Training for muscular strength versus endurance

Most weight - training experts believe that muscular strength and muscular endurance are closely related.  As one improves, there is a tendency for the other to improve also.

It is generally accepted that when weight training for strength, heavier weights with a lower number of repetitions should be used. Conversely, endurance training uses relatively lighter weights with a greater number of repetitions.

It has been suggested that endurance training should consist of three sets of 10 to 15 repetitions using the same criteria for weight selection, progression, and frequency as recommended for progressive resistive exercise? Thus suggested training regimens for muscular strength and endurance are similar in terms of sets and numbers of repetitions. Persons who possess great levels of strength tend to also exhibit greater muscular endurance when asked to perform repeated contractions against resistance.

Physiology of Strength Development

A number of theories have been proposed to explain why a muscle hypertrophies in response to strength training. Some evidence exists that there is an increase in the number of muscle fibers because fibers split in response to training. However, this research has been conducted in animals and should not be generalized to humans. It is generally accepted that the number of fibers is genetically determined and does not seem to increase with training.

It has been hypothesized that because the muscle is working harder in weight training, more blood is required to supply that muscle with oxygen and other nutrients. Thus it is thought that the number of capillaries is increased. This hypothesis is only partially correct; few new capillaries are formed during strength training, but a number of dormant capillaries may become filled with blood to meet this increased demand for blood supply.

A third theory to explain this increase in muscle size seems the most credible. Muscle fibers are composed primarily of small protein filaments, called myofilaments, which are the contractile elements in muscle. These myofilaments increase in both size and number as a result of strength training, causing the individual muscle fibers themselves to increase in cross - sectional diameter. This is particularly true in men.

In addition to muscle hypertrophy there are a number of other physiological adaptations to resistance training. The strength of noncontractile structures, including tendons and ligaments, is increased. The mineral content of bone is increased, making the bone stronger and more resistant to fracture. Maximal oxygen uptake is improved when resistance training is of sufficient intensity to elicit heart rates at or above training levels. There is also an increase in several enzymes important in aerobic and anaerobic metabolism.

Factors that Determine Levels of Muscular Strength

Muscular strength is proportional to the cross - sectional diameter of the muscle fibers. The greater the cross - sectional diameter or the bigger a particular muscle, the stronger it is, and thus the more force it is capable of generating. The size of a muscle tends to increase in cross - sectional diameter with weight training. This increase in muscle size is referred to as hypertrophy. Conversely, a decrease in the size of a muscle is referred to as atrophy.

Strength is a function of the number and diameter of muscle fibers composing a given muscle. The number of fibers is an inherited characteristic; thus an athlete with a large number of muscle fibers to begin with has the potential to hypertrophy to a much greater degree than does someone with relatively fewer fibers.

Strength is also directly related to the efficiency of the neuromuscular system and the function of the motor u-nit in producing muscular force. Initial increases in strength during a weight-training program can be attributed primarily to increased neuromuscular efficiency.

Fast - Twitch versus Slow - Twitch Fibers

All fibers in a particular motor unit are either slow - twitch or fast - twitch fibers, each of which has distinctive metabolic and contractile capabilities. Slow - twitch fibers are also referred to as type I fibers. They are more resistant to fatigue than are fast - twitch fibers; however, the time required to generate force is much greater in slow - twitch fibers. Because they are relatively fatigue resistant, slow - twitch fibers are associated primarily with long - duration, aerobic - type activities.

Fast - twitch fibers (also referred to as type II fibers) are capable of producing quick, forceful contractions but have a tendency to fatigue more rapidly than do slow - twitch fibers. Fast - twitch fibers are useful in short -term, high - intensity activities, which mainly involve the anaerobic system. Fast — twitch fibers are capable of producing powerful contractions, whereas slow - twitch fibers produce a long - endurance type of force. There are two subdivisions of fast - twitch fibers. Although both types of fast - twitch fibers are capable of rapid contraction, type IIa fibers are moderately resistant to fatigue whereas type IIb fibers fatigue rapidly and are considered the "true" fast - twitch fibers.

Within a particular muscle are both types of fibers, and the ratio in an individual muscle varies with each person. Those muscles whose primary function is to maintain posture against gravity require more endurance and have a higher percentage of slow — twitch fibers. Muscles that produce powerful, rapid, explosive strength movements tend to have a much greater percentage of fast - twitch fibers. Because this ratio is genetically determined, it may play a Large role in determining ability for a given sport activity. Sprinters and weight lifters, for example, have a large percentage of fast - twitch fibers in relation to slow - twitch fibers. Conversely, marathon runners generally have a higher percentage of slow - twitch fibers.

