Secondary Logo

Journal Logo

Brief Review

Sex Differences in Resistance Training

A Systematic Review and Meta-Analysis

Roberts, Brandon M.1; Nuckols, Greg2; Krieger, James W.3

Author Information
Journal of Strength and Conditioning Research: May 2020 - Volume 34 - Issue 5 - p 1448-1460
doi: 10.1519/JSC.0000000000003521
  • Free

Abstract

Introduction

It is well-established that both males and females can increase muscle size and strength in response to resistance training (RT) (29). Furthermore, several studies have shown RT has multiple benefits for overall health (39,41,58). Although there have not been any studies that use dose-response models to determine whether males and females respond differently to chronic RT, several studies have compared the adaptations of males and females using the same training protocol. However, whether there are sex-specific adaptations to the same training is still unclear.

In most studies, males increase absolute strength more than females (10,12,68). Yet, some find that the relative increase in muscle strength and hypertrophy are similar between sexes (1,21,28,30,32,36,40,67,70,78,85). However others find females have a greater relative strength increase (7,9,29,34,36,38,48,55,56,63,79). In one of the largest studies to date, Hubal et al. (29) found females have higher relative strength increases than males.

A key consideration in comparing the responses in males and females is that pre-training levels of muscle size and strength are generally greater in males, independent of training status (3,35,67). Another well-known set of differences between males and females are hormonal, which may influence muscle hypertrophy and strength adaptations. There also may be some differences in types of occupation that could cause basal strength differences. However, there is currently no review bringing together the major differences between sexes at the neuromuscular, muscular, and hormonal level in the context of RT.

Considering the importance of muscle strength and size to overall health and exercise performance, it is important to understand sex differences in response to RT if they exist. Therefore, the purpose of this study is to determine whether there are different responses to RT for strength or hypertrophy in young to middle-aged males and females.

Methods

Experimental Approach to the Problem

Inclusion Criteria

Research publications were considered eligible for this systematic review if they (a) were experimental in design, (b) were published in a peer-reviewed, English-language journal, (c) were conducted in human populations, (d) included at least 1 method of estimating changes in muscle mass and/or dynamic, isometric, or isokinetic strength, and (e) had subjects who were between 18 and 50 years old (Table 1).

Table 1-a
Table 1-a:
Overview of studies meeting inclusion criteria.*
Table 1-b
Table 1-b:
Overview of studies meeting inclusion criteria.*
Table 1-c
Table 1-c:
Overview of studies meeting inclusion criteria.*

Exclusion Criteria

Studies were considered ineligible for this review if (a) the training protocol lasted for <5 weeks, (b) the study involved subjects with medical conditions, pregnancy, or injuries impairing training capacity, (c) subjects were taking supplements or hormone replacement therapy. Case studies were not included. Studies that were not written in English, conference abstracts, thesis, or posters were also excluded from this review.

Search Strategy

Our protocol was pre-registered with PROSPERO (CRD42018094276). The systematic review was performed in accordance with the guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A literature review was conducted up until April 2018 using Medline and SportDiscus. Combinations of the following terms were used to produce search results: gender or sex AND strength training or RT or powerlifting AND strength or hypertrophy or 1 repetition maximum. Search terms were added using the NOT term to reduce the number of irrelevant studies according to exclusion criteria (concurrent, children, disease, supplement). Citations from studies were also scanned for additional studies (Figure 1).

Figure 1
Figure 1:
PRISMA diagram.

Subjects

A total of 1,162 studies were identified using the aforementioned search terms, and 24 were additionally identified through other sources. Eighty studies were identified as being eligible for the review. After full-text review, 30 were removed for not meeting the inclusion criteria. Ultimately, 50 studies were deemed to have satisfied the inclusion criteria. Of those studies, 10 were analyzed for hypertrophy measures, 17 for upper-body strength, and 23 for lower-body strength.

Procedures

Coding of Studies

Studies were independently searched and coded by 2 of the authors (G.N. and B.M.R.) for the following variables: descriptive information (age, sex, training status), the number of subjects per group, training mode, duration of study, training frequency, repetition range, mode of muscle measurement (magnetic resonance imaging, fiber cross sectional area [fCSA], ultrasound, and computed tomography). Results were cross-checked between coders, and any discrepancies were resolved by mutual consensus.

