Strength training or resistance training involves the performance of physical exercises that are designed to improve strength and endurance. It is often associated with the lifting of weights. It can also incorporate a variety of training techniques such as calisthenics, isometrics, and plyometrics.[1] When properly performed, strength training can provide significant functional benefits and improvement in overall health and well-being, including increased muscle, tendon, ligament, and bone strength and toughness, improved joint function, reduced potential for injury,[2] increased bone density, increased metabolism, increased fitness[3][4] and improved cardiac function.[5] Training commonly uses the technique of progressively increasing the force output of the muscle through incremental weight increases and uses a variety of exercises and types of equipment to target specific muscle groups. Strength training is primarily an anaerobic activity, although some proponents have adapted it to provide the benefits of aerobic exercise through circuit training.[6] Strength training typically produces lactate in the muscles, which is a limiting factor of exercise performance. Regular endurance exercise leads to adaptations in skeletal muscle which can prevent lactate levels from rising during strength training. For many sports and physical activities, strength training is central or is used as part of their training regimen.
The benefits of strength training include greater muscular strength, improved muscle tone and appearance, increased endurance, cardiovascular health, and enhanced bone density.[7] Increased physical attractivenessMany people take up strength training to improve their physical attractiveness. There is evidence that a body type consisting of broad shoulders and a narrow waist, attainable through strength training, is the most physically attractive male attribute according to women participating in the research.[8] Most men can develop substantial muscles; most women lack the testosterone to do it, but they can develop a firm, "toned" (see below) physique, and they can increase their strength by the same proportion as that achieved by men (but usually from a significantly lower starting point). An individual's genetic make-up dictates the response to weight training stimuli to a significant extent. Training can not exceed a muscle's intrinsic genetically determined qualities, though polymorphic expression does occur e.g., myosin-heavy chains.[9] Studies also show that people are able to tell the strength of men based on photos of their bodies and faces, and that physical appearance indicates cues of strengths that are often linked to a man's physical formidability and, therefore, his attractiveness.[10] This is aligned with studies that reveal those who undergo strength training attain more self-esteem and body cathexis when compared to individuals who do not.[11] In addition, people who undergo strength training tend to have a more favorable body image even than those who also engage in regular physical activities such as walking and running.[12] Workouts elevate metabolism for up to 14 hours following 45 minutes of vigorous exercise.[13][14] Increased general physical healthBones, joints, frailty, posture and in people at riskStrength training also provides functional benefits. Stronger muscles improve posture, provide better support for joints, and reduce the risk of injury from everyday activities. Older people who take up weight training can prevent some of the loss of muscle tissue that normally accompanies aging (sarcopenia)—and even regain some functional strength—and by doing so become less frail.[15][16][17] Progressive resistance training may improve function, quality of life and reduce pain in people at risk of fracture, with rare adverse effects [18] Weight-bearing exercise also helps to prevent osteoporosis and to improve bone strength in those with osteoporosis.[19] The benefits of weight training for older people have been confirmed by studies of people who began engaging in it even in their 80s and 90s.[20] Cardiovascular system and metabolismThough strength training can stimulate the cardiovascular system, many exercise physiologists, based on their observation of maximal oxygen uptake, argue that aerobic training is a better cardiovascular stimulus. Central catheter monitoring during resistance training reveals increased cardiac output, suggesting that strength training shows potential for cardiovascular exercise. However, a 2007 meta-analysis found that, though aerobic training is an effective therapy for heart failure patients, combined aerobic and strength training is ineffective.[21] Strength training may be important to metabolic and cardiovascular health. Recent evidence suggests that resistance training may reduce metabolic and cardiovascular disease risk. Overweight individuals with high strength fitness exhibit metabolic/cardiovascular risk profiles similar to normal-weight, fit individuals rather than overweight, unfit individuals.