Anatomy of a Figure Skating Injury Book

Has anyone read this book, Anatomy of a Figure Skating Injury ? I had a question on this segment of the book:

"Achilles tendonitis also may occur when practicing off-ice exercises, such as box jumping, jumping rope, and jumps. In rare cases, it may result from improper use of off-ice conditioning equipment."

"Coaches and athletes both need to be carful not to overload too much off-ice jump training on top of increased jumping on ice. For example, avoid adding jumping rope and box jumping off-ice while skaters are already sore from jumping on ice."

Would you say it's bad to do a lot of off ice training? I know a lot of skaters do jumps off ice and would think it'd actually be safer to practice the jumps off ice as a warm up or jump rope. What would be a good amount of time to spend off ice training or would you not do it all?

I think it a lot depends on the skater.

For my 9-year old (pre-juv), I was recently told that she needs to "warm up" at least 5 minutes with off-ice jumps before her lesson. That is in addition to her 1-hour a week off-ice workout with her off-ice trainer.