to an individual's expectation including past experiences which differ in race and ethnic groups. There are essentially three different classes of pain, the noxious stimuli. This is the physiological pain that is felt when touching a stimulus that may vary in being hot, cold or even sharp. This noxious pain is also known as nociceptive pain, this is considered as a high threshold pain (Woolf, 2010). It occurs when there is a high intensity stimuli, it can be protective in a sense that it requires an immediate reaction this is called reflex, the reflex occurs when there is a sensation elicited which creates an emotional distress.

Another type of pain is adaptive and protective, this occurs when there is inevitable tissue damage which the pain will assist in aiding to heal the injured part of the body (Woolf, 2010). It does so by creating a discomfort in movement and any physical contact. In order to reduce the risk of any further damage and promoting recovery pain becomes hypersensitive. The immune system activates due to tissue injury or a possible infection; this is called inflammatory pain. Lastly there is a maladaptive pain which occurs as a result of abnormal functioning of the nervous system. It is considered as a pathological pain which is a symptom of a disease of the nervous system itself. It can occur after there has been damage to the nervous system and also with the absence of damage and inflammation. Nociceptive pain is considered to be an essential pain in order to maintain bodily integrity due to its protective role. Pain has been said to play an integral role in its ability to protect the body from damaging stimuli; consequently pain can also inhibit engagement during tasks (Astokorki and Mauger, 2016). Pain is a perception that is entirely recognised by all, each individual processes and senses pain in their own way. As there are different categories of pain, they each occur from different stimuli, leading to exert responses that are correspondingly different (Ellingson et al., 2013). The general consensus of pain would suggest that pain is a subjective sensation, it is said to be independent of the level of tissue damage that is present (Olesen et al., 2012). Although there are several studies that focus on the relationship there is between pain and exercise; a study has been done to use experimental pain to investigate the relationship to test their hypothesis (Ellingson et al., 2013). It is agreed that other studies may have proven to have great validity and reliability, this study disagrees that they sufficiently epitomise the etiology of exercise induced pain (Olesen et al., 2012). Exercise induced pain can occur from an accumulation of different noxious biochemicals (O'Connor, P.J. and Cook, D.B., 1999). To be able to test the relationship between pain tolerance during exercise and a trained endurance athlete, a replication must be made pain similar to exercise induced pain (Mauger, 2013). Having an in depth knowledge of pain will aid exercise specialists, scientists and coaches. It will allow them to be educated and have knowledge that will progress the performance for their athletes. This study (Ellingson et al., 2013) focuses on the relationship between traditional experiments of pain, exercise induced pain tolerance whilst participant perform a cycling timed trial. The hypothesis of this study is exercise induced pain tolerance would produce greater results of cycling performance than experimental induced pain. This study found there to be more variance with the timed trial cycling through tolerance induced pain than in pain tolerance and threshold. Research suggest that physical activity and in particular endurance training, can decrease pain perception (Scott and Gijsbers, 1981). This study (Ellingson et al., 2013) expresses that there are no previous studies using experimental pain when investigating the differences in pain perception between trained and untrained athletes. The study states that this can limit the understanding of the relationship between exercise and pain. My study will be able to develop an insight into how training levels will show a difference between pain tolerance and pain threshold.

Exercise is believed to have an influence on pain perception (Koltyn, 2002). Research shows that individuals who are healthy are considered to experience a decrease in pain sensitivity with exercise. Exercise induced hypoalgesia with and during high intensities during aerobic exercise are experienced as painful (Hoffman et al., 2004). Exercise is claimed to not only induce pain but also relieve pain.

