Resistance Training: An Overview

A lot of people don’t realize that dieting alone has never proven to be an effective intervention for permanent weight loss and sustained weight management; and the exercise program should not be limited to only aerobic activity (e.g., walking, running, cycling) [7]. In fact, a sensible combination of diet, aerobic activity, and resistance training can produce simultaneous fat loss and muscle gain [7]. Muscle is metabolically active tissue that is highly responsive to the stimuli of progressive resistance exercise [2]. With proper training, muscles grow and become stronger; without proper training, muscles diminish and become weaker [2]. Properly performed resistance training has a positive impact on the entire musculoskeletal system [2].

Resistance Training Benefits Include

• Improved muscle strength and tone (to protect your joints from injury).

• Maintaining flexibility and balance, which can help you remain independent as you age.

• Weight management and increased muscle-to-fat ratio (as you gain muscle, your body burns more kilojoules when at rest).

• May help reduce or prevent cognitive decline in older people.

• Greater stamina (as you grow stronger, you won’t get tired as easily).

• Prevention or control of chronic conditions such as diabetes, heart disease, arthritis, back pain, depression, and obesity.

• Pain management.

• Improved mobility and balance.

• Improved posture.

• Decreased risk of injury.

• Increased bone density and strength and reduced risk of osteoporosis.

• Improved sense of wellbeing (improve your mood and body image as well as boost your self-confidence).

• Improved sleep and avoidance of insomnia.

• Increased self-esteem.

• Enhanced performance of everyday tasks.

Influential Factors

There are several factors that influence the development of muscular strength and size (hypertrophy), i.e., genetics, hormones and age, gender, technique, and experience.

Genetics. The genetic influence is attributed to limb length, insertion points of tendons, muscle length, and types of muscle fibers. Limb length and tendon insertion points affect strength performance but don’t affect muscular size. For example, assuming equal biceps muscle strength and tendon insertion points, an individual with a shorter forearm can curl a heavier dumbbell than an individual with a longer forearm [2]. Alternatively, assuming equal biceps muscle strength and forearm lengths, an individual with a tendon insertion point farther from the elbow joint axis can curl a heavier dumbbell than an individual with a tendon insertion point closer to the elbow joint [2]. Muscle length compared to bone length, on the other hand, plays a vital role in muscular size. Individuals with relatively long muscles have a greater potential for muscle development than those with relatively short muscles. There are two muscle fiber categories, known as type I fibers (slow-twitch muscle fibers) and type II fibers (fast-twitch muscle fibers). Strength training increases the cross-sectional area of both type I and type II muscle fibers, but type II fibers experience greater size increases than type I fibers [2]. This being the case, individuals who are born with higher percentages of type II fibers (e.g., sprinters) may have more potential for muscular hypertrophy than individuals who are born with higher percentages of type I fibers (e.g., marathoners).

Hormones and age. Hormone levels and age also have an impact on muscular strength and size. Testosterone and human growth hormone (HGH) are two hormones that are associated with tissue growth and development [2]. Higher levels of these anabolic hormones are advantageous for increasing muscular strength and size. Testosterone and HGH concentrations decrease with age, which contribute to reduced muscle mass and strength in older adults [2]. Nonetheless, people of all ages respond favorably to progressive resistance exercise and gain muscle at about the same rate during the initial training period [2]. However, the potential for total-body muscle mass diminishes during the older-adult years [2].

Gender. Gender doesn’t affect muscle quality, but it influences muscle quantity. Because of larger body size, higher lean weight percentage, and more anabolic hormones (i.e., testosterone), men typically have greater muscle mass and overall muscular strength than women [2]. However, men and women respond to strength training programs similarly and attain comparable benefits [7].

Technique. Training technique can have a profound influence on strength development, muscular size development, and injury prevention. For example, an individual can perform a 75-lb. barbell curl with strict form without the aid of larger muscle groups. However, by bending forward and initiating the same movement with the large hip extensor muscle to give the barbell upward momentum, this same individual can now cheat-curl 125 lbs. All factors considered; this individual will experience better biceps development by performing the strict 75-lb. curl than by performing the 125-lb. cheat curl [7]. Generally, the use of momentum and assisting muscle groups reduces the training stimulus to the target muscle group and is associated with a higher risk of injury occurrence. Another aspect of training technique is the use of the pre-stretch. Muscle produces greater tension when it is stretched just prior to contraction (e.g., a standing long jump is initiated by a quick downward movement to pre-stretch the thigh muscles, so that they can contract more forcefully; or more force can be exerted on the upward phase of the bench press by quickly lowering the bar) [7]. Because quick movements with heavy weight loads may increase injury risk, pre-stretching as a strength training technique is ill-advised.

Experience. Training experience influences how much progress you make and at what rate. For someone who has been training regularly for two years will make smaller strength gains than someone who has been training for two weeks. This is due primarily to motor learning (i.e., a neurological response to performing a new exercise) during the early stages of a strength training program [7]. As the new exercise is practiced, more effective motor units (muscle fibers) are automatically activated to facilitate the specific movement and force production. As the individual’s strength approaches their genetic potential, the increases are much smaller and less frequent. A typical three-month strength training period will show a 40% strength gain in the first month of training, a 10% gain in the second month, and a 2.5% gain in the third month [7]. Therefore, if you continue to perform the same routine, progress will plateau after several months of training. So, it is in your best interest to routinely alter your training program to experience continual progress.

