Resist the urge to start where you left off in your 20s. Any exercise program for your age should include cardio at least five days a week, but start at a moderate pace, walking briskly on a treadmill or pedaling an elliptical or stationary bike at a moderate pace at which you can talk easily but singing would be difficult. If you've been seriously inactive, start with as little as 10 minutes per session, building to at least 30 minutes for health maintenance and one hour to lose weight.
If you plan on hitting the gym on all of those five days, you'll have to do an upper- and lower-body split so you don't work the same muscles two days in a row; the exception to this is abs. Start with machine work until you learn proper form. On days one and three, do two sets of eight to 12 repetitions on the shoulder and chest press machines. Next, hit the seated row, doing two sets with your elbows tucked in for your lats and two with your elbows out, squeezing your shoulder blades, for your back deltoids. Follow it with biceps curls and triceps extensions. On days two and four, do two sets of leg presses, followed by hip abductions and adductions for your inner and outer thighs. Finish each day with ab work, and then devote day five entirely to abs and balance exercises.
If you'd rather hit the gym only three days per week, take a brisk walk on your off days or go up and down your stairs for at least 20 minutes on bad weather days. Do all the exercises you did on your split days when you go to the gym, doing some ab and balance exercises at home on your off days. Again, be sure not to work any muscles but your abs on consecutive days.
Abs, Core and Balance
Middle-aged men who don't exercise often develop large bellies -- a sign of dangerous visceral fat. While your cardio work and diet are what will burn that fat, abs and core work will build muscle to improve posture and avoid back strain. Lie on your back with knees bent and feet flat on the floor for crunches and twist crunches. Make sure to exhale and pull your navel toward your spine on the exertion. Next do some front, side and back planks. Hold each as long as you can, building to one minute. On ab-only days, add in balance work, standing on an inflatable dome and raising your extended arms from in front of your thighs to chest level and down again while holding a light weight. If you have trouble balancing to start, lift only one arm, using your other hand to lightly support yourself against a wall.
You may have heard of high-intensity interval training, cardio training where you alternate intervals of low intensity with very high intensity, that is, as much as 95 percent of your maximum heart rate for about four seconds at a time. As noted by IDEA Health and Fitness Association, this type of training appears to increase aerobic fitness more and faster than endurance training, or doing moderate cardio for longer periods of time. While this training has been incorporated into some cardiac rehab programs, according to IDEA, if you haven't trained in years, or ever, you should still start slowly. You might want to check with your physician before trying HIIT cardio workouts.