Lack of exercise is a major cause of chronic diseases, it can be used as a primary
prevention against 35 chronic conditions (35), and serve as therapy in 26
chronic diseases (36).
Strength
training is significantly associated with decreased overall
mortality (37). Improved physical
capacity, muscle strength and functional ability can be achieved in
response to resistance (weight) training (38,39) and resistance training
combined with aerobic exercise (40-46).
A big study (400.000) showed that people who exercise an average of 92 minutes a
week, or 15 minutes a day, were 14% less
likely to die for any reason (1). The risk of heart disease, diabetes and
cancer can be reduced by 15 minutes or more of exercise each day. Four of the
most common reasons for not getting those 15 minutes are lack of time, lack of energy, lack of motivation, and lack of
information (even possibly misinformation).
Pain and diseases
Strength training can improve pain management,
disability and quality of life (2). The same study show that cardiovascular
exercises alone improve body composition by reducing body fat levels and
improve flexibility.
Strength training can also reduce neck pain (3). Three 20-minute sessions
per week, focusing on exercises to target the trapezius muscles, led to an
incredible 79% reduction in pain symptoms, and 29% strength.
Strength training is useful for increasing muscle
strength in Parkinson disease and to
a lesser extent multiple sclerosis
(47).
Bone density
Another benefit of strength training is increase in bone density
and a lower risk of osteoporosis. As the skeleton adapts to forces
applied to it, when a certain threshold is reached, changes in cellular
activity occur and increase the strength of the bone.
This is known as the Piezoelectric effect: mechanical stress
exerted by a tendon on a bone generates a voltage. Due to stress, a charge is
then released from within the collagen fibers and attracts the oppositely
charged osteoblasts which are cells responsible for new bone formation.
Osteoblasts deposit minerals at the site resulting in a localized increase in
bone density.
As a result of lack of physical activity there’s a reduction of bone
density, however regular exercise will reverse this decline.
High intensity exercise (70-80% RM) promotes greater bone formation than
moderate intensity (40-60%RM), in elderly population. If we cease regular
exercise most improvements in muscle mass and bone density will be lost. This
is known as the reversibility principle.
A meta-analysis indicated
that exercise prevented or reversed approximately 1% bone loss per year in
adult and older adult women (4). A more recent review revealed that resistance
training increased bone mineral density (BMD) by 1-3% in premenopausal and
postmenopausal women (5). Another study, a 2-year study (6) indicated that
resistance training resulted in a 3.2% improvement in BMD.
An important note is that BMD change is related to
different responses in different bones; the effects of resistance training
are site specific. A review showed that resistance training is positively
associated with high BMD (7). Resistance training is more effective aerobic and
weight bearing exercise for increasing bone density.
Tendons and ligaments
Strength training also strengthen tendons and ligaments. This helps
stabilizing the joints with shock-absorbing benefits, and reduces the stress in
the articular cartilage on the end of the bones.
Inflammation, diabetes,
obesity and metabolic syndrome
Exercise is even anti-inflammatory for chronic diseases as
rheumatic diseases (8). Skeletal muscle is a secretory organ and releases anti-inflammatory
proteins called myokines. These myokines then circulate in the bloodstream
and communicate with other organs.
Strength training enhances control of blood sugar levels, and
positively affects these conditions (9). Progressive strength training program
is shown to lower the value of glycosylated hemoglobin – a key measure
of the average blood glucose concentration over prolong period.
In another
review article resistance training is recommended in the management of obesity and metabolic disorders (10). Increased
resting metabolic rate, improved insulin
sensitivity (11,12,13,14), and enhanced sympathetic activity are possible
means by which resistance training may decrease intra-abdominal fat stores.
There’s also improvements
in blood lipid profiles resulting from resistance training (15,16,17).
A 2009 review suggests resistance training is effective in reducing LDL cholesterol (18). Furthermore, combined resistance
training and aerobic activity improves blood lipid profiles better than either
exercise performed independently.
Exercise reduces the
catecholamine response (19), improve arterial and endothelial function (20,21)
and maintain muscle metabolic capacity with ageing (22).
Wellbeing
A study published in www.cancer.org (23) showed resistance training
twice per week for six months significantly enhanced the quality of life for
women treated from breast cancer. Improvements were noted in both physical
and psychosocial aspects, concluding that changes in strength and body
composition led to greater feeling of empowerment.
Resistance training can significantly reduce anxiety symptoms
(24). Anxiety may be linked to depression, negative mood swings, disturbances
in sleep patterns, tiredness, even weight fluctuations. At least in four studies resistance training had a
positive effect on depression levels in clinically depressed subjects; 18
studies presented positive effects on depression symptoms in healthy adults or
adults with medical problems (24).
Mental health and
cognition
In aging it appears to be a general decline in cognitive function; in
older adults strength training can improve several cognition markers, most
notably in memory. Strength training is also positive to self-esteem, in
both younger and older population subsets.
In a meta-analysis
aerobic exercise combined with resistance training resulted in improvements in
cognition in inactive older adults compared with aerobic activity alone (25).
Resistance training and aerobic activity can also
improve physical self-concept, total mood disturbance, fatigue, positive
engagement, revitalization, tranquility, and tension (26).
Resistance training is associated with reduced
depression levels in older adults. After 10 weeks of exercise, more than 80% of
depressed elders were no longer clinically depressed (27).
Benefits of strength training in the area of mental health (28, 29, 30,
31):
1. Improved memory.
2. Reduced risk of
depression.
3. Less chronic fatigue.
4. Improved sleep
quality.
5. Enhanced cognitive
ability.
6. Improved self-esteem.
Aging
We lose muscle as we age, this is called sarcopenia, which begins
after 30 years of age, leading to a loss of 3-5% of muscle mass per decade,
with a significant acceleration after 65 years of age. The loss of muscle mass
is accompanied with parallel loss of strength. The causes are thought to be a
combination of:
1. Decreased hormone levels: growth hormone and mechanogrowth factor (32), testosterone
(33), these hormones play a role in protein metabolism within the muscle cells,
leading to a decrease in muscle mass;
2. Reduced protein
synthesis: impairs the body’s anabolic ability;
3. Motor unit remodeling: change in motor neurons, nerves that
initiate movement;
4. Lifestyle change: lower
activity levels.
Resistance training has been shown to positively affect all of these
factors. For example protein synthesis improve significantly in 2 weeks;
there’s also improved efficiency of the motor units (increased muscle fiber
recruitment and force production.)
Aging is usually accompanied by a loss of muscle mass, loss of strength,
leading to reduced everyday capability. Resistance training delay and actually
reverse the aging process.
Circuit (short rest) resistance training can increase
mitochondrial density and the oxidative capacity of muscle tissue. With
resistance training, there’s a reversal
in mitochondrial deterioration that typically occurs with aging. Positive
changes were observed in 179 genes
associated with age and exercise; resistance training can reverse aging factors in skeletal
muscle, by reversing that gene expression (34).
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The Epidemiology and Physiology of Sedentary Behavior
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Summary of 47 articles with 49.167 words and 1321 references on
Exercise, nutrition and Science
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