Calculation of Effect Size

For each hypertrophy and strength outcome, a within-group effect size (ES) for each male and female group was calculated as the pretest-posttest change, divided by the pretest standard deviation (SD) (54). A study level ES was then calculated as the difference between the male group ES and female group ES. A small sample bias adjustment was applied to each ES (54). The sampling variance around each ES was calculated using the sample size in each study (6).

Statistical Analyses

Meta-analyses were performed using robust variance random effects modeling for multilevel data structures, with adjustments for small samples using package robumeta in R (27,82). The study was used as the clustering variable to account for correlated group effects within studies. Observations were weighted by the inverse of the sampling variance. Separate analyses were conducted for hypertrophy, upper-body strength, and lower-body strength. A fail-safe N was performed to calculate the number of null studies needed to achieve a p value of 0.05 or greater using the Rosenthal approach.

All analyses were performed in R version 3.5 (The R Foundation for Statistical Computing, Vienna, Austria). Effects were considered significant at P ≤ 0.05. Data are reported as means ± SEM and 95% confidence intervals (CIs) unless otherwise specified.

Methodological Quality

The quality of studies is important for analysis of systematic reviews and meta-analysis. However, due to the nature of studies on sex differences, it is difficult to blind subjects, therapists, assessors, conceal allocation, or randomly allocate, which are integral parts of quality assessment. Because this eliminates half of the questions in most scales, we felt it was unworthy to perform these types of quality assessments.

Results

Hypertrophy

The analysis of hypertrophy comprised 12 outcomes from 10 studies. There was no significant difference between males and females (ES = 0.07 ± 0.06; 95% CI: −0.09 to 0.23; P = 0.31; Figure 2). Heterogeneity was low (I2 = 0) (Figure 3).

Figure 2
Figure 2:
Forest plot of studies comparing changes in hypertrophy in males and females. The data shown are mean ± 95% CI; the size of the plotted squares reflects the statistical weight of each study. CI = confidence interval.
Figure 3
Figure 3:
Percent change in muscle hypertrophy in males and females.

Upper-Body Strength

The analysis of upper-body strength comprised 19 outcomes from 17 studies. There was a significant effect favoring females (ES = −0.60 ± 0.16; 95% CI: −0.93 to −0.26; P = 0.002; Figure 4). Heterogeneity was high (I2 = 72.1). Adding training status (trained or untrained), single or multijoint strength measurements (e.g., leg extension or leg press), training duration (weeks), or sessions per week as covariates did not substantially reduce heterogeneity (I2 = 69.7) (Figure 5).

Figure 4
Figure 4:
Forest plot of studies comparing changes in upper-body strength in males and females. The data shown are mean ± 95% CI; the size of the plotted squares reflects the statistical weight of each study. CI = confidence interval.
Figure 5
Figure 5:
Percent change in muscle upper-body strength in males and females.

Lower-Body Strength

The analysis of lower-body strength comprised 23 outcomes from 23 studies. There was no significant difference between sexes (ES = −0.21 ± 0.16; 95% CI: −0.54 to 0.12; P = 0.20; Figure 6).

Figure 6
Figure 6:
Forest plot of studies comparing changes in lower-body strength in males and females. The data shown are mean ± 95% CI; the size of the plotted squares reflects the statistical weight of each study. CI = confidence interval; the size of the plotted squares reflects the statistical weight of each study.

Heterogeneity was high (I2 = 74.7). Adding training status (trained or untrained), single or multijoint strength measurements (e.g., leg extension or leg press), training duration (weeks), or sessions per week as covariates did not substantially reduce heterogeneity (I2 = 77.4) (Figure 7).

Figure 7
Figure 7:
Percent change in lower-body strength in males and females.

Sensitivity Analysis

Because of the limited sample size, we completed a sensitivity analysis on all 3 outcomes where 1 study at a time was removed to determine whether that a particular study had any significant impact on the outcomes. However, we did not identify any influential studies.

Publication Bias

A rank correlation test for funnel plot asymmetry was performed for the upper-body strength results because there was a significant finding (Figure 8). It was not significant (P = 0.41). We also used a fail-safe N to calculate the number of null studies needed to achieve a p value of 0.05 or greater using the Rosenthal approach. The fail-safe N was 294. Thus, there was no evidence of publication bias for the upper-body strength outcomes.

