PE 9A Information

Section 4: Muscular Strength

Tracey Kobayashi

50 Phelan Ave, NGYM
San Francisco, CA 94112
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tkobayas@ccsf.edu

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Strength training, exemplified by the myth of Milo of Croton, who lifted a calf every day, becoming stronger as the calf grew into a bull, has existed far longer than modern gyms. Strength training has varied benefits, including general fitness maintenance and conditioning, osteoporosis prevention/treatment, injury prevention/management and strength develpment. For those whose goal is to lose weight, strength training boosts metabolic rate, so the fit individual burns more calories than the unfit individual.

The body makes several adaptations in the areas worked to strength training.

• NEURAL: The initial strength change associated with strength training is from increased efficiency of motor unit recruitment -- more muscle fibers are triggered when the neuron fires or the neurons themselves fire more efficiently. Neural changes are highly prevalent in women.
• MUSCULAR: The muscle fibers of the muscles worked hypertrophy -- individual fibers develop more contractile proteins (actin and myosin). Hyperplasia, an increase in the number of actual muscle fibers, does not occur with exercise - the only instances of hyperplasia in humans have been during pathological conditions.
• SKELETAL: Mechanical stress is important to the skeletal system, in the forms of weight-bearing and muscular (tension) stress, because it helps maintain bone density. Also important is the direction in which the bone is stressed. The tension-type force resistance training imparts on weight-bearing bones such as the femur develops them differently than the weight-bearing forces of running, walking or standing.
• HORMONAL: The largest hormonal change is an increase in testosterone levels, particularly in males. In general, testosterone levels are much higher in males than females. Because of this, men have higher hypertrophy potential. However, strength differences in males in females are quantitative only -- muscle tissue quality is identical in males and females.

The Muscular System

Muscles are made up of many fibers, which are made of tinier myofibrils called actin and myosin which interact with each-other to cause a contraction, or shortening, of the muscle. The combination of skeletal muscle contraction and relaxation create movement around a joint. The schematic below shows how a muscle works.

When one strength trains, the number of myofibrils increases (hypertrophy), which increases strength, and can make the muscle look larger. As a result of this increase in muscle mass, the bodyÕs metabolic rate increases. With aerobic training, the size and number of mitochondria increase, allowing the body to respond better to increased energy needs by converting fat and glucose more readily. Thus, a fit person burns more calories because of increased lean mass, and also burns fat more efficiently.

Muscular Contraction and Strength Training Modalities

Skeletal muscles contract and relax, creating tension on the bones to which they are attached. This tension can cause the bone to move, or control movement, around its axis (joint). Muscle strength is directly related to its mass, or hypertrophy. Not all fibers within a muscle are used in a contraction, but selected motor units engage based on the needs of the movement. Each contraction uses fast, intermediate and slow-twitch fibers, depending on movement needs and fatigue level. As motor units fatigue with repeated contractions others are called into play. Strength training fatigues many motor units to induce training effects.

Isotonic contraction causes movement, and has two phases: concentric - the muscle shortens; and eccentric - the muscle lengthens. Most strength programs are based on isotonic movement, and isotonic contractions are common everyday Ð walking, lifting, tapping keyboards are all isotonic. Examples of isotonic training include free weights and isokinetic machines.

Free weights such as barbells and dumbells (and bulls!) are the most common, and the oldest, of isotonic strength training methods. TheyÕre relatively inexpensive, require relatively little space, and can be used for a variety of exercises. Strength machines such as Universal and Soloflex are also isotonic.

Nautilus and Cybex are cam-based machines, which vary torque so, in theory, the muscle contracts with the same amount of force throughout the range of motion Ð with free weights, certain points will seem easier or more difficult depending on joint angle and the muscleÕs angle of pull. This form of isotonic contraction is also known as isokinetic. Isokinetic dynamometers (KinCom and Cybex II) are used for testing and rehabilitation. You can see them at your physical therapistÕs. They accommodate based on individual output by varying resistance or speed.

