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ˇ Equine Cardio Conditioning Articles
| CONDITIONING SPORT HORSES Presented by Dr. Hilary Clayton at the Michigan Veterinary Conference, January 28th, 1999
Introduction Preparation of a horse for competition involves
a combination of training (schooling) and conditioning. Training
develops neuromuscular coordination and mental discipline. Conditioning
induces physiological and structural adaptations that maximize
performance and maintain soundness. Equestrian sports encompass a
diverse range of activities and an equally diverse range of conditioning
methods are needed to address the specific requirements of different
sports. The best results are obtained when conditioning workouts are
tailored to the age and training history of the horse, the nature of the
sport, the level of competition, and previous injuries. This paper
provides background information for advising trainers regarding
development of a conditioning program for a specific horse. There are 3 distinct, but complementary, areas of conditioning:
The volume of work performed over a period of time depends on the frequency, intensity, and duration of the workouts. These variables are manipulated to improve, maintain or reduce the horse's fitness level. If a horse performs the same exercise every day, he reaches and maintains a certain level of fitness but does not continue to become fitter. Improvements in fitness result from gradual increases in the volume of exercise; after each incremental increase the new workload is maintained over the next few workouts to allow the body to adapt before another increase is applied. The alternation of an increment in the workload with a period of adaptation is known as progressive loading. Conversely, if regular exercise ceases or is reduced in volume, the exercise induced changes are reversed. The short term effect of a strenuous workout is to produce microscopic tissue damage which usually heals within 2 days. Through repeated cycles of damage and repair, the tissues adapt to the regular pattern of exercise. In the long term, these adaptations enhance the horse's ability to produce energy is enhanced and the supporting structures (hoof, bone, cartilage, ligament and tendon) are strengthened. Insufficient exercise fails to produce a beneficial adaptation, but too much exercise or insufficient recovery time between workouts leads to overloading injuries. By performing different types of exercise on successive days and by allowing easy days between strenuous workouts, the risk of overloading injuries is reduced. The body tissues vary in their rate of adaptation to exercise. In horses, the cardiovascular and muscular systems respond rapidly, with significant changes being produced in only a few weeks (Knight et al. 1991; Lovell and Rose 1991). In contrast, the supporting structures in the limbs adapt more slowly over a period of many months. The aim is to condition all body systems to withstand the increasing level of exercise without causing any of them to fail. Consequently, in the early stages, the workload must be well within the horse's rapidly increasing cardiovascular capacity to avoid overloading injuries in the tendons and ligaments. Little cardiovascular fitness is lost during a short lay-off of a month or less (Essén-Gusstavsson et al. 1989; Butler et al. 1991), but after a period of inactivity the workload should be reintroduced gradually over several days. If the horse has been off for longer than a month, it is reasonable to assume some loss of cardiovascular fitness. A more significant concern is the rapid loss of strength in the bones, ligaments and tendons. It is not unusual for bucked shins to occur when young Thoroughbreds return to training after a relatively short lay off, for example due to a respiratory virus (Moyer and Fisher 1992). The best advice is to err on the side of caution and progress slowly when the horse returns to work. A reasonable rule of thumb is to allow a month of reconditioning for every month off. Cardiovascular conditioning enhances the horse's ability to produce energy for muscular contraction at a sufficient rate and using an appropriate metabolic pathway for the sport. Regardless of the horse's eventual occupation, the initial stage of conditioning is based on a period of low intensity aerobic exercise, known as long slow distance (LSD). In a horse that has recently been started under saddle, an appropriate frequency of exercise is to be ridden every second day for about 10 min mostly at walk. Over a period of 6-12 months, progressive loading is used to increase the volume of work gradually by increasing the duration, intensity or frequency of exercise. The objective of the LSD phase is to prepare the horse to cope with 45-60 min of easy exercise at a walk, trot, and canter, at an average speed of 5-6 mph, including 2-3 min periods of cantering at moderate speeds 10-12 mph. Upon completion of the LSD phase, it is time to evaluate the competitive objectives in relation to the conditioning requirements. Horses that will be used for pleasure riding or for low intensity sports (e.g. low level dressage, children's hunter) need only maintain their present level of fitness by doing aerobic workouts twice a week between schooling days. For horses that will compete in endurance sports, the progression is from LSD to a more rigorous aerobic program, in which the prime consideration is to build the duration of exercise at a moderate speed. On the other hand, horses that will specialize in power and speed events (jumping, draft horse pull, Quarter Horse racing) train these attributes by including some short duration, high intensity drills. For sports requiring an intermittent pattern of energy expenditure (eventing, combined driving, polo), a combination of conditioning methods is used to maximize the aerobic capacity while maintaining sufficient power for bursts