This workout should be performed on Tuesday and Thursday. Unlike the others, this routine is specifically focused on enhancing your cardiovascular engine and improving your shoulder complex strength. Cardiovascular efficiency is obvious to focus on. But the reason you also want a strong shoulder complex, is to allow you to keep a more upright posture as you're caring a heavy backpack. If you don't keep this upright posture, your lungs will be compressed and your cardiovascular system will be compromised.
Eugene Trufkin @ TrufkinAthletics.com