Isometric (static) contractions are ones in which joint angle remains constant -- for example, pushing against a wall while maintaining your position. Convenience once made Isometric exercise popular - it could be done anywhere with no special equipment - however, since strength gains from isometrics are specific to the joint angle worked, there is little practical value in this form of training for most applications.

Strength machines decrease time of changing weights and donÕt require a spotter. Some units, such as NordicFlex and Soloflex, have small footprints while offering a complete workout. The machine, and not the person, supports the movement, so prime movers are emphasized -- synergistic muscles don't benefit as much. Machines also tend to be sized for "average" people, which may make it difficult for those on size extremes to find optimal adjustments. For most people, a few well-selected free weights make for an efficient, cost-effective workout.

Gross Anatomy

Muscles may be grouped by function as well as location. As muscles contract, they create movements around joints, including: flexion -- joint closes; extension -- joint angle opens; abduction -- limb moves away from midline of body; adduction -- limb moves in towards midline of body. The following chart classifies the major muscle groups around the joints they work. This list is not all-inclusive, however, it contains the main groups.

The knee flexors and extensors, hip extensors, spinal flexors, and groups surrounding the shoulder constitute the major muscle groups. Each major group should be worked 2 to 3 times each week.

Common Strength Exercises

The traditional view of the big muscle men performing big, grunt-inducing lifts are most likely the power lifts (clean, jerk/jump press, snatch), which today are sometimes used to develop general power or speed-strength. The focus of these lifts is to generate enough momentum with the legs to accelerate the bar up into the correct position.

The following exercises are classified by muscle group worked. We will go over most of these exercises in class.

Strength Training Variables

Program variables depend on individual goals. Pure strength programs are more intense than muscular endurance programs. Intensity (load) is usually based on a Repetition Maximum (RM), the maximum amount of resistance one can lift for a given number of repetitions (1RM = max wt for 1 rep). In general, strength programs use higher loads with less repetitions per set and more rest between sets while endurance programs use less load with more repetitions per set and less rest between sets. Here are three basic programs.

Training Variables Based on Goals

As goals range from endurance to strength, load, number of sets and rest between sets increases while repetitions per set decreases. Increased rest between sets allows more phosphagen recovery, and each successive set requires the muscle group to recruit more fresh fibers and motor units. These classifications lie on a continuum with considerable overlap and aren't necessarily discrete groups.

Muscular endurance programs promote use and development of type I, or slow twitch, fibers. Mitochondria (energy factories) within the muscles may increase in size to adapt to increased energy demands.

Hypertrophy programs are most commonly associated with body builders. The increased load requires more fast twitch and intermediate type fibers which tend to be faster and stronger than slow twitch, but fatigue faster.

Strength programs are common with power and speed athletes, and power and weight lifters and also tend to stress fast twitch fibers.

Strength training options include pyramid training and multiple sets same load. In pyramid training, sets progress with ascending loads and descending reps, ex: set 1, 5-6 reps @ 85%; set 2, 4-5 reps @ 85%; set 3, 2-4 reps @ 90%. The pyramid may also continue in the opposite direction. With multiple sets, same load, the same load is used in each set with the ultimate goal of completing the goal number of reps for each set, ex: 3-5 sets of 6-8 reps. These two methods are not recommended for smaller muscle groups, such as the arms, since the long-term effect on smaller joints could be deleterious. For strength training, the supercompensation period occurs about 48-72 hours after the workout, which is why most strength programs involve 2-3 workouts per week, with 2-3 days between workouts.

Workout variables change in an absolute sense with adaptation, but not necessarily in a relative sense. As strength increases a greater load must be used, but the greater load may or may not be the same percent of maximum. There are two ways to increase training load. One is to regularly re-test and base workouts on the new 1RM. Another is to increase workload in small increments based on the 2 for 2 principle -- if you perform 2 extra repetitions per set over your goal reps for each set for 2 consecutive workouts, it's time to increase your workload.

