Friday, June 1, 2007

Strength Training For Women: Debunking Myths That Block Opportunity

Strength Training – Strength Training For Women: Debunking Myths That Block Opportunity.
By William P. Ebben, MS, MSSW, CSCS; Randall L. Jensen, PhD
From The Physician and Sports Medicine- Vol. 26 - No. 5 – May 98
In Brief: Traditional gender roles and differences in absolute strength have resulted in misconceived approaches to strength training for women. Male physiology, more than hormones, explains men's superior absolute strength. When other measures of strength are used, such as strength relative to cross-sectional area of muscle, the strength of men and women is nearly equal. Women who practice the same well-designed strength training programs as men benefit from bone and soft-tissue modeling, increased lean body mass,
decreased fat, and enhanced self-confidence.

Although American women first began strength training for sports in the 1950s to improve their performance in track and field, they have traditionally participated in strength training less than men. Such exercise has not been considered feminine, and a lack of research and information regarding the effects of such training on women has made it a predominantly male activity. Women's participation was particularly limited until 1972, when Title IX mandated equal access to educational programs--including athletics—for men and women in schools that receive federal funding. Since then, women's sports participation has burgeoned, traditional gender roles have loosened, and strength training has grown in popularity among active women.

Nevertheless, the social stigma and lack of accurate information persist and feed misconceptions that keep women away from strength training or prevent them from training in optimal ways (see "Dispelling Misconceptions," below). Though gender differences regarding absolute strength exist, women are as able as men to develop strength relative to total muscle mass. Consequently, women should strength train in the same ways as men, using the same program design, exercises, intensities, and volumes, relative to their body size and level of strength, so they can achieve the maximum physiologic and psychological benefits.

Gender Stereotypes
Our culture has traditionally viewed strength as a masculine trait and promoted a small, frail body as feminine. Consequently, girls have been discouraged from participating in gross-motor-skill activities and strength development. Such sex role stereotypes, formed early in childhood, can dictate behavior and limit women's and men's ability to express their full humanity. This means that some women may have never achieved their potential for physical well-being, fitness, and athletic participation.

The advent of the women's movement in the 1970s allowed many women to overcome such traditional socialization and participate more freely in sports and strength training. However, change occurs slowly, and physical strength and strength training are still not as common or accepted for women as they are for men.

A Gender Gap in Strength?
Research (1,2) on male and female strength potential reveals that women possess about two thirds of the strength of men. However, the measurement of strength in absolute terms fosters misconceptions about the strength of women, how women see themselves, and the way they exercise.

What causes this strength difference? Are there ways to conceptualize strength that affirm women's potential and encourage their development?

The role of hormones. Hormones play a role in the development of absolute strength in men and women, but the exact influence is not clear. The androgens that come from the adrenal glands and ovaries are the hormones most likely to influence strength. The most important androgens for strength development are testosterone and androstenedione. The absolute androstenedione response to weight lifting is similar in females and males (3).

The role of testosterone in strength development is complex and significantly more variable than that of androstenedione. Though women on average have about one tenth the testosterone of men (4), the level of testosterone varies greatly among women and influences women's strength development more than is typical in men (3). Women who have higher testosterone levels may have a greater potential for strength and power development than other women. An individual woman's testosterone level fluctuates, so a woman who is near the upper limit of her testosterone threshold may have an advantage in developing strength compared with other women. Though hormones may influence strength development potential among women, they most likely do not account for significant male-female differences in absolute strength.

Physiologic factors. Physiologic differences such as size and body structure are more likely explanations for the average absolute strength differences between men and women. For example, the average American male is about 13 cm taller than the average female and about 18 kg heavier. Men average about 18 to 22 kg more lean body mass and 3 to 6 kg less fat than women. Men typically have a taller, wider frame that supports more muscle, as well as broader shoulders that provide a greater leverage advantage.

