The use of weights to improve the functional efficiency of the human is probably as old as sport itself. The celebrated Milo of Croton is reputed to have started his athletic training by raising a new-born calf over his head and continuing the practice daily, he grew in strength until the animal reached maturity. He provides a good illustration of the use of progressive resistance exercise. In subsequent centuries man has continued to search for ingenious methods of resisting muscle action to enhance his function as well as derive a variety of lifting and throwing competitions. This article outlines some common uses of weight training and suggests ways that injuries associated with the practice may be avoided.
It is first necessary to distinguish between weightlifting and weight training. Weightlifting is a competitive sport contested in the Olympic Games whereas weight training describes the employment of weights in the training regimes of non-athletes as well as athletes. The two Olympic lifts most commonly demonstrated to illustrate the sport are the snatch and the clean and jerk. These are known as the quick lifts because of the agility and coordination required for their execution. The rules for each event determine how the lift is performed.
In the snatch, the weight must be brought from the floor to a position overhead without interruption. This action involves pulling the weight as high as possible, then splitting the legs apart in the sagittal plane to nip underneath as it ascends. The arms must lock straight promptly as the weight reaches the peak of its ascent. The lifter must then stand upright with the weight held overhead.
THE CLEAN AND JERK
This is performed in two phases. The clean requires that the weight be pulled to the chest in an uninterrupted motion. This has some similarity with the snatch though heavier loads can be lifted. Preparatory to the next phase the lifter stands with the load at his chest. He flexes his knees, then jumps upwards with the weight, throwing it to an overhead position as he again parts his legs to get underneath the ascending weight. Here also the upright position must be assumed with the weight held overhead to achieve a valid lift.
There are a few observations about weightlifting that also help to illuminate the field of weight training. Weightlifting is a heavy resistance weight-bearing action, necessitating great explosive power and the ability to hold great weights momentarily under control. The lifter uses maximal efforts against extremely heavy loads in training and in competition. It is at these intensities that stresses on the articulo-skeletal system are greatest. The lifts are rapidly executed, taking in toto less than six seconds per lift. Studies of weight-lifters show that over a two-hour training session they may be actually working for only two to six minutes, though this work will be extremely strenuous. It is essential that correct techniques be applied to reduce the strain at body sites of greatest vulnerability – the knee, the back and the wrist.
The knee joint is particularly vulnerable at the initiation of the lift before the quadriceps contract powerfully. The back experiences high levels of strain, the force acting on a lumbo-sacral disc being calculated to exceed 1000kg in the study of Morris and co-workers (1961). The load on the spine is to an extent alleviated by the intra-abdominal pressure induced. For these reasons it is essential that the lift be carried out in a manner that minimises mechanical strain on the spine. Frequently the annulus fibrosus cartilage is strained. Efficient lifting actions should be practised, imperfections being corrected during the early stages of learning the techniques. Deterioration at the wrist may occur due to hyperextension associated with repetitive lifting and holding weights overhead. Fractures of the distal radial epiphysis have been reported in adolescent weightlifters executing the military press (Ryan and Salciccioli, 1976). Rowe (1979) reported a comminuted fracture of the distal end of the radius and fracture of the ulnar styloid process on sudden hyperextension of the wrist on losing control of the weight. Finally, it is important not to suspend breathing during the moment of extreme exertion. With the breath held and the epiglottis closed the chest is compressed and intrathoracic pressure builds up. This precipitates the Valsalva manoeuvre, resulting in a reduced venous return to the heart and consequent rapid drop in blood pressure with possible loss of consciousness. International weightlifters have fainted during competition as a result of failure to time their breathing correctly.
CONVENTIONAL WEIGHT TRAINING EXERCISES Quite apart from the Olympic lifts used at the International Weightlifting Federation’s competitions, the British Amateur Weightlifters’ Association recognises 31 lifts. From this battery a number have been adopted over the last two decades or so by athletes for use in general conditioning. In most cases the lifts have been modified to provide an action compatible with the athlete’s specific requirements. A typical sample of such exercises, which can also be used by sedentary individuals for positive health purposes follows. These exercises are divided according to the degree of skeletal muscle involvement into light muscle group (for example arm and shoulder) or large muscle group (thigh or trunk) work. Emphasis is placed on the correct execution of the routines since injury frequently results from using a faulty technique.
