I agree with a good deal of it but not all of it. I agree with the first part of the article concerning the physiology and dynamics of the various fiber types (although it’s quite simplified…..probably because the target audience is track coaches and not physiologists) as well as his suggestion to personalize training programs. I don’t however think the tests Karp desribed for determining fiber type are valid tests. As I’ve said before here, the only way I’m aware of accurately determining fiber type is through a muscle biopsy. This is not feasible in most cases and ultimately I don’t think it makes that much of a difference. For most coaches I think current performance indicators rather than physiology are the best indicators of how training should be tailored. Also, at most levels, especially in a team format, making truly customized training programs becomes a logistical nightmare and ultimately not worth it.