Pain can be measured through a visual analog scale (VAS) (Hawker et al., 2011). VAS is a unidimensional measure of pain intensity which is greatly used over a diverse population of adults and those with rheumatic diseases (McCormack, de L. Horne and Sheather, 1988). The VAS scale was developed from the field of psychology where continuous visual analog scales were used. In terms of using this scale for pain intensity, it is anchored by 0 being ‘’no pain at all’’ to somewhat painful and 10 the highest number is unbearable pain. Verbal descriptors are placed beside each number so that there is a clear depiction of each score. Considering to be an economical and efficient test as the scale can be retrieved from public domain at no cost. This test does not require much training when administering as long as the participant is being supervised (Aitken R. C., 1969).There are little to no influences placed on the respondent who is using the scale as they are identifying which number they feel at that given point. Lower scores indicate lower pain intensity, higher scores greater pain intensity. The test is considered to be a reliable objective marker, can be tested and re-tested an example being at the beginning of a trial, during as well as at the end of the trial. The test is very simple and can be adapted accordingly depending to population and setting that it is being used for. However there a limitations to using this test such as with respondents who may suffer from cognitive impairments or older patients. In testing for pain tolerance and threshold the VAS scale has proven to be the best method to test a sample size group of 20.

https://onlinelibrary.wiley.com/doi/full/10.1111/sms.12659

https://kar.kent.ac.uk/62527/

https://www.peakendurancesport.com/endurance-injuries-and-health/muscles-and-tendons/managing-pain-athletes/

If there is sprain in an ankle or the hamstring muscle is torn, it hurts. For last four centuries, the scientific and medical world has sought diagnosing pain with the identification of the specific tissue of injury. For instance, there has been a proposition from philosopher René Descartes that the transmission of the pure pain sensation from a body that is damaged to a wholly separate mind and organ makes for striking at the same instant as bell that has been hanging at the end (Koltyn, 2002). Descartes made separation between the brain and the body, and it must be noted that even in the current time people usually distinguish between mental pain and the physical pain (Koltyn, 2002). In sport, especially, this is the case.

With the diagnosis’ classical view, there have been some problems. For example, nerve related extensive network supplies in the back with different tissues that makes them potentially the pain sources when injured (Manning and Fillingim, 2002). If the spinal tissue that is damaged is identified with the use, for instance, MRI, the explanation of pain is possible.

The MRI findings have some problems of severe damage to nerves or discs having association with pain experiences. The studies could not demonstrate a clear association between the pain of the patient and the majority of the damaged tissues observable on MRI. Moreover, about 40 percent of the people without a history of back pain are having damaged and abnormal spines over a single spinal level when MRI scanned it (Marcora, 2010). In the same way, the ultrasound investigation showing damage of the athletes with patella tendons that are painful necessarily does not directly corresponds to the magnitude of pain that the athlete experiences (Marcora, 2010).

Painful process

A theory that in 1965 was first proposed had been suggestive that spinal cord and human brain can inhibit or increase the pain signal’s transmission (Busch, 2007). Gate control theory had been ground breaking as it had a proposition of brain mechanism having modulating influence on what generates all pains rather than only mental pain. While originally the theory has been expanded and modified, essentially it has stood the test of time and 40 years of scientific research has supported it (Busch, 2007).

The pain generally is only pain and not separated into mental or physical compartments. The evoking of pain is not only pure sensory response, but an array of emotions and thoughts as well (Baker and Kirsch, 1991). The emergence of pain has been combined and integrated action of the pain system (Baker and Kirsch, 1991). This system is considered as the nervous system’s three separable parts, all of which does pain modulation.

Two athletes with identical experience of injury, but different pain (Sub heading)

The studies have shown that there is different response from the people to painful stimulation of similar levels (Norton et al., 2010). There is existence of difference not only to a painful stimulus of individual sensitivity, but also in the pain related perception and the way it is displayed by the individuals. Pain is associated with individualism, even though it is not the case with stimulus. While it cannot be ascertained with regards to the experience of others, the brains undergo activity that is similar when someone else’s pain is confronted with (Norton et al., 2010). This has been the root of empathy and to acknowledge that someone’s pain is important and normal.

The sensitivity of an individual to pain is explained in part by the individual’s genetic makeup, while studies that involve twins have indicated that it also has importance for the learned behaviors (Pollock et al., 1979). The pain’s division into mental and real cannot be helpful and the pain variation between two athletes having identical injury lies at pain system’s all levels. The same athlete even has variation in pain sensitivity under different circumstances and has the chance of becoming less significant during competition.

