Over the past 30 years there has been a dramatic increase in the number of women participating in activities once viewed as the domain of men. Women are now participating successfully at every level of sporting and athletic competition.
Part of that success has been due to the inclusion of resistance training and the development of strength. However, strength development is not just for the elite. Females at any age will benefit from a well planned strength training programme. Strength development is necessary for optimal structural health and has been associated with a positive mental attitude. Many daily activities such as shopping, gardening and carrying children require a minimum level of strength. Unfortunately, many misconceptions surround women, resistance training and strength development.
Historically strength has been associated with size and masculinity. This type of sex role stereotype has typically discouraged many women from participating in gross motor skill activities and strength development. Consequently, this may result in females never achieving their full potential for optimal well-being.
Females do have unique needs such that today’s trainers need to understand gender differences before exercise participation. Characteristics such as body composition, stature, pregnancy, menstruation and nutritional status all affect the exercise response. Equipped with this knowledge the diligent trainer will be best placed to educate and prescribe appropriate exercise.
Anatomical and Physiological Differences in Males and Females
There are a number of anatomical and physiological differences between genders. These differences include:
- lean body weight
In general females have smaller and lighter bones than those of males. However, of primary anatomical significance are the gender differences in the structure of the pelvis. In comparison to the male pelvis, the female pelvis is broader, flares out more to the front and has a wider sacrum at the back creating a greater pelvic cavity. A broader pelvis is perfectly designed for child bearing (Hamill and Knutzen, 1995). Unfortunately, a broader pelvis causes the femur to articulate with the pelvis at a more acute angle than the more linear articulation between the male pelvis and femur, resulting in a slight mechanical disadvantage affecting the knee. This is due to a tendency for females to excessively internally rotate the femur creating increased valgus stress at the knee, especially during activities such as jumping and squatting. If excessive, this valgus force can have devastating consequences to the ligaments of the knee. Women also have shorter legs giving them a slightly lower centre of gravity (COG), an advantage in activities requiring balance.
Biomechanical differences also exist at the knee joint. Females have a tendency for a greater Q-angle (quadriceps angle) in comparison to the male knee joint due to their wider hips. The Q-angle is the measure of deviation from a straight line between the centre of the patella to the tibial tuberosity and a line from the centre of the patella to the centre of the anterior superior iliac spine (fig. 28.2). 10 to 15 degrees are considered to be normal. Q-angles greater than 20 degrees are considered excessive and may lead to pathological changes (Levangie and Norkin, 2001), such as chondromalacia patella (degeneration of the undersurface of the patella). This can be due to the lateral displacement of the patella.
Lean Body Weight:
Distribution of lean body weight differs between the genders; females have a higher percentage of lean body weight on their lower bodies. In comparison to females, males are generally taller have larger bones with bigger and broader shoulders. A larger structure allows for more muscle mass, which is a definite advantage when developing upper and lower body strength and power (power output is approximately 33% greater in men than women [Brooks et al, 1996]). The female’s smaller structure makes it much more difficult to develop strength, especially in the upper body.
Generally speaking, muscle strength in females is about two thirds that of men (Hettinger, 1961 cited in NSCA position paper, 1989). Because of this, males continually demonstrate greater absolute strength for the same training experience; yet, the relative strength differences are less significant. In the lower body, Wilmore and Costill (1999), found no appreciable difference using strength to lean body weight ratio. It would appear that females have the same capacity for the development of strength as males when strength of both is compared per cross-sectional area of muscle.
On average males have 18 to 22 kilogrammes more lean body mass and 3 to 6 kilogrammes less fat weight than females (Brooks et al. 1996). This again goes some way to explain sex differences in physical performance.
Hormone production also differs between the sexes. Of significance is that males exhibit higher androgen levels, particularly that of testosterone (TST). During puberty gonadotropin hormones are secreted from the anterior pituitary gland (follicle stimulating hormone and luteinizing hormone). These hormones stimulate the gonads (ovaries and testes), which in turn stimulates the production of the sex hormones, TST in males and oestrogen in females.
TST and oestrogen account for the gender-characteristic body compositional differences between males and females. TST is an important hormone for protein synthesis. In males TST increases lean body mass and inhibits the development of body fat, whereas oestrogen in females stimulates adipose tissue (increased fat cells).
