Strength training is any exercise that involves contracting a muscle against weight or resistance, in order to produce stronger, larger muscles—often with an accompanying reduction in body fat. This increase in muscle-to-fat ratio has probably been the most popular draw of strength training; everyone wants to look more lean and toned. However, strength training can do so much more. Strength training counteracts osteoporosis and other age-related problems such as muscle loss, joint pain, and slowing metabolism. For all ages, strength training can increase capacity to do everyday activities—work and recreation, alike. Strength training is not as time-consuming as most aerobic activities, so if done properly, it is a quick way to get most of the general benefits of exercise (Mayo Clinic 2016).
Strength training works on skeletal muscles. (Smooth muscles, as those lining the intestinal wall, are not under the brain’s voluntary control.) Most skeletal muscles are composed of some combination of slow-twitch and fast-twitch muscle fibers (BBC Home 2014). Slow-twitch muscle is fueled mostly by aerobic respiration; fast-twitch muscle is fueled mostly by anaerobic respiration. In other words, slow-twitch muscle gets its energy from the usual oxygen-consuming metabolic process; fast-twitch muscle gets energy from a less efficient metabolic process that does not require oxygen and is usually engaged when there is oxygen depletion, as when muscles are being pushed to do extensive work within a short period of time. Since strength training involves intensely engaging certain muscles in a focused way, anaerobic respiration will likely happen. The “burn” that people describe after an intense workout is the sensation of lactic acid (a byproduct of anaerobic respiration) in their muscles. Exercise-induced lactic acid buildup is harmless; given time, the body clears the buildup and reenergizes the muscle fibers to the point of being able to resume normal aerobic respiration. This process, along with muscle growth and maintenance, requires energy (calories) even after the workout. Together, these calorie-burning processes create “after burn.”
At the gym, one is faced with a variety of contraptions for strength training—a range of free weights and rows of weight machines; many gyms also have resistance tubes or bands that can be attached to a wall or prop and pulled against. As great as all of this is, one can also do effective exercises at home with very little equipment (Mayo Clinic 2016). Using one’s own body weight is legitimate exercise; anyone who has gotten down to do pushups and found him/herself “stuck to the floor” knows this. Another option: Isometric exercises involve muscles contracting against force that is proportional to the intensity of contraction—as when you press your hands together in front of you at chest level or stand in a sturdy doorway and press your arms against the frame. In effect, isometric exercises become harder the harder you can push.
Research suggests that doing one set of 12 reps of a challenging strength training exercise is just as effective as doing three of such sets. Strength training only needs to be performed 3 times a week to be effective, ideally with a day of rest between training sessions involving a given muscle group. Most proper regimens seem to 20 to 30 minutes, three to four days a week. Warming up with a light aerobic activity for a few minutes before strength training reduces chance of injury. If one feels unsure of proper technique or level of intensity, it is wise to consult a professional trainer (Mayo Clinic 2016).
BBC Home. Science: Human Body & Mind. 24 September 2014. (Accessed 6 August 2017) <http://www.bbc.co.uk/science/humanbody/body/factfiles/fastandslowtwitch/soleus.shtml>.
Mayo Clinic Staff. “Strength training: Get stronger, leaner, healthier.” 22 April 2016. Accessed 6 August 2017. <http://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/strength-training/art-20046670>.