of high intensity exercise. The exercise intensity dictates the rate of energy expenditure. The horse's heart rate is a good indicator of exercise intensity when it is in the range of 140-210 beats/min. Below 140 beats/min, psychogenic factors have a marked influence, whereas above 210 beats/min the heart rate levels off as it approaches its maximal value. Speed is a major determinant of exercise intensity: the faster a horse travels on level ground, the more energy is expended and the higher the heart rate. At constant speed, exercise intensity can be increased by working the horse with more impulsion, incorporating gradients, adding extra weight, or working on a loose, deep surface. At low to moderate exercise intensities most of the energy is produced in the muscles by aerobic metabolism, but at higher intensities anaerobic metabolism is also utilized. The anaerobic threshold is the intensity at which anaerobic metabolism starts to play an increasingly important role and at which lactate starts to accumulate. Further increases in exercise intensity are associated with a greater reliance on anaerobic metabolism and a consequent rise in muscle and blood lactate. When the objective is to increase cardiovascular fitness, workouts are initially performed 2 or 3 times per week. In the later stages of the program, however, it may be necessary to reduce the frequency so that the quality (intensity) and quantity (duration) of the workouts can be maintained while still allowing sufficient time for tissue repair between successive workouts. This reduction in frequency applies particularly to endurance horses that are being prepared for rides longer than 25 miles and to eventers and combined driving horses competing at or above the intermediate level (Clayton 1991). To maintain the desired level of fitness, workouts are performed once or twice a week at a constant exercise intensity. Fitness may be lost if the workouts are performed less frequently than once per week or if the regular workload is reduced. Most conditioning programs comprise a mixture of continuous training and interval training. Continuous training (CT) implies a fairly constant intensity of exercise over a period. This is in contrast to interval training (IT) in which short periods of exercise (works) alternate with recovery intervals that allow partial, but not complete, recovery of heart and respiratory rates, and partial lactate removal from the muscles. A series of alternating works and recovery intervals is called a set, and successive sets are separated by longer set rests. The great advantage of interval training is that, by subdividing the work into a series of short bursts, the horse is able to perform more work per day than in a single bout of CT, while the incidence of fatigue-related injury is reduced by the partial-recovery intervals. The horse is kept moving during the recovery intervals to maintain circulation to the muscles, and enhance lactate removal by using it as an energy substrate for the on-going aerobic exercise (Marlin et al. 1987). Methods of increasing the workload in an IT program include raising the intensity or duration of the workouts, reducing the duration of the recovery intervals or set rests, increasing the number of workouts per set or increasing the number of sets. A common misconception is that IT consists of a series of flat out bursts of speed. On the contrary, IT is appropriate for both aerobic (endurance) and anaerobic (power and speed) conditioning, and the intensity of the IT workout ranges from moderate to high according to the conditioning objectives. A work:recovery ratio in the range of 2:1 to 1:2 is used for aerobic IT, compared with 1:5 to 1:6 for anaerobic IT in which a relatively longer recovery period is needed for removal of lactate from the muscles after the more intense bouts of exercise. In the later stages of the conditioning program, the nature and intensity of the conditioning workouts should simulate the competitive situation in their reliance on aerobic and anaerobic energy production. An IT program is formulated in which the exercise intensity and the work:recovery ratio mimic that of the competition. The duration of the workouts and recovery intervals may be variable if this simulates the competitive situation. For sports that involve galloping at speeds above the anaerobic threshold, heart rates greater than 170 beats/min are achieved either by working the horse at fast speeds or by using uphill gradients, which reduce concussion on the limbs. Some horses get unduly excited by the stop and start routine of conventional IT and often respond better to speed play (Fartiek training), in which brief sprints are superimposed on a background of slower exercise. Speed play is particularly useful in preparing for sports that have an intermittent pattern of energy expenditure. Workouts are performed at the gait used in the sport: the canter and gallop are used for eventers and polo ponies, whereas the trot is more appropriate for combined driving horses. Both gaits are used for endurance racers. When speed play is introduced, the sprints are short, they are separated by relatively long recovery periods at a slower speed, and the accelerations and decelerations are gradual in nature. Progressive loading is accomplished by increasing the number, speed or distance of the sprints in accordance with the sport-specific requirements. When a large aerobic capacity is the primary requirement an effective technique is to work the horse in the aerobic-anaerobic transitional zone for brief periods: 15-20s bursts at a heart rate of 170-180 beats/min are separated by 40-60s of slower cantering at a heart rate of 130-140 beats/min. This is a good technique for raising the anaerobic threshold and for bringing the horse to a fitness peak in sports like eventing. Each time the horse changes speed or direction, energy is used to overcome the