MA Thesis: Women‘s Strength Training Around the Menstrual Cycle

Abstract

Autoregulation and fixed load programming have been shown to yield strength increases in trained male participants but gender differences, specifically the menstrual cycle, may mean that these findings cannot be transferred to female populations. The aims of this study were to a) see which programming strategy yielded the greatest strength increases in women and b) observe if there were any clear patterns in training when comparing the early follicular, mid follicular, ovulation and mid-luteal phase of the menstrual cycle. This 8 week intervention study had three recreationally trained groups initially test back squat and goblet squat 1RM strength. Group 1 and 2 were females following fixed load programming (FL) or autoregulated programming (AR) respectively and group 3 was comprised of men following fixed load programming (CON). Strength was tested again around a week after finishing the programme. The female participants tracked menstrual symptoms, bleeding and basal body temperature during this time so a phone application, Natural Cycles, could detect ovulation. The data was analysed using a series of mixed analyses of variances. The results showed significant differences between FL and AR’s pre-test strength scores (p < 0.001). All groups significantly increased post-test strength scores but there were no differences between experimental groups. No significant differences were noted in the volume performed between stages in the menstrual cycle. It was therefore concluded that fixed load and autoregulated programming are valid methods for recreationally trained women wanting to increase strength. Longer studies would be required to clarify if FL or AR are equally effective at increasing strength in women and if menstrual symptoms are likely to influence adherence to a training programme.

Key words: Eumenorrheic Menstrual Cycle; Auto – Regulation Method, Fixed – loading Method; Strength Training; 8 Week Training Intervention; Female Athlete.

 Introduction

Resistance training has proven to be an important and effective strategy for maintaining health biomarkers, improving quality of life and reducing risks of obesity, cardiovascular disease (35), osteoporosis (27) and diabetes (37) in many populations. It has also been shown to increase muscle strength (11), improve maternal and neonatal health during pregnancy (31), support healthy body composition (29) and relate to improved health in later life (4). Periodisation of exercise programming is accepted and embraced by the fitness communities to be the optimal strategy to maximise benefits of strength training (43). However, there are multiple established periodisation strategies and research is varied on the most optimal method for particular target groups. Periodisation provides structure and informs the trainee how the exercises should be progressed between sessions as well as within and between training blocks. Autoregulation is a training framework that allows adjustments to be made to intensity based off of an individual’s readiness, fitness and fatigue and how well they are coping with stressors (sleep, recovery from previous training, nutrition, sickness, life stresses) (15). The alternative to autoregulation is fixed load programming where intensity is usually prescribed as a percentage of the athlete’s maximal strength, after a one-repetition-maximum test (1RM) (23).

Growing research into autoregulation training has yielded comparable or superior results when compared to better established fixed load programming where load is defined in advance based off of a 1RM strength test for improving strength and performance (13, 46). Graham and Cleather (14) looked at autoregulation compared to fixed load programming and found that autoregulation can also be used to increase strength in well trained men. These men has been training consistently for more than two years and had to meet the prerequisite of being able to back squat below parallel with their body weight with correct form. They found that autoregulation increased strength by a greater magnitude than fixed load programming (Front Squat: η2 = 0.255 and Back Squat: η2 = 0.233) (14). The autoregulation group trained at a higher intensity, which potentially contributed to their greater increase in strength. This shows that autoregulation can be used to facilitate a relative intensity that reflects the athlete’s readiness on that particular day as well as ensuring that relative intensity matches the intended intensity of the programme, thus maximizing performance, recovery and strength gains (14, 15). However, Zhang and colleagues (46) stated that it is still unclear whether autoregulation yields better results than fixed load but both frameworks are widely considered to be useful and valid tools to use with athletes trying to get stronger. The studies included by Zhang (46) looked at different exercises and therefore different muscle groups and interventions of different lengths. It may be due to these differences that there are inconsistacies

 in the research. It appears that autoregulation may have an advantage in the short term (<8 weeks) but over a longer period of time (>8 weeks) this advantage may diminish (46). Few studies have been done in this area that are longer than 8-10 weeks.