Figure 8
Figure 8:
Funnel plot, using data from studies with upper-body strength outcomes.

Discussion

This review meta-analyzed studies that compared strength or direct measures of hypertrophy in males and females who used the same RT program. A majority of the studies were completed in untrained individuals. The main finding was that effect sizes in hypertrophy and lower-body strength were similar between sexes. However, there was a significant effect in favor of females for upper-body strength (ES = −0.60; 95% CI: −0.93 to −0.26; P = 0.002).

Muscular strength increases in response to RT are a combination of neurological and muscular adaptations. Initial, rapid improvements in strength seem to result primarily from neurological adaptation, whereas subsequent gains are primarily the result of muscular adaptations (53). In one of the first studies comparing untrained males and females, Wilmore et al., found that strength was similar when normalized to body weight after 10 weeks of intensive RT (90). Interestingly, relative upper-body strength increased 29% in females compared with 17% in males, whereas relative increases in lower-body strength were similar (90). These data were the first data to indicate there may be differences in strength changes between sexes. However, a limitation was that both groups experienced considerable decreases in body fat percentage over the course of the study, indicating they were likely not in an optimal nutritional environment for gaining or maintaining muscle mass or strength (90). More recent data have indicated that both sexes respond to upper-body strength in a similar manner (18). Yet, in the largest study to date with ∼342 females and ∼243 males, there was a significant difference in relative upper strength changes in favor of females (29). Herein, we cover a number of potential variables that could help explain the differences in strength we and others have found.

Neuromuscular adaptations are one factor that could explain the larger increase for females in upper-body strength. However, one study compared the number of motor units in the biceps brachii and vastus medialis but found no differences between sexes (50). The same research group also found no difference in motor unit activation for elbow flexion or knee extension (50). Others have found that males are no better able to activate motor units than females (5,91). Yet, neuromuscular fatigue from RT is generally greater in males than females, and acute recovery may be slower in males (20). Because the included studies are short in nature, this could have an effect on strength adaptations if subjects are not fully recovered during testing. The average untrained female may also have a lower initial level of fitness compared with a male (74). This could cause a ceiling effect for motor skills that may explain differences in upper-body strength because the studies were conducted in mostly untrained subjects. Ultimately, there are very few known differences at the neuromuscular level between sexes that could explain our findings, but more research is warranted.

It is well established that sex differences exist in skeletal muscle mass and distribution (35). Females often have less total and lean body mass, a higher body fat percentage, and a smaller muscle fiber cross-sectional area (65,78). One explanation of why differences could occur in strength or hypertrophy is muscle phenotype. Females have a greater proportion of type I fibers (65,75) in the vastus lateralis and the biceps brachii (3,50,69). There are currently no studies that compare the number of muscle fibers between sexes, but a classic study has shown the muscle fiber number decreases with age in males, although our data did not include those over 50 (44). Furthermore, there seem to be similar responses in muscle protein synthesis between sexes (47,76,86), and muscle damage due to RT is also similar between, yet the inflammatory response may be attenuated in females compared with males (80). However, there are some data to indicate that although there are similar indirect markers of muscle damage after RT, males could have longer-lasting muscle soreness than females (11). On a single fiber level, force per CSA and contractile velocity of type I and type II fibers are similar when comparing sexes (83). Taken together, there are relatively few differences in skeletal muscle between sexes, which helps explain our finding that hypertrophy is similar.

