New Research from Dr. Emma Hilton

Biological Differences in Males and Females

Males have increased utilization of oxygen (VO2 max)

Males have more myonuclei in their muscles which results in:

Males have more myonuclei in their muscles which results in:

  • Male blood typically contains higher levels of hemoglobin 
  • Males have larger lungs and hearts.

Combined these help the male body utilize more oxygen at a faster rate than a female. 

Males have more myonuclei in their muscles which results in:

Males have more myonuclei in their muscles which results in:

Males have more myonuclei in their muscles which results in:

Males Do Not Have A Uterus

Males Do Not Have A Uterus

Males Do Not Have A Uterus

Males bones are different

Males Do Not Have A Uterus

Males Do Not Have A Uterus

  • On average, Males have denser bones.
  • Females have shorter long bones, an increased Q angle, and the angle of the pelvis required for childbirth increases the curvature of the lower spine. This also makes the centers of gravity a bit different between the two sexes
  • Males have longer arms and shorter torsos 

Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance

  • published by the Endocrine Society at Oxford Academy.
  • supports lowering  testosterone limit to 5nmol/L in womens sports 
  •  "Testosterone is responsible muscle mass and strength"

Women and Men in Sport Performance: The Gender Gap has not Evolved since 1983

  • Journal of Sports and Science Medicine
  •  "Results suggest that women will not run, jump, swim or ride as fast as men "
  • " Sex is a major factor influencing best performances and world records "

Comparing Athletic PerformancesThe Best Elite Women to Boys and Men

  • published by Duke Law
  • " This differential isn’t the result of boys and men having a male identity, more resources, better training, or superior discipline. It’s because they have an androgenized body."
  • " There is no other physical, cultural, or socioeconomic trait as important as testes for sports purposes."

Exploring the Biological Contributions to Human Health: Does Sex Matter?

  •   National Center for Biotechnology Information 
  • "The hallmark of human biology is variation, and much of the observed variation both within and between the sexes is encoded within the human genome."

Different Endurance Characteristics of Female and Male German Soccer Players

  • Biology of Sport - US National Library of Medicine
  • " During incremental testing, the running performances of female and male players reflect different distributions of aerobic and anaerobic metabolic pathways. The revealed gender differences should be considered for soccer endurance training."  

Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining

  • Proceedings of the National Academy of Sciences of the United States of America
  • " .. and because anabolic steroids facilitate more myonuclei, nuclear permanency may also have implications for exclusion periods after a doping offense "

Skeletal muscle mass and distribution in 468 men and women aged 18–88 yr

  • American Physiological Society | Journal of Applied Physiology


Changes in muscle strength and muscle cross-sectional area following cross-sex hormone treatment

Anna Wiik 1 , Mats Holmberg 1 , Tommy Lundberg 1 , Mats Lilja 1 , Daniel Andersson 1 , Stefan Arver 1 , Thomas Gustafsson 1 1. Karolinska Institutet 

"Background Many biological differences seen in men and women are driven by relative differences in estrogen and testosterone levels. In transgender individuals, gender-affirming treatment includes inhibition of endogenous sex hormones and subsequent replacement with the cross-sex hormones. Yet, the effect of this treatment on functional muscle strength and mass remains poorly described. The aim of the current study was to assess the effects of an altered sex hormone pattern on muscle strength and cross-sectional area. 

Methods Twelve transgender individuals, 6 trans women and 6 trans men who had been accepted to start gender-affirming medical intervention, were recruited. Knee extensor and flexor muscle strength was assessed using isokinetic dynamometry at three different angular velocities (0, 60 and 90 °/s). The assessments were made at four time points: (T1) before treatment initiation, (T2) four weeks after initiated gonadal hormonal down regulation but before hormone replacement, (T3) three months after hormone replacement therapy and (T4) eleven months after hormone replacement therapy. The cross-sectional area and radiological density of the thigh muscles were assessed by CT scans performed bilaterally at the midpoint of femur of each subject at baseline and after 11 months of cross-sex hormone treatment. 

Results and Conclusions Muscle area increased 17% in trans men (p<0.001) with an 8% increase in radiology density after eleven month of cross-sex hormone treatment. No change was seen in trans women. There were significant (P<0.05) group x time interactions at each angular velocity. Thus, while the trans men increased their strength over the four time points, strength levels were generally maintained in the trans women. When averaging the three strength tests, knee extension (16%) and knee flexion (34%) strength increased from T1 to T4 in trans men. The corresponding changes in the trans women group were -6% and 0%, respectively. CONCLUSIONS: These results show that ~1 year of cross-sex hormone treatment results in increased muscle strength in trans men. Cross-sectional area and radiological density is also increased after testosterone treatment. However, trans women maintain their strength levels as well as cross-sectional area and radiological density throughout the treatment period. We conclude that the altered sex hormone pattern induced by gender-affirming treatment deferentially affect muscle strength in trans men vs. trans women."

*Trans Women are men who self identify as women*

Presented at EPATH

This study was presented on 4/11/19 at the 3rd biennal conference of EPATH (European Professional Association Transgender Health)

Dr. Gregory A. Brown

Dr. Brown is an accomplished Professor of Exercise Science in the Department of Kinesiology and Sport Sciences at the University of Nebraska Kearney.  

He has submitted this report in the Title IX case against the Department of Education on behalf of female athletes including Selina Soule and Alanna Smith.

"Doctor joins Title IX complaint"

Dr. Helen Waite

 Sports sociologist and former elite athlete Presented on 12 October 2019, “New Myths of a Level Playing Field in Women’s Sport” 

Dr. Kristopher Hunt, MD

An excellent presentation by Dr. Kristopher Hunt, an emergency physician,  and the current chair of USA Powerlifting's therapeutic use exemption committee. 

An analysis of Transwomen in elite sports

Comparison of Men’s & Women’s Athletic World Records

The Female Athlete Triad

Medicine & Science in Sports & Exercise: October 2007 - Volume 39 - Issue 10 - p 1867-1882  written for the American College of Sports Medicine by by Aurelia Nattiv, M.D., FACSM (Chair); Anne B. Loucks, Ph.D., FACSM; Melinda M. Manore, Ph.D., R.D., FACSM; Charlotte F. Sanborn, Ph.D., FACSM; Jorunn Sundgot-Borgen, Ph.D.; and Michelle P. Warren, M.D. 

"The female athlete triad (Triad) refers to the interrelationships among energy availability, menstrual function, and bone mineral density, which may have clinical manifestations including eating disorders, functional hypothalamic amenorrhea, and osteoporosis. 

With proper nutrition, these same relationships promote robust health. Athletes are distributed along a spectrum between health and disease, and those at the pathological end may not exhibit all these clinical conditions simultaneously "

Updated 5/13/2020

Is there something we should add? Let us know!