Introduction
Female soccer is one of the fastest growing sports in the world, gaining more and more attention throughout the years. However, the literature within female soccer is fairly limited. Females represent only thirty nine percent of the athletes studied while the remaining sixty one percent are male athletes (Costello et al., 2014). According to Bruinvels et al. (2017), female subjects have been excluded from scientific studies until 1993, because the effects of menstrual cycle produced “white noise” in the results. Hence, it is of major importance for the research community to develop a better understanding of the physical characteristics and demands, as well as of the health and performance needs of female soccer players in order to provide evidence based recommendations.
There is a clear understanding that high aerobic capacity, strength, and lower limb control are required to improve performance and reduce the risks of common injuries (Turner et al., 2013). Despite the fact that menstrual cycle may influence performance, injury risk, and psychological traits of the female athletes, only a few studies exist related to soccer and performance. Moreover, the existing data is conflicting which makes it even harder for coaches and sports staff to gain understanding and practically apply research results.
The aim of this review is to find and summarize the gaps in the literature so that future research can give answers to how menstrual cycle affects certain aspects of athletic performance in female soccer players. By knowing how various physiological parameters are altered throughout the menstrual cycle we can improve performance, reduce injuries and positively impact the game of soccer.
It is well known that much of the research in the field of sports science has been conducted on males and the findings of this research have been inappropriately applied to female athletes neglecting the fact that female athletes need to be studied separately than men due to their different physiology. Moreover, when studying the female population, many gaps in the literature exist due to inconsistent research design, discrepancy in the number of menstrual phase comparisons between studies, as well as heterogeneity of the participant groups (sedentary, healthy, active, elite). Poor methodology, such as inadequate menstrual phase identification and verification in many studies makes it difficult to generalize and apply results to the population of interest.
To date, the effects of fluctuations in estrogen and progesterone across the menstrual cycle on exercise performance are inconsistent, with studies reporting improved performance outcomes during the early follicular, ovulatory and mid luteal phases, whereas others have shown no changes in exercise performance between menstrual cycle phases. Subsequently, no clear evidence based guidelines for managing exercise across the cycle exist for female athletes. According to Meignie et al. (2021), limited studies on elite athletes currently exist despite the fact that elite athletes are probably more sensitive to individualization of training.
The menstrual cycle
A typical menstrual cycle is divided into two phases, the follicular and luteal, which are separated by ovulation. In eumenorrheic women, the cycle lasts between twenty one to thirty five days, during which female hormones such as estrogen and progesterone fluctuate in a cyclical manner. The follicular phase starts with the onset of menses (days 1-5) and is characterized by low concentrations in both estrogen and progesterone. There is a gradual increase in estrogen in the late follicular phase (days 6-12) with a peak just before ovulation (days 12-14), which is accompanied by a sharp and brief increase in testosterone. During that phase progesterone levels remain low. The early luteal phase (days16-19) is characterized by decreased estrogen levels and a rise in progesterone while mid-luteal phase (days 20-23) is the phase when both estrogen and progesterone are high. The last phase of the cycle, late luteal phase (days 24-28), is characterized by a decline in both estrogen and progesterone.
Although the primary function of these hormones is to support reproduction, research has highlighted that the changing concentrations of estrogen and progesterone across the menstrual cycle can affect multiple physiological systems such as, cardiovascular, respiratory, metabolic and neuromuscular, which could have subsequent implications for exercise performance (Constantini et al., 2015).
Estrogen is considered to have an anabolic effect on skeletal muscle and has been shown to play a role in substrate metabolism changes through increased muscle glycogen storage in the liver and increased fat utilization. This metabolic hormonal shift may contribute to women’s enhanced capability for ultra-endurance exercise, compared with men. This greater dependence on fat stores for energy is primarily seen in low to moderate exercise intensities, whereas greater relative efforts depend increasingly on blood glucose and muscle glycogen substrates (Brooks et al., 1999). Moreover, estrogen can influence central nervous system function by promoting the activation of glutamate releasing neuron receptors that cause an excitatory response in the nervous system (Smith & Woolley, 2004). When estrogen rises during the late follicular and ovulatory phases and remains elevated in mid luteal phase, it is possible to affect muscular performance or maximal and submaximal intensity exercise performance (Isacco et al., 2017). Moreover, according to the endocrinologist DiGirolamo, the body may use muscle glycogen more efficiently during the follicular phase compared to the luteal phase, which may benefit explosive muscle strength and sprint ability during the first half of the cycle. Additionally, a surge in testosterone during the late follicular phase may benefit performance during short intense activity, via increases in motivational drive and enhanced calcium kinetics in the muscle cell (Bateup et al., 2002).