body's inertia. Movements that use a lot of energy in overcoming inertia include accelerating, decelerating, turning abruptly, and jumping. Overcoming inertia accounts for a significant proportion of the total energy expenditure in sports like polo, cutting, reining, show jumping, eventing, and driving. Preparation for these sports includes inertia drills based on rapid accelerations and decelerations, sharp turns, or multiple jumping efforts in quick succession, with the drills being repeated in an IT format. Strength training improves the strength, power or endurance of the muscles. It is often neglected in preparing the equine athlete and, although horses can succeed without strength training, it is probable that many fail to reach the pinnacle of success through lack of strength. Improvements in muscular strength enhance performance and reduce injuries through stabilizing the joints more effectively. The importance of joint stability should not be underestimated; in human athletes it has been suggested that more than half of the injuries in sports could be prevented by proper strength training (Riley 1977). However, irrelevant muscle mass acts as a handicap when a high ratio of strength to body mass is required (jumping) and when extra energy must be expended to transport excess body weight over a distance (endurance racing, eventing). Therefore, strength training, like cardiovascular conditioning, should be sport specific. Strength is the force produced in a single maximal effort; power is the rate of force generations; and endurance is the ability to perform repeated submaximal contractions before local muscular fatigue occurs. It is important to determine whether the primary requirement in a sport is for muscular power or muscular endurance, and to base the strength training program on exercises that simulate the range and speed of joint motion and the neuromuscular activation patterns used in competition. Muscular power is the prime requirement in sports that call for explosive bursts of activity, as in taking off over a jump or accelerating rapidly from a standing start. For these activities, high intensity strength training is used, with a relatively small number of repetitions of the exercise. Progressive loading is accomplished by increasing the intensity rather than the duration of exercise i.e. by making the muscles work harder not longer. Muscular endurance is required when submaximal contractions are performed repeatedly, as in many of the dressage movements, such as the piaffe. Strength training for these sports is performed at a lower intensity, but a larger number of repetitions are performed. Progressive loading is achieved by increasing the number of repetitions. In the early stages, strength training workouts are performed 3 times a week on alternate days, which balances the need for sufficient muscular stimulation with enough rest for tissue regeneration. As strength training progresses to a higher intensity, the frequency is reduced to twice weekly, which allows a longer recovery period between sessions. Once per week is sufficient for maintenance of muscular strength. Because horses cannot be trained to lift weights or work resistance machines, we must be somewhat innovative in devising strength training exercises that load the relevant muscle groups in an appropriate manner. Gradients, gymnastic jumping, and sport-specific movements repeated in an IT format with a work:recovery ratio of 1:6 have been used to good effect. Gradients are the foundation of equine strength training. Steep uphill gradients develop propulsive power in the hindquarters for galloping and jumping. When an IT format is used for strength training on steep, uphill gradients, the ascent is the work and the descent at a walk is the recovery. A gradual downhill gradient is useful for strength training in sports that call for a high degree of collection because the effort required to establish and maintain collection on a slope is exaggerated compared with working on the flat. In negotiating a steep downhill slope the horse relies heavily on eccentric muscular contractions, which are likely to cause some post exercise muscle soreness. This is minimized by a good warm down with plenty of suppling exercises. A certain amount of downhill conditioning at a trot and/or canter is necessary for horses that are being prepared for eventing, combined driving and endurance racing. However, this type of exercise should be limited in amount because the associated joint trauma precipitates the development of arthritic changes. The use of gymnastic jumping for strength training is based on jumping a grid of fences in an IT format: jumping through the grid is the work, and the return to the start of the exercise at a walk or trot is the recovery interval. Variables in the construction of a jumping grid include the height, width and number of fences, and the distance between them. For sports that call for a high degree of collection, it is appropriate to use small fences (1˝ -2' high) set at bounce or one-stride distances. During each landing and take off the joints of the hind limb flex then extend in a similar manner to that of weight-bearing during collection. Progressive loading is accomplished by increasing the number of fences or by increasing the number of repetitions in a set, while maintaining the small size of the fences. When the development of muscular power is of prime importance, the grid consists of fewer fences with larger dimensions. This type of gymnastic is particularly appropriate for jumpers and eventers. More difficult distances between the fences are used for highly specific strength training, but repetitions of the exercise should only be introduced after the horse has mastered the technical skills and can perform the exercise in good form. Another method of strength training is to repeat the movements of the sport in an IT format. For example, in