Strength Training

Original Editor - Manisha Shrestha

Top Contributors - Lucinda hampton, Manisha Shrestha, Cameron Wells, Kim Jackson, Tony Varela, Damon Harrell, Dante Gracia, Rucha Gadgil, Candace Goh and Wanda van Niekerk  

Introduction

Squatting with resistance band for upper extremity

Physical activity is defined here as any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure. Exercise is defined as the physical activity that is planned, structured, and repetitive. Resistance exercise is one of the modalities of exercise chosen for physical conditioning. Resistance training is any activity that causes muscles to contract against an external force. It is also known as strengthening exercises. It falls under anaerobic exercise which means it produces energy via anaerobic metabolism.

Resistance exercise can serve as a potent stimulus to the musculoskeletal system necessary to bring about gains in muscle size, strength, endurance, and power. The goal of resistance training is to progressively overload the musculoskeletal system. Weight machines, dumbbells, resistance bands, and barbells are usually used as resistance. Along with that own body weight can also be used as resistance.

The fundamentals of effective resistance training are:

• perform each set or at least the last set(s) of an exercise to fatigue (the state where the subject cannot lift one more repetition with good form).
• workload is gradually increased over time.

Effect of Resistance Training

Strength training stimulates a variety of positive neuromuscular adaptations that enhance both physical and mental health. Studies have shown that regular progressive resistance training develops:

• The strength and size of muscles
• Increases bone mass from young male athletes to older women.
• In addition, resistance exercise might be even more beneficial than aerobic exercise for fat loss.

Resistance exercise has produced beneficial outcomes for numerous physiological factors, including

• Increased blood glucose utilization
• Reduced resting blood pressure
• Improved blood lipid profiles
• Enhanced vascular condition
• Increased gastrointestinal transit speed
• Increased bone mineral density
• Improved body composition.

It also has been shown to improve function in post-coronary patients (by offering greater development of muscular strength, endurance, and mass) and chronic obstructive pulmonary disease (COPD) patients, as well as to reduce discomfort in people with low back pain and arthritis. In addition, strength training has proved effective for decreasing depression and for reducing the risk of metabolic syndrome, cardiovascular disease, and premature all-cause mortality.

Criterion Measures

There are various guidelines for prescribing progressive resistance exercise training which is person-centered i.e based upon age and health conditions. Before involving in any progressive resistance exercises, it is very important to undergo a pre-participation health screening to ensure exercise training can be safely initiated. It is also important to do exercise testing used for diagnostic (i.e., identify abnormal physiologic responses), prognostic (i.e., identify adverse events), and therapeutic (i.e., gauge impact of a given intervention) purposes as well as for physical activity counseling and to design a prescribed exercise programme.

1RM (One Repetition Maximum)

There is an inverse relationship between the amount of weight lifted and the number of repetitions. So the strength training literature is often based on a percentage of one-repetition maximum (1RM) in order to define the individualized intensity of training to ensure a participant's safety.

1RM is the maximum amount of weight one can lift in a single repetition for a given exercise.

1RM test is done of only one exercise per day or made at different times and intervals higher than 24 hrs in order to avoid possible neural fatigue. For instance, 1RM testing on chest press, leg press, lat pull down, triceps push down, knee extension, seated row, and biceps curl at different intervals. It is considered the gold standard for assessing muscle strength in non-laboratory situations.

Based on 1 RM intensity, resistance exercises are determined to ensure safety( Haslam et al found intra-arterial blood pressures during weight lifting in cardiac patients to be within a clinically acceptable range at 40% and 60% of 1 RM).

It can be either calculated directly using maximal testing or indirectly using submaximal estimation methods. There are various formulas to calculate 1 RM via submaximal estimation method. Submaximal estimation method is preferred as it is a safer and quicker method for those participants with co-morbidities and beginners.

Evidence

There are various guidelines (majorly, American College of Sports and Medicine and American Heart Association) for the prescription of resistance exercises in a healthy population and population with different co-morbidities and different age groups.