There are a number of methods employed to facilitate autoregulation. Shattock and Tee (36) categorized methods of autoregulation as subjective and objective. The main objective measure of autoregulating training is the use of a tool that measures bar velocity at each repetition. Subjective methods were centered around the athlete’s perception of intensity by asking them to gauge how many more repetitions left in reserve after a set was finished (RIR) or using a scale to describe rate of perceived exertion (RPE). Subjective methods can also be used in conjunction with one another by selecting a number to represent perceived intensity based off of proximity to failure (14, 47). For example, if a set has an RPE of 9, this could mean that only one more repetition was possible before technical failure; if a set had an RPE8, two more repetitions were possible at the end of the set and an RPE10 means technical failure was reached. This combination may be more accurate than RPE used alone because it gives a more tangible significance to a number on the RPE scale, giving this method more uniformity (17). Furthermore, Hackett and colleagues (16) found that trainees could estimate repetitions to failure with a good degree of accuracy and therefore this tool could be used in a practical setting to gauge athlete’s intensity and facilitate autoregulation of a training programme in trained subjects. However, it appears to be less reliable in untrained subjects (42) so a period of familiarization with this method may be required for less experienced populations. This may be due lesser trained subjects not needing to or not being willing to train to failure and thus not being familiar with the sensations associated with technical failure. Inversely, better trained subjects may have more need to reach muscular failure in their training to stimulate muscular adaptations and thus are likely to be more familiar with their muscles’ limits.  Larsen, Kristiansen and Van den Tillaar (23) supported the use of autoregulation using RIR as a tool to increase maximal strength in trained participants as it can take into account the daily fluctuations in readiness that occur in trainees. Subjective methods, whilst successfully yielding increases in strength, may not be as successful as the objective method (37). However, subjective methods have the advantage of requiring no equipment and therefore being accessible to virtually everyone. However, a vast majority of the research into autoregulation has been done on male participants (47) and therefore lacked gender specificity, leaving a gap in the research to explore the use of this method in female populations. The research on males may not be transferable because there are a number of hormonal and physiological differences between sexes and many of these can be accounted for by the menstrual cycle (19).

Prado and colleagues (32) acknowledge the menstrual cycle and the premenstrual period as a possible barrier women may have to exercise. This may be because exercise protocol and programming in the presence of some cycle-related symptoms is not well understood by many in the general population, especially with regards to strength training specifically. Julian and colleagues (19) consider the menstrual cycle to be one of the most important things to consider when working with female athletes due to adverse symptoms experienced as a result of the hormonal fluctuations of the menstrual cycle (2, 6, 46). The menstrual cycle is made up three main phases: the follicular phase from the beginning of menses until ovulation; just before ovulation lutinising hormone tises and an egg is released and the luteal phase begins from ovulation until the onset of menses where the next cycle/follicular phase begins. In the early follicular phase, both oestrogen and progesterone are minimal until the mid-follicular phase when oestrogen rises. The luteal phase sees an elevation in the levels of both oestrogen and progesterone (19). McNulty et al. (25) and Julian et al. (18) stated that oestrogen likely impacts substrate metabolism by increasing fat utilization and glycogen storage and having an anabolic effect on skeletal muscle whilst progesterone is anti-oestrogenic. It is therefore credible to suggest that the hormonal fluctuations of the menstrual cycle may impact exercise performance as these studies suggest that the stage in the menstrual cycle may contribute to a trainee’s readiness to participate in strength training at certain times of the cycle (28).

Williams and Krahenbuhl (46) and . Bäckström and colleagues (3) noted negative symptoms such as pain, lethargy, depression, anxiety, heavy bleeding and increased fatigue (2, 6, 46) started mostly post ovulation and were the most concentrated in the mid-luteal phase.. Pallavi and colleagues (28) noted increased hand grip strength in healthy women in the follicular phase when compared to the luteal phase. However, this study was contradicted by the findings of studies looking into smith machine squats (34) and leg extension strength (11) who found no significant differences in strength between stages of the menstrual cycle. Friden and colleages (11) also looked into handgrip strength and muscular endurance in moderately active women and did not observe any notable differences.