The metabolic capabilities of both fast - twitch and slow - twitch fibers may be improved through specific strength and endurance training. It now appears that there can be an almost complete change from slow - twitch to fast - twitch and from fast - twitch to slow - twitch fiber types in response to training.

Strength Improvement

To improve strength, muscles must be progressively and gradually challenged or placed under additional stress. A conditioning program's effects are specific to the type of stress applied. The SAID principle (Specific Adaptation to Imposed Demands) stales that as the body is placed under stress of varying intensities and durations, it attempts to overcome the stress by adapting specifically to the imposed demands. For example, muscles around a joint can be developed and conditioned to provide optimal stabilization of the joint. Likewise, when a muscle primarily produces motion of a joint, proper conditioning can prevent the muscle from undergoing an unwanted movement. The demands of a specific athletic event must be a progressive stress applied in that athlete's training.

Other components of strength conditioning which contribute to injury prevention are the ability of the muscle to contract or exert force at an accelerated speed, and muscular endurance, which allows the athlete to maintain an appropriate strength level over a period of time.

Preventing Exercise Cold Injuries

·Avoid wind - exposed race courses.

·Caution athletes concerning wind - chill factor, adequate clothing, etc.

·Acclimatize to cold conditions - ten days is an ideal acclimatization period.

·Use muscle glycogen loading to maximize heat production. Avoid caffeine and alcohol. Hydrate before and during a race.

·Wear layers of material which will draw sweat from the skin and allow evaporation. Wear head cover.

·Control pace to avoid late slowing and reduced heat production.

Preventing Exercise Thermal Distress

The problems of thermal distress can be minimized by following a few simple heat injury prevention principles:

1. Ensure that athletes are in good physical condition. There should be a gradual increase in intensity and duration of training in the heal until the athletes are fully acclimatized.

2. Ensure that athletes avoid becoming overheated before exercising in a hot environment (i.e., that they avoid pre-exercise heat storage).

3. Be aware of the early symptoms of heat injury, such as thirst, fatigue, lethargy, and visual disturbances.

4. Clinical signs of hyperthermia are typically more meaningful than temperature measurements. Core temperature is often underestimated because common sites of temperature measurement (i.e., mouth or axillary sites) are too superficial.

5. Athletes should not run faster than their normal training intensity.

6. Athletes should not compete if they have any illness accompanied by fever or had a fever shortly before the event. Other conditions that decrease heat tolerance include sleep loss, glycogen depletion or hypoglycemia, or recent heavy alcohol consumption (i.e., "hangover") for heat injury prevention.

7. Schedule practice sessions and games during the cooler times of the day.

8. Modify or cancel sessions when the wet bulb globe temperature is 25.5 degrees or greater. Wet bulb temperature is used to determine humidity and black globe temperature is an indication of radiant heat.

9. Plan for regular fluid breaks. Have athletes drink approximately 200 ml (1 cup) of fluid replacement beverage every 15-20 minutes.

10. Supply a drink that’s cold (8 - 13t) and contains some carbohydrate (6-8g/100ml), with a small amount of electrolytes (sodium/potassium).

11."Tank - up" before practice or games by drinking 600 ml (2.5 cups) of fluid two hours before the activity and an additional 400 ml (l.5 cups) 15 minutes before.

12. Fluid replacement should be particularly encouraged during the early stages of practice and competition. As exercise progresses, splanchnic blood flow decreases, which diminishes water absorption from the gut.

13. Athletes should be weighed every day before practice. Any athlete showing a decrease of 2 - 3% should consume extra fluid. Athletes with weight losses of 4 - 6% should decrease training intensity, and those with weight losses greater than 7% should consult a physician. People who lose a lot of weight in the heat should be identified and closely monitored for heat injury prevention.

14. Salt tablets are prohibited. However, athletes should be encouraged to consume ample amounts of salt at mealtime.

Thermal Distress and Heat Injury - Heat stroke and Heat Syncope

Heat stroke is difficult to distinguish from heat exhaustion, because sweating may continue. Heat stroke represents thermoregulatory failure, with reduction in skin blood flow in order to maintain the central circulation. Core temperature is more elevated, usually 40 degrees Celcius or higher.

