SC IENCE OF MAN V HORSE

Transcription

1 SC IENCE OF MAN V HORSE

2 AN ANALYSIS OF HOW A HUMAN MAY BE ABLE TO RUN FASTER THAN HORSES IN A LONG ENDURANCE EVENT. INTRODUCTION The annual Man vs Horse Marathon (MVH) takes place across the demanding terrain of Llanwrtyd Wells, Wales. The typically 22 mile (35 km) race has produced just two Homo sapien winners in its 35 year history. This article aims to explore the contributing factors that may allow man to triumph. Firstly, the results history of the race will be analysed to identify the required endurance capacity of any potential human victor. Secondly, a physiological and biomechanical comparison between the two species will be made to identify strengths and weaknesses of each. Thirdly, the environmental conditions of the race itself will be considered including an analysis of the course route and potential weather conditions that may increase the probability of a human athlete succeeding. Finally, this article will aim to identify possible performance enhancing strategies for athletes to use in their training to enhance their physiological responses.

3 DISCUSSION The first athlete to win this famous race since its creation in 1980, was Huw Lobb in 2004, with a time of 2:05:19. Florian Holzinger repeated the feat in 2007 with a time of 2:20:30. However from 2008 to 2013 the time difference between athlete and horse increased each year and is currently at 19 minutes and 56 seconds in favour of the horse. Since the course alteration in 1982, the mean winning equine time is (± 17.4) minutes whilst the mean winning individual running time is (± 11.0) minutes. Winning times vary considerably depending on the course route and weather conditions on race day. However, through using the mean winning individual running times over the past 33 years, we would suggest that runners would need a marathon time of less than 2:40:00 (this equates to a 3:48 min/km or 6.07 min/mile pace) to have a good chance of being the fastest athlete. To have a good chance of beating the fastest horse, the fastest athlete would need a marathon time of less than 2:20:00 (this equates to a 3:20 min/km or 5:21 min/mile pace).

4 Figure 1. Fastest winning times (minutes) by horse (blue) and athlete (red) since Before discussing potential methods an athlete may be able to use to enhance their chances of beating the horse, it is important to first understand the physiological strengths of horses in comparison to humans. Table 1 shows a comparison of key race statistics.

5 Table 1. Comparison of key physiological performance parameters between e lite endurance runners and e lite endurance horses. Parameter Horse Human Max HR (bpm) Age Stroke Volume (l) Maximum Cardiac Output (l/min) Total Lung Volume (L) 55 6 VO2 max (ml/min/kg) Lactate Tolerance (mmol/l) 30 4 Maximal Haematocrit (%) As Table 1 shows, horses have a huge advantage over humans in terms as their physiological characteristics, allowing them to deliver and utilize oxygen to the working muscles very efficiently in comparison to humans. Elite horses are able to reach maximum running velocities of 80 km/h in comparison to a mere 44 km/h for Usain Bolt. There is large difference at first glance at the physiological capabilities between humans and horses. However it is possible for a human to beat the horse, as both Huw Lobb and Florian Holzinger proved.

6 Despite the physiological advantages horses possess over humans, humans do possess a biomechanical advantage over horses. Both humans and horses exploit the mass-spring mechanism when moving. Collagenrich tendons and ligaments in the leg store elastic strain energy during the initial support phase of a gait and then release this energy in the propulsive phase of the stride through recoil. This helps reduce the metabolic cost of transport in both species. Horses have a U-shaped metabolic cost of transport curve when galloping, which means that they have a narrow range of preferred speeds to minimize metabolic cost. In comparison, humans have a relatively flat shaped curve, allowing them to continually adjust running speed without a change of gait or a metabolic cost over a large range of speeds (Figure 2). Figure 2. Comparison of the metabolic cost of transport (COT) in humans and horses. Dotted rectangles represent the mostenergy efficient speeds. Source: Bramble. D., & Lieberman. D. (2004).

7 Humans also increase their running speed through increasing their stride length rather than their stride rate (speed = stride length x stride rate). As a result of this, humans keep relatively long ground contact times which helps reduce the metabolic cost of transport. In contrast, horses tend to increase their stride rate greater than humans, which requires a greater metabolic cost to oscillate their long legs. It is believed that humans biomechanical running style has evolved to be ideally suited for long distance running due to the hunter-gatherer origins of Homo sapiens, allowing them to run many mammals to exhaustion before capturing them. This biomechanical advantage over long distances is also aided by a high percentage of slow twitch muscle fibres. Elite marathon runners have been shown to have more than 80% of slow twitch muscle fibres. These contract more slowly than fast-twitch muscle fibres, are more efficient in utilizing oxygen and have a greater resistance to fatigue, making them ideal for long distance running. In comparison, horses tend to be more predominant in fast twitch muscle fibres which fatigue faster, are less efficient at utilizing oxygen and therefore are less suited to endurance riding.