Arm and shoulder work
The athlete lies supine on the bench with feet apart and supported on the ground on either side. Two spotters are used for precautionary reasons. The bar is taken from supporting stands by the spotters and handed to the athlete on his upper chest.
Taking the bar in too high near the throat is to be avoided on safety considerations. Normally a wide knuckles-up grip is taken. A wider hand hold is used to handle greater weights, though this defeats the purpose of imposing greatest resistance on pectorales majores, anterior deltoids and triceps. However, care must be taken that the grip is sufficiently wide not to jeopardise security and continual concentration is required of the spotters as 40kg is sufficient to lacerate the facial bones from a fall of half a metre. The weight is pushed vertically from the chest. Prior to the movement it is necessary to have the chest full of air to provide a rigid base from which the weight is moved. The performer exhales after the weight ascends. The bar should be lowered slowly so as to permit complete control of the weight throughout. Altering the hand spacing affects the pattern of muscular involvement. Dumb-bells may be used to replace the barbell and, though this invariably means a lower resistance, it allows movement through a greater range.
An alternative procedure is to have the assistants lift the barbell, the athlete’s task being to control its lowering by eccentric muscle contractions. This overcomes the limitation of performing only uni-directional work. Heavier loads can be handled than in concentric work. The benefits of the training programme are enhanced when both concentric and eccentric actions are employed.
Bench pressing is ubiquitous in the weight-training programmes of sportsmen. It has been widely accepted by runners, jumpers and games players. It would seem particularly beneficial to rugby-forwards, swimmers and weight-throwers.
Overhead press can be performed standing upright or sitting on a bench. The starting position can be from the chest but usually the weight is pressed vertically from behind the neck until the arms are at full stretch overhead, an inflated chest acting as a platform from which the action takes place. In the standing posture heavy weights may produce compensating movements in the legs or trunk to allow the action to be completed. In younger individuals acquiring the technique, an assistant can apply light pressure at the scapulae to prevent swaying .
Alternatively, it may help if the action is performed with immediate visual feedback from a mirror. If dumb-bells are used the line of action of the specific competitive performance can be employed. Shot putters, for example, may use one or both arms alternately or simultaneously at an angle of release in the sagittal plane of approximately 45°.
Rowing may be performed from an upright or a bent-forward posture. The action should be restricted to the arms and shoulders, with careful attention given to the exclusion of the back and trunk. In both forms, the downward movement of the bar should be controlled. An observer can ensure the posture does not get progressively higher with each succeeding effort in bent-forward rowing. This can indicate the performer is tiring and it is when fatigued that he is most likely to handle weights incorrectly. Again, the use of a mirror in learning the technique is recommended. A partner may be used to exert light pressure on the upper back to prevent accentuation of the lordotic curve. If performed in a quick jerky manner with the knees locked, damage to the intervertebral discs can occur with pressure on the disc forcing its fluid-like centre, the nucleus pulposus, to project posteriorly causing medical complications. This can be avoided either by resting the forehead on a padded table while the lift is performed or bending the knees to about 15° flexion. This releases tension from the muscles of the posterior thigh and back and allows the lumbar spine to retain a normal curvature. The muscles isolated in this exercise are the latissimus dorsi, teres major and rhomboids.
In upright rowing a narrow grip is used with the elbows pointing upwards. In bent-forward rowing the elbows assume a more lateral orientation. Both procedures are widely used by individuals seeking an increase in upper body strength.
This exercise may be performed with the athlete lying supine on a bench and feet supported on the ground. The arms may be held straight or flexed. A mild flexion is recommended to reduce strain on the shoulder joint. The weights lifted should not be unduly heavy, otherwise they will be difficult to control at the outer ranges of movement. The barbell may be taken from a position on the ground in a circular motion forward to a position over the chest or continued further to rest on the thighs. Endurance athletes can usefully employ this exercise because the serratus anterior is stretched as the weight is lowered to recommence the movement. Correct timing of breathing is important, inhalation occurring as the weight descends towards the ground and exhalation as the load is taken back up.
