Resistance Training Guidelines for Healthy Adult

The following resistance training guidelines are recommended for the apparently healthy adult:

•Perform a minimum of 8 to 10 separate exercises that train the major muscle groups

 A primary goal of the program should be to develop total body strength in a relatively time - efficient manner. Programs lasting longer than one hour per session are associated with higher dropout rates.

•Perform one set of 8 to 12 repetitions of each of these exercises to the point of volitional fatigue

•Perform these exercises at least 2 days per week

 While more frequent training and additional sets or combinations of sets and repetitions elicit larger strength gains, the additional improvement is relatively small

•Adhere as closely as possible to the specific techniques for performing a given exercise

•Perform every exercise through a full range of motion

•Perform both the lifting (concentric phase) and lowering (eccentric phase) portion of the resistance exercises in a controlled manner

•Maintain a normal breathing pattern, since breath - holding can induce excessive increases in blood pressure

•If possible, exercise with a training partner who can provide feedback, assistance, and motivation.

Muscular Fitness

Although aerobic activities have been shown to be effective for developing cardiorespiratory fitness, most have little influence on muscular strength or muscular endurance, especially of the upper body. Every activity - including ADL - requires a certain percentage of an individual’s maximal strength and endurance. The maintenance or enhancement of muscular strength and muscular endurance enables an individual to perform such tasks with less physiological stress. The physiological stress induced by lifting or holding a given weight is proportional to the percentage of maximal strength involved.

Resistance training of moderate intensity (i.e., sufficient to develop and maintain muscular fitness and lean body weight) should be an integral part of adult fitness and rehabilitative exercise programs. In addition to the development and maintenance of muscular strength and muscle mass, the physiological benefits of resistance training include increases in bone mass and in the strength of connective tissue. These adaptations are beneficial for middle — age and older adults, and, in particular, postmenopausal women who rapidly lose bone mineral density. Other health benefits which have been ascribed to resistance training include: modest improvements in cardiorespiratory fitness, reductions in body fat, modest reductions in blood pressure, improved glucose tolerance, and improved blood lipid and lipoprotein profiles. These health benefits have been most often associated with circuit weight training, which is a method of resistance training in which a series of exercises are performed in succession with minimal rest between exercises.

Muscular strength and endurance are developed by the overload principle - by increasing the resistance to movement or the frequency or duration of activity to levels above those normally experienced. Muscular strength is best developed by using weights that develop maximal or nearly maximal muscle tension with relatively few repetitions. Muscular endurance is best developed by using lighter weights with a greater number of repetitions. To elicit improvement in both muscular strength and endurance, most experts recommend 8 to 12 repetitions per exercise.

Any overload will result in strength development, but higher intensity effort at or near maximal effort will produce a significantly greater effect. The intensity of resistance training can be manipulated by varying the weight, the number of repetitions, the length of the rest interval between exercises, or the number of sets of exercises completed. Caution is advised for training that emphasizes lengthening (eccentric) contractions, compared to shortening (concentric) or isometric contractions, as the potential for skeletal muscle soreness is accentuated.

Muscular strength and endurance can be developed by means of static or dynamic exercises. Although each type of training has strengths and weaknesses, dynamic resistance exercises are recommended for most adults. Resistance training for the average participant should be rhythmical, performed at a moderate - to - slow speed, involve a full range of motion, and not interfere with normal breathing. Heavy resistance exercise combined with breath - holding can cause a dramatic, acute increase in both systolic and diastolic blood pressure.

Psychological Fatigue During The Exercise

Eventually our understanding of the brain will advance to the point where its underlying physiology and biochemistry are understood and the effects of afferent input can be predicted. For the present, however, sports therapist can really only begin to address the question of how afferent input during competition (pain, breathlessness, nausea, audience response) can lead to psychological fatigue. For now, a behavioral (psychological) approach to understanding these questions of psychological fatigue may be beneficial. Through training or intrinsic mechanisms, some athletes learn to minimize the influences of distressing afferent input and therefore approach performance limits set in the musculature. At times, such as at high altitudes, athletes slacken their pace to reduce discomforting inputs to a tolerable level. Consequently, work output decreases, but not because of a muscle limitation.