Progesterone, on the other hand, is thought to have an anti-estrogenic or catabolic effect. The higher temperature during luteal phase, when progesterone levels are high, may reduce the safe margin for heat accumulation when exercising, leading to fatigue more easily. Especially under conditions of extreme heat and humidity, female athletes may be at a thermoregulatory disadvantage for training and competing (Cheung et al., 2000). However, progesterone may raise core and skin temperature and positively influence nerve conduction which can benefit the performance of explosive strength related tasks (Franssen & Wieneke, 1994).
Performance might be is expected to be worse in the early follicular phase because menstrual bleeding is a leading cause of iron deficiency anemia. Iron is an essential component of hemoglobin in red blood cells, which transports oxygen to the working muscles, and when this is deficient, an athlete cannot use their aerobic pathways effectively (Brinvels et al., 2022). Therefore, it is expected that exercise performance may be influenced by the different hormonal profiles across the menstrual cycle.
Discussion
In elite sport both physical and psychological factors may play a crucial role to the athlete’s performance and have negative or positive implications to training and game performance. Thus, it is of major importance to study not only the physical capacities of the players, but their psychological well-being as well, which might be affected by the hormonal fluctuations throughout the menstrual cycle.
Subjective performance
Research suggests that women in the premenstrual phase are more anxious, emotional and irritable (Kishali et al., 2006). Therefore, knowing how these changes affect their decision making is of paramount importance as decision making plays a crucial role in an elite athlete’s career. Based on several studies on females’ perceived performance, female athletes identify their performance to be relatively worse during the early follicular and late luteal phase. Foster et al. (2019), evaluated fifty two professional female soccer players using the Brunel mood scale. Premenstrual syndrome (PMS), such as fluid retention, weight gain, mood changes, and dysmenorrhea were associated with a decline in performance and reduced physical capacities in female soccer players.
Moreover, Hooper et al. (2011), found that the rate of perceived exertion (RPE) and perceived pain increases in sedentary individuals in the early follicular phase, compared to the late follicular and luteal phases. However, the research is further limited in its usefulness to elite athletes.
Additionally, Martin et al, (2018) studiedthe perceived side effects of menstrual cycle in four hundred and thirty elite female athletes. A high percentage of non-hormonal contraceptives users reported negative side effects during their menstrual cycle, primarily during the first two days of menstruation. The most commonly reported side effects were stomach cramps, unspecified cramps, back pain and headaches/migraines. Surprisingly, only 4.2% of the athletes stated that they refrained from exercise at certain points of their menstrual cycle, despite their demanding lifestyles. A possible explanation for the small percentage might be that athletes build a strong mental capacity, have high motivation and might have higher tolerance of pain compared to non-athletes, which makes them perform even under conditions of high pain and stress related to menstrual cycle.
Findlay et al. (2020) interviewed fifteen international female rugby players. Almost all athletes reported menstrual cycle-related symptoms with more than half of them considering these symptoms impaired their performances. The most common physical symptoms reported werestomach cramps/ abdominal pain, low energy levels, flooding and general discomfort. Psychological symptoms includedworry, distraction, negative mood states, feeling tearful and emotional, reduced motivation and agitation.
Moreover, Ergin et al. (2020) investigated menstrual cycle and sporting performance perceptions of one hundred and thirty elite volleyball athletes and found that a high percentage of participants reported “sport related menstrual problems” and perceived that menstruation has affected their participation in training and competition.
Objective performance
Studies examining objective performance such as aerobic, anaerobic and strength related tests, do not report clear consistent effects of the impact of menstrual cycle phase on physical performance. According to Kissow et al. (2022), maximal muscle strength appears greater in the follicular and ovulation phase than in the luteal phase in untrained and trained females. Interestingly, recovery and reconstruction of muscle fibers have been shown to be faster in the mid follicular phase than the luteal phase after eccentric exercise (Haines et al., 2017). However, more research needs to be done in female athletes.
