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Suspensories / Internal heat

People have known for centuries that livestock with cryptorchid (undescended) testes are infertile. The reason for the animals’ infertility was not understood until the 1920s: a small increase in the temperature of the testes has a large negative impact on the production of sperm (spermatogenesis). This is true of human spermatogenesis as well.

Suspensories are specially designed briefs that hold the testes closer to the body, raising their temperature. Because the change in temperature is only a few degrees, suspensories must be worn daily to provide effective contraception. Clinical trials show that suspensories can suppress sperm counts and make the remaining sperm poor swimmers.

How does it work?

The testes are located outside the body cavity and are usually 1-2º C cooler than body temperature (Rock 1965). Warming the testes by a few degrees has a significant negative impact on spermatogenesis. Suspensories do just that: a custom brief holds the testes close to the body, warming the testes to body temperature. Researchers have reported resultant decreases in both the rate of spermatogenesis and the quality of the sperm produced. To understand how even mild heating has this effect, read How heat works.

How effective is it?

A team of researchers in France have carried out clinical trials of various suspensory designs as male contraceptives (Mieusset 1994). Their results showed that men who wore one suspensory design with a rubber ring to hold the testes in the inguinal canals had 100% effective contraception. All trial participants achieved very low motile sperm counts, between 0 and 1.6 million sperm per milliliter. There was one pregnancy during this trial, but the man subsequently admitted that he had stopped wearing the suspensory for 7 weeks. Consistent daily usage is critical for the effectiveness of this method.

How is it delivered?

Suspensories are not just a pair of typical brief-style men’s underwear. They simulate cryptorchidism, a condition in which the testes do not descend from the abdomen, where the testes are formed before birth. Around the time of birth, the testes of most boys descend into the scrotum via channels known as the inguinal canals.

There are many different suspensory designs, but generally they look from the outside like a normal pair of brief underwear or an athletic support. Some suspensory designs leave the scrotum and penis free. All designs hold the testes inside the lower ends of the inguinal canals. Suspensories must be worn every day during waking hours to be effective.

How long does it take?

The men in Dr. Roger Mieusset ’s (1994) trial all used a secondary form of contraception until they had 2 consecutive sperm counts below 1 million normally swimming (motile) sperm per milliliter. There was a wide range in how long it took for the method to reach this level of effectiveness: for some men it took only 2 months, for others it took 9 months. Because it takes 2 months for newly formed sperm to travel through the male reproductive system, the shortest possible time to effectiveness would be 2 months.

What side effects are expected?

The only side effect reported during a suspensory trial was chafing while the weather was hot (Rock 1967). More recent suspensory designs have not caused chafing.

Like external heat, there is a concern about the genetic integrity of future sperm. Dr. Mieusset (2005) has proposed to carry out animal tests on the genetic viability of eggs fertilized with heat-treated sperm. This issue is of particular concern at the beginning and end of suspensory treatment, when men are subfertile but potentially still capable of fathering a child. The children fathered at the end of Mieusset’s (1994) trial were all normal, but the sample size is too small to make any definitive statements.

How long does it take to reverse?

Tests of suspensories have all shown full recovery to pre-treatment sperm count and motility levels. The length of time to recovery depends on the duration of the treatment. In a 1 year trial, men returned to pre-treatment levels within 12-18 months. However, full recovery is not necessary to achieve a pregnancy; one man fathered a child 3 months after stopping treatment (Mieusset 1994). Shorter trials have shown full recovery within 6-8 months (Mieusset 1991, 1987). There are no reports of suspensories causing irreversible infertility.


  • Mieusset, R (2005) Email correspondence to Elaine Lissner, Male Contraception Information Project. 15 October.
  • Mieusset, R, and L Bujan (1994) “The potential of mild testicular heating as a safe, effective and reversible contraceptive method for men.” International Journal of Andrology 17: 186-191.
  • Mieusset, R, L Bujan, A Mansat, H Grandjean and F Pontonnier (1991) “Heat induced inhibition of spermatogenesis in man.” In Zorgniotti (ed.) Temperature and Environmental Effects on the Testes. Plenum Press, NY.
  • Mieusset, R, L Bujan, A Mansat, F Pontonnier and H Grandjean (1987) “Hyperthermia and human spermatogenesis: enhancement of the inhibitory effect obtained by ‘artificial cryptorchidism’.” International Journal of Andrology 10: 571-80.
  • Rock, J and D Robinson (1967) “Intrascrotal hyperthermia induced by scrotal insulation: effect on spermatogenesis.” Obstetrics and Gynecology 29(2): 217-23.


More info on heat methods

» Suspensories

   External heat

   How heat works