Curls implicate elbow flexion and may be performed with barbells or with one or two dumb-bells. It is difficult to operate at maximal loads in standing without other muscle groups being introduced to assist fatiguing elbow flexors. Again, care should be taken so that with heavy loads the lordotic curve is not overemphasised. Isolation of elbow flexion is facilitated by conducting the exercise with the limb supported at the elbow on a bench or table. Attention should also be given to elbow extension work to avoid imbalanced arm strength development.
Large muscle-group work
The resistance is normally provided by approximately half the body mass which the abdominal muscles must move against gravity. The load on the abdominals in a sit-up action from supine lying can be increased by holding a loaded barbell on the chest . This is preferable on comfort criteria alone to holding a disc behind the neck. An assistant is needed to hold the ankles of the athlete to facilitate the action. Another variation is to sit-up with a twist, arms behind the head, to touch each knee alternately with contra-lateral elbows. femoral condyle and the tibial plateau (O’Donoghue, 1970). For these reasons performance of partial squats is advised, though full squats may be permitted at much less frequent intervals to provide maximum overload and maintain the joint’s range of movement.
Maintenance of stability may present a problem during this exercise. Initially the athlete assumes a starting position with feet apart underneath the hips to best support the bodyweight. Stability is achieved by keeping the line of gravity within the base of support. This is effected by pushing the hips back slowly as the bodyweight is lowered. By retaining heel contact with the ground the base of support is kept relatively large and stability facilitated.
One manoeuvre to assist balance is to elevate the heels by means of an inclined board or to perform the exercise with a board placed underneath the heels. A more satisfactory procedure is to use a steel rack which arrests movement of the bar in the fore and aft direction and which incorporates obvious additional safety factors. These racks are installed in all well-equipped gymnasia.
Since greater weights can be lowered than lifted, a useful modification of the half-squat is to overload the individual beyond his lifting capacity and allow him to slowly lower the weight under eccentric muscular control. A weight about 120 per cent of lifting capacity can easily be handled for six repetitions (Johnson et al, 1976). If the stretching force is 130 to 140 per cent of one concentric repetition maximum (1RM), it is not possible to slow the lowering sufficiently in a free movement resisting gravity to permit involved muscles to develop maximal tension. For safety the load must be supported by pins at the end of the eccentric movement.
A loaded barbell is supported on the back of the neck. Sometimes a piece of foam rubber or a towel is used to alleviate pressure on the cervical vertebrae. The body is lowered from standing to a squat position, from which its weight plus the loaded barbell must be lifted by powerful contraction of the knee extensors. This exercise has come in for much criticism because of the risk of knee joint degeneration from strain on the patellar bursae (Reilly, 1977). During deep knee bending without attendant weights the patello-tendon force has been calculated by Reilly and Martens (1972) to reach 7.6 times bodyweight.
In the full squat position with posterior aspects of thigh and calf in contact, the knee ligaments are overstretched and long-term ligamentous damage may be caused (Klein, 1962). In this position the lateral meniscus may also suffer from being caught between the
This exercise involves approximately the same energy demands as a full squat (Reilly, 1971). The weight is lifted from the floor to above head height in one complete movement. Special attention to technique is needed in the initial lifting movement. There has been considerable discussion for many years of the relative demerits of the back-lift with knees straight (the derrick lift) and with the trunk erect and knees flexed (the knee action) in various industrial contexts. Whitney (1962), for example, compared the strength of the lifting action in both types of lift. The knee lift is preferable, with the back straight to prevent the turning of the spine into a cantilever with consequent spinal strain. Correct placement of the feet is essential prior to attempting the lift. The athlete should become accustomed to performing the action with the head erect and looking directly ahead and so avoid the natural temptation to look down at the weight as he attempts to overcome its inertia. As the forces on the spine are a function of the distance the weight is away from it, it is recommended to keep the weight close to the body as it is being iifted.
