Are we talking about increasing the volume of high intensity type work or recoveroy type workouts.
It’s been said that recovery type workouts are more about quantity whereas high intensity type workouts are about the quality.
I would like to get Charlie´s input into this. But I will throw my two cents in. IMO intensity is the most important factor in training for max speed and max strength, but volume cannot be overlooked.
For Westside thoughts on volume, go to the elite fitness site and look at the Westside article by Jim Wendler - Beginner´s Mistakes Part I and also the Louie Simmons article - The Importance of Volume.
I can´t remember where Charlie described one of Ben´s sprint workouts - in CFTS or in Speedtrap, but it would be too much for many sprinters. High quality and high volume. Pretty wild stuff. But he had a great foundation.
I think this is one area (how much?) where coaching and training get into a gray area - science or art.
A coach of mine used to quote Charlie (or at least he said it was from Charlie) `2 mistakes a coach can make are to train too little or too much - and too little is the better option´. - Paraphrased.
Louies guys try to consistently raise volume. They use a variety of means to do this (Weighted GPP, Weights, etc).
The extra workouts tend to be lower intensity than their four main workouts. I would think of their extra sessions being kind of like tempo running. Low intensity work to raise GPP/Fitness levels. It’s always said that beginners to the WSB system use too much volume/GPP work. So they don’t just jump into 14 workouts a week. You start at the four main ones, and slowly, as GPP increases, add extra work into the program.
Finally, some of thw WSB lifters are fat. Recently though I’ve noticed a slimming trend. For example George Halbert(sp?) benched 683@198 and 733@215 With numbers at such a small bw you have to assume he is all muscle. Also in the special strengths video Chuck V Does many squat workouts and he looks very lean too. you can even see louie’s abs/six pack in one segment (that suprised me).
Bear in mind, we are talking about two different sports.
Powerlifting/weightlifting versus sprinting.
This is an issue I am trying to figure out at the moment. How do you know what volume level to use at a given stage of your training?
David W, have you had success with such tests mentioned in the original post?
How can you tell if you are doing too much, before incurring an injury? Do you look for the CNS overtraining signs, is that a reliable/valid predictor? Different signs for muscles&tendons/nervous systems?
How about the recommendations at the top of Louie Simmons’ article for lifters (link below)?
Autoregulatory systems I guess 
You have your max effort or speed work days. If you cannot fully recover for those you need to reduce your volume. It’s that simple. Also, as you get faster their is a greater risk of injury in training and an injury that takes 10 days out of your training schedule will impact your running more than not running a few extra 80m sprints. How do you know if you can add more volume? If you’re making progress and staying healthy.
I’m thinking of those injuries that come apparently out of nowhere. You can go along for weeks thinking you are not overtraining, then one day, bang - tendon pain/muscle tear.
I am thinking you can feel you have recovered from a session, but in reality there is not 100% recovery, but you can’t tell the difference. If you can just tell by if you feel recovered, then why do people get overuse injuries (especially elite ones, as they should know best of all)?
Ideally there is some way of predicting how much an athlete can handle? Some of it must be down to the judgment of the coach and athlete, but can you be helped by tests/signs, and to what extent? The AREG approach might be one way, but I’m not sure that training can be reduced down to a few numbers that apply to all athletes in all situations.