Typically females have on average 6-10% more fat than males, with active females having lower body fat levels than sedentary females (Wilmore and Costill, 1999). Females characteristically store fat around the mammary glands, pelvic and thigh region due to high lipoprotein lipase activity (enzyme produced in fat cells to store fat) compared to other fat storage areas (Wilmore and Costill, 1999). Unfortunately, this makes it difficult to lose fat from these areas. This difference in fat distribution and storage is thought to be for reproductive purposes.
Understanding this Hormonal Cycle is paramount to programme design for female clients.
Over the (lets’s just say month for argument’s sake) cycle, energy levels will change, food cravings will change with this, strength will fluctuate as will focus and drive. There will be processes going on internally that maybe your client’s may not even be aware of.
Take a look at this research based video from Elsie Alkurabi.
Cardiorespiratory gender differences include: women have smaller heart volumes for a similar body size (lower stroke volume and about 10% less cardiac output); for similar bodyweights women have 20% lower blood volume compared to men; women also have about 10% less haemoglobin (red blood cells) than men for the same blood volume and about 10% less vital capacity (Neely, 1998). This explains why women generally have slightly higher heart rates compared to men during any given level of exercise intensity. The highest VO2 max recorded for a female athlete is 77 ml/kg/min whereas the highest recorded VO2 max for a male achieved a value of 94 ml/kg/min (Wilmore and Costill, 1999). These cardiorespiratory differences allow men to have a greater oxygen carrying capacity.
Strength Training Benefits
Women should be actively encouraged to include resistance training as part of their overall programme of conditioning for the following reasons:
- increased bone strength and density
- enhanced joint stability
- increased lean body mass.
- improved body image and self-perception
- improved posture
Increased bone strength and density:
A lifetime of structural health is dependent on strong bones if bone diseases such as osteoporosis are to be avoided. Females are more at risk of developing the bone disease osteoporosis than males, so it’s important for females to maximise their peak bone mass (PBM). Genetic, mechanical, hormonal and nutritional factors all affect PBM, which is largely established by the end of adolescence or early adulthood (Anderson, 1996).
From the age of 30 onwards PBM starts to decline, and women can expect an annual bone loss of about 0.5% to 1.0% total bone mass from the age of 40. Affected sites include the vertebrae and neck of femur. During the first 5 to 10 years after menopause (cessation of normal menses) this bone loss accelerates at a rate of about 2% per annum (Kanis, 1994). Thus, women can easily lose 15% to 30% of their PBM by age 60 (Kanis, 1994). According to the World Health Organisation (1993) criteria, up to 30% of all postmenopausal women have osteoporosis, with another 54% having osteopenia (low bone density).
Weight-bearing exercise has repeatedly been shown to increase bone density. In one controlled study (Shimegi et al, 1994) of 25 women aged 49-61, lumbar spine bone mineral density (BMD) was significantly higher in those who jogged or played volleyball than in those who had no regular activity. Therefore, a bone loss prevention programme is focused around the preservation and enhancement of bone material through consumption of adequate calcium, exposure to the sun for the generation of vitamin D and vigorous exercise to increase lean body tissue.
The personal trainer should keep in mind some basic principles when prescribing exercise for the prevention of, or treating osteoporosis. Principles include the following:
- everybody is different so it would not be appropriate to recommend the same type of exercise to all. Younger healthier individuals can tolerate higher loads during activities such as running and jumping, whereas, older individuals may present with some significant structural and physiological changes, so lower level weight-bearing activities such as walking and weight training should be recommended
- the stimulus must be varied and greater than that of activities performed during normal daily life
- the effects of exercise are specific to each site so only the bones that are loaded will benefit. Therefore, exercises for both the upper and lower body should be performed
- impact activities done quickly place the highest forces on bones and have the greatest affect on bone remodeling
- to maintain a positive effect on bone tissue, the programme must be continued throughout ones life
Enhanced joint stability:
During physical activity females may be at increased risk of injury in comparison to males. Female participation in recreational activities has grown in popularity over recent years. More now than ever before women are actively participating in activities that involve jumping, landing and pivoting such as gymnastics, netball, volleyball and football (football is now the fastest growing female sport in the UK) (Arendt and Dick, 1995; Ferretti et al, 1996). There has however been a dramatic increase in the rate of non-contact injuries especially to the anterior cruciate ligament in the knee. In fact, evidence demonstrates that female athletes are 3-6 more likely to sustain a rupture to the anterior cruciate ligament (ACL) than men participating in the same sports.
