Most regular exercisers have heard comments from less enthused folks that our knees won’t make it or that we are going to wear out our bodies in some fashion. Usually the people who say this don’t get much exercise but is there some truth to what they say? Can we do too much exercise?

I ran 42 miles on the final day of running across North Carolina and pedaled back-to-back century rides (over 100 miles) on my bike trips several times. Those distances pale when the real athletes who train for exceptional distances run over 100 miles and bike over 250 miles a day in competition. This type of competition requires simulating the effort for many hours in training.

We all know that exercise is good for our health and fitness, and it’s tempting to assume that more is automatically better. But as with so many other good things in life, there comes a point of diminishing returns, and it’s possible to overdo it.

Exactly what constitutes too much physical activity depends on our individual abilities and goals. It is generally accepted that 2.5 to 3 hours a week of moderate exercise gets you the benefits that I talk about each week, such as cardiovascular health, less chance of diabetes and other health risks, along with mental clarity, focus and a sense of well-being. Going past that amount is for purpose and performance and the process gets more complicated.

“When you’re exercising for performance — whether it’s to get stronger in the gym, run a marathon or improve your tennis game — it’s possible to stress your body beyond what it can bounce back from,” said Kristen Dieffenbach, an exercise scientist and director of the Center for Applied Coaching and Sport Sciences at West Virginia University. She says the purpose of training is to induce a so-called training response. We work out, and our body responds by getting fitter, stronger and faster. These improvements don’t happen during the workout itself but occur during the recovery period. That’s when your body repairs the damage brought on by hard exercise, like micro tears in your muscle fibers, and makes adaptations, like increasing the energy-producing mitochondria in your cells.

“As long as your body is able to keep up with this repair work, your workouts will continue to aid your performance,” Dr. Dieffenbach said. But when the stress from your workouts builds up beyond your capacity to recover, you have entered the zone of too much, known in the endurance world as overtraining.

“What makes things tricky is that the line between training hard and overtraining is fuzzy. There’s no formula or number that can tell you what’s too much,” Dr. Dieffenbach said. Instead, what matters is how your body responds to the exercise you’re doing. Dr. Dieffenbach suggested thinking of exercise and the physical and emotional resources it requires as calling upon money in a bank. You have only so much in your budget, and if you try to overspend, you’re going to end up worn down or injured.

During my competitive years, I sometimes had a lingering tiredness, and all workouts became hard for days or even a week at a time. Along with that came trouble sleeping, a higher resting pulse rate and a lingering cold. The body is miraculous but if exercise has to be forced and doesn’t enrich your life, then as hard as it is to admit, it might be time for a break. Experiment with lower intensity workouts, a few days off and cross training. Some extra sleep and time away from the training watch both could help.

Our local Halloween double is just ahead on Oct. 29 and 30 with the St. Matthews and Spooky Sprint 5Ks. Look for these and a busy November schedule as well at www.salisburyrowanrunners.org.