Age and Sex Related Differences and Their Implications for Resistance Exercise

Preadolescent Youth Refers to a period of time before the development of secondary sex characteristics and corresponds to ages: 6-11 in girls 6-13 in boys

Chronological Age vs. Biological Age age in months and years Biological Age: skeletal age, physical maturity, or sexual maturation Children do not grow at a constant rate Individualize training based on the child’s maturity level, training age (length of time resistance training), and needs

Peak Height Velocity Peak Height Velocity Pubertal growth spurt About age 12 in females and age 14 in males There is weakness in the bones Muscle imbalance between flexor and extensor groups around a joint Bone growth is faster than the muscle tendon unit

Pubertal Growth Spurt During pubertal growth spurts personal trainer’s need to emphasize the following: Flexibility Correct muscle imbalances Decrease volume and intensity of R.T. Risk Factors: overuse injuries growing pain complaints (growing pains don't hurt around the bones or joints only in the muscles)

Pubertal Growth Spurt As a trainer, if a young athlete complains of pain or discomfort during a growth spurt, you should be suspicious of an overuse injury rather than labeling the complaints as “growing pains”

Muscle and Bone Growth Peak muscle mass occurs between the ages of: 16-20 in females 18-25 in males

Bone Growth Bone formation occurs in the diaphysis which is the central shaft of a long bone and in the growth cartilage

Bone Growth Growth cartilage is located at three sites in children: Epiphyseal plate Joint surface Apophyseal insertions of muscle tendon units

Bone Growth Damage to the growth cartilage may impair the growth and development of the affected bone

Children The Growing Child Muscle and Bone Growth Muscle mass steadily increases throughout the developing years. During puberty, a 10-fold increase in testosterone production in boys results in a marked increase in muscle mass, whereas in girls an increase in estrogen production causes increased body fat deposition, breast development, and widening of the hips. When the epiphyseal plate becomes completely ossified, the long bones stop growing.

Muscular Strength and Adolescence Muscle mass increases first then strength The development of the nervous system is related to the expression of muscular strength Primarily the development of the myelin sheath Why?

If Myelination of Nerve Fibers is Absent or Incomplete Fast reactions and skilled movements cannot be successfully performed High levels of strength and power are impossible

Muscular Strength and Adolescence The myelination of motor nerves is incomplete until sexual maturation As the nervous system develops, children improve their performance in skills that require balance, agility, strength, and power. Personal Trainers should not expect children to respond to training in the same way as adults until they reach neural maturity

Muscular Strength and Adolescence Physiological functions are more closely related to biological age than chronological age What that means is that early-maturing children will probably have an advantage when it comes to measures of absolute strength when compared to later-maturing children of the same sex Nervous system development is incomplete until sexual maturation

Muscular Strength and Adolescence In boys, peak gains in strength typically occur about 1.2 years after peak height velocity and 0.8 years after peak weight velocity. In girls, peak gains in strength also typically occur after peak height velocity, although there is more individual variation in the relationship of strength to height and body weight. On average, peak strength is usually attained by age 20 in untrained women and between the ages of 20 and 30 in untrained men.

Body Types Mesomorph muscular and broader shoulders Endomorph rounder and broader hips Ectomorph slender and tall

Recommendations for Personal Trainers Who Train Children Prior to participation, adolescents should be evaluated by a physician. Parents should be educated about the benefits and risks of physical activity. Parents should understand the importance of physical activity. Children and adolescents should be encouraged to participate in year-round physical activity.

Recommendations for Personal Trainers Who Train Children Provide close supervision Speak to children in a manner they can understand Design activities that ensure enjoyment Offer a variety of exercises and avoid regimentation

Program Design Considerations for Children There is no minimal age requirement for R.T. in children All children should be screened for any injury or illness There is no scientific evidence to suggest that supervised and well designed youth resistance training programs stunts growth of children

Program Design for Children Personal trainer’s should not expect children to exercise in the same manner as adults It is not recommended that children perform 30 minutes of continuous exercise with a predetermined THRR because prolonged activity will decrease their motivation to exercise

Program Design Considerations for Children Each child should understand the benefits and risks associated with resistance training. Competent and caring fitness professionals should supervise training sessions. The exercise environment should be safe and free of hazards. All equipment should be in good repair and properly sized to fit each child. Dynamic warm-up exercises should be performed before resistance training.

