I had a period of severe, severe exercise intolerance. I took about two months off of all exercise when my BFS started because I noticed the more I used my muscles, the more they would twitch. So I decided to stop using them. This was beneficial, until it started backfiring. An inactive body eventually begins to degrade. I started having breathing issues, very tight breathing, difficulty getting deep breaths at times, muscle pain, aching, migrating stabbing aches in muscles, severe joint pain, tendon pain, sensory issues, numb limbs, etc... So I started back working out. I would do 1 rep of every muscle group, on very light weight (we used to joke that we used the pink dumbbells) ... and then walked for 5 minutes on the treadmill, at a speed of 3.0 and incline of 5.0 .... and I would then literally collapse on the couch for at least 45 minutes with (what felt like) black circles under my eyes. Just that utterly dead, drained feeling. I felt like an old man, and would feel the perkolating and popping and wriggling of my muscles in my legs, shoulders, arms, back afterwards. A couple hours after the workout, however, I would have a bodywide sensation of emotional, physical, and mental well-being. I felt utterly outstanding. I did not feel energetic. I just knew that something about getting my body moving, was rejuvinating me, and helping in the deepest, most important ways. 24 hours after the full body light workout, I would continue to go downhill energy-wise. My worst moment was always 24 hours after the workout. My twitching would increase up until this point, as my body was weak from the workout. After the 24 hour mark, the body begins to repair from the workout. At the 48 hour mark, I was always feeling much better. Twitching would decrease 50% at least. By the third day - this was always my best day. I was fully recovered from the granny workout, and my twitching would be at a minimum. Strangely however ... if I went 4, 5, 6, 8, 10 days without getting back to working out, things would worsen. My muscles would begin to tighten up again. My breathing and chest would feel labored. My sleep would become very very poor (waking up with agitation, overstimulation, shaking nerves),etc. I was tense, and generally degrading back to a bad state. So I had to keep a cycle of about once-every-four-day workouts. Always full body. Always including deep breathing, and minimal aerobics. And always with a solid 2-3 days of complete rest in between. The twitching would flow like a wave, increasing after the workout, then decreasing as my body rested and recovered. Each cycle, i noticed, I would improve more and more. As long as I did not push myself too far, and rested sufficiently in between, I began to see that I was improving. This is how I started to develop a cause-effect awareness with my BFS. I noticed that as I lacked cellular energy, my twitching would get worse. As my body recovered and was 'more strong again' my twitching would decrease. This lead me to a theory regarding cellular energy insufficiency - mitochondrial damage. I ran the gamut of theories from mitochondrial toxicities due to medications, environmental toxins, etc. Ultimately I began taking Ubiquinol 100mg, RLA, ALA, and PQQ for Mitochondrial / cellular energy support, and have been on it ever since, four days a week. I also began reading about adrenal insufficiency and HPA Axis dysfunction. I noticed that immediately after meals containing gluten or stimulants (breads, pastas, soy, glutamine, etc) my twitching would worsen. So I stoppe eating that stuff. Likewise... while on a full Paleo diet ... I noticed I would twitch more because of the low carbs. So i added a couple mashed potatoes per day. It was amazing. As hours would pass after a meal, twitching might begin to increase, as I would begin to "tire". But then I would have an energy supplying carb meal like chicken veggies and a big mashed potato (no skin) ... my twitching would instantly reduce. So again .. cause effect. If i tired myself out, I would get worse. If I rested and supplied sufficient cellular energy, I would improve. This theory was further verified when Dr. Rey from the Klimas Clinic (CFS Experts) did a full workup on my immune system. Instead of seeing what I was sure I would see (autoimmunity and overactive immune system), she said my immune system and hormone levels were utterly burned out. She said I must have at some point literally fried my system, and all kinds of resulting damage had ensued. This can happen from constant adrenaline, cortisone, testosterone, and immune system stressors on the body (bringing us back to adrenal insufficiency) as well as depletion of neurotransmitters like dopamine and serotonin (which are the most abundant in the gut). The steroid chemicals, stress levels, anxiety, and months of fear I had put myself through can directly damage the gut as well, which may explain why diet changes and gut healing regimen was so huge for eliminating my symptoms (along with anxiety and stress reduction). Its interesting how its all tied together, but I truly thank everyone here for the input they gave me when I was going through all this. My energy levels seemed to improve every time I did the cyclical iteration of very light exertion, then sufficient rest. The dietary changes were unbelievably huge for symptoms, senory issues, and cramping and pains ... and stress reduction was a foundational element to it all. Without each of those three things, the other two probably wouldn't have mattered. I cant stress this enough: The type of exercise that helped me was very careful, methodical, and only to the point of "relieving tension" all over my body. I would not go past that, or I would live to regret it.As a side note, there's several guys here who have low testosterone as a result of this. I am one of them. I dropped from an average of 700 before BFS to an average of 230. That is the Testosterone level of an 85 year old man. There's a guy on here who opted to go on testosterone replacement therapy and has told me that his debilitating flu-like fatigue immediately disappeared and hasn't returned. He is also on neurotransmitter support (dopamine, serotonin, etc catalysts). Things like 5HTP, and is seeing great results. This allllllllllllllllllllll fits in with adrenal fatigue and damage to nerves, muscles, the gut, electrolyte muscle firing action potential somethingoranothers, myelin damage, testosterone levels, cortisol levels, inflammatory immune markers, etc. Its all part of the same system. Hope this helps some.-BFSB-