It was once postulated that females achieved small increases in muscle size after RT because of low androgen levels whereby a lesser amount of work-induced muscle hypertrophy would prevent them from gaining strength to the same extent as males (85). Although it is true that absolute hypertrophy and gains in strength are larger in males after RT, it seems that relative increases in both muscularity and lower-body strength are similar between the sexes, and relative gains in upper-body strength may be larger in females. Indeed, it is well established that females have lower levels of testosterone, free-testosterone, and insulin-like growth factor-binding protein 1 compared with males (65). Heavy training decreases gonadotropin-releasing hormone pulsatility in females (66). Males exhibit lower serum cortisol due to chronic RT, whereas females do not (78). Females do not experience elevations in postexercise testosterone compared with males (16,86). This differential change in testosterone has led to speculation that females may have an attenuated potential for resistance exercise-induced hypertrophy, which we did not find in our analysis (72). Another difference is that males have more upper-body muscle, which has more androgen receptors (37). Gentil et al. (18) suggest that this could affect strength gains over time. Another potential confounder is the menstrual cycle. Some evidence suggests that females who complete training during the follicular phase can have larger strength gains and more muscle growth (59, 81, 88) while females may take longer to recover during the luteal phase (46), and most of the studies included did not adjust for menstrual cycle. However, other evidence suggests that the changes in protein kinetics across the menstrual cycle may not play a large role in muscle accrual (51). Although some studies suggest that hormonal differences play a role in changes, larger and well-controlled studies are needed to understand why that occurs or how it affects strength or hypertrophy adaptations.

In a recent review, Hunter presents evidence that sex differences in muscle fatigue of repeated dynamic contractions are specific to the task requirements (31). Females may have less skeletal muscle fatigue compared with males during single-limb isometric contractions. It has also been suggested that there are independent responses to fatiguing contractions (31). Likewise, shortening velocity is a potential factor to tease out the contribution of voluntary activation and contractile mechanisms (73). There is also evidence that female tendons have a smaller capacity for adaptation to training (52,87), which may be exacerbated by oral contraceptive use (26) and could potentially affect strength adaptations.

Although a strength of this study is that it is the first meta-analysis completed on sex differences, there are several limitations. First, most subjects included in the analysis are untrained individuals. It is possible that a longer training duration or other factors could change the results. In addition, the untrained subjects could have different levels of basal activity between studies as it is often not well described in exercise science research. The studies included also vary with regard to mode, duration, and intensity of exercise utilized. However, our analysis of upper-body strength found no evidence publication bias and no single studies of major influence. It has been argued (1) that many of the earlier studies conducted on sex comparisons for both strength and muscular hypertrophic changes were hampered by low statistical power resulting from small sample sizes (all ≤20 subjects). Another potential limitation is missing studies due to unused search terms or databases. There is also a possibility that male subjects could be more familiar with upper-body movements (e.g., bench press) that could have resulted in females having greater neuromuscular adaptations. Finally, heterogeneity was high for the outcomes of studies assessing both upper and lower-body strength, yet incorporating training status, testing modality, duration, or sessions did not substantially decrease heterogeneity. Although there was a mean effect in favor of females for upper-body strength gains and no significant difference between the sexes for lower-body strength gains, more research is needed to understand the sources of this heterogeneity.

We found that males and females adapted to RT with similar effect sizes for hypertrophy and lower-body strength, but females had a larger effect size for relative upper-body strength. Current research indicates there are few differences at the skeletal muscle level between sexes. However, hormonal fluctuations, daily physical activity, and exercise recovery may play a role in our findings. In sum, well-designed studies with a primary goal of comparing male and females are relatively few, and our understanding of sex differences in the physiology of RT is incomplete, which makes studies on sex-differences warranted.

Practical Applications

Given the moderate effect size favoring females in the upper-body strength analysis, it is possible that untrained females display a higher capacity to increase upper-body strength than males. Further research is required to clarify why this difference occurs only in the upper body and whether the differences are due to neural, muscular, or motor learning adaptations. In practice, it is important to know that both males and females can considerably increase muscle strength and size with RT. Because there are is a paucity of studies comparing multiple RT programs between sexes, it is currently difficult to know if exercise prescription should be different between sexes.

