I think its two things…
First one is overall work capacity. We adapt to a certain amount of work we need to do. Our body wants to work optimally so we only have muscle and energy for what we need daily. If you only lift a bit for years, and you work, and have everyday stress about work and traffic and bills, you basically end up being able to do just that. Sex is pretty intense thing for one. And to be horny, you need to feel good. When we lack energy, food or health, the first thing that goes is the sexual function because our body is designed NOT to procreate when we dont have food or our living conditions suck. At least thats how we are programmed since the ice age. Species tries to procreate when living conditions are ok-ish.
So the interest in sex goes away first. Because your work capacity is only as much as you need it daily. And when you “force” sex, you cant perform, well - again, because you dont have the energy to do it.
Now imagine doing 2 hours of extra cardio a day(just an example) and adapting enough that these 2 hours feel like a daily routine. Nothing hard, nothing special, just your life, your lifting, and everyday 2 hour cardio. Now imagine 12 months later, you skip 2 sessions… What happens? You have the capacity, you have the ability, but you dont have anywhere to put it.
I rmb when i was fighting a lot, my every day night session started at 8PM. But since i was like 27 at the time, i had the “Tinder era” so i used to skip some, to go on a date. As soon as 8PM hit, my hands started shaking, my legs were skipping around, my body was producing energy to DESTROY shit, but i was on a date. So when it came to later in the bedroom, the energy i saved because of the missed training, was put to use. 90mins of energy that was used to break arms, and knee people in the face was smashed right in someones fuckholes.
So the first thing about cardio is work capacity. If you lift, its not a lot of work. So when you take the rest day, all you get extra is the small amount of energy needed to complete some lifting sets lasting 10 seconds each followed by 3 minute breaks in between. But when you pump burpees, and jump squats and hill sprints daily, and then you take a rest day, you recover and you have the extra energy needed for that. Its called work capacity.
You dont feel so tired from every day stuff, you recover twice as fast when you skip a day and you get all that energy to do stuff.
Now the second one is the sex itself. If your training consists of 10-15sec sets followed by minutes of breaks, you basically move like 7 minutes total and most of the gym time is breaks. Now, what kind of sex can be done if we follow these principles?
Basically, you start having sex and you feel tired, sweaty, every position sucks because you cant hold a plank for 2 minutes, you cant support yourself on your arms because you bench for 10 seconds, instead of 100 reps in 2 minutes, etc. You are basically NOT conditioned for sex.
Now when you spar for 3 minutes and have only 1 minute break, you are basically functioning at 160 beats for 3 mins, having only enough rest to change a partner, and go again, you condition yourself to pump your dick into the hole even if you are tired, even if you feel pain, even if your nose is broken, and you enjoy the sex, because your training sucks so much more, that having higher heart-rate is the least of your worries.
It is hard to be interested in fucking, changing positions, even enjoying the view of the woman, if sex is the most intense, most vigorous activity in your life.
When you will start doing high intensity you would notice, that you can put on your favorite porn, and do your circuit, you will not be interested in the process and 1 hour after. Why? Because you are so exhausted that your body has so many problems, that it doesnt even realize you have a dick.
That is why i believe this answer has 2 parts, and that is why i believe people need to do endurance work AND high intensity.
Endurance provides work capacity so you have energy to think nasty shit and want to do it. High Intensity provides you with a conditioning, so sex is not the hardest thing in your life.
If you cant survive a 5min high intensity work, you cant fuck for 5min, which means you will be tired if you try, and it is not enjoyable when you are tired, isnt it?
So your training needs to be the most sucky part. It needs to be twice the length you want to have sex, and twice the intensity, in order for you to be able to do everything you want, and not be breathing heavy and sweating like you are doing a stairmaster while you have sex.
So the next time you run a 15% incline, and it says that you did it for 2min, your heart rate is 170, and you feel like falling down, understand that you are conditioned to have sex for like 1 minute before you feel like shit.
And since you feel so horrible during sex, why would you wanna do it? Thats how libido is lost. No one wants to do extra work at night when tired. So you need to NOT be tired.
There are many approaches but i usually go by at least 1:1 principle. If i spent 30mins in a weight section, i will spend 30min in a crossfit or cardio machine session.
Now when you will feel like you have time only for one, you pick cardio. At least for now. No point of having muscles or strength if you cant even fuck anyone. And you wont lose a gram of muscle if you skip a session or two.
Another thing you can try is to change how you view training as such.
You can use cardio as your assistance work. Lets say you wanna bench and then do some bench assistance, like some extra push movements for chest, and some triceps.
So what you can do is make a circuit that has some sprints, with pushups, dips, some skip rope, or med-ball throws. Need back assistance? Do the rowing machine.
Need legs? Add bodyweight squats and kettlebell swings.
Train more like an athlete. You can train all the pushing and pulling and leg stuff with circuits and bodyweight stuff and your muscles will burn and so will your lungs.
After that, go pump the biceps if you want and you are done.
There is no need to separate cardio from weights. Do any crossfit WOD bullshit. I mean, just skip the leg day and do 500 bodyweight squats as fast as you can. Your cardio will be trained, and your legs will be more fucked that you could ever do that with weights.
Jim Wendler is a legendary powerlifter but his views has changed as he got older and he writes about some good stuff nowdays. He does the weight vest stuff, and lots of pushups and squats and pullups. He did MURPH every day for a month, etc. All of that is great stuff for muscle and for conditioning.
Maybe you could save a lot if time by changing how you view the training it self, train more like an athlete or a fighter, combine strength with intensity, so some rowing or sprinting in between sets, and you will be better in every aspect of your physical being.
Maybe even join a kickboxing or BJJ class, so cardio doesnt feel like a chore. 90mins of cardio will go by in a flash and you will also learn something new.
Maybe do 2 gym sessions and some 2 MMA sessions in any local class. It doesnt even need to be good, you just need to move and not be bored. Or do some crossfit, who cares - these classes are the best because you get in HUGE amounts of cardio minutes and since its fun, the time goes by so much quicker…
3 minutes on stairs is a pain in the ass. 3 minutes trying to to get kicked in the face goes by in a zip, haha.
Imagine you do some 2 MMA classes a week. Thats like 180 minutes of combined cardio right there. You dont even need to plan it, or think about it. You would need to do at least 25minutes on a treadmill or rower or stairs every day to get in that amount of time.
Also if you chose to do some fighting, crossfit or hey - do the NFL thing if you are american. Thats an epic sport. Or just some Rugby. I mean, it usually gives people some new goals to be better. You will WANT to have better cardio and be more athletic if you find a team or a class in which you want to be good at. Your training will have new meaning.
