Unit 3

Muscular Fitness

Objectives

Define the difference between muscular strength and muscular endurance.
Identify the types of muscle actions and muscle fibers
Outline the benefits of muscular fitness.
Understand the physiological adaptations to weight training.
Develop a resistance training program with the appropriate guidelines for training.

Focus Questions

What are the various types of muscle fibers and what are their functions?
What is the first physiological adaptation that occurs with a resistance training program?
What are the benefits of muscular fitness?
What is a safe and effective resistance training program for a healthy adult beginner?

Concepts

Concentric, eccentric, and isotonic contractions
Physiological adaptations to resistance training
Training for strength versus endurance

Readings

Chapter 4: Wellness: Choices for Health and Fitness
Study Guide: Link opens new browser window.

Introduction

Muscular fitness is the strength and endurance of your muscles relative to your body weight. Muscular strength refers to the maximum force that a muscle can exert at one time. Muscular endurance refers to a sub-maximal force that a muscle can exert over a period of time.

The types of muscle action are:

Concentric Contraction: Creating force while the muscle shortens
Eccentric Contraction: Creating force while the muscle lengthens – training for eccentric contraction has been shown to increase strength and endurance in the muscles at a much more rapid pace. Your muscle can handle more work in the eccentric contraction phase. To train this way you can: raise the weight up in 2 and lower in 4, or computerized machines can be set to give you a “heavy negative” or more weight for the eccentric part of the exercise.
Isometric Contraction: Creating force with no change in muscle length. Tension exists – remember wall sits?

The initial training effect in a muscular fitness program is neuromuscular response involving the nervous and muscular systems - the brain sends a signal, then the motor nerve innervates certain numbers of muscle fibers telling them to contract. Over the course of training, the nervous system increases the number of muscle fibers recruited in order to magnify the force of the muscular contraction. This allows the muscle to lift heavier loads.

The next stage of muscular fitness improvement is seen in the structural changes in muscle fibers where an increase in contractile protein within the muscle fibers occurs. The textbook illustrates this in the reported study from Stanford. Researchers found that an increase of 22% in cross-sectional area of fast-twitch leg muscle fibers was associated with a 120% increase in leg strength in older women.

Metabolic changes are also part of the training effect with an increase in enzymes that catalyze (enhance) the processes involved in immediate and anaerobic energy production. The number of mitochondria & capillaries in muscle tissue can decrease with training, the opposite as with aerobic training. This speaks to the training principle of specificity.

Muscle fiber types

Slow-twitch Oxidative (SO): fatigue resistant fibers, red in color due to lots of oxygen-carrying myoglobin. SO fibers use the oxidative (aerobic) energy pathway. High amounts of SO fibers are found in postural muscles; low-intensity and long duration training such as the type endurance athletes engage in utilize SO fibers.
Fast-twitch Oxidative Glycolytic (FOG: utilize both methods of energy, high percentage of myoglobin in FOG fibers. FOG uses both oxidative and glycolytic pathways.
Fast-twitch Glycolytic (FG): high glycogen content and rapid rate of fatigue. FG fibers use the glycolytic (anaerobic) energy pathway. The gastrocnemius (calf) has a high proportion of FG fibers to conduct the high-intensity and short duration training seen in speed and power athletes.

Benefits of Muscular Fitness:

Musculoskeletal system: Reduces chronic back problems and improves bone density.
Body Composition: More lean mass equates to better body composition – in general this will occur, if you do not change other parts of your routine, such as your diet. If, however, you are doing heavy weight training, no aerobic work, and are increasing your food intake you may increase your lean mass, but you probably will not see a decline in body fat.
Cardiovascular system: Some reduction in blood pressure has been found.

Frequency

Muscular Strength: 2-3 days/wk Muscular Endurance: 2-3 days/wk be sure to work each muscle group twice a week, and not just “go to the weight room” twice a week. Also, do not work muscle groups two days in a row, exception abs and calves. If you have worked properly you have overloaded your muscle system, causing breakdown within the muscle fibers. Repairing this breakdown is part of the adaptation, or training effect, that makes you stronger, but you need to rest for the repair process to occur properly.

Intensity

Muscular Strength: 60-85%1-RM Muscular Endurance: 50%1 or 15-RM Another method is to make sure that you are working out at a high enough intensity for the reps that you choose. So, choose your reps, say 10 and then choose an intensity or weight where you can do at least 7 but barely be able to do 10. Then you know you are overloading the system enough for improvement. Once you can do 10 reps without breaking your pace, then it is time to move the weight up.

Duration

Muscular Strength: 3sets/5-7reps Muscular Endurance: 3sets/12-15reps If you are just starting out, 1 set is plenty. Research has shown that 2 set improvements are not double the level of 1 set improvements, but doing 2 sets takes double the amount of time. You can do 2-3 sets or more, if you are experienced or have a goal that requires more total weight work.

Rest

Muscular Strength: 3-5 min/48 hrs Muscular Endurance: 15-60 sec/48 hrs High intensity strength building work needs a longer rest period between sets, but since you are working for repeated contractions in the endurance mode, shorter rests are essential. Circuit training also works great for endurance building. Be sure to give each muscle group 48 hours rest for muscle fiber repair.

Mode

Muscular Strength: Weights Muscular Endurance: Resistance To gain strength increases, one typically needs to add weight to the body and maximize resistance. To gain endurance increases many forms of resistance (body as resistance, elastic bands, etc.) will be effective.