Biking can raise the PSA due to the pressure on the pelvic area (where the prostate is.) So can sex. In both cases, it's probably more likely with extensive vigorous activity than more limited casual activity, but who really knows. It's just an association. If there were more cowboys, we might know that hard riding of horses had a similar association?! Pole dancing? Gymnastic pommel horse? Anyway, you get the drift.
Without the prostate, there is less PSA, but also less data. Who really knows if biking has any effect. If you did a long bike ride and got a higher PSA, you could always retest without the biking or other strenuous activities involving the pelvic area and see if it's lower. Or vice versa.
I suppose if you want to minimize PSA "shedding," you could spend a couple days laying in bed or on the beach?! before each PSA test. I kind of like that. A "medically necessary" couple days laying on the beach or by the pool. I definitely think you should do this with your husband @jwoy . You heard it here, on this unauthoritative forum. It might also lower blood pressure?!