Program Design Considerations for Children Static stretching exercises should be performed after resistance training. Carefully monitor each child's tolerance to the exercise stress. Begin with light loads. Increase the resistance gradually (e.g., 5% to 10%) as strength improves. Children should be encouraged to drink plenty of water before, during, and after exercise

Program Design Considerations for Children Children should be encouraged to drink plenty of water before, during, and after exercise Regular participation in R.T. along with a calcium rich diet maximizes bone density It is better to underestimate than overestimate children’s abilities

Program Design for Children Frequency Daily. Frequent activity sessions three or more each day Intensity Moderate to vigorous. Alternating bouts of activity with rest periods Duration It is recommended that children expend 6-8 cal/kg/day equal to a caloric expenditure of 60 minutes or more of active play Example: A girl who weighs 88 pounds (44 kg) should expend 264 calories per day ( 44 kg x 6 cal)

R.T. Program Design for Children Supervision and Instruction 5-10 minute warm-up 1-3 sets of 6-15 reps on multijoint and single joint exercises Intensity should be increased gradually as strength improves (5-10%) 2-3 nonconsecutive training sessions per week is recommended

R.T. Program Design for Children Advanced multijoint exercises (clean and jerk, snatch) can be used but the focus must be on appropriate loads and proper form

Program Design for Children Example of a Personal Training Session Circuit of 8-12 stations that include: Jumping rope Jumping jacks Push-up’s Body weight squats Medicine ball tosses Balancing drills Shuttle runs Cone drills

Older Adults Often debated, but a person over the age of 65 is defined as an older adult Various medical conditions are common among older adults Heart disease Cancer Diabetes Depression Obesity Low back pain Frailty

Older Adults Age-Related Changes in Musculoskeletal Health Loss of bone and muscle with age increases the risk for falls, hip fractures, and long-term disability. Bones become fragile with age because of a decrease in bone mineral content that causes an increase in bone porosity. After age 30 there is a decrease in the cross-sectional areas of individual muscles, along with a decrease in muscle density and an increase in intramuscular fat.

Bone Loss Bone becomes fragile with age because of a decrease in bone mineral density Everyday activities may cause bone fractures (especially hip, spine and wrist)

Osteopenia and Osteoporosis bone density at the spine or hip between -1.0 and -2.5 standard deviations below the average for healthy young adults can be a precursor to osteoporosis Osteoporosis: a disease in which the bones become extremely porous, are subject to fracture, and heal slowly, occurring especially in women following menopause and often leading to curvature of the spine from vertebral collapse.

Muscle Loss (Atrophy) Sarcopenia: decreased muscle mass Adults lose about one-half pound (.2 kg) of muscle per year in their 30’s and 40’s Adults 50 and older lose about 1 pound of muscle per year The average aging American adds 10 pounds of body weight each decade of adult life Loss of muscle may be responsible for fat gain

Causes of Bone and Muscle Loss Lack of regular physical activity Change in protein metabolism Endocrine system changes (hormones) Loss of neuromuscular function Altered genetic expression Apoptosis (cell death) Inadequate nutrition

Resistance Training and Sarcopenia Recent studies show that resistance training improves the balance of protein within the muscle, allowing more muscle protein synthesis than breakdown, allowing muscle maintenance or even hypertrophy.  Chronic resistance training  increases both muscle protein synthesis and breakdown, but synthesis at a greater magnitude.  This creates a positive protein balance, restoring protein in those who’ve lost mass as well as preventing muscle mass loss in those not already sarcopenic. 

