Short answer
Men belong in the fertility conversation. Spermmaxxing is the internet's name for trying to improve sperm health through habits, supplements, temperature and underwear choices. The useful question is what each change has actually been shown to do.
Start with the outcome.
Sperm count, concentration and motility are semen measurements. They are not interchangeable with pregnancy or live birth. A study reporting a change in one measurement is not proof that a product helps a couple conceive.
Heat: a real research question.
10 MEN · REPEATED SAUNA EXPOSURE
In a small human study, semen measures worsened during a repeated sauna programme and recovered after exposure stopped. The study did not test cooling underwear or prove that wearing an insert cancels sauna exposure.
For the fuller context, read our sauna and sperm guide. Discuss repeated heat exposure with a clinician if you are concerned about fertility.
Cooling: promising questions, limited answers.
A systematic review found too little evidence for firm conclusions about scrotal cooling and fertility. Small studies and changes in semen measures do not establish a reliable pregnancy benefit. Read the cooling review.
Do not put ice directly against skin. A social-media icing routine is not an individual treatment plan. Follow product instructions and ask a clinician about fertility concerns.
Underwear: separate fit from fibre.
“Boxers versus briefs” and “polyester versus wool” are different comparisons. A 2026 review found limited fabric-specific evidence and no clear pregnancy-outcome benefit from underwear choices. Read the review.
Polyester is a plastic-based fibre. That does not establish that everyday polyester boxers lower sperm count, or that merino improves it. Our polyester and microplastics guide separates material facts from medical claims.
Give assessment a place in the plan.
If conception is taking longer than expected, or you have a known concern, seek appropriate assessment. AUA/ASRM guidance recommends considering both partners concurrently during an infertility evaluation. Bring your questions about heat, medications, supplements and semen testing to that appointment. Read the guidance.
Questions worth asking before buying a “protocol”.
- Was this tested in people, and how many?
- Did the study examine this exact product or a different exposure?
- Was the result a semen measurement or a pregnancy outcome?
- Does the seller explain uncertainty as clearly as the headline?
Where NUMBNUTS fits.
We make merino boxers with reusable cooling inserts for cooling comfort. NUMBNUTS has not been shown to improve sperm count, pregnancy or IVF outcomes. Explore the Cool System for its materials and design, or take the educational Heat Check to reflect on everyday heat habits.
