Peer-reviewed research concerning heat stress, summarized and appraised in plain language with every source cited.
This is a narrative review, which means the authors gathered and discussed existing work rather than running a study of their own. It asks whether the damage COVID-19 does to…
This meta-analysis set out to work out how high ambient temperature affects sperm quality. It pooled nine studies covering 356 men in Iran, Italy, Thailand, China and Egypt, comparing men…
This meta-analysis set out to see whether repeatedly getting the body used to heat raises HSP70 (heat shock protein 70, a protein cells make to protect themselves from heat damage)…
This study set out to find which stage of sperm production is most sensitive to mild heat. Five healthy volunteers wore a specially designed underwear that held the testicles up…
This study asked what a mild, sustained rise in testicular temperature does to the chromosomes inside sperm. Five fertile volunteers wore specially designed underwear that held the testicles up against…
This study looked at whether the type of underwear men wear affects markers of testicular function, such as sperm count and hormone levels. Researchers surveyed 656 men seeking fertility treatment…
This experiment followed what whole-body heat does to sperm as they are made, in laboratory mice. Adult males were held at 37 to 38 degrees Celsius (98.6 to 100.4 degrees…
This study set out to see what repeated heat does to sperm. Twenty men with normal semen results were randomly split into two groups, and both had their testicles warmed…
This study set out to see what sustained scrotal heating does to semen and to the sperm's genetic material in fertile men. Nineteen healthy volunteers wore a warming belt at…
This study looked at what sustained scrotal heating does to semen and to the sperm's genetic material in already fertile men. Twenty-five healthy volunteers wore a warming belt at 40…
This review gathers what is known about why heat harms sperm production, and how. It sets out the things that raise testicular temperature, from the surroundings a man is in…
This study set out to see how regular sauna use affects sperm health in men whose sperm counts were normal to begin with. Ten men used a Finnish sauna twice…
This study tested ways to prevent scrotal overheating in men using laptop computers. Twenty-nine healthy men had their scrotal temperature measured during three one-hour sessions: sitting with legs close together,…
This experiment asked whether heat reaches sperm that have already been made, rather than only the ones still forming. Fourteen C57BL/6 mice (a laboratory strain bred so that individuals within…
It has been suggested that cycling warms the testicles as a ride goes on, and that this in turn harms semen quality. This study tested the first half of that…
This study set out to see how posture and clothing affect scrotal temperature in fertile men. It tested 13 men in different positions (standing, seated with legs apart, seated with…
This review looked at how heat stress on the testicles affects semen quality in men. It examined studies on factors like prolonged sitting, tight underwear, sauna use, and fever, and…
This study reviewed how the scrotum's role in keeping the testicles cooler than core body temperature affects sperm production. It looked at evidence from men with conditions like undescended testicles…
This experiment asked whether heat makes sperm worse at their actual job, or simply leaves fewer of them. Male mice were held at 36 degrees Celsius (96.8 degrees Fahrenheit) for…
This study set out to measure how much using a laptop on your lap raises scrotal temperature, a known risk factor for male infertility. Researchers measured scrotal temperature in 29…
This study looked at what a fever does to semen quality in healthy men. Twenty-seven men with a median age of 24.4 years gave a semen sample every month and…
This study set out to look at how scrotal temperature affects semen quality in healthy men. It tracked 99 men over 24 hours, measuring scrotal skin temperature continuously and collecting…
This study asked why men differ so much in how warm their testicles run. Scrotal skin temperature was logged every five minutes for 24 hours in 48 men, made up…
This study set out to find which parts of an ordinary day actually move scrotal temperature. A thermistor (a small temperature sensor) was clipped to the underwear of 101 men…
This study looked at whether reducing genital heat could improve semen quality in men with a poor sperm count, poor movement and abnormal shape. It compared those men against men…
This study asked whether the ordinary, everyday variation in scrotal temperature is enough to matter for sperm. Sixty men from a group of couples planning their first pregnancy wore a…
This study set out to test whether driving a car for long stretches raises scrotal temperature, a known risk factor for sperm health. Nine men had their scrotal temperature measured…
This lecture is the field's own summary of why the testicles sit outside the body and what happens when they get warm. It sets out the evidence that the testes…