On the opposite end of the spectrum,  sports therapist frequently see examples of inexperienced or foolhardy athletes who set a blistering pace for most of a race, and then experience real muscle fatigue before the end. In track events, these are the competitors who, in the home stretch, look like someone reading the newspaper. In order to perform optimally in an activity, the experiences of prior training and competition are often necessary for an athlete to evaluate afferent inputs properly and to utilize them in determining the maximal rate at which physiological power can be meted out during competition in case of any psychological fatigue.

Psychological Factors Preparations for Physical Training

Athletes need to be psychologically prepared for practices and competition in order to reduce the risk of injury. Research has demonstrated a positive relationship between stressful life situations, especially those with high negative stress, and injury occurrence. In understanding the stress - injury relationship, Nideffer points out that muscle tension increases in response to stress. Increased tension in the antagonist and agonistic muscle groups results in reduced flexibility and loss of motor coordination. Increased muscular tension also slows reaction time, which reduces the athlete's ability to respond.

Mental, as well as physical, fatigue can contribute to injury occurrence. The attention factor - the ability to maintain a high level of concentration - requires a large amount of energy; when combined with a rigorous training program, reduced attention can result. This may lead to slowed reaction times and loss of neuromuscular coordination, thus increasing the potential for injury. Athletes who have sustained an injury realize that they have to be ready mentally for return to sport to avoid risking reinjury. The role of attentional focus and muscular tension can be a major problem. Fear and/or worry about a second injury can cause stress and increased muscular tension. Preliminary studies have addressed hardiness (commitment, control, and challenge) of the athlete as a moderating factor in the stress - injury relationship. Athletes who exhibit greater qualities of this trait may be better able to control the attentional processing of information and in turn reduce the potential for occurrence of a second injury.

Appropriate Equipment for Physical Training

Proper fitting shoes can mean the difference between a low and a high risk of injury for a track and field competitor. Training in improperly fitted shoes can result in chronic abnormal pressures to the foot and cause stress injuries or structural deformities. Minor skin irritations such as calluses and blisters can prove to be major hindrances to a runner. Improperly fitted or worn-out shoes can lead to mechanical disturbances and postural, muscular, and joint dysfunctions.

Shoes arc the most critical piece of track athlete s equipment and should be individually and carefully selected. The recent revolution in shoe research, design, and production has created a plethora of shoes from which to choose. However, the athletes' shoes must meet their biomechanical requirements and adapt to the demands of the individual's event. Shoe surveys can be useful in analyzing the specific qualities of shock absorbency, foot control, and flexibility, but athletes and coaches must be aware that new injury syndromes have been produced by new shoe models.

Field event implements must meet use and safety specifications. Every member of the sports team (coach, official, sports medicine personnel, and athlete) must be aware of any hazardous field situation where the field event practices and competitions take place, and take action to assure the highest level of safety.

Interval Training for Improving Cardiorespiratory Endurance

Unlike continuous training, interval training involves more intermittent activities. Interval training consists of alternating periods of relatively intense work and active recovery. It allows for performance of much more work at a more intense workload over a longer period of time than if working continuously?

It is most desirable in continuous training to work at an intensity of about 60% to 80% of maximal heart rate, Obviously, sustaining activity at a relatively high intensity over a 20 - minute period would be extremely difficult. The advantage of interval training is that it allows work at this 80% or higher level for a short period of time followed by an active period of recovery during which an individual may be working at only 30% to 45% of maximum heart rate. 13 Thus the intensity of the workout and its duration can be greater than with continuous training.

Most sports are anaerobic, involving short bursts of intense activity followed by a sort of active recovery period (for example, football, basketball, soccer, or tennis) . Training with the interval technique allows the athlete to be more sport specific during the workout, with interval training the overload principle is applied by making the training period much more intense.

There are several important considerations in interval training. "The training period is the amount of time that continuous activity is actually being performed, and the recovery period is the time between training periods. A set is a group of combined training and recovery periods, and a repetition is the number of training and recovery periods per set. Training time or distance refers to the rate or distance of the training period. The training - recovery ratio indicates a time ratio for training versus recovery.

An example of interval training would be a soccer player running sprints. An interval workout would involve running two sets of four 400meter dashes in under 70 seconds, with a 2 minute 20 second walking recovery period between each dash. During this training session the soccer player s heart rate would probably increase to 85% to 90% of maximal level during the dash and should probably fall to the 30% to 45% level during the recovery period.