Resistance Exercises and Chronic Diseases

Abdominal obesity, insulin resistance, hypertension, and dyslipidemia are major factors for chronic diseases like cardiovascular disease. Although the mechanisms for improvement may be different, both aerobic endurance exercise and resistance training appear to have similar effects on bone mineral density, glucose tolerance, and insulin sensitivity.

Resistance training assists the body in expending calories via an increase in lean body mass and basal metabolic rate helping in maintaining body composition.

Cardiovascular Disease (CVD)

Blood Pressure Lowering Treatment Trialists Collaboration, 2014 reported that the magnitude of resistance exercise-induced reductions in SBP (5–6 mmHg) and DBP (3–4 mmHg) are associated with an 18% reduction of major cardiovascular events.

A study was done by Mcleod et al, 2019 recommended low-to moderate intensity resistance exercise training(RET) (30–69% of 1RM) is safe and effective even in individuals with CVD or at risk for developing CVD.

According to the AHA, a comprehensive resistance-training program of 8 to 10 exercises for 20 to 30 minutes with an intensity of ≈50±10% of 1 RM with a minimum of 2 days per week and, if time permits, progress to 3 days per week is recommended. Exercise need to be done at a comfortably hard level (13 to 15 on the RPE [rating of perceived exertion]) and without valsalva maneuver. Progession of exercise can be done by increasing 5 % of weight if the participant can comfortably lift the weight for up to 12 to 15 repetitions. If the participant cannot complete the minimum number of repetitions (8 or 10) using good technique, the weight should be reduced.

Type 2 Diabetes

American Diabetes Association, 2014 has reported lifestyle modifications (i.e diet and exercise) were associated with a greater reduction on glycemic control than medication with more emphasis on aerobic exercise training. However there are other studies showing benefits of resistance exercise on glycemic control.

There is a contradictory result showing the level of intensity of resistance exercises in glycemic control. But the study done by Mcleod et al. 2019, recommends the inclusion of general whole-body resistance exercises twice in week in routine without worrying about exercise intensity.

Cancer

There is a role for resistance exercise in reducing cancer risk, cancer recurrence, cancer mortality, and improving prognosis during adjuvant therapies. In breast and prostate cancer, resistance exercise has been apparent. Further work needs to be done to address the optimal dose, intensity, and mechanisms specific to resistance exercise-induced benefits to cancer.

Resistance and the Older Population

With an increase in age, there comes various co-morbidities and fragility syndrome. Among those fragility syndrome, sarcopenia and osteoporosis are most common conditions which decline of physical mobility, increase the risk of fall and increase co-morbidities.

Evidence suggests that resistance exercises can play a vital role in the improvement of functional mobility than aerobic exercises in the older adult. Since resistance exercise is a potent stimulus for muscle hypertrophy and increasing bone density which is affected by sarcopenia and osteoporosis. Resistance exercise incorporated with combined exercise training ( balance exercise, aerobic exercises) has shown to be the best strategy than resistance exercise alone for improvement in functional mobility in older adults.

Resistance exercise training where one’s own body weight is used for resistance and in which activities of daily living are simulated (i.e., body-weight squat) can improve functional mobility in older adults to a similar extent as conventional RET (requiring external load). Even though high-intensity resistance exercise training (≥70% of 1RM) ) is more beneficial in combating mobility decrement than low-to-moderate intensity RET (30–69% of 1RM), low to moderate RET is helpful.

Resistance exercise:1-4 sets of 8–15 repetitions (at 50–85% of 1RM) often performed to fatigue with rest period 1-2 minutes between each set The regular time required to complete the resistance training program is within 30-45 minutes 2-3 times a week is recommended in this article. Exercise prescription given by ACSM is widely used for the older population.

Resources

• (2014) ACSM's guideline for exercise testing and prescription.
• Resistance Exercise in Individuals With and Without Cardiovascular Disease-American Heart Association
• Effects of weight-lifting or resistance exercise on breast cancer-related lymphedema: A systematic review

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