In summary, if you're only interested in a basic understanding of HIT methodology and where much of it originated I would suggest starting with a far less technical book. I suggest starting with the last published edition of Ellington Darden's "The Nautilus Book" and perhaps "Total Fitness: The Nautilus Way". If you like what you read and want to dig a little deeper into the evolution of HIT read Darden's more recent book, "The New High Intensity Training: The Best Muscle-Building System You've Never Tried". If the gears in your head are in high gear after that and you really want to get DEEP into what evolved from the original Nautilus protocol _then_ you go for "Superslow" or preferably "The Renaissance of Exercise: A Vitruvian Adventure Volume 1". When your grasp of all the aforementioned material is truly solid then move on to Doug McGuff's writing. McGuff's ideas do not surpass or supplant Hutchins' but rather sharpen the points with brilliant thoughts and clinical observations from a medical physician's perspective. Doug McGuff, MD published his "Ultimate Exercise: Bulletin #1" in the late 90's and later updated that with "Body by Science: A Research Based Program to Get the Results You Want in 12 Minutes a Week", both of which are hugely valuable contributions to the literature on HIT methodology and philosophy. His article about "Stoicism in Training" is critical reading.
* Exercise isn't supposed to be fun or enjoyable (that's what recreation is for). Exercise is a means-to-an-end. It shouldn't be something you look forward to, nor should you dread doing it; it should just be part of your lifestyle... like eating or sleeping. If you DO look forward to it, and even crave it, you could be hooked on the endorphin rush you get from doing an activity that is considered by the body to be over-doing it. And since the body would rather you not do this, it would be prudent to respect the body's wishes.

If your immune system is constantly fighting both its internal and external environment, it can be more challenging to live, work and exercise with the greater cognitive dysfunction, headaches, allergies, tender lymph nodes and both joint and muscle pain.  Yes, I do get it. However, I want you to be successful. Living myself with M.E, and lyme co-infections, the right approach is essential to making exercise work for us, not against us. 
14.  If you don't feel like working out, don't! Listen to your body. Just because it's your "scheduled day" doesn't mean you must work out. If your body is taking a little longer to recover than usual, so be it. It won't hurt you to lay off for an additional day or two; you will not lose anything you've gained. If your body isn't ready, it's better to skip days than to work out anyway. Every seven days is only a target (some people have found every eight or nine days reap the same benefits).
Gentle stretching and progressive loading of the Achilles' tendon is necessary to successfully treat Achilles tendinopathy.  Some studies indicate that eccentric loading of the tendon is favorable to other types of exercise.  The Alfredson protocol is a method that is used to progressively load your injured Achilles' tendon to treat the tendinopathy.
5.  Even when you can't complete another repetition, keep trying to complete this "impossible rep". Even though you aren't moving, metabolic work is being done, and a more thorough "inroad" to muscular failure is accomplished. "Pushing to failure" signals the body to upgrade its capabilities ("adaptive response")... something it will not do unless given a good reason to.

Inappropriate exercise can do more harm than good, with the definition of “inappropriate” varying according to the individual. For many activities, especially running and cycling, there are significant injuries that occur with poorly regimented exercise schedules. Injuries from accidents also remain a major concern,[85] whereas the effects of increased exposure to air pollution seem only a minor concern.[86][87]
Dietary nitrate supplementation increases circulating nitrite concentration, and the subsequent reduction of nitrite to nitric oxide is promoted in hypoxic environments. Given that PO2 is lower in Type II compared with Type I muscle, this article examines the hypothesis that the ergogenicity of nitrate supplementation is linked to specific effects on vascular, metabolic, and contractile function in Type II muscle.
An evidence-based journal club of 9 faculty members and fellows reviewed the articles and extracted and tabulated the data. Individual outcomes for pain, range of motion (ROM), strength, and function were organized. Intragroup and between-groups outcomes were assessed for the effectiveness of treatment, and statistical outcomes were recorded when available. Clinical importance was determined when statistical value was P < .05 and the effect size or difference between treatments was 20% or more. Sixa major categories were created to organize the components of the physical therapy programs used in each study: ROM, flexibility and stretching, strengthening techniques, therapist-driven manual therapy, modalities, and schedule. Components from these categories were used to create a synthesized physical therapy program.
Thus, little is known about the effects of monitored vigorous exercise in elderly people. While significant benefits for basic motor tasks (such as balance and gait) can be achieved through different kinds of physical activity (i.e., stretching exercises, treadmill, Pilates, and strength and balance training), no conclusive relationship has been proven between its intensity and such improvements. Recently, Pau et al. [14] reported that spatiotemporal gait parameters and sit-to-stand performance significantly improve through vigorous (but not light) exercises, thus suggesting that higher levels of intensity might be more suitable in generally improving static and dynamic daily motor tasks.