The training principles that improve performance in competitive athletes can be used by all exercisers, even those who have never exercised previously, and can help to prevent heart attacks and prolong lives.

Exercise helps to prevent heart attacks because exercise makes muscles stronger, including your heart muscle. All people lose heart muscle as they age, which increases risk for frailty and heart failure. Strengthening your heart muscle helps you to live a more vigorous lifestyle and to protect you from heart failure. Intense exercise also helps to stabilize plaques in arteries and widens heart arteries to help protect you from a heart attack.
• Regular exercise and a Mediterranean-style diet, individually and combined, are associated with reduced risk for heart attacks and strokes (Eur J of Prev, June 26, 2018).
• An extensive review of major studies showed that exercise helps to prevent heart attacks and strokes (J of Clinical and Preventive Cardiology, 2017;6(3):109-114).
• The amount of time teenagers spend exercising intensely predicts markers of arteriosclerosis and inflammation far more than the amount of time they spend sitting (PLoS Medicine, Sept 2018;15(9):e1002649).
• Even low intensity exercise, such as slow walking, is associated with reduced likelihood for heart attacks and strokes (Am J Lifestyle Med, Jul 1, 2009;3(1 Suppl):44S-49S).

The SUN Study on 18,737 middle-aged people showed that those who exercise intensely have half the rate of heart attacks as those who do the same amount of exercise less intensely (Am J of Cardiology, Sept 11, 2018). Vigorous exercise is associated with a much lower rate of pre-diabetes and diabetes than low-intensity exercise (American J of Prev Med, April 2017;52(4):e95-e101).

How to Make Muscles Stronger
Muscles are made up of thousands of individual fibers just like a rope is made of many fibers. Each fiber is a series of blocks called sarcomeres lined up end to end. Each sarcomere is attached to the one next to it at the “Z line.” Muscle fibers do not contract equally along their lengths; they contract only at each “Z line.” If you want to make a muscle stronger, you have to exercise it hard enough to damage the muscle fibers at the “Z lines” and when they heal, they will be stronger than they were. You can tell you are causing muscle damage because of soreness in that muscle you feel four to eight hours later (Strength & Conditioning Journal, October 2013;35(5):16-21). This is called Delayed Onset Muscle Soreness (DOMS).

When a muscle is damaged, your immune system repairs the damaged tissue with the same cells and chemicals that are used to kill germs when you have an infection. This causes inflammation, characterized by soreness (pain), increased blood flow to the injured fibers (redness), and increased flow of fluid into the damaged area (swelling). The immune cells release tissue growth factors that heal the damaged muscle fibers. The healed muscle fibers become larger and increase in number by splitting to form new fibers. If you do not wait until the soreness goes away before exercising intensely again, the fibers can be torn, the muscles can weaken and you can become injured.

What to Do When You Have DOMS
You can take off when you have DOMS if you want to, but you will become stronger by taking easy workouts while your muscles are sore. Athletes do not usually plan to take off workouts during recovery, even though resting when the muscles feel sore will allow muscles to heal faster than exercising at a low intensity. If you exercise at low intensity during recovery, your muscles will become more fibrous and resistant to injury when you stress them in the next intense bout of exercise. If you are a runner, run faster two or three times a week and much more slowly when you feel soreness on the days after running fast. If you are a weightlifter, lift heavy weights once or twice a week and much lighter ones on the following day or days when your muscles feel sore. If you are a basketball player, scrimmage hard for several hours on one day, then run plays and practice shooting on the next days when your muscles feel sore. If you play golf, practice your long drives on one day and practice putting on the following days if your muscles feel sore.

Stress and Recover
Elite athletes do not exercise intensely every day. If they did, they would not be able to train because of injuries. To become stronger and faster and have greater endurance, you need to exercise on one day intensely enough to damage your muscle fibers and feel short of breath. Then you exercise at a reduced intensity for as many days as it takes for your muscles to heal and the soreness to disappear. Only then should you take your next intense workout.
• You can usually tell that you are exercising intensely enough when you feel the beginning of burning in your muscles.
• You will not improve your maximal ability to take in and use oxygen unless you exercise hard enough to become short of breath.

Before you start a program with more intense training to improve your endurance, you should have exercised regularly for many months, be in good shape and not have any health conditions that can harm you. CAUTION: Intense exercise can cause heart attacks in people who have narrowed coronary arteries. Check with your doctor before you start a new exercise program or make a dramatic change in your level of intensity.

When you are ready to start your new program, warm up by jogging, cycling or doing your chosen activity at a very slow pace for 10 to 15 minutes. If your muscles do not feel fresh by then, take the day off. If your muscles feel good after your warmup, you are ready to try a more intense interval workout. If you are walking, jogging, or cycling, pick up the pace for 5 to 10 strides or pedal strokes and then slow down. When your leg muscles feel fresh again, pick up the pace again for 5 to 10 steps or pedal strokes. Never time your recoveries and never start your next interval until your muscles feel fresh again. When your legs start to feel heavy or tight, stop the workout for that day. On the next day, plan to go at a very slow pace and stop your workout when your legs feel heavy or you feel any muscle discomfort. Remember, recovery days are for recovery. When your legs feel fresh again, do your next interval workout.

Training Program Example
Sunday — Rest day
Monday — Hard interval day
Tuesday — Easy recovery day
Wednesday — Easy recovery
Thursday — Hard interval day
Friday — Easy recovery day
Saturday — Easy recovery day

As you become stronger, you can extend your intervals up to 30 seconds each. Non-competitive exercisers do not need to do longer intervals. For most people, an interval day can include about 20 repeats of 10 to 30 seconds each, followed by adequate recovery after each interval (as long as it takes until your muscles feel fresh and your breathing has returned to normal). If you do this twice a week, you will become far more fit than if you jog or cycle at the same slow pace for many hours.

I do not recommend taking NSAIDs to relieve muscle soreness; they can interfere with your strength gains. If you feel pain in one spot that does not go away after you slow down, stop that workout immediately. Otherwise you are headed for an injury.
Principles of Training