Question
Hi,
25 years ago I had a successful L5/S1 disk removal.  I say successful because I have experienced many years of active life since then.  This includes light weight lifting, tennis, etc.  Now 67, I also walk maybe 20-30 miles a week and still do some machines and dumbbells at the gym a couple of times a week.  

My question concerns abdominal exercises that will tighten and define my six pack (along with my losing weight) yet which won't damage my back.  I understand that some of these exercises such as sit-ups are bad.  Every exercise seems to involve both the abdominal muscles and the lower back though.  I was thinking about the one where you hang from a bar and just left your knees up to your chest.  Also there is a machine where you kneel and swing back and forth while holding onto handles.  However, this one does mean my back will experience hundreds of reps, so I'm questioning that.  So you see my questions by now.  Please comment on what I'm doing and offer any other exercise better targeting my abdominals without risking back issues.  Thanks.

Answer
Art,

Tightening the abs as you describe may be fashionable, but it is unhealthy.

Tight abs make one into a "chest breather".

A study in Denmark of patients in a hospital cardiac ward found that every one of them was a chest breather.

Chest breathing is inefficient breathing, leads to accelerated heart rate, decreased gas exchange in breathing, and activation of the adrenal glands.

No healthy animal is a chest breather; only an animal being stalked or under attack "chest breathes".

I don't advise it and I teach my clients to breathe a healthy breathing pattern.

http://somatics.com/breathng.htm