There does not seem to be a strong scientific rationale to suggest that maximal strength is physiologically impaired at various stages of the menstrual cycle as evidence in this area is mixed (11, 19, 34, 43). However, multiple studies have shown that putting the majority of the volume in the follicular phase yields greater hypertrophy and strength increases than if the same is performed in the luteal phase (33, 41, 45). It was suggested by Sung and colleagues (41) that the greater ratio of protein synthesis to protein breakdown caused by oestrogen (20) in the follicular phase may have contributed to the greater hypertrophy and force increases seen in follicular based training when compared to luteal based training. This may be explained somewhat by the anabolic effects of elevated testosterone and oestrogen in the follicular phase (41). Pallavi et al. (28) observed that more volume could be performed in the follicular phase than the luteal. In addition, increased inflammation, protein catabolism (possibly caused by progesterone; 20, 41) alongside the increase in menstrual symptoms in the mid-late luteal phase may be ideal for a reduction in load to increase recovery (37) as it appears to be a less productive time for making progress in strength training. This evidence implies that although the maximal capacity of women may not be influenced by the stage in the menstrual cycle, the conditions in the body at different stages may lend themselves better to a different focus in training at different stages in the cycle.

This was supported by Pardo et al. (32) who acknowledged that women’s psychological endurance and motivation for exercise was reduced in the luteal phase as they reported a higher RPE. In the aforementioned study, it was suggested that these symptoms reduce the positive sensations that come from exercise in the follicular phase, making the act of training less pleasant and rewarding. To expand on this, a systematic review by Dubol (9) observed the fluctuations of estradiol and progesterone brought on by the stages of the menstrual cycle in sixty six studies reviewed. They showed structural and functional impacts on the hippocampus, amygdala and other areas of the brain. These changes were concluded to potentially impact on behaviour and possibly contribute towards menstrual symptoms. The study suggested that these changes may increase sensitivity to punishment and negative feedback in the mid-luteal phase, whereas a higher sensitivity to positive feedback may be likely in the follicular phase. Thus, it may be sensible to suggest that these findings may accentuate the challenges faced during exercise and day to day life during the mid-luteal phase when compared to the follicular phase. This may explain why the perception of performance in female athletes is lower in the mid-luteal phase (2) and may also explain why motivation for training can suffer around this time. Thus, it appears that there are simply times in the cycle of many women when athletes have more energy, less pain and generally feel better (2, 3, 32, 46), possibly allowing for optimal mindset, strength training and recovery. The evidence seems to lean towards the idea that the follicular phase in the menstrual cycle is where resistance training efforts may be best placed for greater adaptations and conversely, parts where a reduction in volume or intensity may be required in the luteal phase (33, 41, 45).

In recreationally trained female populations where attendance and performance in training sessions is somewhat non-essential, the fluctuations in menstrual symptoms throughout the phases of the menstrual cycle may explain some fluctuations in motivation, attendance and performance in the mid-luteal, ovulatory and mid-follicular phase. It is possible that increased sensitivity to negative feedback in the luteal phase may account for missed sessions, reduced self-esteem and motivation. This information can help exercise professionals and trainees prepare and plan sessions to reduce these feelings and promote consistency in women’s training routines. That said, Julian and Sargent (37) looked into the practical implications of periodisation around the menstrual cycle and noted that it can be labour intensive and expensive. To get the best possible understanding of an athlete’s hormonal fluctuations throughout the menstrual cycle blood and saliva samples may need to be taken at regular intervals over a period of months. This is expensive, invasive and specialist training is required. For those with a eumenorrheic menstrual cycle, it is possible to simplify this process down to tracking ovulation and bleeding. This gives some insight into the hormonal fluctuations throughout the month but can drastically simplify the process and reduce costs. The use or testing strips that detect levels of urinary lutinising hormone is the most common and accurate way to do this at home. More recently, evidence based phone applications to track the menstrual cycle have become popular and more accessible. Some use basel body temperature and unique dynamic algorithms to calculate when ovulation took place retrospectively, within 1-2 days (21). In addition to this, as well as the highly individual nature of symptoms of the menstrual cycle, it is important to determine the value of taking the time to gather this data to structure a female’s programme with the menstrual cycle in mind. If, when autoregulation is encouraged, this may be a way to ensure relative training intensity matches the intended intensity at every stage of the menstrual cycle without labour intensive and time consuming tracking and specific programming. The main aim of this study is to begin to evaluate if there is a programming style that works best for increasing strength in recreationally trained women. A secondary aim is to observe any differences in volume performed between stages of the menstrual cycle.

The research supports the hypothesis that both experimental groups are likely to increase strength as a result of the intervention. Furthermore, the evidence may suggest that larger increases in the AR group could be predicted. According to previous research, the training taking place in the late follicular phase is likely to yield greater volume when compared to the mid-luteal phase.