All i have is my own experience.
So basically when i was into fighting, i was around 220lbs very lean, always fasting, doing hours of cardio a day in work, 3 training sessions and also doing 1 hour after each gym session. Basically i did a looot of cardio. I never felt tired. Even after the hardest training, when i was all beat up, i always had energy to jump around, swing my arms(like stupid fighters do when they walk the streets). I had energy after 10PM training to go on Tinder dates at 11PM, and walk around with a chick and then fuck her at 3AM. Then wake up, repeat the whole day. I lived like that for years, never really tired. My libido was through the roof - i used to get up in the middle of the night because i couldnt breathe deep enough because of how much i wanted to brutally rape any average looking chick. I tought it was tren.
So then i started all this strength stuff, 531 and i also decided to see how much muscle i can pack on if i start to force feed.
The Covid hit so all the fight stuff was dead. I also had trouble eating so i stopped all cardio to preserve calories. In a year or so, what happened was that not only was i always tired. My libido was shit also. I did gym session and i was DONE. I was ready to end the day even if it was 10AM. I was still on tren but no libido, no agression, no energy at all. Also i got higher BP.
Then i started doing only some super high intensity cardio and all i got was headaches and got even more tired.
So the key here is - to start gradually. I suggest mixing HIT with LISS.
Maybe at first do like 20-30mins of walking incline at around 122-125BPM… Then introduce some burpees and bodyweight interval stuff - @ChongLordUno has great stuff for this. Do like 5-10mins every day of whatever he is doing, and add the 20mins of LISS. When doing higher intensity try to push at 135-140BPM, then walk 20mins at 125BPM.
You goal would be to up the intensity and time over long periods of time. In 2 months, my libido is back from 0-1 time a day to 2-3, sometimes even 4.
I also sleep much better and dont feel tired almost never.
But yes, the first month is horrible - you feel like garbage, even more tired.
My theory is that it has to do with total work capacity. Gym doesnt spend much energy but when its all you do, you whole work capacity is this 150kcal work of energy. Now when you take a rest day, you save the 150kcals and thats your “rest” that you get. Its nothing, basically so even taking deloads doesnt do shit. You are still tired.
Now when you add and add and add the cardio, you add 200-300-500-1000kcals of extra work a day and it becomes your new normal.
Now when you take a day off you get 150kcal from the gym and 1000kcal from the cardio you skipped. Now that is 10 times the recovery ability and energy you saved that goes towards you feeling fresh and having huge libido.
Now when i compare my starting abilities with @ChongLordUno - it took me like 20mins for what he does in like 5. Now imagine him doing 60mins worth of work daily and then taking a day off. He saves, recovers and rests 12 TIMES the energy i would at that times. That whole energy goes to feeling good and wanting to fuck that energy out of yourself.
The problem with this is that if a gym session is your maximum work capacity, it will take month or two for a person not to feel even worse than he is used to. But it is worth it.
Some weeks ago i noticed that i was going down the street at night, swinging my arms like punches. Like i did 3 years ago when i felt good every time. For years i wasnt doing it because i always felt like shit trying to conserve every gram of energy i had. Now it just bursts out of me, and i dont even control it.
I am still LOOOONG way from being where i was and where i want to be.
But my theory is that you need to build up work capacity, which then in rest days turns into a monstrous saved energy that goes towards feeling good.
Im like 2-3 months in doing some HIT and some LISS every day, and my libido is more than twice as high. I sleep at least 1-2 hours more than before. I am never tired in the evening, besides muscle soreness that feels good. And my BP is down from average 140/70 to average 130/60 (i am on 1,5grams of gear).
I still take same gear. I still do same lifting. I still eat for mass same shit foods. The ONLY thing that has changed is that i force myself to do cardio every day… 20-45mins every day. If i feel a bit more tired from lifting i will do 30-45mins of 125-130BPM cardio. If i feel a bit more fresh, i will do like 10-20mins of bodyweight circuits of 140BPM+ and finish with 20mins of 125BPM.
I used to take a full rest day once a week. Now i take one maybe once every 2 weeks, but i would prefer doing 30mins of 122BPM incline walk and some stretch instead because - if these 30min walks used to be a pain in the ass when i started the cardio, now i dont even feel them, i can walk or watch stuff on youtube while breezing through em.
I also have the chest strap to know correct HR and i keep a log on everything i do, and the maximum and avg heart rates so i can slowly progress.