This involves basically the same gross muscular action and equivalent energy expenditure as power cleans (Reilly, 1979). The barbell is taken from the floor to a height roughly in line with the clavicles. The athlete may increase the work done by coming up on to his toes to complete the lift, good coordination being demanded for this. The elbows are raised above the bar at its high-point, which does not go overhead. Again it is important to keep the back straight during the lift as jerking into back extension, particularly during the early phase of the action, can be damaging.
Here the athlete jumps high into the air from a squat or partial squat position with a loaded barbell supported on his shoulders. Good coordination is essential to prevent overbalancing on landing. Frequently a towel is used underneath the bar to cushion its jarring effect.
When ascending it is necessary to pull down hard on the bar to avoid its bouncing against the back of the neck . It is particularly beneficial to athletes who during performance move the body explosively against gravity.
Bodyweight plus a weighted barbell provide the resistance as the athlete steps repeatedly on to a bench with load supported on the shoulders . Ideally the bench height should be matched to the stature of the individual, otherwise quadriceps tear is a risk where the smaller athletes operate with a high bench. With too heavy weights the rhythm of stepping may be disrupted with consequent danger of overbalancing and injury.
ACCOMMODATING RESISTANCE MODES
Isokinetics describes the form of exercise permitted by machinery with the facility to adapt resistance to the force exerted. Normally when weights are lifted through a range of movement the maximum load is limited to that sustainable by the muscles involved at the weakest point in the range. Consequently other points within the range undergo sub-maximal training stimuli. With isokinetic machines this problem is overcome as the speed of contraction is pre-set, a speed governor in the apparatus allowing the resistance to adapt to the force applied. In this way, the greater the effort exerted the greater is the resistance, and maximal effort can be performed throughout the complete range of movement. Where comparisons have been made, training programmes using isokinetic machines have proved superior to isometric and typical progressive resistance programmes with high speeds producing best results (Thistle et al, 1967; Pipes and Wilmore, 1975).
Using Mini-Gym, Lumex or Cybex isokinetic apparatus, the weight-thrower can go through the pattern of shoulder and arm motion of his competitive event, so getting a training effect suitable for his specific purpose. Accessory equipment can be attached to the machine to accommodate specificity training for a range of sports.
A limitation of isokinetic exercise is that it may interfere with the natural pattern of acceleration employed in the competitive action. Additionally it provides opportunity for just concentric work. However, muscle soreness from eccentric action is avoided as recovery is passive (Talag, 1973). It is likely specially to benefit swimmers since they contract their arm muscles more or less isokinetically when pulling through water.
An alternative form of accommodating resistance is provided by Nautilus equipment. This is not isokinetic machinery since the speed of contraction may vary. The apparatus provides stretching the involved muscle group in the starting position and resistance throughout the range of movement correlated to the force exerted. A specially shaped cam compensates for the variations in force by changing the moment arm and the resistance is increased or decreased even though the machine loading remains constant. The machinery allows a rotary movement in 17 different stations for various exercises. The cams for each machine are designed according to the strength curves of the different muscle groups with varying angles. As a result the resistance is lowest at the joint’s weakest position and greatest in its peak strength position.
USES OF WEIGHT TRAINING
Weight training can be exploited to achieve different results. Since the classic report of De Lorme (1945) it has been known that few repetitions of high intensity work produce a strength training stimulus while many repetitions at low or moderate intensity improve local endurance. Skeletal muscle is an extremely adaptable tissue and exercise of an endurance nature, although it produces biochemical changes leading to greater oxidative capacity, leaves the size of the musculature relatively unchanged. Maximal intensity of relatively short duration tends to promote growth in skeletal muscle, its connective tissue and tendonous attachment. The important ultra-structural change in muscle hypertrophy is increase in the myofibril content of the cell.
It appears that an important factor determining the extent of hypertrophy is the speed of contraction as well as the work intensity. There is, as yet, no exact demarcation in physiological terms between a strength training stimulus and a power training stimulus. In studies of women throwers, appreciable gains in strength using maximal resistance are found without evidence of the muscle hypertrophy that might be unwanted in females for social reasons (Brown and Wilmore, 1974). There is ample evidence that weight training can improve speed of limb movement and muscular coordination in addition to strength (Jensen and Fisher, 1972) and enhances conventional conditioning programmes (Clarke, 1973). Masley et al (1953) showed that performance in fencing could be improved by engaging in specific weight training exercises. Undoubtedly weight training aptly used can have manifold benefits beyond the seasoning of muscular strength.