[22] Mortality, longevity, muscle and body compositionA scientific review indicates that, based on mostly observational studies, strength training appears to be associated with a "10–17% lower risk of all-cause mortality, cardiovascular disease (CVD), total cancer, diabetes and lung cancer".[23] Two key outcomes of strength training are muscle hypertrophy and muscular strength gain which are associated with reduced all-cause mortality.[24] Strength training causes endocrine responses that could have positive effects.[25] It also reduces blood pressure (SBP and DBP)[26][27] and alters body composition, reducing body fat percentage, body fat mass and visceral fat,[28] which is usually beneficial as obesity predisposes towards several chronic diseases and e.g. body fat distribution is one predictor of insulin resistance and related complications.[29] Neurobiological effectsStrength training also leads to various beneficial neurobiological effects – likely including functional brain changes, lower white matter atrophy,[30] neuroplasticity[31] (including some degree of BDNF expression),[32] improvements of mental health[33] and white matter-related structural and functional changes in neuroanatomy.[34] Lipid and inflammatory outcomesMoreover, it also promotes decreases in total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), and C-reactive protein (CRP) as well as increases in high-density lipoprotein (HDL) and adiponectin concentrations.[35] Strength training can substantially prevent sports injuries[36] and may share many further health benefits of physical activity/exercise – or (types of) aerobic training in specific – to various degrees. For rehabilitation or to address an impairmentFor many people in rehabilitation or with an acquired disability, such as following stroke or orthopaedic surgery, strength training for weak muscles is a key factor to optimise recovery.[37] For people with such a health condition, their strength training is likely to need to be designed by an appropriate health professional, such as a physiotherapist or an occupational therapist. Increased sports performanceStronger muscles improve performance in a variety of sports. Sport-specific training routines are used by many competitors. These often specify that the speed of muscle contraction during weight training should be the same as that of the particular sport.[38] For the pleasure of the activityOne side effect of intense exercise is improved mood, with the effect being most noticeable when mood is poor before exercise. When exercise is competitive, effects depend on the degree of success. Regular physical exercise has been shown to be related to lower depression, fewer symptoms of anxiety, lower emotional distress, and lower fatigue. Even physically fit people who did not regularly exercise were in poorer mood than physically fit people who did. People who did not regularly exercise were more likely to have developed depression after an 8-year follow-up.[39] Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ. That is, contracting muscles release multiple substances known as myokines which promote the growth of new tissue, tissue repair, and various anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases.[40] The basic principles of strength training involve repeated overloading of a group of muscles, typically by lifting and lowering a heavy weight for 4-12 consecutive repetitions until failure.[41] Equally important is to progressively increase the lifted weight by each week of training.[42] When lifting the weight, involved muscles are shortening; performing so called concentric muscle contraction. The weight thereafter is lowered while the same muscles perform so called eccentric muscle actions at an identical load. The eccentric muscle loading has shown essential to develop both maximal strength and muscle hypertrophy.[43] A manipulation of the number of repetitions, sets, tempo, exercises and force are suggested to cause specific and desired changes in strength, endurance or size, although recent scientific studies have weakened the support for such anticipations.[44] The specific combinations of reps, sets, exercises, resistance and force depend on the purpose of the individual performing the exercise: to gain size and strength multiple (4+) sets with fewer reps must be performed using more force. A wide spectrum of regimens can be adopted to achieve different results, but the classic formula recommended by the American College of Sports Medicine is:
Typically, failure to use good form during a training set can result in injury or an inability to meet training goals. When the desired muscle group is not challenged sufficiently, the threshold of overload is never reached and the muscle does not gain in strength. There are cases when cheating is beneficial, as is the case where weaker groups become the weak link in the chain and the target muscles are never fully exercised as a result. TerminologyStrength training has a variety of terms used to describe parameters of strength training:
Realization of training goalsFor developing endurance, gradual increases in volume and gradual decreases in intensity is the most effective program.[46][47] Sets of thirteen to twenty repetitions develop anaerobic endurance, with some increases to muscle size and limited impact on strength.[48] It has been shown that for beginners, multiple-set training offers minimal benefits over single-set training with respect to either strength gain or muscle mass increase, but for the experienced athlete multiple-set systems are required for optimal progress.[49][48][50][51] However, one study shows that for leg muscles, three sets are more effective than one set.[52] Beginning weight-trainers are in the process of training the neurological aspects of strength, the ability of the brain to generate a rate of neuronal action potentials that will produce a muscular contraction that is close to the maximum of the muscle's potential.[53]
Weights for each exercise should be chosen so that the desired number of repetitions can just be achieved. Progressive overloadThe basic method of weight training uses the principle of progressive overload, in which the muscles are overloaded by attempting to lift at least as much weight as they are capable. They respond by growing larger and stronger.[55] This procedure is repeated with progressively heavier weights as the practitioner gains strength and endurance. However, performing exercises at the absolute limit of one's strength (known as one rep max lifts) is considered too risky for all but the most experienced practitioners. Moreover, most individuals wish to develop a combination of strength, endurance and muscle size. One repetition sets are not well suited to these aims. Practitioners therefore lift lighter (sub-maximal) weights, with more repetitions, to fatigue the muscle and all fibres within that muscle as required by the progressive overload principle. Commonly, each exercise is continued to the point of momentary muscular failure. Contrary to widespread belief, this is not the point at which the individual thinks they cannot complete any more repetitions, but rather the first repetition that fails due to inadequate muscular strength. Training to failure is a controversial topic with some advocating training to failure on all sets while others believe that this will lead to overtraining, and suggest training to failure only on the last set of an exercise.[56] Some practitioners recommend finishing a set of repetitions just before reaching a personal maximum at a given time. Adrenaline and other hormones may promote additional intensity by stimulating the body to lift additional weight (as well as the neuro-muscular stimulations that happen when in "fight-or-flight" mode, as the body activates more muscle fibres), so getting "psyched up" before a workout can increase the maximum weight lifted. Weight training can be a very effective form of strength training because exercises can be chosen, and weights precisely adjusted, to safely exhaust each individual muscle group after the specific numbers of sets and repetitions that have been found to be the most effective for the individual. Other strength training exercises lack the flexibility and precision that weights offer. Split trainingSplit training involves working no more than three muscle groups or body parts per day, instead spreading the training of specific body parts throughout a training cycle of several days. It is commonly used by more advanced practitioners due to the logistics involved in training all muscle groups maximally. Training all the muscles in the body individually through their full range of motion in a single day is generally not considered possible due to caloric and time constraints. Split training involves fully exhausting individual muscle groups during a workout, then allowing several days for the muscle to fully recover. Muscles are worked roughly twice per week and allowed roughly 72 hours to recover. Recovery of certain muscle groups is usually achieved on days while training other groups, i.e. a 7-day week can consist of a practitioner training trapezius, side shoulders and upper shoulders to exhaustion on one day, the following day the arms to exhaustion, the day after that the rear, front shoulders and back, the day after that the chest. In this way all mentioned muscle groups are allowed the necessary recovery.[57] Intensity, volume, and frequencyThree important variables of strength training are intensity, volume, and frequency. Intensity is the amount of work required to achieve the activity and is proportional to the mass of the weights being lifted or the difficulty of the exercise. Volume refers to the total number of muscles worked, exercises, sets, and reps, either during a single session or measured over a longer period. Frequency refers to how many training sessions are performed per week.[58] A training frequency of two or three times per week has greater effect on muscle size than once per week.[59] Training volume has more effect on muscle strength than training frequency.[60] A common training strategy is to set the volume and frequency the same each week (e.g. training 3 times per week, with 2 sets of 12 reps each workout), and steadily increase the intensity (weight) on a weekly basis. However, to maximize progress to specific goals, individual programs may require different manipulations, such as decreasing the weight, and increase volume or frequency.