Julian et al. (2017) foundno differences in sprinting ability in 3 x 30m sprints with two minutes recovery, and countermovement jump in two phases of the menstrual cycle (early follicular and mid luteal) in nine sub elite soccer players. However, the distance covered in the Yo-Yo IET in mid luteal phase was reduced compared to early follicular, which is consistent with previous findings (Lebrun et al., 1995). A possible explanation for the negative influence in maximal endurance capabilities in luteal phase could be the differences in heat regulation, substrate availability, and metabolism during the different phases. The increased temperature due to progesterone rise during luteal phase is suggested to limit prolonged exercise capabilities and increase cardiovascular strain (Janse de Jonge, 2003). Moreover, a lower running economy was found at eighty but not at fifty five percent of maximal aerobic capacity during the luteal phase, with associated changes in ventilator drives and fluctuations in mood state (Williams & Krahenbuhl, 1997). Again the small sample size and the fact that only two phases have been investigated, cannot lead to definite conclusions. Further studies should test the pre-ovulation phase when estrogen is elevated without the presence of progesterone. Knowing that estrogen has a positive effect on muscular strength we may hypothesize an improved performance in countermovement jump during that phase compared to luteal phase. Additionally, repeated sprint ability in more than three sprints interspersed by shorter recovery periods must be evaluated, as it is closer to the sports’ nature.
Tounsi et al. (2018), studiedeleven high level soccer players and found no impact of menstrual cycle phase on repeated sprint ability or Yo-Yo IRT distance covered in three different phases (early follicular, late follicular and mid luteal) , contrary to the results found by Joulian et al., 2017. Repeated shuttle sprint ability test consisted of 6 x 40m shuttle runs with twenty seconds passive recovery. Knowing that muscle glycogen availability is greater during follicular phase and that there is a possible correlation between drop in muscle glycogen and decline in sprint performance (Krustrup et al., 2020), one would expect improved performance during the follicular phase in repeated sprints.
Another study by Somboonwong et al. (2015),including thirteen Thai female national soccer athletes did not find any difference in early follicular and mid luteal phases in 3 x 40yard sprints with three minute-recovery. Further research including the pre-ovulation phase, when there is a rise in estrogen and a surge in testosterone, might possibly lead to different results.
Anaerobic capacity, the ability to rapidly use creatine phosphate and ATP stores in the muscles, is of major importance in a sport like soccer, due to its intermittent nature and the need for short and explosive actions during the game. Some studies found no difference in anaerobic power output between cycle phases while some others concluded to a greater anaerobic capacity and peak power during the luteal phase (Masterson, 1999). Those studies, however, did not take place in elite level athletes making it hard to generalize their results.
A recent study by Juillard et al. (2024) who studied ten elite soccer players in two different phases of the menstrual cycle (early follicular and mid-luteal), found no differences in agility measured via Illinois Agility test and no significant difference in physical performance or psychological subjective feeling throughout the cycle (Hooper Questionnaire). The small sample size, the fact that they did not take into account the competitive context of each week and the limited phases studied make it difficult to generalize the results. Also, another parameter that might have more significance in field based sports such as soccer is reactive agility, the ability to respond to an external stimulus. Whether and how is this parameter affected by the menstrual cycle is a great question to be answered in future studies.
Furthermore, Igonin et al. (2022), studied the influence of three different phases (early follicular, late follicular and mid-luteal) on the movement patterns of eight sub-elite soccer players during competitive matches over three consecutive seasons, concluding that menstruation days may negatively affect performance by decreasing the distances covered at different velocities. Specifically, the results showed significantly lower distances covered at moderate and high velocity in the early follicular phase than the other two phases of the cycle. The total distance covered and the number of sprints were also reduced during early follicular compared with late follicular phase. High intensity running and repeated sprint ability are a crucial component in soccer (Vescovi & Jovanovic, 2021) with such actions relying not only on glycogen availability and glycolytic enzyme activities but also on neuromuscular features and fatigability, which might be affected by the menstrual cycle phase. Motivation, pain, discomfort and disturbed mood are some psychological factors that should be taken into account to explain the lower performance during the early follicular phase. This study had some limitations as well, such as small sample size and absence of sex hormone measurements to validate the different menstrual cycle phase or ovulation test.
