Accordingly, the first group improved and the second group actually did worse.
These findings were corroborated by Duncan and colleagues (Duncan et al. 2009). In this study, 12 athletes were given caffeine alongside a placebo and tested in anaerobic cycling to failure. The athletes were split into four groups again, in every combination: 1) given caffeine and told it was caffeine 2) given caffeine and told it was placebo 3) given placebo and told it was caffeine 4) given placebo and told it was placebo. Participants were provided with literature reviewing the published research on caffeine and high intensity exercise performance and detailing anecdotal evidence relating to caffeine use among elite team game performers. This study was also extremely thorough in regards to procedures, setups in timing so as not to interfere with athletes’ circadian rhythms and measuring of blood lactate levels. In concluding this study, peak power output, mean power output and rating of perceived exertion were all significantly higher in the Caffeine trial, and significantly lower in the placebo trials.
All these studies and more were summarized in a metanalysis (Bérdi et al. 2011) that concluded mixed results, but an overall positive trend, finding that placebos have a small to moderate effect on sports performance. The positive values in these studies would seem to indicate that there are some practical values to be gained, but methodological problems in the studies question their validity. For example, one problem is comparing the placebo group to its own baseline may lead to overestimation. Second, outside the laboratory setting, with a host of other factors involved, equipment, opponents, pressure and judges could influence the placebo effect. Third, the literature shows a high degree of variability showing the effect varies widely from person to person. If the placebo effect can be thought of as a way to mobilize psychophysiological reserves, these reserves could be different from one individual to another.
Aside from strictly athletics, the placebo effect has been observed in all manner of outward physical changes (Krum and Langer, 2007). One study took a number of female hotel cleaning staff and split them into two groups. One group was told that their work meets the required daily exercise guidelines set forth by the Surgeon General and the other group was told that they do not. Over the next four weeks, without a change in behavior, a decrease of weight, blood pressure, and body fat were observed in the first group. The term placebo effect is typically used in a medical context, but this phenomenon occurs when subconscious beliefs cause physical changes in any situation. Subjects in contact with fake poison ivy developed rashes and people undergoing fake knee operations experienced real swelling in the tendons and ligaments (Krum and Langer, 2007). It is quite possible that the well-known benefits of exercise in addition to the actual exercise itself can result in better health.
Fatigue can be defined as the fall of force or power in response to contractile activity (Allen et al, 2008). Fatigue is an incredibly complex concept with both physical and mental components. In regards to the physical, it is an incredibly complex process. On the cellular level, fatigue occurs when Adenosine Triphosphate (ATP) consumption exceeds production, causing changes in certain metabolites (Allen and Trajanovska, 2012). The concentration of inorganic phosphate increases, substantially impairing myofibrillar performance. But fatigue also has a mental component. It could be argued that fatigue is a brain derived emotion (Noakes, 2012), though ultimately the situation is more complicated and explained in more detail in the following sections.
There are four models of fatigue: 1) the traditional model: the physical 2) the energy supply/energy depletion model 3) the biomechanical model 4) the central governor model. The traditional model is cardiovascular/anaerobic model that has been the standard model of fatigue most widely accepted in the literature for the last 90 years. Essentially, the model holds that fatigue occurs when the cardiorespiratory system’s ability to pump oxygen to the exercising muscles is exceeded by the demand for oxygen, prompting a shift into anaerobic metabolism. This model has existed since the foundational paper of (Hill, 1925), where Hill proposed that the three types of fatigue which were fatigue after quick explosiveness, exhaustion after moderate intensity over a period of time, and general wear and tear. Since then, volumes of research have been published on the factors that cause fatigue. The three factors that cause fatigue are maximal oxygen consumption (VO2 max), the lactate threshold’ and efficiency (the speed at which one can use the consumed oxygen) (Joyner and Coyle, 2008). This model has been challenged with the criticism that if this model is true, then the heart would be the first to be affected by fatigue. But it is not; that honor is reserved for the muscles. Opponents of this model also argue that psychological factors play a role in fatigue.
The biomechanical model supply is also a cousin to the previous model and this model proposes that fatigue is not caused by the failure to deliver oxygen, but rather the failure to deliver ATP (Noakes, 2000). It was Hill himself who wrote that it was ultimately an inability to deliver energy to the muscles that resulted in fatigue (Hill, 1927). It is generally agreed that middle and long distance running is dependent on this energy delivery. Therefore, according to this model, the purpose of training should be to improve the energy systems and their efficiency. The criticism for this model is that it is only hypothetical, and has not been proved enough. Fatigue will physically always appear on the surface to be an ATP problem. To truly prove this model, the other models need to be disproved.
The central governor model is a model involving muscles with respect to physics. The model holds that muscles operate like springs and produce torque (Noakes, 2000). The more efficient the muscle is, the more it behaves like a spring producing less torque and being more elastic. This would slow down accumulation of the metabolites and the rise of temperature, both of which cause fatigue.
This particular model has become popular and hotly debated in recent years. The thesis of this model is that there is a central subconscious regulator that employs fatigue when the myriad systems of the body are in danger, thereby protecting the whole body and maintaining homeostasis. Thus, fatigue is a conscious sensation. The mechanism through which the fatigue is induced is because of the failure of the central nervous system. Noakes’s (2000) study found the following:
This model holds that the brain concentration of serotonin (and perhaps other neurotransmitters, including dopamine and acetylcholine) alters the density of the neural impulses reaching the exercising muscles, thereby influencing the rate at which fatigue develops, especially during exercise. (p.15)
An extension of this model is the concept of teleoanticipation (Ulmer, 1996). The central governor attempts to judge the end time of the exercise after gathering signals, and then perceived effort increases linearly until it peaks at the completion of the exercise. As if forecasting, the brain calculates the exercise duration that can be maintained without disrupting homeostasis, then produces a sensation of exertion. A study was conducted (Noakes et al. (2004) that tested Rating of Perceived Exertion (RPE) as subjects engaged in timed trials. The result showed that RPE linearly increased until peaking at completion of the exercise. The results were verified with another study three years later (Eston et al. 2007). Another study (Crew, 2008) substantiated this claim using timed cycling trials. Detractors of this model point out that the model is internally inconsistent, unnecessarily complex, and biologically implausible (Marcora, 2008). The extension of the model with the RPE is unnecessarily complex, as well as the fact that the central governor would not need to induce a conscious sensation of fatigue, seeing as it already has control over the nervous system and muscle recruitment. Critics also attack the methodologies of the studies in support of this model.
The two important concepts involved in this study are the placebo effect and fatigue. The placebo effect is largely the context and environment of the treatment or drug being administered. When used with athletes, the placebo effect has been remarkably useful. Fatigue has both a physical and psychological component. The traditional model of fatigue is purely physical, but has been recently challenged by the more psychological models.