Factors that Limit Body Flexibility

A number of factors may limit the ability of a joint to move through a full, unrestricted range of motion. The bony structure may restrict the endpoint in the range. An elbow that has been fractured through the joint may deposit excess caldum in the joint space, causing the joint to lose its ability to fully extend. However, in many instances bony prominences stop movements at normal endpoints in the range.

Excessive fat may also limit the ability to move through a full range of motion. An athlete who has a large amount of fat on the abdomen may have severely restricted trunk flexion when asked to bend forward and touch the toes. The fat may act as a wedge between two lever arms, restricting movement wherever it is found. Skin might also be responsible for limiting movement. For example, an athlete who has had some type of injury or surgery involving a tearing incision or laceration of the skin, particularly over a joint, will have inelastic scar tissue formed at that site. This scar tissue is incapable of stretching with joint movement. Muscles and their tendons, along with their surrounding fascial sheaths, are most often responsible for Limiting range of motion. When performing stretching exercises for the purpose of improving flexibility about a particular joint, one is attempting to take advantage of the highly elastic properties of a muscle. Over time it is possible to increase the elasticity, or the length that a given muscle can be stretched. Athletes who have a good deal of movement at a particular joint tend to have highly elastic and flexible muscles. Connective tissue surrounding the joints, such as ligaments on the joint capsule, may be subject to contractions. Ligaments and joint capsules do have some elasticity; however, if a joint is immobilized for a period of time, these structures tend to lose some elasticity and shorten. This condition is most commonly seen after surgical repair of an unstable joint, but it can also result from long periods of inactivity.

It is also possible for an athlete to have relatively slack ligaments and joint capsules. These individuals are generally referred to as being loose - jointed. Examples of this would be an elbow or knee that hyperextends beyond 180 degrees Frequently there is instability associated with loose - jointedness that may present as great a problem in movement as ligamentous or capsular contractures.

Skin contractures caused by scarring, ligaments, joint capsules, and musculotendinous units are each capable of improving elasticity to varying degrees through stretching over lime. With the exception of bony structure, age, and gender, all the other factors that limit flexibility may be altered to increase range of joint motion.

Continuous Training for Improving Cardiorespiratory Endurance

Cardiorespiratory endurance may be improved through a number of different methods. Largely, the amount of improvement possible will be determined by initial levels of cardiorespiratory endurance. Continuous training involves four considerations:

1) Mode

The type of activity used in continuous training must be aerobic. Aerobic activities are those that elevate the heart rate and maintain it at that level for an extended time. Aerobic activities generally involve repetitive, whole - body, large muscle movements performed over an extended time. Examples of aerobic activities are running, jogging, walking, cycling, swimming, rope skipping, stair climbing, and cross - country skiing. The advantage of these aerobic activities as opposed to more intermittent activities, such as racquetball, squash, basketball or tennis, is that aerobic activities are easy to regulate by either speeding up or slowing down the pace. Because we already know that the given intensity of the workload elicits a given heart rate, these aerobic activities allow us to maintain heart rate at a specified or target level. Intermittent activities involve variable speeds and intensities that cause the heart rate to fluctuate considerably. Although these intermittent activities improve cardiorespiratory endurance, they are much more difficult to monitor in terms of intensity.

2) Frequency

To see at least minimal improvement in cardiorespiratory endurance, it is necessary for the average person to engage in no less than three sessions per week. If possible, one should aim for four or five sessions per week. A competitive athlete should be prepared to train as often as six times per week. Everyone should take off at least 1 day per week to allow for both psychological and physiological rest.

3) Duration

For minimal improvement to occur, an individual must participate in at least 20 minutes of continuous activity with the heart rate elevated to its working level. Recent evidence suggests that even shorter exercise bouts of as little as 12 minutes may be sufficient to show improvement. Generally, the greater the duration of the workout, the greater the improvement in cardiorespiratory endurance. The competitive athlete should train for at least 45 minutes with the heart rate elevated to training levels.

4) Intensity

Of the four factors being considered, the most critical factor is the intensity of training, even though recommendations regarding training intensities vary. Hiis is particularly true in the early stages of training, when the body is forced to make a lot of adjustments to increase workload demands.