Signs/symptoms:

CNS symptoms predominate: unsteady gait, confusion, combative behavior, reduced consciousness, and coma , These s/s represent a medical emergency.

Treatment:

1）Move to a cool, shaded area. Lie down with feet elevated.

2）Loosen or remove clothing.

3）Begin cooling at once, if temperature is elevated. In the field, it may necessary to assume that temperature is elevated, as  taking a rectal temperature may not be feasible. Oral or axillary temperature is quite unreliable. Apply cool water, and fan to increase evaporation. Apply ice packs over major vessels in neck, axillae, groin. Cool to a rectal temperature of 39 degrees Celcius.
4）Re-hydrate, orally if conscious and not nauseated;
5）Evacuate to a medical facility if serious mental or neurologic defects occur. Manage as a medical emergency, with  monitoring of cardiac, neurologic, and renal function, and electrolyte balance.

Heat Syncope is syncope is related to heat exhaustion but can occur even without major sweat loss. It typically occurs after exercise - the person stops moving, blood pools in the lower extremities, and the person faints. It tends to occur in unacclimatized people at the beginning of summer. Heat syncope can occur secondarily to heat exhaustion or can occur independently.

Thermal Distress and Heat Injury - Heat exhaustion

Heat exhaustion is a serious heat injury caused by increased exercise heat load plus dehydration.

-Signs/Symptoms:

"core" (rectal) temperature elevated, usually not above 39.5t; "goose flesh", headache, lethargy, altered consciousness, nausea, vomiting, incoordination.

-Treatment:

*Move to a cool, shaded area.

*Remove excess clothing.

*Begin immediate cooling with cold or iced cloths, sponges, etc. to torso, axillae, groin, other exposed areas.

*Begin hydration with cool fluids, orally if possible, otherwise start IV fluids (D/W, D/0.5N saline).

*Monitor vital signs, rectal temperature if possible.

*Consider transfer to hospital, depending on response to therapy.

-Heat exhaustion/Heat Injury Prevention：

*Avoid competition under adverse conditions, or adjust pace to existing conditions.

*Utilize acclimatization measures prior to competition.

*Pre-hydrate; emphasize hydration during the competition.

*Wear appropriate clothing which will "breathe" and allow sweat to evaporate.

Thermal Distress and Heat Injury

With the popularity of distance running and competitive sports for the weekend athlete, thermal distress and heat injury are becoming increasingly common. Fortunately, many of the severe effects of heat stress in athletics can be avoided if the necessary precautions are taken. Heat injury includes dehydration (loss of body fluid) ,heat cramps, heat exhaustion, heat syncope (fainting in the heat) , and heat stroke.

•Heat cramps are caused by loss of sodium and potassium associated with heavy sweating in the unacclimatized.

-Signs/symptoms: painful muscle spasms, usually of the calves or abdomen.

-Treatment: fluid/electrolyte solutions, generally taken orally.

-Heat cramps/Heat Injury Prevention: added salt to food; eat a balanced, high K+ diet.

•Dehydration commonly accompanies exercise in warm, humid conditions, when fluid replacement is inadequate. It complicates heat exhaustion and heat stroke.

-Signs/symptoms: fatigue, lethargy, irritability, incoordination, faintness, altered consciousness.

-Treatment; cool fluids; dilute electrolyte solutions.

-Dehydration/Heat Injury Prevention: pre-hydrate; adequate fluid replacement during activities.

Vitamins and Exercise

Vitamins are substances needed in very small quantities. They are involved in numerous metabolic reactions and must be consumed in the diet. Vitamins are water - soluble or fat - soluble. Water - soluble vitamins, such as vitamin C, tend to act as coenzymes (work with enzymes lo cause a chemical reaction). They are stored in small quantities, so regular intake is essential. Fat - soluble vitamins do not act as coenzymes and are stored in greater quantity than water - soluble vitamins. With a few exceptions, active people do not benefit from vitamin supplements. The best dietary strategy for adequate vitamin intake continues to be selecting a balanced diet from the basic food groups.

A variety of vitamins has been used as ergogenic aids. These substances, although essential, are required in extremely small quantities. Because mitochondria increase due to endurance training, more vitamins may be needed to support the increased metabolic activity. However, vitamin deficiency in athletes has not been consistently demonstrated. In fact, most athletes take many times the minimum daily requirement for these substances. Only levels of vitamin C, thiamin, pyridoxine, and riboflavin decrease with exercise (due to increased metabolism). These vitamins are not lost in sweat.

