Put it this way..out of everyone I see for injuries, jogging is waaay up there beyond any other population.

Many reasons which i'll gloss over, too late for rants..basically any biomechanical faults blow up joints/tissues due to repetition. Muscle imbalances develop (tension/weaknesses), posture degrades..and that isn't even going into any of the metabolic reasons why it sucks for fat loss and arguably health and longevity.

Crunches...ah the number 2 reason after sitting behind desks for 8 hours a day for destroying lower backs. 'Core' muscles are designed for stabilising, not flexing. Repetitive Lower back flexion is not something you want to put your lumbar spine through. Plus crunches won't make a lasting difference to getting your belly fat off or abs on show...and that's assuming you will even recruit your rec ab as prime movers..most people just use their hip flexors and wonder why their backs hurt.

Moderate your carbs, walk and get to a field to sprint train 3 times a week. Get lean in a matter of months and laugh at the thousands of joggers busting their balls and not making any changes.

Then thanks me