Because heart rate is linearly related to the intensity of the exercise and to the rate of oxygen consumption, it becomes a relatively simple process to identify a specific workload (pace) that will make the heart rate plateau at the desired level. By monitoring heart rate, we know whether the pace is too fast or too slow to get heart rate into a target range.

Several formulas identify a target training heart rate. Exact determination of maxireal heart rate involves exercising an individual at a maximal level and monitoring the heart rate using an electrocardiogram. This is a difficult process outside a laboratory. However, an approximate estimate of maximal heart rate for both males and females is that maximal heart rate is thought to be about 220 beats per minute. Maxima heart rate is related to age. As age increases, maximal heart rate decreases. Thus a relatively simple estimation of maximal heart rate (HR) would be Maximal HR = 220 - Age. If an athlete is working at 70% of maximal rate, the target heart rate can be calculated by multiplying 0.7 ( 220 - Age).

Regardless of the formula used, it should be clear that to see minimal improvement in cardiorespiratory endurance, the heart rate should be elevated to at least 70% of its maximal rate.  In a trained individual it is not difficult to sustain a heart rate at the 85% level.

Aerobic versus Anaerobic Metabolism

Two major energy systems function in muscle tissue: anaerobic and aerobic metabolism. Each of these systems generates ATP. During sudden outburst of activity in intensive, short - term exercise, ATP can be rapidly metabolized to meet energy needs. After a few seconds of intensive exercise, however, the small stores of ATP are used up. The body then turns to glycogen as an energy source. Glycogen can be metabolized within the muscle cells to generate ATP for muscle contractions.

Both ATP and muscle glycogen can be metabolized without the need for oxygen. Thus this energy system involves anaerobic metabolism (occurring in the absence of oxygen). As exercise continues, the body has to rely on the metabolism of carbohydrates (more specifically, glucose) anti fats to generate ATP. This is second energy system requires oxygen and is therefore referred to as aerobic metabolism (occurring in the presence of oxygen).

In most activities both aerobic and anaerobic systems function simultaneously. The degree to which the two major energy systems are involved is determined by the intensity and duration of the activity. If the intensity of the activity is such that sufficient oxygen can be supplied to meet the demands of working tissues, the activity is considered to be aerobic. Conversely, if the activity is of high enough intensity or the duration is such that there is insufficient oxygen available to meet energy demands, the activity becomes anaerobic. Consequently, an oxygen debt is incurred that must be paid back during the recovery period. For example, short bursts of muscle contraction, as in running or swimming sprints, use predominantly the anaerobic system. However, endurance events depend a great deal on the aerobic system. Most sports use a combination of both anaerobic and aerobic metabolism.

Body Balance and Flexibility

Balance and proprioceptive training enhance motor control, which is needed to decrease the risk of injury or reinjury during practice or competition. When injury to a joint or musculotendinous structure occurs, somatosensory information is altered, adversely affecting motor control. Hence, rehabilitation should emphasize restoring the athlete's balance strategies. This will also decrease the risk of recurrent injury. The balance training tasks must be specific to the type of balance strategies required by the athlete s event.

Efficient performance requires a full range of motion, and adequate joint flexibility also decreases an athlete s susceptibility to injury. Normal muscular length - tension and adequate extensibility upon stretch aid in protecting the body from injury. The athlete s entire body is able to work more efficiently and safely after a period of warm - up, stretching, and skill - drills that are related to the athlete's event.

The warm - up period before practice or competition increases tile body' s tissue temperature prior to subjecting the musculotendinous structures to repeated stretch and contraction. Connective tissue has viscoelastic properties which allow elongation of the tissue. Temperature has a significant influence on the mechanical behavior of connective tissue under tensile stretch. Higher temperatures at low loads produce the greatest elongation with the least damage to connective tissue. Increased connective tissue temperature also increases extensibility.

Optimal stretching occurs only when voluntary and reflex muscle resistance is eliminated. Ballistic stretching is not a favorable method because as the muscles stretch rapidly, the intrafusal muscle spindles may be activated, causing a reflex protective muscle contraction. Forceful ballistic stretching can also cause microtrauma of muscle fibers.

Strength Training For the Women and Female Athlete

Strength training is critical for the female athlete. The average female is incapable of building significant muscle bulk through weight training. Significant muscle hypertrophy is dependent on the presence of the anabolic steroidal hormone testosterone. Testosterone is considered a male hormone, although all women possess some testosterone in their systems. Women with higher testosterone levels tend to have more masculine characteristics such as increased body hair, a deeper voice, and the potential to develop a little more muscle bulk.