At present it is unclear as to exactly what factors lead to the high incidence of ACL injuries seen in jumping, landing and pivoting activities however a number of theories have been proposed to explain the high incidence of non-contact ACL injuries in females. Possible theories include:
The wider hips and increased Q angle at the knee predispose to ACL injury.
Hormonal fluctuations over the course of the menstrual cycle may affect the ligaments and neuromuscular coordination around the knee. This would result in a reduction in dynamic knee stability thus increasing the likelihood of injury (Liu et al, 1997).
When stabilising the knee men seem better able to activate their hamstring muscles than females, who rely more on their quadricep muscles (Huston and Wojtys, 1996). This is a significant finding as this coincides with the fact that early hamstring activation, as seen in males, may have a protective effect on the knee joint position and reduces the likelihood of ACL disruption. This may be due to the fact that the hamstring muscles function is to decelerate both hip flexion (therefore, controlling the upper body’s forward momentum) and knee internal rotation.
Improved body image and self-perception:
Body image can be defined as:
“The mental picture of the physical self, with feelings about this image being based on cultural ideals” (Melpomene Institute, 1990).
Today’s women find themselves under increased social and psychological pressure to conform to media driven feminine ideals. Body image beliefs can be formed as early as two to four years of age and follow the preferences of adults. Research supports the notion that males and females differ in their beliefs concerning what is an acceptable body image (somatotype). Mesomorphic physiques are the most popular, endomorphic physiques are the least popular, whereas, ectomorphic physiques are more acceptable to girls than boys. Women are also more likely to reject the fat image (Polivy et al. 1986, cited in NSCA position paper, 1989). These images often alter a women’s perception of herself and her desire for body compositional change. This can have little or no resemblance to how a female actually looks, weighs or measures objectively in terms of fat or muscle.
Whether this perceived pressure is driven from within or from an external influence, researchers agree that there is a strong relationship between distorted perception of body image, abnormal eating and exercise patterns in females. This can lead to eating disorders such as anorexia nervosa (AN) and bulimia nervosa (BN) (prevalence of eating disorders in female, AN 0.5 to 3.7% and from 1.1% to 4.2% BN respectively, [Sundgot-Borgen, 1994]). Eating disorders have a catastrophic effect on long-term health and well-being.
Women often desire to feel good about themselves rather than to conform to a specific weight or size. A positive body image has long been associated with an overall sense of self-esteem, normal eating and exercise habits (Bresolin, 1990). The type of exercise performed may influence a woman’s perception and attitude towards her body. Current research is supporting the belief that weight training can result in positive changes in self-esteem for women of varying ages and abilities. In a recent study (Ahmed et al, 2002), researchers investigated the relationship between strength training and perception of body image. 49 female subjects participated in a 12 week strength training programme. The programme was performed twice a week using various levels of intensity (6-15 reps). All participants improved their strength levels at the end of 12 weeks, but more importantly 97.5% indicated that they felt healthier and fit, 51.2% of participants indicated that perceptions of their body image improved and 85% of participants indicated an improved attitude toward their physical self. Other comments included that they felt more toned up, better about themselves, more confident, healthier, and more positive about their body at the end of the study than at the start.
Culturally, men are expected to be big and strong, and there is good evidence to support this. In childhood boys are encouraged to participate in gross motor play and rough and tumble games, whereas girls are discouraged from such activities (Greendorfer, 1978, cited in NSCA position paper, 1989). Sex stereotype belief structures formed in childhood may result in conflict between strength training and what is supposed to be appropriate behaviour. Feelings of inadequacy, myths of the masculinisation effects and the fear of adding weight can all be reasons for avoiding resistance training. However, for many women resistance training can provide a satisfying opportunity for physiological and psychological improvement.
Increased lean body mass:
For many women a common training objective is to look and feel better about themselves. To do this often involves a reduction in unwanted body fat and an increase in muscle tone. Unfortunately, many women follow inappropriate exercise programmes (overuse of aerobic exercise) and never achieve their full fitness potential.
Resistance training has been shown to have a favourable effect on body composition. Several studies have found that weight training decreases body fat and increases fat free weight in women (Borgen and Cobin, 1987, cited in NSCA position paper, 1989). Nonetheless, many women have avoided resistance training (especially heavy resistance training) out of fear of increasing muscle size or bulk.