Graja, (2020), studiedthe effect of menstrual cycle phases(follicular, luteal, and premenstrual) in ten national level handball athletes on physical, neuromuscular, and biochemical responses after repeated sprint exercise (RSE). The protocol consisted of twenty five-second cycle ergometer sprints interspersed with twenty five seconds of rest. Results indicated reduced knee extensor maximal voluntary contraction after the repeated sprint protocol in late luteal (premenstrual phase) compared to late follicular /mid luteal phases and reduced peak power in the final six cycle ergometer sprints in late luteal compared to the late follicular. The percentage of decrement in peak power output over the test (i.e., fatigue index) decreased significantly during premenstrual phase but not in late luteal compared with follicular phase. These findings suggest that RSE induces more peripheral fatigue associated with muscle damage in premenstrual phase. Therefore, follicular phase might be the right time for intense training to improve strength performance.
Sleep and performance
It is worth to note that menstrual cycle may also affect sleep which can lead to negative consequences in performance. According to a recent study by Ishikura et al. (2024), women presented better sleep efficiency and sleep latency during mid/late follicular phase compared to menstruation and luteal phase. Poor sleep may negatively affect performance parameters such as sprinting during intermittent exercise (Skein et al., 2011); therefore, coaches and team staff may need to incorporate strategies to improve female athlete’s sleep during the aforementioned phases in order to avoid any decrements in performance. O’Donnell and Driller (2017), monitored the sleep of twenty six elite female netball players and their results showed that one hour of education on sleep hygiene has a positive acute effect and may be useful on improving sleep quality and quantity.
According to Leeder et al. (2012) sleep quality and quantity is reported to be the single best psychological and physiological recovery strategy available to elite athletes. Sleep loss brings negative effects on athletic performance via psychological and physiological responses and it is linked to reduced immune function via reductions in natural killer cells (Reilly & Edwards, 2007). Hormonal fluctuations have an impact on sleep quality which can be detrimental to the following day’s performance due to undermined cognitive functions which may also lead to a higher risk for injury (Nedelec et al., 2015).
Conclusion
Given the recent increase in the number of women participating in sport and the lack of consensus regarding the effects of the menstrual cycle on athletic performance, there is a growing need to determine the effects of the fluctuations in estrogen and progesterone across the menstrual cycle on performance. A one size fits all approach is absurd as athletes often respond differently to a given training stimulus, and the training load required for adaptation may differ significantly between sexes (Pedersen et al., 2019).
In most studies, the most common comparison used when investigating the effects of the menstrual cycle on performance is between the early follicular and mid luteal phase, as the difference in the hormonal milieu is typically at its greatest between these phases (De Jonge et al., 2019). This comparison, however, ignores the late follicular and ovulatory phases of the menstrual cycle, when estrogen is high and progesterone is low. Additionally, if we want to have reliable data we must construct a solid methodology such as Schaumberg et al’s (2017); a three step method which combines calendar mapping of menses, ovulation testing, and hormone testing to confirm cycle stage. Additionally, standardization of variables that may affect subsequent performance, such as the time of the day, nutritional status, or psychological motivation of the subjects need to be controlled in order to lead to more accurate conclusions.
Finally, our aim is to provide evidence based recommendations for training individualization related to performance. It is apparent that minimal research is conducted specifically on elite female athletes and field based team sport athletes, such as soccer players, indicating future research could be conducted in these populations to address the gap in the literature and aid in advancing the field of performance optimization in female athletes.
Reference List
Allen, A. M., McRae-Clark, A. L., Carlson, S., Saladin, M. E., Gray, K. M., Wetherington, C. L., McKee, S. A., and Allen, S. S. Determining menstrual phase in human biobehavioral research: A review with recommendations. Experimental and Clinical Psychopharmacology, 24(1), 1–11, 2016.
Bateup, H.S., Booth, A., Shirtcliff, E.A. and Granger, D.A. Testosterone, cortisol, and women’s competition. Evolution and human behavior,23, 181-192, 2002.
Brooks, S.P.J., Dawson, B.A., Black, D.B. and Storey, K.B. Temperature Regulation of Glucose Metabolism in Red Blood Cells of the Freeze-Tolerant Wood Frog. Cryobiology, 39,150-159, 1999.
Bruinvels, G., Hackney, A.C. and Pedlar, C.R., Menstrual Cycle: The Importance of Both the Phases and the Transitions Between Phases on Training and Performance. Sports Medicine, 52(7), 1457-1460, 2022.