With weight training, the female sees some remarkable gains in strength initially, even though muscle bulk does not increase. For a muscle to contract, an impulse must be transmitted from the nervous system to the muscle. Each muscle fiber is innervated by a specific motor unit. By overloading a particular muscle, as in weight training, the muscle is forced to work efficiently. Efficiency is achieved by getting more motor units to fine, causing a stronger contraction of the muscle. Consequently, it is not uncommon for a female to see extremely rapid gains in strength when a weight training program is first begun. These tremendous initial strength gains, which can be attributed to improved neuromuscular system efficiency, tend to plateau, and minimum improvement in muscular strength will be realized during a continuing strength - training program, These initial neuromuscular strength gains will also be seen in men, although their strength will continue to increase with appropriate training.

Perhaps the most critical difference between males and females regarding physical performance is the ratio of strength to body weight. The reduced strength - body weight ratio in women is the result of their higher percentage of body fat. The strength - body weight ratio may be significantly improved through weight training by decreasing the body fat percentage while increasing lean weight.

Circuit Training for Muscle Strength and Endurance Improvement

Circuit training employs a series of exercise stations that consist of various combinations of weight training, flexibility, calisthenics, and brief aerobic exercises. Circuits may be designed to accomplish many different training goals. With circuit training one move rapidly from one station to the next and performs whatever exercise is to be done at that station within a specified time period. A typical circuit would consist of 8 to 12 stations, and the entire circuit would be repeated three times.

Circuit training is most definitely an effective technique for improving strength and flexibility. Certainly, if the pace or the time interval between stations is rapid and if workload is maintained at a high level of intensity with heart rate at or above target training levels, the cardiorespiratory system may benefit from this circuit. However, there is little research evidence that shows that circuit training is effective in improving cardiorespiratory endurance. It should be and is most often used as a technique for developing and improving muscular strength and endurance.

Some free exercises have an isometric or holding phase instead of using a full range of motion. Examples of these are back extensions and sit - ups. When the exercise produces maximum muscle tension, it is held between 6 and 10 seconds and then repeated one to three times.

Muscle Isokinetic Exercise

An isokinetic exercise involves a muscle contraction in which the length of the muscle is changing while the contraction is performed at a constant velocity. In theory, maximal resistance is provided throughout the range of motion by the machine. The resistance provided by the machine will move only at some preset speed regardless of the force applied to it by the individual. Thus the key to isokinetic exercise is not the resistance but the speed at which resistance can be moved.

Several isokinetic devices are available commercially; Cybex, Biodex, Kin - Com, and Lido are among the more common isokinetic machines. In general, they rely on hydraulic, pneumatic, and mechanical pressure systems to produce constant velocity of motion. The majority of the isokinetic devices are capable of resisting both concentric and eccentric contractions at a fixed speed to exercise a muscle. A major disadvantage of these units is their cost. Many of them come with a computer and printing device and are used primarily as diagnostic and rehabilitative tools in the treatment of various injuries.

Isokinetic devices are designed so that regardless of the amount of force applied against a resistance, it can be moved only at a certain speed. That speed will be the same whether maximal force or only half the maximal force is applied. Consequently, when training isokinetically, it is absolutely necessary to exert as much force against the resistance as possible (maximal effort) for maximal strength gains to occur. This is one of the major problems with isokinetic strength - training program.

Anyone who has been involved in a weight - training program knows that on some days it is difficult to find the motivation to work out. Because isokinetic training requires a maximal effort, it is easy to "cheat" and not go through the workout at a high level of intensity. In a progressive resistive exercise program, one knows how much weight has to be lifted with how many repetitions. Thus isokinetic training is often more effective if a partner system is used primarily as a means of motivation toward a maximal effort.

When isokinetic training is done properly with a maximal effort, it is theoretically possible that maximal strength gains are best achieved through the isokinetic, training method in which the velocity and force of the resistance are equal throughout the range of motion. However, there is no conclusive research to support this theory. Whether changing force capability is in fact a deterrent to improving the ability to generate force against some resistance is debatable. In the athletic training setting, isokinetics are perhaps best used as a rehabilitative and diagnostic tool rather than as a training device.