There are a variety of methods to enhance muscular strength, size, endurance, and performance [2]:

• Performing primary, multi-joint linear exercises followed by secondary, single-joint rotary exercises for a specific muscle group (e.g., squats followed by leg extensions).

• Alternating upper- and lower-extremity exercises within or between training sessions.

• Grouping pushing and pulling movements or targeting joint agonists and antagonists during a session (e.g., chest and back or triceps and biceps).

• Performing supersets or compound sets where exercises are done in sequence with little or no rest between them.

Simply training will not guarantee results, therefore organizing your training sessions and selecting the most effective exercises and methods will enhance the outcomes.

Additional Considerations

Safety. Adherence to correct exercise form is critical, otherwise risk of muscle, tendon, and connective tissue injury may be increased, and improvement potential may be decreased. Another important aspect of strength training is making sure that you train muscle antagonists [7]. Training one muscle without training its opposing muscle will lead to a muscle imbalance, which will, in time, compromise joint integrity because one muscle will become disproportionately stronger than its antagonist. More safety considerations include proper warmups and breathing techniques. Warming up increases internal body temperature, which, in turn, enhances muscle elasticity and extensibility; therefore, individuals who warm up before engaging in strength training should be less prone to muscle, tendon, and connective tissue injury [7]. Examples of warmup activities include stationary cycling, jogging in place, calisthenics, and performing lighter lifting sets prior to doing the heavier sets. Holding your breath while strength training may create an undesirable “Valsalva maneuver.” This can be avoided with a proper breathing pattern while training, i.e., inhaling during the eccentric phase and exhaling during the concentric phase of each repetition [7]. Other safety considerations include using a well-trained spotter, wearing proper clothing, and effectively managing muscle soreness [7].

Adaptation Principle. Given enough time, the training stimulus can either have a positive or negative impact on the human body. In other words, there exists a threshold at which the body’s positive adaptation or overcompensation will seize, and any added stress on the body will have a negative effect, known as overtraining [1]. If the stress is too high during a training session (i.e., high levels of tissue microtrauma occurrence), the muscles could react negatively. It is common to experience several days of muscle weakness, fatigue, and discomfort, known as Delayed Onset Muscle Soreness (DOMS); however, this may not lead to enhanced muscle size and strength [1]. Conversely, when muscles are systematically stressed in a progressive way where the training stress is adequately high, the resulting low levels of tissue microtrauma elicits muscle-remodeling processes that lead to larger and stronger muscles [1]. Positive adaptation is dependent on a few factors [1].

• Perform each exercise through a full range of motion (ROM).

• Muscular adaptation happens faster than tendons and ligaments, therefore, the latter requires more training time to respond adequately and reduce injury risk.

• To develop strength of arms and legs, it is necessary to develop the trunk (i.e., core).

• The primary muscles work better when the muscle stabilizers are strong.

• Recovery time is proportional to the stress intensity.

ROM. Performing each exercise through a full range of motion (ROM) will develop full-range strength, enhance joint flexibility, and make you less prone to injuries [7]. Strength training will not make you “musclebound” [7]. Furthermore, full-range muscle strength is especially important for people with low back pain, therefore, full ROM resistance exercise should be performed whenever possible [7].

Reversibility. Muscle reversibility is the phenomenon of gradually losing muscle size and strength due to detraining (ceasing resistance exercise). If you stop performing resistance exercise, you will lose strength at about one-half the rate that it was gained [2]. In other words, if you increased your squat strength by 50% over a 10-week training period, you would lose half of that strength gain after 10 weeks of no resistance training and all your strength gain after 20 weeks of no resistance training. Detraining also results in reversal of many health and fitness benefits associated with regular resistance training [7]. Therefore, if you wish to keep your gains, it is in your best interest to make resistance training a regular component of an active lifestyle.

Conclusion

Many assume that muscle and bone loss, metabolic slowdown, and fat gain are inevitable consequences of the aging process. This is simply not true. Research demonstrates that by performing resistance training consistently and properly, men and women of all ages can add muscle, rebuild bone, recharge metabolism, and reduce fat [7]. However, without incorporating basic resistance training into a daily or weekly regimen, you will lose up to 10% of your muscle mass and up to 30% of your bone mass per decade [7]. Nobody wants this, and it's never too late to start. We hope that this overview has provided you with a solid foundation on the basics of resistance training.

Sources

[1] Bertucci, D. R., & Ferraresi, C. (2016). Strength Training: Methods, Health Benefits and Doping. Nova Science Publishers. https://eds-s-ebscohost-com.ezproxy.umgc.edu/eds/ebookviewer/ebook/bmxlYmtfXzExMzQ0NTZfX0FO0?sid=b5e6955f-8aa1-4fff-906c-5bba28f3d5d2@redis&vid=1&format=EB&rid=1

[2] Bryant, C. X., Jo, S., & Green, D. J. (Eds.). (2014). ACE Personal Trainer Manual (5th ed.). American Council on Exercise.

[7] Westcott, W. L. (2020). Strength Training Essentials. Healthy Learning.