1. Muscular Strength & Endurance
Fitness Concepts
PEAC 1621
Kirk Evanson

2. Muscle Physiology Muscle Composition and Organization
Muscle fiber (muscle cell)- composed of myofibrils
Myofibrils → muscle fibers → fascicles → muscles
Muscle fiber types
Slow-twitch (aerobic)- relatively fatigue resistant, but they don’t contract as rapidly or strongly as fast-twitch fibers.
Fast-twitch (aerobic or anaerobic)- contracts more rapidly and forcefully than slow-twitch fibers but fatigue more quickly.

3. Muscle Physiology Muscle
Most muscles contain a mixture of slow-twitch and fast-twitch fibers
Endurance activities (e.g. jogging, swimming) primarily utilize slow-twitch while power activities (e.g. weight lifting) utilize fast-twitch
Motor unit- the motor nerve and the muscle fibers that are innervated by that nerve
The body recruits only the minimum number of motor units needed to produce the required amount of force. The greater the force, the greater the recruitment of motor units.

4. Benefits of Muscular Strength and Endurance
Injury Prevention
Good muscle strength in areas such as the abdomen, hips, lower back, and legs can support the back in proper alignment and help prevent low-back pain
Training also improves the strength of tendons, ligament, and cartilage cells, which decreases the risk for injury

5. Benefits of Muscular Strength and Endurance
Improved Body Composition
Strength training improves body composition by increasing muscle mass
Increases in muscle mass increase basal metabolic rate.
BMR can increase up to 15%
The body requires more calories, therefore there is less fat deposition

6. Benefits of Muscular Strength and Endurance
Improved Muscle and Bone Health with Aging
Strength training prevents muscle and nerve degeneration commonly associated with aging
Also decreases the risk of hip fracture and other life-threatening injuries
Decreases the progressive loss of muscle tone with age (sarcopenia)
By age 75, 25% of men and 75% of women will be unable to lift 10 lbs.
Weight training can mitigate these changes

7. Benefits of Muscular Strength and Endurance
Prevention and Management of Chronic Disease
Strength training improves glucose metabolism
Modifies the risk factors for cardiovascular disease
Decreases diastolic blood pressure
Positive alterations in cholesterol
Increases in HDL, decreases in LDL
Strength training improves bone mineral density
Beneficial in the prevention of osteoporosis and associated bone fractures
Aberrations in glucose metabolism are associated with type 2 diabetes

8. Types of Exercise Static (isometric) Exercise
Involves a muscle contraction without a change in the length of the muscle or the angle in the joit on which the muscle acts.
Common for early physical therapy
Do not build muscle throughout the range of motion
Dynamic (isotonic) Exercise
Involves a muscle contraction with a change in the length of the muscle

9. Types of Exercise Dynamic Exercise (cont.)
Constant resistance exercise
Fixed weight- easier at certain joint angles due to mechanical advantages based on muscle insertion points and length
Variable resistance- resistance is varied throughout the movement to maintain intensity throughout all joint angles

10. Types of Exercise Dynamic Exercise (cont.)
Eccentric- involves placing a load on a muscle as it lengthens
Plyometrics- the sudden eccentric loading and stretching of muscles followed by a forceful concentric contraction
(video)

11. Types of Exercise Dynamic Exercise (cont.)
Isokinetic- the resistance can be moved at a fixed speed. Measurements can be made for multiple muscle groups in addition to group comparisons (quadriceps/hamstring ratio)
(video)

12. Exercise Equipment Free vs. Machine weights Free weights Pros Cons
More muscles needed for the movement
Improvements made in multiple areas
Requires more calories than machine weights
Cons
Movements are more complex and require more strength- the risk of injury increases
Spotters may be needed

13. Exercise Equipment Free vs. Machine weights Machine weights Pros Cons
Reasonably easy to perform
Many safety mechanisms in place to decrease (but not eliminate) the risk of injury
Cons
The intensity of the movement has a limit- can only recruit so many muscles to do a controlled movement
It can be difficult to find the ‘perfect’ machine to work the desired target area

14. FITT Principle Exercise frequency Exercise intensity and volume
2-3 days/week
48 hours of rest needed to allow for adequate recovery
Exercise intensity and volume
Repetitions and Sets
Low repetitions- maximal effort- increase in strength
High repetitions- medium effort- increase in muscular endurance

15. FITT Principle Exercise intensity and volume (cont.)
Repetitions and Sets
3-5 sets
Sets can be determined based off of the intensity of the set
Type or mode of exercise
Variety is the spice of life- work multiple muscle groups

16. Exercise Training Specificity The body will adapt to stress
A leg press will not appreciably improve lower body muscle endurance, however jogging will
Exercises should be selected based off of individual exercise goals