Originally Posted by
Kansan
I don't have Rip's vast coaching experience but I believe it would be unlikely for a Medrol Dosepak to have significant effects on training. The first day is essentially a burst of cortisol to treat the inflammation which is causing the problem, followed by a taper to minimize the disruption to your endogenous cortisol production.
40mg per day for 10 days is more concerning. Still not a long term, chronic dosage but it is likely enough to disrupt the adrenal axis. However, breathing is important.
I do not know how stressful your training sessions are but cortisol is released in response to stressful situations (physiological stress) and if your adrenal axis is inhibited by the exogenous prednisone you may not be able to respond to the stress appropriately and have an adrenal crisis, which can be an emergency.
Personally I think that is unlikely from training, but it is a risk and you should be aware of it. It would likely be wise to lighten your weights while on prednisone, and probably for a week or two after it is finished.
The long term catabolic effects of corticosteroids are real and cause significant damage throughout the body but are usually restricted to the people who are on daily prednisone for years (in the past it was asthma, now mostly RA or other autoimmune diseases), but I am sure there instances where people on short term steroids suffered injuries which may or may not have been a result of the medication.