The relationship between exercise and fertility gets discussed mostly in extremes. Too little is bad. Too much is bad. The sensible guidance, a moderate aerobic baseline, maintained consistently, tends to get lost between the two. The actual question worth asking is not 'how much' but 'what kind, and timed to what'.
The evidence base: moderate aerobic exercise (around 150 minutes a week of activity where you can talk but wouldn't easily sing) is associated with better fertility outcomes, particularly in women with PMOS (previously called PCOS) where insulin sensitivity is a direct mechanism. High-intensity training in people with a low BMI or in caloric deficit suppresses GnRH pulsatility, disrupting the hormonal cascade that triggers ovulation.
The clinical term is hypothalamic amenorrhoea; it's more common than it gets diagnosed, and irregular or absent periods alongside a high training volume is a flag worth raising.
On the male side, regular moderate exercise improves semen parameters, sperm count, motility, morphology, across multiple meta-analyses. Excessive cycling (over five hours a week on a hard saddle) is the one specific negative finding with decent replication, thought to relate to scrotal temperature and perineal pressure. That's a niche finding, not a reason for most men to stop cycling.
During a treatment cycle, once stimulation starts, high-impact exercise should stop. This isn't overcaution, enlarged ovaries are at genuine risk of torsion during high-intensity activity. Walking, swimming, and yoga are all fine. The two-week wait has no specific physical restriction from a clinical standpoint, but most people find lower-intensity movement helps with anxiety without adding physical load.
The pelvic floor angle gets less attention than it deserves. Strong, coordinated pelvic floor function supports blood flow and uterine mobility. Overworked pelvic floors, common in people who do a lot of high-impact sport, can cause tension and restricted mobility.
If you've been told to 'do more kegels' without someone first assessing whether your pelvic floor is underactive or overactive, that's incomplete guidance.
What to actually change
Start with your baseline. If you're doing less than 150 minutes of moderate-intensity movement a week, build up to that with whatever form you'll actually maintain. Don't launch a new exercise regime during stimulation, that's the wrong time to start.
If you're running high training volumes, particularly if your periods are irregular or your luteal phase is short, pull back for two to three cycles and see what changes. That's useful information regardless of what you decide next.