TLDR
I did an experiment based on some new data I discovered about tendons. My 8-year knee tendinitis is gone as of 2014. It had to do with exercising more frequently. I got a lot stronger in just 3 weeks. After 6 weeks, I hit my then all-time squat max of 365 for an easy single rep.
Training Efficiently
In my own life experience, perhaps the safest and least time-consuming way to pursue total body fitness is to train with somewhere between 6 and 12 exercises and train with perfect form, taking each exercise to a state of complete positive muscular failure, briefly resting and then moving to the next exercise. Your muscles are getting an intense workout, your hardest reps happen when the muscles are producing the least force (because they are tired) and none of the movements are "explosive" thus accelerating the weight to very high velocities and risking injury. During workouts of this nature, your heart feels like it might explode out of your chest, you breath very hard, and your veins pump lava or pieces of broken glass. The problem with training this way, at least for me, is psychological. Every workout must be all out if you wish to make steady progress. Other problems are related to trying to plan for enough rest and when you train this way the metabolic demands are high. Research shows that muscle protein adaptations last for up to 21 days after the most recent bout of training. Energy system adaptations can begin to regress within 4-7 days. I wish I could remember where I found that data, but I remember everything but the name of the study and it's authors...which means nothing. Nevertheless, training like every workout is a zero-sum game can be psychologically defeating. Also, the training is seldom enough that other types of adaptations apparently cannot happen (more on that later, as it is the point of the article).