In men, intense weight training (especially large muscle groups), causes an increase in testosterone production.  

When I am bulking, my libido goes through the roof.  Not only is the libido enhanced, but refractory period is shortened and I can go more often.

Good news for me, bad news for my ATF.

Regular exercise leads to a better cardiovascular response mechanism, where the smooth muscle lining the inner portions of blood vessels are able to relax and expand more efficiently. This promotes better blood flow upon demand, thereby delivering more oxygen to muscles under increased load. Caffeine and alcohol interfere with this mechanism, so another good reason to restrict or eliminate their usage any time close to sex being initiated.

Increased blood flow on demand leads to longer and stronger erections, and (ultimately) a better orgasm response.

Couple exercise with proper nutrition and supplementation so that your body has the nutrients and reserves it needs to produce sufficient quantities of nitric oxide (a blood component that also prompts the blood vessel muscle lining to relax) and you have the keys to better sex, orgasms and overall health.

Put thru the paces!

Regular exercise, particularly aerobic exercise, increases sexual fitness dramatically. It not only improves sex drive, but also the quality of erections.

Probably one of the most important things a person can do to improve his/her sexual wellbeing is exercise.

In addition, I should add that kegel exercises for men ALSO improve erections as well as assisting with premature ejaculation.

When I see men who are....

in there 70's...and they can keep it up...and give me sooo much Pleasure...and they tell me it's because they work out..both at the gym and in the bedroom...I have no doubt staying in shape...does a body a whole lot of Good

Good sex reguires good blood flow to the genital area. Working out improves blood flow to all areas of the body. Those who are overweight but have no medical limitation can vastly improve their sexual performance by losing weight via excercise and control of food portions and food types.

I've never been the fittest...I fluctuate between a size 14 to 16 but my not being so fit has never hurt the umph of my orgasms, I have knockout orgasms lol. But i've read and heard from a few people that the smaller you are the more enjoyable sex can be.

If the guy is humping and grunting and sweating and getting tired trying to have an orgasm it would be distracting to say the least.