Exercise helps to prevent disease and prolong life. The Copenhagen City Heart Study found that those who exercised 2.6 to 4.5 hours per week were 40 percent less likely to die over the next 25 years than the less active people (Mayo Clinic Proceedings, August 17, 2021). Participants were 8697 healthy adults who recorded their time in leisure-time sports activities such as tennis, cycling, swimming, jogging, calisthenics, health club activities and weightlifting. Surprisingly, those who worked out more than 10 hours per week lost some of that advantage, but were still better off than the less active people. Another recent study following 2110 people for almost 11 years found similar results (JAMA Netw Open, 2021;4(9):e2124516). Those taking at least 7000 steps per day had a 50 to 70 percent lower death rate than the more sedentary group, but taking over 10,000 steps per day did not increase that advantage.
I think that both of these studies do not give you the whole picture because they did nothing to measure the level of fitness achieved by the exercisers; they looked only at hours spent exercising or number of steps. A huge study from the Cleveland Clinic that used treadmill stress tests to classify fitness levels found that the more fit a person was, the less likely they were to die (JAMA Network Open, Oct 19, 2018;1(6):e183605). This study followed more than 120,000 patients for up to 27 years, and there was no limit to the increase in benefits from improving fitness. The elite athletes (top quartile) had an 80 percent reduction in risk for death during the study period, compared to the group with the lowest fitness level (bottom quartile). See You Can’t Be Too Fit
More Is Not Always Better
There may be an upper limit to the amount of exercise people need to help retain their health. A study from the Karolinska Institute showed that people who tried to do intense workouts on an almost daily basis developed damage to their mitochondria (Cell Metab, Mar 13, 2021;S1550-4131(21):00102-9). The Million Women Study found that women who tried to exercise strenuously every day were at increased risk of blood clots, strokes and heart disease (Circulation, Feb 16, 2015;131:721–729). Some people are at increased risk for heart attacks because of lifestyle factors such as a pro-inflammatory diet or genetics, and intense exercise or inadequate recovery from a previous exercise session could dislodge their unstable arterial plaques to cause a heart attack.
Most athletes know that they should not train intensely every day; they take a harder workout on one day, feel sore on the next day, and then go at a slower pace until their muscles feel fresh again. If you do not have heart problems, you probably should do the same. Compared to exercising at the same leisurely pace every day, you become more fit by taking a workout of slightly increased intensity on one day, feeling muscle soreness on the next day, and then going at a reduced pace for as many days as it takes for your muscles to recover. See Recovery: the Key to Improvement in Your Sport
Why Non-Athletes Should Exercise Every Day
Forty percent of North Americans die of heart attacks. One of the common causes of the arterial damage that precedes heart attacks is a high rise in blood sugar after meals. Blood sugar always rises after meals and because of faulty lifestyle habits, most North Americans have blood sugars that rise too high. Resting muscles remove no sugar from the bloodstream, but contracting muscles remove sugar rapidly from the bloodstream and can do so without even needing insulin. This effect is strongest during exercise and diminishes to no benefit about 17 hours after you stop exercising. If you want to use exercise to help control blood sugar, you should try to do it every day.
If you are just starting out, spend at least six weeks at a slow pace until you are comfortable in your activity. Then you are ready to alternate more intense days with easier workouts.
I think that every healthy person should try to exercise every day. You will gain a much higher level of fitness by “stressing and recovering, ” where you exercise more intensely on one day, feel sore on the next and go slowly until the soreness is gone, then try to pick up the pace again.
Caution: Intense exercise can cause a heart attack in susceptible people. Check with your doctor before you start a new exercise program or increase the intensity of your current program. Stop any workout immediately if you feel unusual discomfort or pain. If you feel chest pain, excessive shortness of breath or any other severe symptom, call 911 or if the pain subsides in a few minutes, check with your doctor before you work out again.