Cheung, S.S., McLellan, T.M. and Tenaglia, S. The Thermophysiology of Uncompensable Heat Stress Physiological Manipulations and Individual Characteristics. Sports Medicine, 29(5), 329-359, 2000.
Constantini, N.W., Dubnov, G. and Lebrun, C.M. The Menstrual Cycle and Sport Performance. Clinics in Sports Medicine, 24(2), 51-82, 2005.
Costello, J.T., Bieuzen, F. and Bleakley, C.M. Where are all the female participants in Sports and Exercise Medicine research?European Journal of Sports Science, 14(7), 847-851, 2015.
Findlay, R.J., Macrae, E.H.R., Whyte, I.Y., EASTON, C. and Forrest, L.J. How the menstrual cycle and menstruation affect sporting performance: experiences and perceptions of elite female rugby players. British Journal of Sports Medicine, 54, 1108-1113, 2020.
Foster, R., Vaisberg, M., Bachi, A., Dos Santos, J., De Paula Vieira, R., Luna-Junior, L., Araujo, M., Parmigiano, T., Borges, F. and Di-Bella, Z.K.J. Premenstrual Syndrome, Inflammatory Status, and Mood States in Soccer Players. Neuroimmunomodulation, 26(1), 1-6, 2019.
Franssen, H. and Wieneke, G.H. Nerve conduction and temperature: necessary warming time. Muscle & Nerve, 17, 336-344, 1994.
Graja, A., Kassem, M., Hammouda, O., Borji, R., Bouzid, M.A., Souissi, N., and Rebai, H. Physical, Biochemical, and Neuromuscular Responses to Repeated Sprint Exercise in Eumenorrheic Female Handball Players: Effect of Menstrual Cycle Phases. Journal of Strength and Conditioning Research, 36(8), 2268-2276, 2020.
Haines, M., Mckinley-Barnard, S.K., Andre, T.L., Gann, J.J., Hwang, P.S. and Willoughby, D.S. Skeletal Muscle Estrogen Receptor Activation in Response to Eccentric Exercise Up-Regulates Myogenic-Related Gene Expression Independent of Differing Serum Estradiol Levels Occurring during the Human Menstrual Cycle. Journal of Sports Science and Medicine, 17, 31-39, 2018.
Hooper, C.A.E., Bryan, A.D. and Eaton, M. Menstrual Cycle Effects on Perceived Exertion and Pain During Exercise Among Sedentary Women. Journal of Women’s Health, 20(3), 439-446, 2011.
Igonin, P., Rogowski, I., Boisseau, N. and Martin, C. Impact of the Menstrual Cycle Phases on the Movement Patterns of Sub-Elite Women Soccer Players during Competitive Matches. International Journal of Environmental Research and Public Health, 19(8), 4465, 2022.
Isacco, L and Boisseau, N. Sex Hormones and Substrate Metabolism during Endurance Exercise. Sex, Hormones, Exercise and Women, 35-58, 2017.
Ishikura, I.A., Mouses-Oliveira, M., Fernandes, G.L., Hachul, H., Tufik, S. and Andersen, M.L. How do phases of the menstrual cycle affect sleep? A polysomnographic study of the EPISONO database. Sleep and Breathing, 2024.
Janse de Jonge, X.A.K. Effects of the Menstrual Cycle on Exercise Performance. Sports Medicine, 33(11), 833-851, 2003.
Janse de Jonge, X., Thomspon, B. and Han, A. Methodological Recommendations for Menstrual Cycle Research in Sports and Exercise. Medicine and Science in Sport and Exercise, 2610-2617, 2019.
Janse de Jonge, X.A.K., Thomspon, M.W., Chuter, V.H., Silk, L.N. and Thom, J.M. Exercise Performance over the Menstrual Cycle in Temperate and Hot, Humid Conditions. Medicine and Science in Sports and Exercise, 44(11), 2190-2198, 2012.
Juillard, E., Douchet, T., Paizis, C. and Babault, N. Impact of the Menstrual Cycle on Physical Performance and Subjective Ratings in Elite Academy Women Soccer Players Sports, 12(16), 2024.
Julian, R., Hecksteden, A., Fullagar, H.H.K. and Meyer, T. The effects of menstrual cycle phase on physical performance in female soccer players. Plos One, 12(3), 2017.
