Depending upon your personal health and fitness, you may be wise to use a snowblower or have someone younger and stronger shovel the driveway until you are able to do so without risk. Be sure to check with your physician regarding your physical capacity for vigorous activity such as shoveling snow, raking leaves, hoeing the garden, and exercise.
However, even if you are in good shape, I strongly recommend shoveling small layers of snow at a time, rather than hoisting foot high loads on the end of your shovel. Three shoveling sessions may seem like a lot, but the overall effect is much better tolerated and far less likely to cause injury, because every shovel lift is relatively light and easy to perform. On the other hand, waiting until all of the snow has fallen makes every shovel lift a near maximum effort. Although the total time expenditure may be a little longer by clearing the driveway three times, it is time well spent from an exercise perspective, and time wisely spent from an injury prevention perspective. Your back, shoulders, arms, and legs will be most appreciative if you do three low effort work bouts rather than a single high effort session.
This same reasoning process may be applied to raking leaves. It's okay to do one section of your lawn a day, rather than feel compelled to eliminate every leaf on your property before putting the rake away. Working in sections is a much more sensible approach than doing it all and feeling it all for several days following your yard session.
Of course, this same philosophy is equally relevant to your exercise program. Research shows that three 10-minute walks on a given day are equivalent in fitness benefit to one 30-minute walk. In other words, it is fine to break your exercise program into manageable segments, rather than completing a comprehensive workout and feeling fatigued for several days following.
We like to encourage this exercise approach in our fitness center, even on the strength training equipment. For example, instead of doing two exercises for each muscle group during long and infrequent workouts, we recommend doing one exercise for each muscle group on Monday, a different exercise for each muscle group on Wednesday, and back to the first exercise protocol on Friday. This approach permits a consistent exercise program without overtraining and experiencing overuse injuries.
Another favorite for people over forty is interval training. Instead of maintaining a steady state of uninterrupted aerobic exercise for the entire workout, consider alternating between higher effort and lower effort periods throughout your exercise session. For example, if you really find your 40-minute runs too demanding to be enjoyable, consider the following interval training approaches.
Approach A: Harder Training Day
Run 6 minutes; jog/walk 2 minutes
Run 6 minutes; jog/walk 2 minutes
Run 6 minutes; jog/walk 2 minutes
Run 6 minutes; jog/walk 2 minutes
Run 6 minutes; jog/walk 2 minutes
Approach B: Easier Training Day
Run 4 minutes; jog/walk 4 minutes
Run 4 minutes; jog/walk 4 minutes
Run 4 minutes; jog/walk 4 minutes
Run 4 minutes; jog/walk 4 minutes
Run 4 minutes; jog/walk 4 minutes
Being compulsive may be acceptable if you are twenty, but a more relaxed approach to physical labor and exercise is definitely preferred for those of us over 40, at least for purposes of general conditioning. Competitive athletes must obviously put greater effort into their training programs. However, if your primary goals is physical fitness, you should be pleasantly surprised by how well your body responds to regular and reasonable exercise sessions.