References

1. Abe T, DeHoyos DV, Pollock ML, Garzarella L. Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women. Eur J Appl Physiol 81: 174–180, 2000.
2. Ahtiainen JP, Walker S, Peltonen H, et al. Heterogeneity in resistance training-induced muscle strength and mass responses in men and women of different ages. Age (Dordr) 38: 10, 2016.
3. Alway SE, Grumbt WH, Gonyea WJ, Stray-Gundersen J. Contrasts in muscle and myofibers of elite male and female bodybuilders. J Appl Physiol (1985) 67: 24–31, 1989.
4. Alway SE, Grumbt WH, Stray-Gundersen J, Gonyea WJ. Effects of resistance training on elbow flexors of highly competitive bodybuilders. J Appl Physiol (1985) 72: 1512–1521, 1992.
    5. Belanger AY, McComas AJ. Extent of motor unit activation during effort. J Appl Physiol Respir Environ Exerc Physiol 51: 1131–1135, 1981.
    6. Bornstein M. Introduction to Meta-Analysis. Hoboken, NJ: John Wiley & Sons, 2009.
    7. Carlsson T, Wedholm L, Nilsson J, Carlsson M. The effects of strength training versus ski-ergometer training on double-poling capacity of elite junior cross-country skiers. Eur J Appl Physiol 117: 1523–1532, 2017.
    8. Colliander EB, Tesch PA. Responses to eccentric and concentric resistance training in females and males. Acta Physiol Scand 141: 149–156, 1991.
    9. Cureton KJ, Collins MA, Hill DW, McElhannon FM Jr. Muscle hypertrophy in men and women. Med Sci Sports Exerc 20: 338–344, 1988.
    10. Daniels WL, Wright JE, Sharp DS, et al. The effect of two years' training on aerobic power and muscle strength in male and female cadets. Aviat Space Environ Med 53: 117–121, 1982.
    11. Dannecker EA, Liu Y, Rector RS, et al. Sex differences in exercise-induced muscle pain and muscle damage. J Pain 13: 1242–1249, 2012.
    12. Dias RM, Cyrino ES, Salvador ES, et al. Impact of an eight-week weight training program on the muscular strength of men and women. Revista Brasileira de Medicina do Esporte 11: 213–218, 2005.
    13. Donges CE, Duffield R. Effects of resistance or aerobic exercise training on total and regional body composition in sedentary overweight middle-aged adults. Appl Physiol Nutr Metab 37: 499–509, 2012.
      14. Dorgo S, Edupuganti P, Smith DR, Ortiz M. Comparison of lower body specific resistance training on the hamstring to quadriceps strength ratios in men and women. Res Q Exerc Sport 83: 143–151, 2012.
      15. Fernandez-Gonzalo R, Lundberg TR, Alvarez-Alvarez L, de Paz JA. Muscle damage responses and adaptations to eccentric-overload resistance exercise in men and women. Eur J Appl Physiol 114: 1075–1084, 2014.
      16. Fujita S, Rasmussen BB, Cadenas JG, et al. Aerobic exercise overcomes the age-related insulin resistance of muscle protein metabolism by improving endothelial function and Akt/mammalian target of rapamycin signaling. Diabetes 56: 1615–1622, 2007.
      17. Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab 21: 97–104, 2011.
      18. Gentil P, Steele J, Pereira MC, et al. Comparison of upper body strength gains between men and women after 10 weeks of resistance training. PeerJ 4: e1627, 2016.
      19. Guadalupe-Grau A, Perez-Gomez J, Olmedillas H, et al. Strength training combined with plyometric jumps in adults: Sex differences in fat-bone axis adaptations. J Appl Physiol (1985) 106: 1100–1111, 2009.
        20. Häkkinen K. Neuromuscular fatigue and recovery in male and female athletes during heavy resistance exercise. Int J Sports Med 14: 53–59, 1993.
        21. Häkkinen K, Kallinen M, Izquierdo M, et al. Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people. J Appl Physiol (1985) 84: 1341–1349, 1998.
        22. Häkkinen K, Kallinen M, Linnamo V, et al. Neuromuscular adaptations during bilateral versus unilateral strength training in middle-aged and elderly men and women. Acta Physiol Scand 158: 77–88, 1996.
        23. Häkkinen K, Newton RU, Gordon SE, et al. Changes in muscle morphology, electromyographic activity, and force production characteristics during progressive strength training in young and older men. J Gerontol A Biol Sci Med Sci 53: B415–B423, 1998.