Kishali, N.F., Mamoglu, O., Katkat, D., Atan, T. and Akyol, P. Effects of menstrual cycle on sports performance. International Journal of Neuroscience, 116(12), 1549-1563, 2006.
Kissow, J., Jacobsen, K.J., Gunnarsson, T.P., Jessen, S. and Hostrup, M. Effects of Follicular and Luteal Phase-Based Menstrual Cycle Resistance Training on Muscle Strength and Mass. Sports Medicine (Auckland), 52(12), 2813-2819, 2022.
Krustrup, P., Mohr, M., Nybo, L., Draganidis, D., Randers, M.B., Ermidis, G., Ørntoft, C., Roddik, L., Batsilas, D., Poulios, A., Ørtenblad, N., Loules, G., Deli, C.K., Batrakoulis, A., Nielsen, J.L., Jamurtas, A.Z. and Fatouros, I.G. Muscle metabolism and impaired sprint performance in an elite women’s football game. Scandinavian Journal of Medicine and Science in Sports, 27-38, 2021.
Lebrun, C.M., McKenzey, D.C., and Taunton, J.E. Effects of menstrual cycle phase on athletic performance. Medicine & Science in Sport & Exercise. 27(3), 437-444, 1995.
Leeder, J., Glaister, M., Pizzoferro, K., Dawson, J. and Pedlar, C. Sleep duration and quality in elite athletes measured using wristwatch actigraphy. Journal of Sports Sciences, 30(6), 541-545, 2013.
Martin, D., Sale C., Cooper, S.B and Elliott-Sale, K.J. Period prevalence and perceived side effects of hormonal contraceptive use and the menstrual cycle in elite athletes. International Journal of Sports Physiology and Performance,13(7),926-932, 2017.
Masterson, G. The Impact of Menstrual Phases on Anaerobic Power Performance in Collegiate Women. Journal of Strength and Conditioning Research, 13(4), 325-329, 1999.
Nedelec, M., Halson, S., Abaidia, A., Ahmaidi, S. and Dupont, G. Stress, Sleep and Recovery in Elite Soccer: A Critical Review of the Literature. Sports Medicine, 45, 1387-1400, 2015.
O’Donnell, S. and Driller, M.W. Sleep-hygiene Education improves Sleep Indices in Elite Female Athletes. International Journal of Exercise Science, 10(4), 522-530, 2017.
Pedersen, A.V., Aksdal, I.M. and Stalsberg, R. Scaling Demands of Soccer According to Anthropometric and Physiological Sex Differences: A Fairer Comparison of Men’s and Women’s Soccer. Frontiers in Psychology, 10(762), 2019.
Reilly, T. and Edwards, B. Altered sleep–wake cycles and physical performance in athletes. Physiology & Behavior, 90(1-2), 274-284, 2007.
Schaumberg, M.A., Jenkins, D.G., Janse de Jonge, X.A.K., Emmerton, L.M. and Skinner, T.L. Three-step method for menstrual and oral contraceptive cycle verification. Journal of Science and Medicine in Sport, 20(11), 2017.
Skein, M., Duffield, R., Edge, J., Short, M.J. and Mundel, T. Intermittent-Sprint Performance and Muscle Glycogen after 30 h of Sleep Deprivation. Medicine and Science in Sport and Exercise, 1301-1311, 2011.
Smith, S.S. and Woolley, C.S. Cellular and Molecular Effects of Steroid Hormones on CNS Excitability. Journal of Clinical Medicine, 71, 4-10, 2004.
Somboonwong, J., Chutimakul, L. and Sanguanrungsirikul, S. Core temperature changes and sprint performance of elite female soccer players after a 15-minute warm up in a hot-humid environment. Journal of Strength and Conditioning Research, 29(1), 262-269, 2015.
Tounsi, M., Jaafar, H., Aloui, A. and Souissi, N. Soccer-related performance in eumenorrheic Tunisian high-level soccer players: effects of menstrual cycle phase and moment of day. The Journal of Sports Medicine and Physical Fitness, 58(4), 497-502, 2018.
Vescovi, J.D., Fernandes, E. and Klas, A. Physical Demands of Women’s Soccer Matches: A Perspective Across the Developmental Spectrum. Frontiers in Sports and Active Living, 3, 2021.
Williams, T.J., and Krahenbuhl, G.S. Menstrual cycle phase and running economy. Medicine and Science in Sport and Exercise, 29(12), 1609-18, 1997.