Related Experiment Video
Updated: Jul 20, 2026

Determining the Contribution of the Energy Systems During Exercise
Published on: March 20, 2012
[Testosterone deficiency related to "relative energy deficiency in sport"]
Nasima Olawi1,2, Loa Nordkap2, Niels Jørgensen3
1Endokrinologisk Afdeling, Københavns Universitetshospital - Amager og Hvidovre Hospital.
Abstract:
In this case report, a 29-year-old formerly healthy man presented with fatigue, reduced libido, and erectile dysfunction. He had lost 12 kg due to extensive training and disordered eating. Blood tests showed hypogonadotropic hypogonadism, low insulin-like growth factor-1, and anaemia. His condition was due to functional testosterone deficiency related to "relative energy in sport" (RED-S). Symptoms and testosterone levels improved following reduction in training load and weight gain, underscoring the importance of addressing energy imbalance rather than opting for testosterone therapy in this condition.
Related Concept Videos
Energy Supply for Muscle Contraction
Muscle Recovery and Fatigue
Exercise and Muscle Performance
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Exercise and Cardiac Output
Sustained exercise increases the muscles' oxygen demand, which can be met...
Exercise and Cardiovascular Response
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
Energy Balance