Eat a well-balanced diet

Remember having to memorize the four food groups when you were a kid and wondering if you were really going to need this information when you grew up?

Knowing the food groups helps you plan a well- balanced weight-loss diet. But today, thanks to the folks at the U. S. Department of Agriculture (USDA), there are six food groups. A healthy diet should incorporate foods from all of them.

GROUP 1

Grains, breads and cereals provide fiber, vitamins and minerals. Eat 6 to 11 servings daily of foods like rice, pasta, bread, crackers, grits, pancakes, noodles, bagels, biscuits, corn muffins, English muffins. A sample serving is a slice of bread, an ounce of cereal or a half cup of cooked rice.

GROUP 2

Vegetables contain loads of nutrients. Eat 3 to 5 servings daily. A serving is an average-size potato, a Cu of carrots or a medium plate of salad. Be sure to consider the full range of vegetables. Besides potatoes and starchy vegetables, you need dark green vegetables like broccoli spinach and lettuce. Deep yellow and orange veggies carrots should also be on your regular menu.

GROUP 3

Fruits are rich sources of vitamin C and other vitamins and minerals. Eat 2 to 4 servings a day. A serving equals an average size fruit, 6 ounces of fruit juice or 1/4 cup of dried fruit. Make half your daily fruit intake citrus fruits (like oranges) or berries.

GROUP 4

Meat, fish, poultry, eggs, legumes (beans, peas and nuts) and seeds are good sources of protein, of which you need approximately 60 grams per day. These also provide many vitamins and minerals. Eat 2 to 3 servings daily. A serving equals about 5 to 7 ounces.

GROUP 5

Dairy products are good sources of protein, calcium (especially good for children in building strong bones and also for women in helping prevent bone-weakening osteoporosis) and other minerals and vitamins. You should have 2 daily servings of milk, yogurt or cheese. A serving equals a cup of milk or yogurt, or an ounce of cheese.

GROUP 6

Fats, sweets and alcohol are high in calories. They may be tempting, but they're low in nutrition and should be consumed in moderation.

The Techniques of Muscle Progressive Resistive Exercise

Perhaps the single most confusing aspect of progressive resistive exercise is the terminology used to describe specific programs. The following list of terms with their operational definitions may help clarify the confusion:

•Repetitions - number of times a specific movement is repeated.

•Set - a particular number of repetitions.


•Repetitions maximum (RM) - maximum number of repetitions at a given weight.

•Intensity - the amount of weight or resistance lifted.

•Recovery period - the rest interval between sets.

•Frequency - the number of times an exercise is done in 1 week.

A considerable amount of research has been done in the area of resistance training to determine optimal techniques in terms of the intensity or the amount of weight to be used, the number of repetitions, and the number of sets, the recovery period, and the frequency of training. It is important to realize that there are many different effective techniques and training regimens. Regardless of specific techniques used, it is certain that to improve strength the muscle must be overloaded in a progressive manner. This is the basis of progressive resistive exercise. The amount of weight used and the number of repetitions must be enough to make the muscle work at a higher intensity than it is used to. This is the single most critical factor in any strength — training program. It is also essential to design the strength - training program to meet the specific needs of the athlete.

There is no such thing as an optimal strength training program. Achieving total agreement on a program of resistance training that includes specific recommendations relative to repetitions, sets, intensity, recovery time, and frequency among researchers or other experts in resistance training is impossible. However, the following general recommendations will provide an effective resistance training program.

For any given exercise, the amount of weight selected should be sufficient to allow six to eight repetitions maximum (RM) in each of the three sets with a recovery period of 60 to 90 seconds between sets. Initial selection of a starting weight may require some trial and error to achieve this 6 to 8 RM range. If at least three sets of six repetitions cannot be completed, the weight is too heavy and should be reduced. It is possible to do more than three sets of eight repetitions, the weight is too light and should be increased. Progression to heavier weights is determined by the ability to perform at least 8 RM in each of three sets. An increase of about 10% of the current weight being lifted should still allow at least 6 RM in each of three sets.

A particular muscle or muscle group should be exercised consistently every other day. Thus the frequency of weight training should be at least three times per week but no more than four times per week. It is common for serious weight trainers to lift every day however, they exercise different muscle groups on successive day3. For example, Monday, Wednesday, and Friday may be used for upper body muscles, whereas Tuesday, Thursday, and Saturday are used for lower body muscles.