        24. Häkkinen K, Pakarinen A. Serum hormones and strength development during strength training in middle-aged and elderly males and females. Acta Physiol Scand 150: 211–219, 1994.
        25. Häkkinen K, Pakarinen A, Kraemer WJ, et al. Selective muscle hypertrophy, changes in EMG and force, and serum hormones during strength training in older women. J Appl Physiol (1985) 91: 569–580, 2001.
          26. Hansen M, Couppe C, Hansen CS, et al. Impact of oral contraceptive use and menstrual phases on patellar tendon morphology, biochemical composition, and biomechanical properties in female athletes. J Appl Physiol (1985) 114: 998–1008, 2013.
          27. Hedges LV, Tipton E, Johnson MC. Robust variance estimation in meta-regression with dependent effect size estimates. Res Synth Methods 1: 39–65, 2010.
          28. Hostler D, Crill MT, Hagerman FC, Staron RS. The effectiveness of 0.5-lb increments in progressive resistance exercise. J Strength Cond Res 15: 86–91, 2001.
          29. Hubal MJ, Gordish-Dressman H, Thompson PD, et al. Variability in muscle size and strength gain after unilateral resistance training. Med Sci Sports Exerc 37: 964–972, 2005.
          30. Hunter GR. Research: Changes in body composition, body build and performance associated with different weight training frequencies in males and females. Natl Strength Cond J 7: 26–28, 1985.
          31. Hunter SK. The relevance of sex differences in performance fatigability. Med Sci Sports Exerc 48: 2247–2256, 2016.
          32. Hurlbut DE, Lott ME, Ryan AS, et al. Does age, sex, or ACE genotype affect glucose and insulin responses to strength training? J Appl Physiol (1985) 92: 643–650, 2002.
          33. Ivey FM, Roth SM, Ferrell RE, et al. Effects of age, gender, and myostatin genotype on the hypertrophic response to heavy resistance strength training. J Gerontol A Biol Sci Med Sci 55: M641–M648, 2000.
          34. Ivey FM, Tracy BL, Lemmer JT, et al. Effects of strength training and detraining on muscle quality: Age and gender comparisons. J Gerontol A Biol Sci Med Sci 55: B152–B157, 2000. discussion B158-159.
          35. Janssen I, Heymsfield SB, Wang ZM, Ross R. Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr. J Appl Physiol (1985) 89: 81–88, 2000.
          36. Jozsi AC, Campbell WW, Joseph L, Davey SL, Evans WJ. Changes in power with resistance training in older and younger men and women. J Gerontol A Biol Sci Med Sci 54: M591–M596, 1999.
          37. Kadi F, Bonnerud P, Eriksson A, Thornell LE. The expression of androgen receptors in human neck and limb muscles: Effects of training and self-administration of androgenic-anabolic steroids. Histochem Cell Biol 113: 25–29, 2000.
          38. Kell RT. The influence of periodized resistance training on strength changes in men and women. J Strength Cond Res 25: 735–744, 2011.
          39. Kelley GA, Kelley KS. Impact of progressive resistance training on lipids and lipoproteins in adults: A meta-analysis of randomized controlled trials. Prev Med 48: 9–19, 2009.
          40. Kosek DJ, Kim JS, Petrella JK, Cross JM, Bamman MM. Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults. J Appl Physiol (1985) 101: 531–544, 2006.
          41. Kovacevic A, Mavros Y, Heisz JJ, Fiatarone Singh MA. The effect of resistance exercise on sleep: A systematic review of randomized controlled trials. Sleep Med Rev 39: 52–68, 2018.
          42. Lemmer JT, Ivey FM, Ryan AS, et al. Effect of strength training on resting metabolic rate and physical activity: Age and gender comparisons. Med Sci Sports Exerc 33: 532–541, 2001.
          43. Lemmer JT, Martel GF, Hurlbut DE, Hurley BF. Age and sex differentially affect regional changes in one repetition maximum strength. J Strength Cond Res 21: 731–737, 2007.
          44. Lexell J, Henriksson-Larsen K, Winblad B, Sjostrom M. Distribution of different fiber types in human skeletal muscles: Effects of aging studied in whole muscle cross sections. Muscle Nerve 6: 588–595, 1983.
          45. Liu D, Sartor MA, Nader GA, et al. Skeletal muscle gene expression in response to resistance exercise: Sex specific regulation. BMC Genomics 11: 659, 2010.
          46. Markofski MM, Braun WA. Influence of menstrual cycle on indices of contraction-induced muscle damage. J Strength Cond Res 28: 2649–2656, 2014.