[61] A meta-analysis found that periodized training yields better strength improvements than non-periodized training.[62] Making program alterations on a daily basis (daily undulating periodization) has similar effect to other periodization models.[63] Strength training exercise is primarily anaerobic.[51] Even while training at a lower intensity (training loads of ~20-RM), anaerobic glycolysis is still the major source of power, although aerobic metabolism makes a small contribution.[64] Weight training is commonly perceived as anaerobic exercise, because one of the more common goals is to increase strength by lifting heavy weights. Other goals such as rehabilitation, weight loss, body shaping, and bodybuilding often use lower weights, adding aerobic character to the exercise. Except in the extremes, a muscle will fire fibres of both the aerobic or anaerobic types on any given exercise, in varying ratio depending on the load on the intensity of the contraction.[51] This is known as the energy system continuum. At higher loads, the muscle will recruit all muscle fibres possible, both anaerobic ("fast-twitch") and aerobic ("slow-twitch"), in order to generate the most force. However, at maximum load, the anaerobic processes contract so forcefully that the aerobic fibers are completely shut out, and all work is done by the anaerobic processes. Because the anaerobic muscle fibre uses its fuel faster than the blood and intracellular restorative cycles can resupply it, the maximum number of repetitions is limited.[65] In the aerobic regime, the blood and intracellular processes can maintain a supply of fuel and oxygen, and continual repetition of the motion will not cause the muscle to fail. Circuit weight training is a form of exercise that uses a number of weight training exercise sets separated by short intervals. The cardiovascular effort to recover from each set serves a function similar to an aerobic exercise, but this is not the same as saying that a weight training set is itself an aerobic process. Strength training is typically associated with the production of lactate, which is a limiting factor of exercise performance. Regular endurance exercise leads to adaptations in skeletal muscle which can prevent lactate levels from rising during strength training. This is mediated via activation of PGC-1alpha which alter the LDH (lactate dehydrogenase) isoenzyme complex composition and decreases the activity of the lactate generating enzyme LDHA, while increasing the activity of the lactate metabolizing enzyme LDHB.[66] Exercises for specific muscle groupsA back extension Weight trainers commonly divide the body's individual muscles into ten major muscle groups. These do not include the hip, neck and forearm muscles, which are rarely trained in isolation. The most common exercises for these muscle groups are listed below. The sequence shown below is one possible way to order the exercises. The large muscles of the lower body are normally trained before the smaller muscles of the upper body, because these first exercises require more mental and physical energy. The core muscles of the torso are trained before the shoulder and arm muscles that assist them. Exercises often alternate between "pushing" and "pulling" movements to allow their specific supporting muscles time to recover. The stabilizing muscles in the waist should be trained last. Advanced techniquesA number of techniques have been developed to make weight training exercises more intense, and thereby potentially increase the rate of progress. Many weight lifters use these techniques to bring themselves past a plateau, a duration where a weightlifter may be unable to do more lifting repetitions, sets, or use higher weight resistance. Set structureDrop setsA drop set is an easy method of strength training where you perform a set of any exercise to failure or right before failure, and then reduce the weight and continue to lift for more repetitions with the decreased weight. Pyramid setsPyramid sets are weight training sets in which the progression is from lighter weights with a greater number of repetitions in the first set, to heavier weights with fewer repetitions in subsequent sets. A reverse pyramid is the opposite in which the heavier weights are used at the beginning and progressively lightened. BurnoutsBurnouts combine pyramids and drop sets, working up to higher weights with low reps and then back down to lower weights and high reps. There are a few different ways one could perform burnout sets but the main idea is to perform an exercise until failure. You should start with a weight that is 75% of the amount of the maximum amount of weight you can lift for 1 rep. Once you've performed the exercise to exhaustion, reduce the weight and perform another set until failure, which will usually consist of much fewer repetitions. Burnout sets sound very similar to supersets but there are differences in the results they produce. Supersets help increase muscle mass, but are more efficient for producing muscle definition and shape. Burnout sets help increase muscle growth because of the buildup of lactic acid in the muscle when it's forced to the point of failure. Diminishing setThe diminishing set method is where a weight is chosen that can be lifted for 20 reps in one set, and then 70 repetitions are performed in as few sets as possible.