Quantifying the Relationship between Testosterone and Aerobic Capacity in Career Firefighters

• Career firefighters rely on their aerobic capacity to perform their critical and essential occupational tasks (1)
• It is well-documented that testosterone levels decreases throughout the lifespan of males(2)
• A previous study reported that firefighters with higher aerobic performance (i.e., longer running time) displayed decreased odds of having low testosterone (3)

PURPOSE: The purpose of this study was to determine the relationship between testosterone and VO2peak in career firefighters.

PARTICIPANTS

• Data from 1151 career firefighters (age = 39 + 9 years, BF% = 30.2 + 1.5%) were examined from an annual routine health screening
• Firefighters were from local fire departments across the United States

BODY COMPOSITION

• Body composition was assessed through a multi-frequency bioelectrical impedance analysis (MF-BIA) device (InBody 570, InBody. USA, Cerritos,CA, USA)

CARDIOPULMONARY EXERCISE TESTING

• Participants performed grades testing exercise on a cycle ergometer to determine maximal oxygen consumption (VO2PEAK)

SERUM TESTOSTERONE

• In the morning, following a 9-hour fast, participants visited a local lab in order to acquire blood samples via venipuncture
• Testosterone levels can be categorized as low range (<264 ng/dL), borderline range (264-399 ng/dL), reference range (400 – 916 ng/dL), and above reference range (>916 ng/dL)

STATISTICAL ANALYSIS

• Linear mixed effect models were employed to use VO2peak as the dependent variable %BF and testosterone category as independent variables

The linear mixed-effect models indicated that participants’ VO2PEAK was higher for those within testosterone categories below:

• Firefighters with testosterone levels in the borderline range have lower V02PEAK indicating reduced aerobic capacity
• V02PEAK increases with higher testosterone levels, with those in the reference and above reference ranges exhibiting significantly higher V02PEAK compared to those in the borderline range.
• Future studies could explore more refined categorizations of testosterone to better understand its relationship with V02PEAK

1. Hare, M. M., Wohlgemuth, K. J., Jesko, A, Conner, M. J., Frost-Piedrahita, V., & Mota, J. A. (2024). Climbing the Ranks: A Study of Firefighter Health Disparities. Healthcare, 12(2), 227. 2. Bhasin, S .. Brito, J.P .. Cunningham, G. R .. Hayes, F. J., 􀁯. H. N., Matsumoto, A. M., Snyder, P. J .. Swerdloff, R. S., Wu, F. C .. & Yialamas, M. A. (2018). Testosterone Therapy in Men With Hypogonadism: Ar, Endocrine Society, Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism, 103(5), 1715-1744. 3.Porto, L. G. G .. Soares, E. M .. Ranadive. S. M., 􀁇Porto, A .. & Smith, D. L. (2024). Association of endogenous testosterone with physical fitness measures during firefighter occupational health evaluations. International Journal of &Mronmental Research and Public Heafth, 21(3), 274.

4. P. M., French, W. J., Herring, M. J.,  Mayeda, G. S., Burstein, S., & Kloner,. R. A. Testosterone and the Cardiovascular System: A Comprehensive Review of the Clinical Literature. Journal of the American Heart Association, 2(6), e000272.

Kornkanok Sophonsakulrat(1), Michael J. Conner(2), Alex Jesko(2), Kealey J. Wohlgemuth(1), Jacob A. Mota(1)

(1)Neuromuscular and Occupational Performance Laboratory, Department of Kinesiology and Sport Management Texas Tech University, TX, USA; (2)Front Line Mobile Health, TX, USA