8 A potentially significant biomechanical difference between horses and humans when running or galloping is that humans are able to run at a higher percentage of their maximum running velocity at the same gradient decline compared to horses. Whilst horses reach their maximum running velocity at 0% gradient, humans actually run fastest on a decline of around % (Self et al., 2012). This is due to potential energy from a decrease in height from centre of mass being absorbed by the muscoskeletal system. In comparison, it is thought that horses run slower at a decline due to the anatomical nature of their front legs which limits weight support and stability. In contrast, both humans and horses move slower when running on an incline due to having to perform mechanical work to raise their centre of mass against the effects of gravity. Evidence comparing the percentage decrease in speed as incline increase between the two species suggests that horses may actually slow down marginally less quickly when running up the same gradient incline compared to humans. It is therefore vital that runners in MVH ensure that they take advantage of the long and steep descents in the race to regain time lost over the flat. The 2015 MVH route is summarised in Table 2 and Figure 3. Horses Athletes Total distance (km) Total Ascent (m) Total Descent (m) Climb 1 Distance of climb (km) Climb 1 Average gradient (%) Climb 2 Distance of climb (km) Climb 2 Average gradient (%) Climb 2 Distance of climb (km) Climb 2 Average gradient (%) Table Course breakdown for horses and athletes.

9 Figure 3. Route profi les for horse rider and runners.

10 One factor that may play a significant role in allowing an athlete to beat the horse is the effect of the race-day weather conditions. Chemical energy in the form of ATP is transformed into mechanical energy in the form of locomotion with energy lost from this system in the form of heat energy. To dissipate this heat from the body, in both humans and horses, the hypothalamus in the brain stimulates blood vessels near the skin to dilate to allow heat to leave the body through sweat and convection. Around 20% of chemical energy in a both species is converted to mechanical energy, with the majority of the remainder transformed into heat energy. However, horses are less efficient at maintaining their core body temperature compared to humans as their surface area to body mass ratio is 40% lower, lowering their ability to dissipate heat as quickly. Dehydration of around 2-4% of body weight during endurance exercise has shown to significantly impair performance in humans. In comparison, a study amongst six horses completing prolonged endurance exercise, showed an average weight loss of 6% at a 21 C despite regular access to water. Horses struggle to maintain their core body temperature during prolonged endurance exercise and with sweat rates approaching litres per hour means they often suffer from heat stress which negatively influences their performance. In both 2004 and 2007 (the only 2 human triumphs) the weather conditions were said to be hot suggesting that weather conditions may be a key determining factor in performance of the horse. Whilst horses may struggle to prevent dehydration, athletes are able to prevent dehydration limiting their performance on race-day. The best method to determine an athlete s sweat rate during long endurance exercise is: 1. Weigh athlete before a long run with minimal clothing (Pre) (kg) 2. Weigh fluids consumed during exercise prior (Fluids) (kg) 3. Weigh athlete immediately post-exercise with exactly the same clothing as pre-exercise (Post) (kg) 4. To calculate athletes sweat loss: (Pre Post) + (Fluids)