[67]: 17 Rest-pauseThe rest-pause training method takes one whole set and breaks it down into a few mini sets. There are two different goals that are associated with rest-pause training, including both hypertrophy and strength. To increase hypertrophy, an athlete typically performs a set at a comfortable weight for 6 to 10 reps and then sets the weight down. Next, they would take 15 seconds' worth of deep breaths, pick the weight back up, and lift to failure. The last step can be repeated any number of times after this, but it is commonly done twice. In order to increase strength using rest-pause method, most people choose a weight that is 85–95% of their one rep max. They then perform 1 rep with this weight, followed by a longer 30- to 45-second break, and repeat this process several times.[68] Giant setThe Giant set, is a form of training that targets one muscle group (e.g. the triceps) with four separate exercises performed in quick succession, often to failure and sometimes with the reduction of weight halfway through a set once muscle fatigue sets in. This form of intense training 'shocks' the muscles and as such, is usually performed by experienced trainers and should be used infrequently.[69] Combined setsSupersets Supersets combine two or more exercises to reduce the amount of rest needed between sets. Supersets can be used to increase the time efficiency of training.[70]Beyond failureTraining beyond failure has traditionally been seen to be of value in developing strength and hypertrophy. However, in recent years new evidence has shown that consistently training beyond failure is a suboptimal training methodology in developing and enhancing strength and/or power in the short and long term.[71] Sets taken closer to this point of failure, along with supramaximal eccentric movements (negative only nordic hamstring curls for example) do still seem to have some benefit in specific injury prevention/rehabilitation settings.[72] Velocity based trainingVelocity based training or VBT is a series of methods used in strength and power training which applies velocity tracking as a method for increasing intent and informing real-time adjustments in a training program or periodisation plan.[73] Since the late 1990s, innovations in bar speed monitoring technology has brought velocity based training closer to the mainstream as the range of hardware and software solutions for measuring exercise velocities have become easier to use and more affordable. Other techniquesVariable resistance training This involves adjusting resistance during a weight training exercise in order that it matches the phases of strength which a person naturally moves through (a.k.a. their strength curve).[note 1] This is done to increase resistance during the phase of a lift where a person is strongest and reduce it at the phase of the lift where they are weakest. In this way the percentage of 1RM for each phase respectively can be maintained, or a discrepancy reduced. For example, when performing a back squat the 1RM for the lower weaker phase may be 60 kg and for the higher stronger phase 90 kg. To ensure the same percentage of 1RM for each phase is lifted, or a comparable amount of resistance overcome, heavy chains or large rubber bands may be attached to the end of the barbell to vary the resistance during the exercise i.e. increase it at the top of the lift and decrease it at the bottom. Alternatively, and to continue the previous back squat example, full reps could be performed with 60 kg and combined with partial reps, which remain in the stronger movement range, at 90 kg.[74][75]Time under tension Time under tension or TUT repetitions are performed with lighter weights. Time under tension refers to the amount of time your muscle under stress during a set. This consists of the time spent in the concentric or the shortening phase, peak contraction phase, as well as the eccentric or the lengthening phase. For example, if you go perform a set of 10 reps and each rep takes 3 seconds to complete, your muscle is under tension for a total of 30 seconds. If you were to perform the same exercise but if you spent 2 seconds in the concentric phase, 1 second to stop during peak contraction, and 3 seconds to lower the weight during the eccentric phase of the rep, the same 10 reps would end up putting your muscles under tension for about 60 seconds. New technology (i.e. smartphones) have been leveraged to validly and reliably measure TUT [76]Using a wrist strap Wrist straps Wrist straps (lifting straps) are sometimes used to assist in gripping very heavy weights. Wrist straps can be used to isolate muscle groups like in "lat pull-downs", where the trainee would primarily use the latissimus dorsi muscles of the back rather than the biceps. They are particularly useful for the deadlift. Some lifters avoid using wrist straps to develop their grip strength, just as some go further by using thick bars. Wrist straps can allow a lifter initially to use more weight than they might be able to handle safely for an entire set, as unlike simply holding a weight, if it is dropped then the lifter must descend with it or be pulled down. Straps place stress on the bones of the wrist which can be potentially harmful if excessive.