chapter 16 Development of Strength and Flexibility Strength

chapter 16 Development of Strength and Flexibility

Strength • Strength is the ability to exert force. • Strength enhances performance of sport and dance skills, as well as daily living activities. • Give examples where lack of strength acts as a rate-limiting constraint to performance of a skill.

Muscle Mass and Strength • Muscle mass growth follows sigmoid pattern. • In part, the force a muscle can exert depends on its cross-sectional area. • Neurological factors are also involved. • Strength does not always change in parallel with muscle size.

Developmental Changes in Strength • Strength increases as children grow. • Boys and girls are similar in strength levels until age 13 years. • Peak strength increases follow peak muscle increases. (continued)

Developmental Changes in Strength (continued) • Among same-size children of different ages, more mature children are stronger. • Endocrine function probably influences strength. • Neural factors likely exert influence (including improved motor unit activation with maturation).

Strength Increases Steadily as Children Grow

Implications What are the implications of the link between strength and maturation for youth sport programs?

Strength in Adolescence and Young Adulthood • Males add more muscle mass in adolescence. • Males are generally stronger, especially in the arms and shoulders. (continued)

Strength in Adolescence and Young Adulthood (continued) • Size does not account for all gender differences. – Cultural norms can affect motivation. – Cultural norms can affect habitual activity levels. • After growth ceases, increases in muscle mass are associated with resistance training.

Strength in Middle and Older Adulthood • Strength generally declines gradually after the 30 s. • Muscle mass declines in the average older adult. • Loss of strength may be greater than loss of muscle mass (possibly due to changes in fiber types, nervous system, vascular system). (continued)

Strength in Middle and Older Adulthood (continued) • Muscular coordination factors might be involved in declining strength. • Some older adults do not lose strength. • Loss of strength is greatly affected by exercise and activity levels.

Strength Training • Prepubescents can increase strength with training. – Improved neuromuscular coordination plays a role. – Youths should be monitored to avoid injuries. • Adolescents and adults can increase strength and muscle mass with appropriate resistance training. – Muscle mass can be increased with training over time. – Those with cardiovascular disease should be monitored.

Percentage Increase in Strength With Training

Strength Training Implications • Does increased muscle size due to training occur in prepubescent children? Why or why not? • What about the growth of the skeletal and muscle systems might dictate a cautious approach to strength training in children? • What are the differences, if any, between the results achieved by adult men and adult women who train for strength?

Development of Strength: Summary • Childhood is a period of steady increase in strength. • Adolescent girls continue a steady increase. • Adolescent boys experience a spurt of growth in strength. • Strength levels are stable in young adulthood. (continued)

Development of Strength: Summary (continued) • Strength declines in older adulthood, gradually at first. • Training can improve strength throughout the life span. • Strength is related to muscle mass and neurological factors.

Assessment of Strength • Force is exerted against resistance. – Isotonic or isokinetic strength if limbs move – Isometric if exerted against immovable resistance • Must specify muscle group, movement, speed of movement, and joint angle. (continued)

Assessment of Strength (continued) • Common isotonic tests use 1 -repetition maximum. • Common isometric tests use dynamometer or cable tensiometer. • Functional strength tests include chin-ups, flexed arm hang, and rope climbing.

Flexibility • Flexibility is the ability to move joints through a full range of motion. • It can benefit sport and dance performance. • Limited flexibility can be a factor in injury. • Flexibility is specific to each particular joint.

Developmental Changes in Flexibility • Infants and toddlers are very flexible; in what positions have you seen babies illustrate this fact? • Studies show that declines in flexibility start in childhood. • Flexible individuals can maintain or improve levels. (continued)

Developmental Changes in Flexibility (continued) • Girls as a group are more flexible than boys. – Flexibility exercises are socially “acceptable” for girls. – Girls participate in activities stressing flexibility. – What are some of these activities? • In adolescence, flexibility is variable; some individuals lose a significant degree.

Changes in Sit-and-Reach Test Performance

Flexibility in Adulthood • Adults gradually lose flexibility, especially in little-used joints and after age 50. • Adults who maintain training for flexibility maintain their levels.

Flexibility Training • Training can maintain range of motion in those with full range. • Training can improve range of motion in those with limited range.

Development of Flexibility: Summary • Range of motion probably reflects activity and training more than age. • Flexibility declines over the life span with limited use (exercise). • Flexibility training can restore lost mobility. • Arthritis can affect individuals of any age, but treatment must be age appropriate.

Assessment of Flexibility • Since flexibility is joint specific, it must be measured for each joint you wish to assess. • A goniometer is often used. – Axis is placed over joint center. – Instrument arm is aligned with limb at extremes of movement range. • Sit-and-reach test is a common measure but has disadvantages.