Muscle Progressive Resistive Exercise

A second technique of resistance training is perhaps the most commonly used and most popular technique for improving muscular strength. Progressive resistive exercise training uses exercises that strengthen muscles through a contraction that overcomes some fixed resistance such as with dumbbells, barbells, or various weight machines. Progressive resistive exercise uses isotonic contractions in which force is generated while the muscle is changing in length. Isotonic contractions may be either concentric or eccentric. If an athlete is performing a biceps curl, to lift the weight from the starting position the biceps muscle must contract and shorten in length. This shortening contraction is referred to as a concentric or positive contraction, If the biceps muscle does not remain contracted when the weight is being lowered, gravity will cause the weight to simply fall back to the starting position. Thus to control the weight as it is being lowered, the biceps muscle must continue to contract while at the same time gradually lengthening. A contraction in which the muscle is lengthening while still applying force is called an eccentric or negative contraction.

It is possible to generate greater amounts of force against resistance with an eccentric contraction than with a concentric contraction. This may be explained by the fact that eccentric contractions require a much lower level of motor unit activity to achieve a certain force than do concentric contractions. Because fewer motor units are firing to produce a specific force, additional motor units may be recruited to generate increased force. In addition, oxygen utilization is much lower during eccentric exercise than in comparable concentric exercise. Thus eccentric contractions are less resistant to fatigue than are concentric contractions. The mechanical efficiency of eccentric exercise may be several times higher than that of concentric exercise.

Various types of exercise equipment can be used with progressive resistive exercise, including free weights (barbells and dumbbells) or exercise machines such as Universal, Nautilus, Cybex, Eagle, and Body Master. Dumbbells and barbells require the use of iron plates of varying weights that can be easily changed by adding or subtracting equal amounts of weight to both sides of the bar. The exercise machines have a stack of weights that are lifted through a series of levers or pulleys. The stack of weights slides up and down on a pair of bars that restrict the movement to only one plane.

There are advantages and disadvantages to both free weights and machines. The exercise machines are relatively safe to use in comparison with free weights. It is also a simple process to increase or decrease the weight by moving a single weight key with the exercise machines, although changes can generally be made only in increments of 10-15pounds. With free weights, iron plates must be added or removed from each side of barbell. Regardless of which type of equipment is used, the same principles of isotonic training may be applied. In progressive resistive exercise it is essential to incorporate both concentric and eccentric contractions. Research has clearly demonstrated that the muscle should be overloaded and fatigued both concentrically and eccentrically for the greatest strength improvement to occur.

Muscle Isometric Exercise

An isometric exercise involves a muscle contraction in which the length of the muscle remains constant while tension develops toward a maximal force against an immovable resistance. The muscle should generate a maximal force for 10 seconds at a time, and this contraction should be repeated 5 to 10 times per day. Isometric exercises are capable of increasing muscular strength; strength gains are specific to the joint angle at which training is performed. At other angles, the strength curve drops off dramatically because of a lack of motor activity at that angle.

Another major disadvantage of isometric exercises is that they tend to produce a spike in blood pressure that can result in potentially life - threatening cardiovascular accidents. This sharp increase in blood pressure results from holding one's breath and increasing intrathoracic pressure. Consequently, the blood pressure experienced by the heart is increased significantly. This has been referred to as the Valsalva effect. To avoid or minimize this effect, it is recommended that breathing be done during the maximal contraction to prevent this increase in pressure.

Techniques of Resistance Training for Strength Improvement

There are a number of different techniques of resistance training for strength improvement, including isometric exercise, progressive resistive exercise, isokinetic training, circuit training, and plyometric exercise. Regardless of which of these techniques is used, one basic principle of training is extremely important. For a muscle to improve in strength, it must be forced to work at a higher level than that to which it is accustomed. In other words, the muscle must be overloaded. Without overload the muscle will be able to maintain strength as long as training is continued against a resistance the muscle is accustomed to.

To most effectively build muscular strength, weight training requires a consistent, increasing effort against progressively increasing resistance. Progressive resistive exercise is based primarily on the principles of overload and progression. If this principle of overload is applied, all three training techniques will produce improvement of muscular strength over a period of time.