[citation needed] Strength training may involve the combining of different training methods such as weight training, plyometrics, bodyweight exercises, and ballistic exercises. This is often done in order to improve a person's ability to apply their strength quickly. Or in other words, to improve their ability to apply explosive power. Loaded plyometricsLoaded plyometrics involve the addition of weights to jumping exercises. The weights may be held or worn. For instance, vertical jumps whilst holding a trap bar or jumping split squats whilst holding dumbbells. This helps to enhance the explosive power of the athlete.[77] Complex trainingComplex training, sometimes incorrectly referred to as contrast training (see below), involves the alternation of weight training and plyometric exercises. Ideally, both sets of exercises should move through similar ranges of movement; such a pairing is called a complex, or contrast, pair. For instance, a set of heavy back squats at about 85–95% 1RM followed by a set of jumping exercises. The intention is to utilise the intense nervous system activation and increased muscle fibre recruitment from the heavy lift in the plyometric exercise; thereby increasing the power with which it can be performed. Over a period of training, this may result in the athlete being able to perform the plyometric exercise more powerfully, without the requirement of the preceding heavy lift.[78] Working on the same principles, a sports specific action may be incorporated instead of the plyometric exercise; the intention, in this case, being to increase the athlete's ability to perform the sports specific action more powerfully. Ballistic trainingBallistic training, sometimes referred to as power training, is based upon the principle of maximizing the acceleration phase of the exercise and minimizing the deceleration phase; this helps to improve the athlete's explosive power. On this basis, ballistic training may include exercises which involve the throwing of a weight, such as a medicine ball, or jumping whilst holding or wearing a weight.[79] Contrast loadingContrast loading is the alternation of heavy and light loads i.e. a heavy bench press set at about 85–95% 1RM followed by a light bench press set at about 30–60% 1RM. The heavy set should be performed fast with the light set being performed as fast as possible. The joints should not be locked as this inhibits muscle fibre recruitment and reduces the speed at which the exercise can be performed. A loaded plyometric exercise, or ballistic exercise, may take the place of the light lift. Similarly to complex training, contrast loading relies on the intense nervous system activation and enhanced muscle fibre recruitment from the heavy lift to help improve the power with which the subsequent exercise can be performed.[80] This physiological effect is commonly referred to as post-activation potentiation, or the PAP effect. By way of explanation, if a light weight is lifted, and then a heavy weight is lifted, and then the same light weight is lifted again, then the light weight will feel lighter the second time it is lifted. This is due to the increased PAP effect from the heavy lift allowing for greater power to be applied and thus making the subsequent lighter lift feel even lighter than before. Explosive power training programs are frequently designed to specifically utilize the PAP effect.[citation needed] It is widely accepted that strength training must be matched by changes in diet in order to be effective. Although aerobic exercise is often observed to have an effect on the dietary intake of macronutrients, strength training has not[81] and an increase in dietary protein is generally believed to be required for building skeletal muscle. A review of 49 research studies found that supplementation of protein in the diet of healthy adults increased the size and strength of muscles during prolonged resistance exercise training; protein intakes of greater than 1.6 g/kg/day did not additionally increase fat-free mass or muscle size or strength.[82] Protein that is neither needed for cell growth and repair nor consumed for energy is converted into urea mainly through the deamination process and is excreted by the kidneys. It was once thought that a high-protein diet entails risk of kidney damage, but studies have shown that kidney problems only occur in people with previous kidney disease. However, failure to properly hydrate can put an increased strain on the kidney's ability to function.[83][84] An adequate supply of carbohydrates (5–7 g per kg) is also needed as a source of energy and for the body to restore glycogen levels in muscles.[85] A light, balanced meal prior to the workout (usually one to two hours beforehand) ensures that adequate energy and amino acids are available for the intense bout of exercise. The type of nutrients consumed affects the response of the body, and nutrient timing whereby protein and carbohydrates are consumed prior to and after workout has a beneficial impact on muscle growth.