Exercise Selection and Order

When choosing exercises for a single workout, include one to three exercises for each major muscle group: chest, back, shoulders, quadriceps, hamstrings, biceps and triceps. Abdmominals may be worked more often. Exercises for minor groups, such as calves and forearms may also be included. Perform two to six sets per muscle group. Successive sets of an exercise fatigue more motor units, while different exercises for the same group may stress different synergystic muscles. Periodically change the exercises you perform for each muscle group -- this prevents "staleness" and allows you to stress different synergystic muscles.

In general, it is best to work compound-to-isolation and large-to-small in terms of muscle groups involved in compound (multi-joint) actions. For example, the chest and triceps groups both contribute in the bench press. To be sure that the chest group, which is larger and therefore stronger, is sufficiently fatigued, it is best to perform the bench press first before performing isolation-type exercises on the chest and triceps groups.

Super sets and compound sets: Super sets consecutively train 2 opposing groups with no rest between the exercises -- ex: alternating between bench press and bent rows. Compound sets are ones in which 2 exercises for the same muscle group are completed consecutively with no rest between -- ex: bench press and pec flies.

Hard-Easy Training

Hard-easy training theory goes back to the basic idea that one simply can't train at a high level every day. There are two basic systems for varying workload on a day-to-day basis: one is to train all muscle groups 3 days/week with 48-72 hours between workouts; another is the split routine, in which one works out every day, but works different muscle groups each day so each group is worked 2 to 3 days/week. Which method an individual chooses depends upon factors such as individual goals and time constraints.

The 3 day/week program is used for general fitness and athletic conditioning. Each workout covers all major muscle groups, with an average of 10 to 12 exercises. This method is time-efficient as there is only a 3 day/week commitment and other factors including those of traveling to and from the gym make it less of an overall time commitment.

The split routine is more time-consuming in that one works out 4-6 days/week, training each muscle group 2-3 days/week. It is mostly used by body-builders who work each muscle group more thoroughly, allowing the individual to: 1. Work out on successive days (by working different muscle groups each day; and 2. Train each muscle group more thoroughly (different muscles within a group may be emphasized by performing a different exercise or the same exercise differently). The split routine requires a time commitment that is quite unnecessary for a general fitness program.

Common Split Routine Schedules -- abdominals worked every day

Women and Strength Training

Weight training has been the traditional domain of males. Fortunately, as research disproves old myths, more women are engaging in strength training as well as many other active pursuits. For example, many women were concerned about "bulking" up, or flexibility or coordination loss. However, when trained correctly, muscles lose no flexibility or coordination. As for bulk, hypertrophy is greatly dependent the bodyÕs testosterone levels, which may be up to ten times higher in men than women. Also, women tend to have more fat (about 8% more than men) which, subcutaneously, helps to visually "soften" muscle definition.

In terms of potential strength, women have lighter skeletons and less muscle mass. They have narrower shoulders and wider hips relative to body size, and a bit more body fat. However, muscle tissue quality is identical in males and females. Strength differences are attributed to QUANTITY of tissue. In females, muscle tissue makes up approximately 23% of total body mass, whereas in males, muscle mass is about 40%. Keep in mind, women may develop equally to men in terms of their potential, although not in absolutes simply because of body structure. Absolute strength differences have more to do with quantity of muscle tissue as well as leverage differences.

Research comparing strength gains in women and men from strength programs shows that more initial strength in women was due to neural changes -- motor unit recruitment became more efficient. Women also increased in strength faster. Based on the theory of potential gain described above, these differences may be attributed to the fact that women had less access to strength training and sport programs in the past.

Training programs for females will be similar for males with the exception that they will usually work with somewhat lighter loads and may need more upper body exercises, where they tend to be relatively weak -- women's centers of mass tend to be lower, so they have relatively more mass on their lower bodies than men.