11 By using the above method, runners in MVH can ensure that they consume the correct amount of fluid during the race to prevent dehydration occurring and thereby gaining an advantage over the horse. Long endurance events in a hot environment will not only result in a high volume of sweat but will also result in the loss of important electrolytes. Of particular importance is the loss of sodium. Carrying out vigorous exercise in a hot environment, an athlete may lose more than 1000 mg of sodium per day through perspiration. Sodium is necessary to maintain homeostasis and is vital in the repolarisation-depolarisation of muscular contractions, therefore a combined loss in sweat loss and a loss in sodium from the blood stream will result in a reduced blood volume and therefore a lower blood pressure, reducing the ability of the cardiovascular system and impairing performance. It is therefore advisable that athletes taking part in MVH ensure they preload on sodium (Coles & Luetkemeier., 2005) before the race to ensure a sufficient electrolyte balance throughout the race. A good guideline to follow would be to consume 1500 mg of sodium per litre of water around 2 hours before the race. Although riders are likely to supplement their horses before and during the race, their sodium losses are significantly higher than humans and therefore it is difficult to maintain their electrolyte balance. Horses trotting for 45 km in ambient conditions have been shown to lose more than 80 g of sodium (Kingston et al., 1999). Through using these methods, athletes can ensure that their performance is not inhibited by high temperature and high humidity on race-day, giving them a significant advantage over horses. An effective training programme should also include a balanced diet and appropriate meals pre and post training. Recovery nutrition has the aims of replenishing muscle and liver glycogen stores, replacing fluid and electrolytes lost in sweat, synthesising new muscle protein, stimulate haematopoiesis, and allowing the immune system to cope with the damage caused by exercise. Eating appropriately post exercise will help to reduce recovery time, maximise muscle repair and replace energy stores lost during prolonged exercise. Peanut butter is an ideal post-exercise food source following long endurance training. Whole Earth Original Peanut Butter contains 26.3 g of protein per 100 g. Long endurance exercise causes an increase in catabolic processes within the muscle but recovery results in an increase in anabolic processes. Consuming protein post-exercise (around 15-25

12 g within the first hour) is thereby crucial to help maximise protein synthesis in the muscle fibres to reduce recovery time. Peanut butter is an excellent source of protein for this purpose. Research (Ivy et al., 2008) suggests that consuming protein with carbohydrates following endurance exercise, enhances the rate of glycogen (energy source) replenishment. By combining the two energy sources, blood glucose levels rise less rapidly, promoting the liver to convert glucose to glycogen instead of fat. This is important to ensure energy stores are maximised as quickly as possible and to allow the body to recover appropriately before training again. There are several supplementation methods that runners competing in MVH can use either in training or on race-day to enhance their performance and reduce their race time. One of these is carbohydrate loading. This is a strategy involving manipulation of training and nutrition in the week prior to the MVH to maximise muscle glycogen stores. It is recommended that athletes consume a high carbohydrate diet (7-12 g per kg of body weight) within 4 days of the race whilst tapering their training regime. This method has been shown to increase muscle glycogen stores by up to 50% and will allow runners to maintain their optimal race pace for a longer period time by delaying the body s need to utilize fat stores which are less oxygen efficient and are slower to break down. It is advisable that athletes using this method should trial it during training at least 3 times before raceday to make you they are comfortable with the process. Nitrate supplementation in the form of beetroot juice has been shown to significantly improve running performance. Nitrate reduces the oxygen cost of submaximal exercise by reducing the ATP cost of muscle contraction. Therefore the fuel efficiency of muscles is increased, allowing athletes to spare fuel stores for later in the race. It is recommended that runners should consume a 0.5 litres of beetroot juice 2.5 hours before a race to see optimal benefits (Lansley et al., 2011).

13 CONCLUSION Despite horses possessing a substantially greater physiological capacity over humans; there are areas in which athletes competing in MVH can exploit weaknesses of the horse. Humans have a biomechanical advantage over horses when running downhill and have been evolutionarily geared towards endurance running. By following the correct hydration and sweat replacement strategies, humans can also ensure they are not limited by the environmental conditions as horses are likely to be. There are also potential nutritional strategies that a human can utilize in training and on race day to maximise their running capacity, including consuming sufficient protein and carbohydrate post training, carbohydrate loading and nitrate supplementation. REFERENCES Bramble. D., & Lieberman. D. (2004) Endurance running and the evolution of Homo. Nature, 432, Coles, M.G., & Luetkemeier, M.J. (2005) Sodium-facilitated hypervolemia, endurance performance, and thermoregulation. International Journal of Sports Medicine, 26, Ivy, J. L., Ding, Z., Hwang, H., Cialdella-Kam, L, C. & Morrison, P.J. (2008) Post exercise carbohydrate-protein supplementation: phosphorylation of muscle proteins involved in glycogen synthesis and protein translation. Amino Acids, 35, Kingston, J.K., McCutcheon, L.J., & Geor, R.J. (1999). Comparison of three methods for estimation of exercise-related ion losses in sweat of horses. American Journal of Veterinary Research, 60, Lansley et al. (2011). Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. Journal of Applied Physiology, 110, Self, Z.T., Spence, A.J., Wilson, A. (2012). Speed and incline during thoroughbred horse racing: racehorse speed supports a metabolic power constraint to incline running but to decline running. Journal of Applied Physiology, 113,