The 6 pack is the Holy Grail sought by countless exercisers. Very few ever achieve it. An entire cottage industry within the fitness industry is dedicated to it, spawning many scams and myths. The myth of spot reduction is one of the most pervasive of these myths. Very often, it seems trying to achieve a 6 pack is more of a vanity project than something done to improve athletic performance; once the core is strong enough(even if the 6 pack is not visible), any additional strength is superfluous or may even weigh you down if you’re a runner.
The truth of the matter is that the abs don’t need to be exercised all that much to improve core strength. In fact, the core is strengthened even when doing resistance exercises that do not target the abdominal muscles. That said, it can still be helpful to include some ab exercises in your fitness routine to build core strength, especially if you sit a lot or have poor posture. Don’t forget to exercise the hips too.
According to research sponsored by the American Council on Exercise, the best ab exercise is the bicycle maneuver. This exercise requires no special equipment and is relatively easy to do. Many other exercises on the best ab exercise list do require equipment, but they are not as beneficial as the bicycle maneuver. So if you want killer abs so people will worship you on the beach, there is no need to waste money on ab devices(some of which are scams).
The bicycle maneuver is a type of crunch or semi-crunch. Ordinarily, I do not advocate crunches or sit-ups since I believe they are bad for the back. However, this maneuver requires very little forward movement of the upper body, so it appears to be safe for the back.
As far as joggling is concerned, it definitely requires a little more core and upper body strength than regular running. It is possible that joggling may help build more core strength than regular running, especially if you joggle with heavy balls(hopefully far away from other people). Also, juggling or joggling with heavy balls may be better for losing weight than juggling with very light balls.
I am not saying joggling will give you killer 6 pack abs, only that it may be better than just running if you want to improve core strength and stability. And it’s more fun!