It should also be noted that in a society, different groups, which have been trained and untrained, may have significant difference in pain responses and this is applicable within sport. A study conducted four decades ago have shown that contact sport athlete have the ability of tolerating experimental acute pain for longer duration compared to non-contact athletes, while tolerating pain by both groups is more compared to the non-athletes (Pollock et al., 1979).

Pain sensitivity can also differ at different times with different people. This is the way variation of pain is displayed by the athletes. This is consistent with both between group of athletes and also between individuals from different sports.

How exercise levels affect pain tolerance and threshold?

In this study (Jones et al., 2014) exercise training is examined to determine whether it has an effect on exercise training. Cross-sectional studies have been carried out that provide evidence to show exercise can increase pain tolerance, not threshold (Ord, 2003).

How pain interacts with the brain?

In the study (Garland, E.L., 2012) pain is described as a biopsychosocial experience that is more than a mere nociception. This study provides an overview of neuroanatomic and neurochemical systems that highlight pain perception. “Pain is an unpleasant sensory emotional experience, associated with or potential tissue damage” (Merskey, H. and Bogduk, N., 1994). Pain perception comprises of a number of psychological processes, the cognitive meaning of the sensation and the behavioural reaction (Garland, E.L., 2012). As pain goes through a process of cognitive appraisal, the individual will knowingly or unknowingly make an evaluation of the meaning of sensory signals. There are sensory signals stemming from the body in which it will determine whether there is any actual harm of a potential. An example of this would be trained athletes such as an experienced runner. The construe pain as a “burn” which they feel in their muscles to be quite pleasurable. It called also be said that when pain is felt it can be seen as a sign of strength and increased endurance levels. In comparison to an untrained athlete who may view the sensation of pain as damage to their tissues rather than a physiological benefit. Some may agree pain intensity is reduced when it is perceived as controllable, even when the individual ensures or not the individual act of controlling the pain. Pain is often viewed as controllable and can be negatively associated with subjective pain intensity. (Ochsner and Gross, 2005). Along with interpreting pain as a sensation that is due to warmth or muscle tightness, this allows individuals to anticipate higher perceptions to control pain (Haythornthwaite et al., 1998).

(Seminowicz and Davis, 2006)

How pain sensors might impact fatigue?

Limitations?

There were a number of limitations whilst conducting this study. The design was created for ten trained and ten untrained participants, however it included 19 trained and11 untrained participants. I originally aimed to have an even number of male and female participants; in turn I had more male trained athletes. Another limitation is the dissertation topic is sports science based rather than therapy. I feel as though this has made it a bit more difficult as I do not directly relate to the sports science aspect of my course as much as therapy.

Hypothesis

Hypothesis 1: Trained athletes will have a greater pain tolerance and threshold than untrained athletes.

Hypothesis 2: There will be difference in pain tolerance and threshold for the untrained athlete.

Chapter III: Methods

It is proposed that we recruit 40 male and female subjects, aged between 18-44 years. Prior to participation, subjects were given a brief study on an information sheet. The information sheet described exactly what they subjects were asked to do. The brief also made the participant aware that all data collected was anonymous and that they will have the right to withdraw from the experiment at any time. Following this they were also asked to complete an informed consent form. The study took place in SSES physiology laboratory in the Medway Building. Subjects only had to report to the laboratory on 1 occasion.

Procedure

Participants visit the lab only on one occasion to complete an RPE clamp test. They were recruited using advertisement emailed through the university. They also had to be considerably healthy individuals with no chronic pain or disease.

The participants were also asked to complete an exercise questionnaire, this detailed the level of training they partake in. Also determining whether they are trained or untrained athletes. RPE clamp test was performed on a cycle ergometer watt bike. The participants were asked to maintain a perceived exertion which between 16 being “hard” and 17 “extremely hard on the Borg scale. This required them to ride the bike continually to gather their power output. The test would be terminated if the participants reached their volitional exhaustion or when their power output drops below 70% of their starting power. 70% of the participants power output was measured on the third minute of the trial. Prior to and after the test, the participants were given a 5 min warm up/ cool down. On every minute of the trial, the participant was asked to report their pain perception on a scale of 0-10.

This study was approved by the University of Kent research ethics and advisory group (REAG).

- Argue that vo2 max isn’t tested

- Participants only doing one visit

References

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