This poses a question “does muscular hypertrophy occur in women as a result of resistance training?” This is not a simple question to answer, because muscle hypertrophy is dependent on the net difference between protein synthesis and degradation, and is influenced by a multitude of different factors: genetics, training status, exercise protocol, nutrition and recovery and hormone response. They all have an effect on muscle growth.
Several investigators have examined the effects of resistance training on females and in general found that strength gains occur with little or no hypertrophy. In one such study Staron et al. (1990) demonstrated that after completing a 20 week programme of heavy resistance training for the lower body, female participants had a decrease in body fat and an increase in muscle tissue; with no change in thigh circumference. Another study by Kraemer et al. (2001), demonstrated that regardless of the type of strength training protocol, women who participated in a resistance based training programme for the upper and lower body improved their performance, especially in activities requiring upper body strength.
Most females do not show an increase in body circumference measurement with resistance training. One possible reason for this may be due to differences in resting and exercise hormonal concentrations between males and females. Of particular interest is the male sex hormone TST. In men TST is mainly produced in the testes, whereas in women small quantities of TST are secreted by the adrenals and traces are produced in the ovaries. Resting and exercise TST levels have been shown to be much higher in men than in women (Hickson et al, 1994). TST has been shown to be responsible for an increased rate of protein synthesis as well as to inhibit protein degradation (Brooks et al. 1996; Kraemer, 2000). Moderate to high volume resistance training (85-95%) using large muscle groups has been shown to increase TST concentrations. However, for the most part females have shown a lack of TST responsiveness to various resistance exercise protocols (Kraemer et al, 1991; Kraemer et al, 1998). Although Hakkinen et al. (1992), demonstrated that women with higher resting TST concentrations experienced the greatest amount of muscle hypertrophy over 8 weeks of training, suggesting that the amount of resting TST concentrations increases the potential for muscle hypertrophy in women.
To conclude, it appears that both genders can experience muscle hypertrophy as a result of resistance training, although it must be pointed out, that only women with the genetic predisposition as seen by some elite female body builders will experience substantial increases in limb size. Muscle hypertrophy will only occur as a result of a large training volume, positive calorie balance, adequate recovery and the genetic predisposition. So, for the average woman resistance training will have a positive effect on body composition, contributing to a reduction in body fat and an increase in strength and power, all without a change in body size.
Females may be at risk of developing abnormal postural states in comparison to males, due to a variety of different factors.
For example, frequent wearing of high heel shoes can cause muscle tightness in the gastrocnemius and soleus muscle groups, thus restricting dorsiflexion at the ankle (10o needed during walking). Restricted ankle dorsi flexion can then cause compensatory changes in muscle length tensions higher up the body. Often the hip flexors will tighten causing the pelvis to tilt anteriorly. Pelvic motion will always affect the curves of the vertebral column. In this example, an anterior pelvic tilt increases the amount of lordosis in the lower back, thus, decreasing its shock absorbing capacity. Consequently, changes also occur in the upper body. This type of postural distortion pattern is called ‘lower and upper cross syndrome’ as seen in figure below.
Consideration must be given to the factors listed above before designing a training programme. Appropriate stretching and strengthening exercises can then be included to improve posture, overall aesthetics and the maintenance of optimal structural health.
To conclude, current research has demonstrated that regular strength training is necessary for women, if they are to maximise musculoskeletal health and well-being. Research has also demonstrated that females respond equally as well to relative increases in strength from resistance training as males do. So resistance based exercise for females should be a key programme feature. The prescribed amount and what type is dependent on the client’s training objective.
Emphasise exercises such as the lunge and its variations, step-ups and variations, deadlifts and squats for the lower body. For the upper body include exercises such as bent over rows, bench press, shoulder press and consider total body exercises such as push press, clean and jerk, DB snatch and jump-based exercises using freeweights and medicine balls. Selecting such exercises provides a great deal of variety, burns plenty of calories and develops functional strength that can be transferred to various sports and daily activities.
By understanding the anatomical and physiological differences between the genders, the trainer will be able to design a suitable exercise programme that can maximise potential and prevent injury.
Finally, women should not be discouraged from training at higher intensities or limit the amount of resistance used. Often, through misinformation and dogma the resistance used is insufficient and far below what is needed to elicit a training effect. Therefore, it must be the responsibility of the trainer to deliver, educate and motivate female client’s to train at an appropriate intensity so to stimulate a training adaptation.
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