[86] Water is consumed throughout the course of the workout to prevent poor performance due to dehydration. A protein shake is often consumed immediately[87] following the workout. Glucose (or another simple sugar) is often consumed as well since this quickly replenishes any glycogen lost during the exercise period. If consuming recovery drink after a workout, to maximize muscle protein anabolism, it is suggested that the recovery drink contain glucose (dextrose), protein (usually whey) hydrolysate containing mainly dipeptides and tripeptides, and leucine.[88] Some weight trainers also take ergogenic aids such as creatine or steroids to aid muscle growth. However, the effectiveness of some products is disputed and others are potentially harmful. A woman doing strength training using weights at a health club with her coach standing behind her. Men have a higher percentage of fast-twitch type II muscle fiber, which gives them strength.[89][90] On the other hand, women have a higher proportion of slow-twitch type I muscle fibers, which contributes to their endurance.[89][90] Since women have a higher percentage of slow-twitch muscle fiber, they can do better with higher reps and higher volume without overtraining the muscle.[89][90] Research has shown that women can have a more significant muscle growth doing reps with a higher range of movement.[89] On the other hand, men can do more explosive movement because men have a bigger motor cortex in the brain, which controls the movement and help men to generate more force.[89] Women recover less well when doing explosive exercise and are less likely to build muscle from doing explosive activities.[89] Women do not have to rest as long between sets as men because women have a lower arterial blood pressure during exercise, which allows more blood and oxygen to go to the muscle.[89] Moreover, women's bodies make less byproduct, lactate, that creates the "burn" feeling in the muscle, resulting in that the muscle tissue can tolerate higher stress for a more extended period of time.[89] Women not only recover faster between sets, they also recover faster after a workout compared to men.[89] Since women don't react well to explosive exercise and have higher endurance, women do better with steady-state cardio and complete reps with a slow and control motion, instead of explosive exercise, such as sprinting.[89] The strength difference between men and women also varies due to the ratio between fat and lean muscle mass in different body parts, and that is the reason why most men have a stronger upper body, while women are stronger than men in the lower body.[90] However, many other studies have pointed out that men are stronger in both the upper body (by around 30%), and in the lower body (by around 5%).[91] These strength differences remain even when relative to body mass (fat to lean muscle mass ratio), since men have significantly more lean muscle mass in the upper body and lower body.[92] Men have a higher testosterone level, which power strength, muscle mass, and strength.[90] Women have a higher estrogen level, which helps them with muscle recovery and supports the muscle's ability to use glucose as fuel.[90] Even though studies has shown that men are more capable of increasing muscle mass compared to women when doing same intensities and years of training, both men and women's bodies produce a hormone that spikes their strength and support muscle building.[90][93] Men's bodies produce more testosterone that helps with muscle building when they are training, while women's bodies produce more human growth hormone that aids with tissue and muscle building.[90] Women's hormone also changes due to the menstrual cycle.[90] During the follicular phase, women have a decrease in progesterone level, which helps prevent muscle damage and aids with recovery.[90] On the other hand, the increase of progesterone levels during the luteal phase can negatively impact the body's ability to recover from muscle damage.[90] It is suggested that women should increase the intensity of training during the week and the week after the menstrual cycle to maximize the training progress.[90] Sex differences in mass gainsDue to the androgenic hormonal differences between males and females, women are generally unable to develop large muscles regardless of the training program used.[94] Normally the most that can be achieved is a look similar to that of a fitness model. Muscle is denser than fat, so someone who builds muscle while keeping the same body weight will occupy less volume; if two people weigh the same (and are the same height) but have different lean body mass percentages, the one with more muscle will appear thinner.