The Strength of Women
Strength, however, should not be viewed in absolute terms. The gender differences in absolute strength, for example, are not consistent for all muscle groups. Women possess about 40% to 60% of the upper-body strength and 70% to 75% of the lower-body strength of men (3). Men may have an advantage in neuromuscular response time that results in greater force production speed than women (5). However, the distribution of muscle fiber types--fast and slow twitch--is similar in the two sexes, and women are able to use a greater portion of stored elastic energy than men during activities in which muscle is prestretched, such as in the countermovement prior to jumping.

More significantly, if the amount of lean body mass is factored into the strength equation, the relative strength difference between men and women is less appreciable. Based on a strength-to-lean-body-mass ratio, women are about equal in strength to men, and when strength is calculated per cross-sectional area of muscle, no significant gender difference exists. For example, a 15 cm2 cross-sectional area of an arm flexor has about 19 kg of force for both women and men (6).

Measuring strength in this way suggests that muscle at the cellular level has a force development capability independent of sex and that women benefit from strength training at least as much as men. Hence men and women should follow strength training procedures that include periodization--variations in the resistance training program that are implemented over a specific time--and exercise performed at intensities and volumes suited to physical ability and level of strength conditioning. Ultimately, each athlete should be assessed as an individual, and training programs should meet individual needs and goals, rather than those based on preconceived ideas about gender.

The Benefits for Women
Women benefit from strength training in several ways (table 1).

Table 1. Strength Training Benefits for Women*
Ø Enhanced bone modeling to increase bone strength and reduce the risk of osteoporosis
Ø Stronger connective tissues to increase joint stability and help prevent injury
Ø Increased functional strength for sports and daily activity
Ø Increased lean body mass and decreased nonfunctional body fat
Ø Higher metabolic rate because of an increase in muscle and a decrease in fat
Ø Improved self-esteem and confidence

-A number of factors may reduce or eliminate these benefits, including the exclusive use of weight training machines, training with loads that are too light, and not progressing in resistance or intensity.

Bone and soft tissue. Women, more than men, need to meet the minimal essential strain required for bone modeling to occur and ultimately for reducing the risk of osteoporosis. Prevention of osteoporosis requires above-normal axial skeletal loading (7,8). The strain tolerance for skeletal bone is believed to be more than 10 times the typical load that humans bear in daily activities (9). Since bone modeling is proportional to the degree of overload (the amount of stress applied beyond the normal load), the greater the overload-- within limits--the greater the amount of bone modeling. Bone modeling helps prevent fractures and insure against osteoporosis.

Cartilage, tendons, and ligaments also have minimal essential strain requirements. Optimal strength development requires loads and intensities that progressively increase the training stimulus or stress. Strong cartilage, tendons, and ligaments are essential for joint integrity, stability, and injury prevention.

Lean body mass and fat. Strength training also increases lean body mass and decreases fat; this results in less nonfunctional fat to carry and a greater proportion of lean body mass, which can provide functional strength. Compared to fat, muscle is metabolically active and increases metabolic rate, fat oxidation, and calorie consumption. Increased muscle mass and muscle cross-sectional area also correlate with increased strength. Participation in "functional" strength training exercises will develop functional strength and most likely improve performance, whether it is an increased ability to spike a volleyball or pick up a child.

Psychological well-being. Finally, studies (3) suggest that women who engage in strength training benefit from improved self-esteem. Female athletes appear to be able to balance strength and femininity; according to one survey, 94% of the participants reported that athletic participation did not lead them to feel less feminine. Strength training also appears to give women a sense of personal power, especially for women who have been raped or abused. Such psychological benefits arise from the physiologic changes that occur as a result of strength training and from the process of encountering and mastering physical challenges. Thus, both the process and the outcome of strength training benefit women (3).

Strength Training Guidelines
Since well-designed strength training programs include exercises with free weights and dumbbells and exercises that use body weight resistance, both women and men should include these in their training, and women should train at the same intensities as men.