Nutritional Supplements for Exercise

Athletes spend a fortune on an endless variety of dietary supplements, such as proteins, vitamins, and weight - gain products. However, an overwhelming body of literature has demonstrated that as long as an athlete is receiving a balanced diet, most dietary supplements have no effect on performance. Of course, if the diet is deficient in any essential nutrient, then supplementation may very well be beneficial. This section focuses on those nutritional supplements that are specifically used as ergogenic aids.

Carbohydrate (CHO) feeding, often in the form of glucose, dextrose, or honey, has long been used as an ergogenic aid to increase strength, speed, and endurance. CHO feeding has no effect on strength, power, or high - intensity, short - term exercise.

Consuming liquid meals before and during exercise has been shown to be beneficial in endurance exercise. Compared to no feeding, carbohydrate feeding during exercise increases blood glucose concentration. During prolonged exercise, carbohydrate intake increases endurance and the ability to exercise intensely late in exercise. The longer exercise continues, the more important ingested carbohydrate becomes as a fuel source. Carbohydrate feeding is most effective in well - trained athletes when exercise duration exceeds three hours. The effective exercise duration decreases with the training status of the subject. In mode rat Iv trained people, carbohydrate feeding may be effective in events lasting as little as 1.5 hours.

Hydration and Fluid Replacement

Thirst is a poor indicator of the need for fluid replacement - athletes must train themselves to drink regularly to maintain hydration. By the time an athlete is 2% dehydrated, their performance can be markedly impaired (up to 15%).

Athletes should ensure that they are well - hydrated in the 3 hours leading up to an endurance event by initially drinking between 500 and 1000ml of water or dilute glucose - electrolyte solution, then 300 - 500 ml of water in the 30 minutes prior to competition. During the ensuing competition, fluids should be replaced at the rate of approximately 150 - 200 ml every 20 minutes. The rate of fluid lost through sweating can exceed 1 liter per hour - the goal is to replace this loss by regular fluid intake. This can be in the form of water, but there is increasing evidence that solutions of up to 8% glucose can be beneficial, especially in events lasting over 90 minutes. The exercising athlete can absorb glucose solution at this concentration as easily as water, although it may take some practice to get used to drinking this type of formulation.

General Recommendations for Athletes' Diet

In general, athletes should minimize their alcohol intake, as this can potentiate dehydration and, by inhibiting gluconeogenesis, can lead to hypoglycemia. A healthy diet also features reduced levels of salt (unless the athlete is sweating heavily - the athlete conserves salt by producing very hypotonic sweat), saturated fats, and refined sugars. Dietary recommendations for training include the following:

•Athletes with high energy needs may have to spread their intake over more meals to be able to ingest enough calories;

•A healthy, balanced diet as previously outlined usually negates the need for vitamin supplementation;

•Supplementation with vitamins or minerals is only an option if dietary adjustment fails to correct the real or perceived deficiency;

•Athletes must ensure that they have adequately replaced fluids lost during exercise, as dehydration adversely affects performance and can be harmful.

Maintaining Caloric Intake

Athletes must maintain sufficient caloric intake to meet energy requirements in order to prevent lethargy or fatigue. With their intensive training programs, caloric intake to meet energy needs may average 4,500 - 5,000/ day in men, and 3,000- 3.500/day in women. Athletes should use a food diary to record the previous week's intake in order to discuss it with a sports dietitian. Meals should include items from the five main dietary groups: bread and cereals, fruit and vegetables, meat and meat derivatives, daily products and butter, and fats and oils, to ensure a balanced diet. Monitoring body weight at regular intervals under standard conditions can be a guide to health and nutritional adequacy.

Here is a myth that high levels of dietary protein are needed to build muscle bulk and strength. Some athletes misguidedly consume up to 30% of their calories in protein, a strategy that does not improve performance and could in fact be detrimental. In fact, there is no evidence that most athletes need more protein than the sedentary person，but athletes in the power events may be the exception!

Large athletes, especially throwers, sometimes consume excess fat in their diet, while the opposite may be true for some endurance runners. Current dietary fads encourage reduction of fat to very low or zero levels. Such a strategy is not healthy, as free fatty acids provide the energy substrate during daily activities and recovery. In ultra - endurance events, fat becomes an increasingly important substrate as muscle and liver glycogen are consumed. There is also increasing evidence that ultra - endurance athletes should ingest a certain amount of fat to replace energy lost in competition, rather than eating only carbohydrates following competition.

