Influence of Menstrual Cycle On Strength Training and Timing
The use of strength training has been well established to improve both performance and health-related variables in both male and female athletes (Stone, Collins, Plisk, Haff, & Stone, 2000). Strength training is now also used by female athletes in order to enhance performance (Holloway & Baechle, 1990). An area of important consideration for coaches is the periodisation of strength training for female athletes and the influence of the different phases of the menstrual cycle. Menstruation occurs in monthly cycles that can vary around an average of 28 days per cycle and refers to the physiological changes that fertile women experience (Frankovich & Lebrun, 2000). The menstrual cycle is important for reproduction is controlled by the endocrine system and is commonly divided into three phases: the follicular phase, ovulation, and the luteal phase (Walker, 1997). The menstrual cycle can affect women in different ways with fluctuations in important hormones such as testosterone, oestrogen, progesterone, growth hormone (GH) and insulin-like growth factor 1 (IGF-1) (Jonge, Boot, Thom, Ruell, & Thompson, 2001). The female sex steroids work on a multitude of physiologic parameters (Frankovich & Lebrun, 2000) and play a vital role in athletic performance and recovery and must be understood by coaches to maximise training results (Hartgens & Kuipers, 2004).
Assessing the roles of the various hormones as to the cause and effect relationships during menstruation in response to exercise stimulus can be complex (Burgess, Pearson, & Onambélé, 2010; Frankovich & Lebrun, 2000). To begin with aerobic vs. resistance loading protocols seem to produce different hormonal responses; in addition, similar studies may yield different results (Jonge et al., 2001; Sarwar, Niclos, & Rutherford, 1996). Hormonal levels in blood and tissues are influenced by their production from the parent organ, clearance from the blood and their binding to specific receptor sites in target organs (Llewellyn, 2010). When free in the bloodstream, steroidal hormones such as androgens, adrenal hormones, and ovarian hormones circulate and interact with specific carrier proteins, with only small amounts available to tissues (Llewellyn, 2010). It is also important to note that an athlete’s state of training and nutrition can also influence metabolic and hormonal outcomes (Reilly, 2000; Hausswirth & Le Meur, 2011).
Actions of Testosterone
Testosterone belongs to a class of male hormones called androgens but is also produced in small amounts in women’s ovaries and adrenal glands (Llewellyn, 2010). Androgens promote protein synthesis and growth of muscle tissues with androgen receptors. Anabolic effects include growth of muscle mass, increased bone density, and strength (Shahidi, 2001). Testosterone levels have been shown to raise during ovulation but no evidence has shown that changes in muscle contractile properties are caused by the hormone (Sarwar et al., 1996).
Actions of Oestrogen
The oestrogens are a group of 18-carbon steroids that are secreted primarily by the ovary and to a lesser extent by the adrenals (Llewellyn, 2010). One of the most important actions of oestrogen during the luteal phase is its effect on the cardiovascular system. This may benefit submaximal exercise of long duration by increasing intramuscular and hepatic glycogen storage and lipid synthesis (Reilly, 2000). Glycogen sparing effects due to enhanced lipolysis in muscle and greater use of free fatty acids have been seen at rest and during exercise at this phase (Frankovich & Lebrun, 2000). Insulin binding capacity decrease in response to elevated levels of oestrogen resulting in deterioration in glucose tolerance and insulin resistance (Frankovich & Lebrun, 2000). Many of these actions are antagonised by progesterone with the time span over which performance may be enhanced to be only a matter of a few days before progesterone falls pre-menses (Reilly, 2000).
Actions of Progesterone
The other major group of female hormones is the progestin, of which progesterone is the main endogenous form (Frankovich & Lebrun, 2000). The progestin group of hormones is known for its androgenic properties with a high progestin state occurring during the luteal phase of a normal ovulatory menstrual cycle (Reilly, 2000). These include thermogenic effects increasing core body temperature and minute ventilation (VE) (Reilly, 2000). During the luteal phase, elevations in VE response to exercise have been attributed to the corresponding surge in progesterone and associated with a higher rating of subjective exertion (Frankovich & Lebrun, 2000). In prolonged sustained exercise, the substrate for oxidative metabolism can influence the level of performance and may determine prestart stores of glycogen in the liver and muscle (Frankovich & Lebrun, 2000). Mechanisms that increase these depots or spare existing stores by increasing fat oxidation can enhance overall performance (Frankovich & Lebrun, 2000).
Actions of Growth Hormone
GH is a protein-based peptide hormone that stimulates growth and cell reproduction (Llewellyn, 2010). GH responds to both aerobic and resistance exercise (Holt & Sönksen, 2009) and attracts athletes due to its anabolic and lipolytic effects, leading to an increase in lean body mass and reduction in body fat (Holt & Sönksen, 2009). GH stimulates muscle growth by facilitating the transport of amino acids across cell membranes thus activating DNA transcription in the muscle cell nucleus leading to increased protein synthesis (Shahidi, 2001). GH levels have been shown to increase with high doses of oestrogen and decrease with high levels of progestins (Frankovich & Lebrun, 2000).
Actions of Insulin-Like Growth Factor
IGF- 1 is a potent anabolic factor and is stored in the liver and peripheral tissues and is believed that some of the anabolic GH actions are mediated through it (Holt & Sönksen, 2009). The regulation of protein synthesis involves the synergistic actions of GH and IGF-1 stimulating protein synthesis, while insulin simultaneously inhibits protein breakdown (Holt & Sönksen, 2009). It appears that the GH and IGF-1 complex plays a significant role in strength development, therefore strength programs for women should focus on maximising GH production (Holt & Sönksen, 2009).
Tailoring Programs To The Menstrual Cycle
Table 1. The different phases of the menstrual cycle and their corresponding physiological, psychological and hormonal states. Adapted and modified from (Hamilton, 2012).
During the early follicular (pre-menses) phase testosterone, oestrogen and progesterone concentrations are low (Jonge et al., 2001) with evidence that women athletes are more vulnerable to errors and incidence of injuries (Reilly, 2000). Therefore training should focus on regeneration and metabolic work. In the mid follicular phase, it is recommended that training intensity increases as oestrogen and GH levels rise and progesterone decreases (Phillips, Sanderson, Birch, Bruce, & Woledge, 1996). It has also been suggested that oestrogen has a positive effect on the strength peaks seen during the late follicular phase just before ovulation where it peaks (Frankovich & Lebrun, 2000). At the same time, progesterone levels remain low hence training should preferably focus on metabolic and strength. Then, for ovulation and early luteal phase strength training should be of high intensity and low volume. Levels of testosterone, oestrogen, and GH are at their highest (Frankovich & Lebrun, 2000) and exercises should involve the large muscle groups of the upper and lower extremities and trunk such as the bench press, squats and Olympic lifts. During mid-luteal, O levels remain stable while P levels raise (Phillips et al., 1996). Submaximal exercise of long duration and low intensity will be most suited for this phase. Finally, late luteal phases are characterised by testosterone, oestrogen and progesterone concentrations returning to their lower levels (Reilly, 2000) (Jonge et al., 2001) and training would similar to early follicular (pre-menses) phase.
Strength training programs for women can be tailored to each athlete’s menstrual cycle. While studies have not been conclusive on the effect of these cyclic hormonal variations on muscle growth and strength development (Frankovich & Lebrun, 2000), strength coaches can still consider devising strength development programs that take into account these hormonal fluctuations.
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