Caution is needed in the early stages of a weight training programme. At first the athlete starts off with modest loads during familiarisation with the exercises. Then the principle of progressive resistance is applied to scheduling the programme. The load is gradually increased as the individual adapts to meet the demands the schedule imposes. To improve further a higher load is needed. This procedure is continuously applied as strength develops. Normally the athlete will perform, say, six repetitions at high intensity, rest completely and repeat a few times before progressing to another exercise. An alternative is the pyramid system where after the first six repetitions or first set, the load is actually increased. This necessarily reduces the number of repetitions the athlete can perform. The load is progressively increased until it is too heavy to be overcome. Equipment for leg pressing provides an ideal set-up for most athletes working on a pyramid system to improve leg strength – even when the load cannot be moved an isometric contraction can be held for a fixed period to terminate the sets.
Another use of weight training is its incorporation in circuit-training for the purpose of conditioning the circulatory system. Circuit-training designed by Morgan and Adamson (1962) is so called because a series of separate exercises is organised for performance in a circle. Individuals rotate around the circle as they pro- gress through the training session. The circuit should allow variation of muscle-groups involved between work stations to avoid cessation of work due to local muscular fatigue. In theory this method is ideal for team training provided the number in the group does not exceed the number of work stations laid out. In practice group organisation invariably presents some problems as do inter-individual differences. Where weight training is included in the circuit, a fixed load may not be suitable for all or many of the group while altering the loads slows up the performance and allows untimely recovery. Ideally a homogeneous group, a thoroughly well organised routine and repetition of the circuit or supplementary training are necessary to achieve objectives.
Multi-station exercise machines overcome the organisational problems of circuit-training and the injury risks of weight training using traditional resistance modes. Resistance is alternately supplied by bodyweight, weighted stacks and isokinetic machines. Muscle groups change from station to station and use of the machine involves abdominals, leg, shoulder, arm, and back muscle work. Physiological studies have shown the training stimulus to the circulatory system is significantly greater than conventional circuit-training routines (Reilly and Thomas, 1978). However, as delay in altering loads at any one station is minimal the circuit of 12 stations can be repeated to perform two or more sets in a training session.
Safety factors are inherent in the design of each station which accommodates a wide range of physiques and capacities. Over a lengthy validation period no accidents or injuries were found with extensive use of the machine. Additionally individual stations provide the facility for training of specific muscle groups. This type of equipment is in use in many professional sports clubs and sport centre complexes.
The use of heavy weights in resistance training emphasises the need for teaching lifting techniques correctly. Most injuries occur when heavy weights are lifted and most back injuries occur when spinal flexion is permitted. This is manifested in the relatively much larger proportion of injuries in male than in female athletes using weight training, females tending to operate at intensities permitting greater safety margins. Special care should be given to young athletes to prevent undue over-exertion in lifting weights. This should be an important consideration before.the epiphyses of the long bones close as further growth might be affected. Safety considerations should override all others where large groups are involved. This may require more careful programming of the gymnasium timetable. Spotters and weight-racks should be used where appropriate. Use of commercially available chalk blocks can ensure a continuing good grip on the bar once the palms commence to sweat. In addition a suitable surface is needed, most lifting exercises being conducted from rubber mats. Appropriate footwear is required to provide sufficient frictional contact with the floor, in most cases the orthodox multi-purpose gymnasium shoe is inadequate. Collars must be used to firmly fix the discs to the bar as many injuries arise from insecurely attached equipment falling on the feet. Weights should be returned to place after exercise to avoid tripping other users.
Frequently athletes do not continue their weight training once the competitive season has commenced. This is an oversight, as the principle of reversibility implies. The training effect obtained from strength training gradually disappears if the training is terminated and the muscles atrophy. In general the loss depends on the rate of acquisition. The gain may be retained by exercising at a frequency much less than when strength was being developed.
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