dressage horses multiple repetitions of the steps of piaffe or passage can be used to improve neuromuscular coordination and strengthen the muscles in a highly sport-specific manner, provided the movement is performed correctly. If the technique is incorrect, the wrong muscles are trained and the results are deleterious to performance. The trainer must guard against the horse's natural tendency to use compensatory actions when the muscles start to fatigue, which is counterproductive to strength training. As soon as fatigue occurs, the strength training exercises are stopped and the horse is warmed down. The key to using the movements of the sport successfully as a strength training aid is to perform sufficient repetitions to stimulate a muscular response without sacrificing good technique. Suppling exercises increase the range of joint motion by reducing tension and resistance in the muscles or connective tissues (tendons, ligaments, joint capsule), and they should be a part of the daily routine throughout the horse's athletic career. Suppleness enhance the horse's athletic ability: for example, in jumping horses flexibility in the shoulders, elbows and carpal joints is necessary for the horse to snap up and fold the front limbs over a fence. A large range of joint motion also allows the horse to apply forces against the ground over greater distances and longer periods, producing increased velocities and accelerations. A greater range of joint motion also facilitates shock absorption, resulting in a reduced incidence of injuries. On the contrary, a limited range of motion is associated with an inferior ability to generate momentum and absorb impact forces. The structure of tendons and ligaments is such that high force, short duration stretching at low temperatures favours elastic deformation, which is a temporary change that is reversed when the force is removed. Permanent lengthening of the ligaments and tendons is encouraged when a low force is applied for a longer duration to tissues that are warm. Furthermore, when the tissues are cold, the fibres are relatively friable and susceptible to tearing. When the tissues are warm, the fibres become more pliable and the risk of tearing (strain) is reduced. Therefore, a warm-up period should precede suppling exercises. Suppling exercises are described as passive or dynamic; both types are useful and effective in horses. Passive suppling involves a slow, controlled movement of a joint to the limit of its range of motion through the application of an external force. Because the force is applied slowly, it avoids stimulating the myotatic stretch reflex, which would result in muscular tension opposing the stretch. The stretched position is held for 20-30 s to enhance permanent elongation. Passive suppling is used to encourage long term increases in the range of motion, particularly in the horse's neck, shoulder, and hips; to promote relaxation; and to reduce post exercise muscle soreness. Dynamic suppling involves rotating a joint rapidly through its range of motion as a result of muscular contraction or weight-bearing, as occurs during locomotion. Examples of dynamic suppling exercises that are part of the normal schooling routine include turns, circles, voltes, and lateral movements (leg yielding, shoulder in/out, haunches in/out, half pass). These movements promote the sliding motion of the scapulae across the chest wall; flexion, bending, and rotation of the vertebral column; and rotation of the joints of the hind legs through a wide arc of motion. Other exercises that have a dynamic suppling effect include walking and trotting over raised rails, gymnastic jumping, working on steep gradients and riding through shallow water or snow. All of these exercises are associated with active limb flexion and extension through a wide range of motion. Dynamic suppling exercises should be a part of every workout. The warm-up starts with an initial period of forward movement to increase the temperature of the tissues, after which dynamic suppling becomes an integral part of the warm-up and the workout. The objectives are to promote the full range of joint motion during the workout and to prevent muscle stiffness after exercise by continuing the suppling exercises during the warm down. Butler, P.J., Woakes, A.J., Anderson, L.S., Smale, K., Roberts, C.A., and Snow, D.H. (1991) The effect of cessation of training on cardiorespiratory variables during exercise. In: Equine Exercise Physiology 3. Eds: S.G.B. Persson, A. Lindholm and L.B. Jeffcott. ICEEP Publications, Davis, California. pp 71-76. Clayton, H.M. (1991) In: Conditioning Sport Horses. Sport Horse Publications, Saskatoon, Canada. Essén-Gusstavsson, B., McMiken, D., Karistrom, K., Undholm, A., Persson, S. and Thorton, J. (1989) Muscular adaptations of horses during intensive training and detraining. Equine vet. J. 21, 27-33. Knight, P.K., Sinha, A.K. and Rose, R.J. (1991) Effect of training intensity on maximal oxygen uptake. In: Equine Exercise Physiology 3. Eds: S.G.B. Persson, A. Lindholm and L.B. Jeffcott, ICEEP Publications, Davis, California. pp 77-82. Lovell, D.K. and Rose, R.J. (1991) Changes in skeletal muscle. In: Equine Exercise Physiology 3. Eds: S.G.B. Perssoin, A. Lindholm and L.B. Jeffcott. ICEEP Publications, Davis, California. pp 215-222. Marlin, D.J., Harris, R.C., Harman, J.C. and Snow, D.H. (1987) Influence of post exercise activity on rates of muscle and blood lactate disappearance in the Thoroughbred horse. In: Equine Exercise Physiology 2. Eds: J.R. Gillespie and N.E. Robinson. ICEEP Publications, Davis, California, pp 321-331. Moyer, W.M. and Fisher, J.R.S. (1992) Bucked shins: effects of differing track surfaces and proposed training regimens. Proc. Am. Ass. equine Practnrs. 37. Riley, D.P. (1977) In: Strength Training by the Experts. Leisure Press, Champaign, Illinois. p 8.
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