Of course, women sometimes experience a phenomenon unique to females in which physical activity must be modified . . . pregnancy! In general, women may safely exercise normally through the first trimester of pregnancy. Beyond the second trimester, avoid a heart rate over 140bpm, activities involving squatting or bearing down, and avoid lying in the supine position for too long. As always, your doctor is the final authority on your individual physical activity restrictions and recommendations.

For the most part, physical activity is perfectly safe before, during and after menses. In fact, many women suffering from pms often find that physical activity helps alleviate cramping and feelings of stress.

Training Through the Ages

With a few exceptions, children may safely participate in strength-type programs. Of primary concern for children is damage to the epiphyseal growth plates of the long bones. Immature bones are more sensitive to high loads -- intense training accelerates the maturation process causing permanent suppression of bone growth. Low intensity training, however, may stimulate long bone length and circumference increses. Because of this, children under the age of about 15 (after the growth spurt has passed) should avoid heavy loads and overhead lifts. To prevent overtraining, children may perform mainly body-resistive and light load exercises, concentrating on volume -- 2-3 sets per exercise of 12-15 repetitions per set, at an intensity where the final repetition feels difficult, but not so exercise technique must be compromised.

As one ages, it has been thought that bone density and strength decrease. However, much of this degeneration has actually been shown to stop, and sometimes even reverse, when elderly people engage in physical activity. Mechanical stress is vital for bone formation, and it has been determined that inactivity is a large factor in bone loss. In general, elderly people can safely follow a strength training program with no problems. It is best to consult a doctor concerning any exercise contraindications before beginning a fitness program.

Weightroom Safety Checklist

This list of safety protocols is not comprehensive -- remember to always use common sense.

• report any possible hazards to the proper personnel
• check cables, belts, pulleys and chains for wear or loose links, welds and pads for wear
• report rough or uneven movement of machines
• adjust levers and seats accordingly and fasten belts securely
• choose appropriate load and insert selector keys securely and fully
• don't allow weight stacks to bounce or hit the pulleys

Free Weights

• use correct lifting, loading and spotting techniques
• check that locks are secure -- don't assume the person before you did it correctly
• use the appropriate load and make sure the load is even
• be aware of others and watch for bars and equipment when walking

Lifting Objects from the Floor

Use a closed grip (thumbs wrapped). Open/false grips make it easy for the bar to slip and fall.

• common width Ð shoulder-width, hands equidistant from plates or center of bar
• grips may be overhand/pronated, underhand/supinated or alternate Ð one hand over, one hand under

Preparatory position -- bar close, hips low, back flat.

• feet flat, toes slightly out, slightly wider than shoulders
• shoulders over or slightly ahead of bar, back flat, shoulder blades back

From floor-to-thigh: straighten legs, don't use back (keep it flat).

• head and eyes level
• place in rack or hand to partner

Rack-to-shoulders: continue pulling, keep hands close to thighs, without resting on them.

• keep bar close, and shrug as legs straighten
• bend elbows at end of shrug, keep them moving up and forward
• flex knees and hips as bar contacts shoulder

Return-to-floor: from shoulders, allow weight to slowly straighten arms

• hips & knees slightly flexed to absorb weight
• lower to floor by bending knees
• remember: bar close, hips low, back flat

Breathing: exhale through exertion phase to prevent decrease in venous return.

Spotting

Assisting as needed in exercise execution, which is crucial for lifting safety, is commonly known as spotting. When spotting:

• move loose paraphernalia away to avoid slipping or tripping
• place body in proper position, hands close to bar without obstructing movement
• place body in good lifting position in case you have to catch the weight
• communicate with lifter -- how many reps?
• use appropriate grips & hand location
• be aware of potential dangers & respond quickly to them

Intro | Facts
Cardio | Strength
Nutrition | Diet Industry
Resources
References