[95] In addition, though bodybuilding uses the same principles as strength training, it is with a goal of gaining muscle bulk. Strength trainers with different goals and programs will not gain the same mass as a professional bodybuilder. Weight lossExercises like sit-ups, or abdominal crunches, performs less work than whole-body aerobic exercises[96] thereby expending fewer calories during exercise than jogging, for example. Hypertrophy serves to maintain muscle mass, for an elevated basal metabolic rate, which has the potential to burn more calories in a given period compared to aerobics. This helps to maintain a higher metabolic rate which would otherwise diminish after metabolic adaption to dieting, or upon completion of an aerobic routine.[97] Arthur Saxon performing a Two Hands Anyhow with an early kettlebell and plate-loaded barbell Until the 20th century, the history of strength training was very similar to the history of weight training. With the advent of modern technology, materials and knowledge, the methods that can be used for strength training have multiplied significantly. Hippocrates explained the principle behind strength training when he wrote "that which is used develops, and that which is not used wastes away", referring to muscular hypertrophy and atrophy. Progressive resistance training dates back at least to Ancient Greece, when legend has it that wrestler Milo of Croton trained by carrying a newborn calf on his back every day until it was fully grown. Another Greek, the physician Galen, described strength training exercises using the halteres (an early form of dumbbell) in the 2nd century. Ancient Persians used the meels, which became popular during the 19th century as the Indian club, and has recently made a comeback in the form of the clubbell. The dumbbell was joined by the barbell in the latter half of the 19th century. Early barbells had hollow globes that could be filled with sand or lead shot, but by the end of the century these were replaced by the plate-loading barbell commonly used today.[98] Strength training with isometric exercise was popularised by Charles Atlas from the 1930s onwards. The 1960s saw the gradual introduction of exercise machines into the still-rare strength training gyms of the time. Strength training became increasingly popular in the 1980s following the release of the bodybuilding movie Pumping Iron and the subsequent popularity of Arnold Schwarzenegger.[99] Orthopaedic specialists used to recommend that children avoid weight training because the growth plates on their bones might be at risk. The very rare reports of growth plate fractures in children who trained with weights occurred as a result of inadequate supervision, improper form or excess weight, and there have been no reports of injuries to growth plates in youth training programs that followed established guidelines.[100][101] The position of the National Strength and Conditioning Association is that strength training is safe for children if properly designed and supervised.[102] Younger children are at greater risk of injury than adults if they drop a weight on themselves or perform an exercise incorrectly; further, they may lack understanding of, or ignore the safety precautions around weight training equipment. As a result, supervision of minors is considered vital to ensuring the safety of any youth engaging in strength training.[100][101] For older adultsOlder adults are prone to loss of muscle strength.[103][104] With more strength older adults have better health, better quality of life, better physical function[104] and fewer falls.[104] In cases in which an older person begins strength training, their doctor or health care provider may neglect to emphasize a strength training program which results in muscle gains. Under-dosed strength training programs should be avoided in favor of a program which matches the abilities and goals of the person exercising.[105] In setting up an exercise program for an older adult, they should go through a baseline fitness assessment to determine their current limits. Any exercise program for older adults should match the intensity, frequency, and duration of exercise that the person can perform. The program should have a goal of increased strength as compared to the baseline measurement.[105] Recommended training for older adults is three times a week of light strength training exercises. Exercise machines are a commonly used equipment in a gym setting, including treadmills with exercises such as walking or light jogging. Home-based exercises should usually consist of body weight or elastic band exercises that maintain a low level of impact on the muscles. Weights can also be used by older adults if they maintain a lighter weight load with an average amount of repetitions (10–12 reps) with suitable supervision. It is important for older adults to maintain a light level of strength training with low levels of impact to avoid injuries.[106] Older people who exercise against a resistance or force become stronger.[104] Progressive resistance training (PRT) also improves physical functioning in older people, including the performance of simple (e.g.: walking, climbing stairs, rising from a chair more quickly) and complex daily activities (e.g.: bathing, cooking).[104] Caution is recommended when transferring PRT exercises for clinical populations, as adverse effects are unclear.[104]
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