Principles Of Sports Injury Prevention

Sports therapist must be familiar with injury prevention principles to be all effective part of the sports medicine team, all team members of sports medicine specialist should stress the importance of injury prevention constantly to athletic trainers and athletes, especially if the training program reveals a lack of awareness or a disregard of these principles.

Physical conditioning is a key principle of injury prevention. An appropriate good exercises program decreases the risk of injury, decreases the severity of an injury should it occur, and can help prevent re-injury. Maximizing the chance for safe athletic performance requires adequate muscular strength and endurance,balance, power,muscular coordination, joint flexibility, cardiovascular endurance, and good body composition for sport.

Improving specific components of fitness and conditioning reduces the risk of injuries. For example, muscular strength exercises help reduce injuries to the area of a joint; regular muscular strength exercises can significantly increase the strength of the ligaments surrounding the knee and prevent knee injuries; muscle development provides increased strength that helps to stabilize joints; and improved movement skill is important in injury prevention.

Body Shape Linked to Your Taste buds

 
Scientists can determine someone's favorite food from their body shape. They have discovered that the arrangement of tastebuds on the tongue varies for different body types. The sci­entist team examined 1000 British adults and divided them into three physiologically recognized body typesectomorphs, endomorphs and mesomorphs. They determined that a person's body type indicated where they were likely to have the most tastebuds- on the sweet, bitter or salty areas of their tongue.

The study showed that ectomorphs, who make up one in three of the population, usually have a small delicate shape, have a sweet tooth but hate bitter foods. Mesomorphs, who make up 20 per cent of the population, usually have a muscular shape and prefer salty or bitter foods but dislike sweet foods. Half the British populations are endomorphs with soft, rounded bodies, and they like most foods. The findings showed that for two in three people food preference was a physiological rather than a psychological choice.

Although it appear that simply by looking at an individual's body shape we can make assumptions about their taste preferences, it is difficult to dictate whether our body shape dictates the food we like, or the food we like dictates bodyshape. It stands to reason people who prefer most types of foods will be fatter and people who are the endomorph shape tend to finds it more difficult to lose weight.

Musculoskeletal Flexibility

Optimal musculoskeletal function requires that an adequate range of motion be maintained in all joints. Of particular importance is maintenance of muscular flexibility in the lower back and posterior thigh regions. Lack of muscular flexibility in this area may be associated with an increased risk for the development of chronic lower back pain. Therefore, preventive and rehabilitative exercise programs should include activities that promote the maintenance of muscular flexibility. Lack of muscular flexibility is prevalent in the elderly among whom this condition often contributes to a reduced ability to perform activities of daily living (ADL). Accordingly, muscular strength exercises for the elderly should emphasize proper stretching routine, especially for the upper and lower trunk, neck, and hip regions.

There are different types of stretching techniques, such as static stretching and ballistic stretching that can be performed.

Properly performed routine stretching exercises can aid in improving and maintaining range of motion in a joint or series of joints. Muscular flexibility exercises should be performed in a slow, controlled manner with a gradual progression to greater ranges of motion. A general sports therapy prescription for achieving and maintaining muscular flexibility should adhere to the following guidelines:
•Frequency: At least 3 days per week
•Intensity: To a position of mild discomfort
•Duration: 10 to 30 seconds for each types of stretching
•Repetitions: 3 to 5 for each types of stretching
•Type: Static, with a major emphasis on the lower back and thigh area

Guidelines for an Optimal Training Load

The optimal training load for an individual athlete depends on various factors, including genetic make - up, lifestyle, and state of initial fitness.

There are no hard and fast rules for determining how and when to adjust the training load, but empirical evidence suggests that an increase of no more than 5 % each week during a training micro - cycle allows for adaptation and recovery.Furthermore, intensity and volume of training should not be increased simultaneously.

Not being able to devise a numerical index for training intensity and volume makes it difficult to quantify the training load. Therefore, training must be carefully documented in the athlete's diary  by athletic trainers. The athletes’ subjective responses to and feelings about the training should be monitored and recorded, as should lifestyle factors such as hours and quality of sleep, nutrition, and other stressors by physical trainers. If signs of over training do become apparent, a careful record of activities should help pinpoint possible causes.