          47. Markofski MM, Volpi E. Protein metabolism in women and men: Similarities and disparities. Curr Opin Clin Nutr Metab Care 14: 93–97, 2011.
          48. Martin Ginis KA, Eng JJ, Arbour KP, Hartman JW, Phillips SM. Mind over muscle? Sex differences in the relationship between body image change and subjective and objective physical changes following a 12-week strength-training program. Body Image 2: 363–372, 2005.
          49. McMahon G, Morse CI, Winwood K, Burden A, Onambele GL. Gender associated muscle-tendon adaptations to resistance training. PLoS One 13: e0197852, 2018.
          50. Miller AE, MacDougall JD, Tarnopolsky MA, Sale DG. Gender differences in strength and muscle fiber characteristics. Eur J Appl Physiol Occup Physiol 66: 254–262, 1993.
          51. Miller BF, Hansen M, Olesen JL, et al. No effect of menstrual cycle on myofibrillar and connective tissue protein synthesis in contracting skeletal muscle. Am J Physiol Endocrinol Metab 290: E163–E168, 2006.
          52. Miller BF, Hansen M, Olesen JL, et al. Tendon collagen synthesis at rest and after exercise in women. J Appl Physiol (1985) 102: 541–546, 2007.
          53. Moritani T, deVries HA. Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med 58: 115–130, 1979.
          54. Morris B. Estimating effect sizes from pretest-posttest-control group designs. Organ Res Methods 11: 364–386, 2008.
          55. O'Hagan FT, Sale DG, MacDougall JD, Garner SH. Response to resistance training in young women and men. Int J Sports Med 16: 314–321, 1995.
          56. Peterson MD, Pistilli E, Haff GG, Hoffman EP, Gordon PM. Progression of volume load and muscular adaptation during resistance exercise. Eur J Appl Physiol 111: 1063–1071, 2011.
          57. Raue U, Trappe TA, Estrem ST, et al. Transcriptome signature of resistance exercise adaptations: Mixed muscle and fiber type specific profiles in young and old adults. J Appl Physiol (1985) 112: 1625–1636, 2012.
            58. Reimers AK, Knapp G, Reimers CD. Effects of exercise on the resting heart rate: A systematic review and meta-analysis of interventional studies. J Clin Med 7: 503, 2018.
            59. Reis E, Frick U, Schmidtbleicher D. Frequency variations of strength training sessions triggered by the phases of the menstrual cycle. Int J Sports Med 16: 545–550, 1995.
            60. Ribeiro AS, Avelar A, Dos Santos L, et al. Hypertrophy-type resistance training improves phase Angle in young adult men and women. Int J Sports Med 38: 35–40, 2017.
            61. Ribeiro AS, Avelar A, Schoenfeld BJ, et al. Analysis of the training load during a hypertrophy-type resistance training programme in men and women. Eur J Sport Sci 15: 256–264, 2015.
              62. Ribeiro AS, Avelar A, Schoenfeld BJ, et al. Resistance training promotes increase in intracellular hydration in men and women. Eur J Sport Sci 14: 578–585, 2014.
                63. Ribeiro AS, Avelar A, Schoenfeld BJ, et al. Effect of 16 weeks of resistance training on fatigue resistance in men and women. J Hum Kinet 42: 165–174, 2014.
                64. Riechman SE, Fabian TJ, Kroboth PD, Ferrell RE. Steroid sulfatase gene variation and DHEA responsiveness to resistance exercise in MERET. Physiol Genomics 17: 300–306, 2004.
                65. Roberts BM, Lavin KM, Many GM, et al. Human neuromuscular aging: Sex differences revealed at the myocellular level. Exp Gerontol 106: 116–124, 2018.
                66. Rogol AD. Growth and growth hormone secretion at puberty: The role of gonadal steroid hormones. Acta Paediatr Suppl 383: 15–20; discussion 21, 1992.
                67. Roth SM, Ivey FM, Martel GF, et al. Muscle size responses to strength training in young and older men and women. J Am Geriatr Soc 49: 1428–1433, 2001.
                68. Rutherford OM, Jones DA. The role of learning and coordination in strength training. Eur J Appl Physiol Occup Physiol 55: 100–105, 1986.
                69. Sale DG, MacDougall JD, Alway SE, Sutton JR. Voluntary strength and muscle characteristics in untrained men and women and male bodybuilders. J Appl Physiol (1985) 62: 1786–1793, 1987.