The use of strength training machines and abdominal exercises need not be discontinued, but emphasis should be placed on the use of free-weight exercises including foot-based lower-body exercises such as the lunge, diagonal lunge, walking lunge, step up, lateral step up, and squat. Women should also include upper-body exercises that employ multiple muscle groups such as the bench press, incline press, latissimus dorsi pull-downs, pull-ups, and back extensions. Finally, women who have developed a strength base should consider total-body exercises such as the push press, hang clean, power clean, clean and jerk, and snatch.

A training program should also stress multiplanar, multijoint, functional exercises because they develop intermuscular coordination, proprioception, and balance and result in strength that transfers to sports and daily activities. For example, the step-up exercise is superior to using the leg-extension machine because it offers functional strength for walking up a flight of stairs while carrying bags of groceries. For athletes who play foot-based sports such as basketball, the squat is superior to using the leg-press machine, since the squat is functionally more similar to the sport and requires greater balance and weight and body control in all three planes of motion.

Fostering Strength
Though sex role stereotypes still powerfully shape our culture and behavior, physical strength is no longer the sole domain of men. More and more women are claiming strength as their own through participation in sports and especially in strength training programs. Such participation helps to counter the stereotypes and fosters an appreciation of strength as desirable for women.

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National Strength and Conditioning Association: Position Paper: Strength Training for Female Athletes. National Strength and Conditioning Association, Colorado Springs, 1990
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Dispelling Misconceptions
Recent studies counter several widely held beliefs that may limit the physiologic and psychological benefits of weight training for women.

Myth 1: Strength training causes women to become larger and heavier. The truth is, strength training helps reduce body fat and increase lean weight (1). These changes may result in a slight increase in overall weight, since lean body mass weighs more than fat. However, strength training results in significant increases in strength, no change or a decrease in lower-body girths, and a very small increase in upper-extremity girth. Only women with a genetic predisposition for hypertrophy who participate in high-volume, high-intensity training will see substantial increases in limb circumference.

Myth 2: Women should use different training methods than men. Women are often encouraged to use weight machines and slow, controlled movements out of a fear that using free weights, manual resistance, explosiveness (high velocity, low force), or exercises that use body weight as resistance will cause injury. In fact, no evidence suggests that women are more likely to be injured during strength training than men. Proper exercise instruction and technique are necessary to reduce the risk of injuries for both men and women. All strength training participants should follow a program that gradually increases the intensity and load. Furthermore, sport-specific exercise should closely mimic the biomechanics and velocity of the sport for which an athlete is training (2). The best way to achieve this is to use closed-kinetic-chain exercise that involves multiple joints and muscle groups and the ranges of motion specific to the sport. For example, the push press--rather than triceps kickbacks--offers a superior arm extension training stimulus for improving the ability to throw the shot put in track and field.

Myth 3: Women should avoid high-intensity or high-load training. Women are typically encouraged to use limited resistance, such as light dumbbells, in their strength exercises. Often such light training loads are substantially below those necessary for physiologic adaptations and certainly less than those commonly used by men. Most women are able to train at higher volumes and intensities than previously believed. In fact, women need to train at intensities high enough to cause adaptation in bone, muscle, cartilage, ligaments, and tendons. When exercise intensity provides insufficient stimulus, physiologic benefits may be minimal (3). To gain maximum benefit from strength training, women should occasionally perform their exercises at or near the repetition maximum for each exercise.

Fox E, Bowers R, Foss M: The Physiological Basis for Exercise and Sport, Madison, WI, Brown and Benchmark, 1993
Stone MH, Borden RA: Modes and methods of resistance training. Strength Conditioning 1997;19(4):18-24
National Strength and Conditioning Association: Position Paper: Strength Training for Female Athletes. National Strength and Conditioning Association, Colorado Springs, 1990

Mr Ebben is a strength coach at the University of Wisconsin in Madison. Dr Jensen is an assistant professor in the Department of Health, Physical Education, and Recreation at Northern Michigan University in Marquette.

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