Resistance Training and Sarcopenia Exercise enhances insulin sensitivity, which stimulates protein synthesis, contributing to the positive protein balance. Protein building cells called satellite cells aid in muscle repair and hypertrophy increase in response to resistance training.

Lack of Physical Activity and Sarcopenia Lack of physical activity, especially resistive training, allows the balance of protein synthesis with breakdown to become negative, breakdown outrunning synthesis.  If more protein is destroyed than manufactured in the muscle, muscle wasting occurs. Low muscle mass before old age predisposes one to sarcopenia.  The more lean muscle mass one has to begin with, the more one can afford to lose before becoming sarcopenic.

Age Related Changes Female age: 20 30 40 50 BW 126 136 146 156 Muscle Weight 45 35 Fat Weight 29 44 59 74 Percent Fat 23 32 47

Health Benefits of Older Adult Exercise Aerobic endurance exercise such as walking, cycling, and jogging is effective for: Increasing calorie utilization Reducing body weight Lessening the risk of high blood pressure Improving sleep Improving digestion Reduces the risk of osteoporosis

Benefits of Resistance Training in Older Adults Lowers the risk of cardiovascular disease Decreases resting blood pressure Two months of R.T. may reduce blood pressure by up to 7 mm Hg Improves cholesterol Reduces the risk of colon cancer (running and R.T. have been shown to speed up Gastrointestinal emptying)

Benefits of Resistance Training in Older Adults Lowers the risk of type II diabetes Improves insulin response and glucose utilization by the cells Reduces low back pain May improve joint function Eases the pain of arthritis

Benefits of Resistance Training in Older Adults Maintain muscle tissue R.T. is the only type of exercise that can maintain muscle and metabolism as people age

What Are the Safety Recommendations for Resistance Training for Seniors? All participants should be prescreened. Warm up for 5 to 10 minutes before each exercise session. Perform static stretching exercises before or after, or both before and after, each resistance training session. Use a resistance that does not overtax the musculoskeletal system.

What Are the Safety Recommendations for Resistance Training for Seniors? Avoid performing the Valsalva maneuver. Allow 48 to 72 hours of recovery between exercise sessions. Perform all exercises within a range of motion that is pain free. Receive exercise instruction from qualified personal trainers.

R.T. Guidelines for Older Adults Frequency 2-3 nonconsecutive sessions per week Recovery 48-72 hours Intensity 40-80% of maximum Repetition 6-12 reps Sets 1-3

Aerobic Endurance Guidelines for Older Adults Frequency 2-5 times per week Duration 20-60 minutes per session Intensity 60-90% of MHR (75% of MHR is recommended) Maximal heart rate decreases with age (10 beats per decade) Taking beta-blockers (heart medications) lowers maximum heart rate Monitor exercise by heart rate, RPE scale or talk test

Resistance Training for Females Men and women respond to R.T. in similar ways Women can increase their strength at the same rate Absolute gains in strength (amount of weight lifted) are greater in males High volume and high intensity training will lead to hypertrophy

Resistance Training for Females In terms of strength, females have about two thirds the strength of men Lower body strength is closer to male values Upper body strength is generally weaker often due to broad shoulders in males

Resistance Training for Females R.T. programs for females can be the same as males Training should incorporate upper body strength (push-up, pull-up…)

Knee Injuries in Female Athletes Studies report that female college aged basketball players are 6 times more likely to incur an ACL tear than male players How Can Female Athletes Reduce Their Risk of Injury? Begin with a preparticipation screening by a sports medicine physician. Participate in a year-round conditioning program that includes resistance training, plyometric training, agility training, and flexibility training.

Knee Injuries in Female Athletes Every exercise session should be preceded by a general dynamic warm-up and a specific warm-up using movements that resemble those involved in the activity. Athletes should wear appropriate clothing and footwear during practice and games. Athletes should be encouraged to maximize their athletic potential by optimizing their dietary intake.

Knee Injuries in Female Athletes