                70. Salvador EPDR, Gurjao AL, Avelar A, Pinto LG, Cyrino ES. Effect of eight weeks of strength training on fatigue resistance in men and women. Isokinetics Exerc Sci 17: 101–106, 2009.
                71. Schmidt D, Anderson K, Graff M, Strutz V. The effect of high-intensity circuit training on physical fitness. J Sports Med Phys Fitness 56: 534–540, 2016.
                72. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res 24: 2857–2872, 2010.
                73. Sheel AW. Sex differences in the physiology of exercise: An integrative perspective. Exp Physiol 101: 211–212, 2016.
                74. Shephard RJ. Exercise and training in women. Part I: Influence of gender on exercise and training responses. Can J Appl Physiol 25: 19–34, 2000.
                75. Simoneau JA, Bouchard C. Human variation in skeletal muscle fiber-type proportion and enzyme activities. Am J Physiol 257: E567–E572, 1989.
                76. Smith GI, Atherton P, Reeds DN, et al. No major sex differences in muscle protein synthesis rates in the postabsorptive state and during hyperinsulinemia-hyperaminoacidemia in middle-aged adults. J Appl Physiol (1985) 107: 1308–1315, 2009.
                77. Spurway NC, Watson H, McMillan K, Connolly G. The effect of strength training on the apparent inhibition of eccentric force production in voluntarily activated human quadriceps. Eur J Appl Physiol 82: 374–380, 2000.
                78. Staron RS, Karapondo DL, Kraemer WJ, et al. Skeletal muscle adaptations during early phase of heavy-resistance training in men and women. J Appl Physiol (1985) 76: 1247–1255, 1994.
                79. Stock MS, Thompson BJ. Sex comparisons of strength and coactivation following ten weeks of deadlift training. J Musculoskelet Neuronal Interact 14: 387–397, 2014.
                80. Stupka N, Lowther S, Chorneyko K, et al. Gender differences in muscle inflammation after eccentric exercise. J Appl Physiol (1985) 89: 2325–2332, 2000.
                81. Sung E, Han A, Hinrichs T, et al. Effects of follicular versus luteal phase-based strength training in young women. Springerplus 3: 668, 2014.
                82. Tipton E. Small sample adjustments for robust variance estimation with meta-regression. Psychol Methods 20: 375–393, 2015.
                83. Trappe S, Gallagher P, Harber M, et al. Single muscle fibre contractile properties in young and old men and women. J Physiol 552: 47–58, 2003.
                84. Washburn RA, Kirk EP, Smith BK, et al. One set resistance training: Effect on body composition in overweight young adults. J Sports Med Phys Fitness 52: 273–279, 2012.
                85. Weiss LW, Clark FC, Howard DG. Effects of heavy-resistance triceps surae muscle training on strength and muscularity of men and women. Phys Ther 68: 208–213, 1988.
                86. West DW, Burd NA, Churchward-Venne TA, et al. Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state. J Appl Physiol (1985) 112: 1805–1813, 2012.
                87. Westh E, Kongsgaard M, Bojsen-Moller J, et al. Effect of habitual exercise on the structural and mechanical properties of human tendon, in vivo, in men and women. Scand J Med Sci Sports 18: 23–30, 2008.
                88. Wikstrom-Frisen L, Boraxbekk CJ, Henriksson-Larsen K. Effects on power, strength and lean body mass of menstrual/oral contraceptive cycle based resistance training. J Sports Med Phys Fitness 57: 43–52, 2017.
                89. Williamson DL, Gallagher PM, Carroll CC, Raue U, Trappe SW. Reduction in hybrid single muscle fiber proportions with resistance training in humans. J Appl Physiol (1985) 91: 1955–1961, 2001.
                  90. Wilmore JH. Alterations in strength, body composition and anthropometric measurements consequent to a 10-week weight training program. Med Sci Sports 6: 133–138, 1974.
                  91. Young A. The relative isometric strength of type I and type II muscle fibres in the human quadriceps. Clin Physiol 4: 23–32, 1984.
                  Keywords:

                  resistance exercise; gender differences; strength; hypertrophy

                  Copyright © 2020 by the National Strength & Conditioning Association.