What Happens During An Intense Exercise?

man lifting weights

When you are performing intense exercises or sports, you tend to move through metabolic pathways. Initially as you begin to exercise, ATP is produced via anaerobic metabolism. With increased breathing and heart rate, there is more oxygen available and aerobic metabolism begins. This continues until the lactate threshold is reached. In case this level is surpassed, the body is not able to provide oxygen fast enough to generate ATP, then once again anaerobic metabolism restarts. The anaerobic system is short-lived and the lactic acid levels rise, thus the intensity cannot be sustained. In that case, you may need to decrease the exercise intensity to remove lactic acid build-up.

Muscle Fatigue

Your muscles can tire especially if you are exercising at a high intensity for long. It ability of your muscles to do work is proportional to the availability of energy to fuel muscle contractions. Muscles use adenosine triphosphate (ATP) as an energy source.

During intense exercises such as the lifting heavy weights, your body muscles rely on anaerobic metabolism, which provides instant ATP energy but they are of limited storage and need to be refilled once used. This causes the muscles to tire soon. On the other hand, aerobic metabolism can produce energy over hours.

Delayed Onset Muscle Soreness (DOMS)

DOMS refers to muscle pain, muscle soreness or muscle stiffness that is felt 8-48 hours after exercise, particularly at the start of a new exercise programme, following a sudden increase in duration or intensity of an exercise or a change in sporting activity is described as Delayed Onset Muscle Soreness (DOMS). This pain is a normal response to exertion and is a part of an adaptation process, which can then lead to and increased stamina and strength as the muscles recover and build. The pain, however, is not the same as fatigue or muscle pain that you experience during exercise.

An acute muscle injury, sprain or ligament tear causes an abrupt, sudden pain that results in swelling or bruising. DOMS on the other hand is worse within the first two days and subsides over the next few days as you continue to exercise. You can get put off by DOMS and many of you may give up exercising because of DOMS.

The cause of DOMS is generally microscopic tearing of muscle fibres. And the tearing and soreness depends upon how much and how long you exercise and what type of exercise you perform. Any movement that you are not used to can cause DOMS. Earlier studies recommended gentle stretching to reduce DOMS. But the recent reports have found that stretching may not really be useful to avoid DOMS.

Steps to deal with soreness or DOMS after exercise:

• Soreness would disappear in 3-7 days as you adapt to your exercise programme
• An ice bath may help reduce muscle soreness
• Perform easy low-impact aerobic exercises to increase the blood flow
• Use the RICE method for treating injuries—Rest, Ice, Compression and Elevation
• Gentle massage may reduce DOMS
• Warm-up before you exercise and cool down with gently stretching
• Yoga may reduce DOMS
• Non-steroidal anti-inflammatory medication for instance aspirin or ibuprofen helps reduce pain and soreness
• If the pain persists for more than 7 days, consult a doctor

Things to be kept in mind

Three things you need to keep in mind, whether you are exercising in order to become fitter, or improve or maintain your health. These include frequency, intensity and duration.


Experts recommend being physically active for at least five days. In fact, if you want to keep in shape, you need to be active for all seven days.

woman exercise gym


Exercise intensity can be described as strenuous, moderate or mild and all these depend upon your current state of health and fitness. The intensity can be measured through gas analysis, looking at how much oxygen the exerciser is taking into the body and delivering to the working muscles. In the gym it can be measured using a heart rate monitor, which records the heart rate at different workloads. It can also be estimated using the Borg Scale, which asks the exerciser how hard they perceive they are working. You can also gauge the intensity by the pace at which you are exercising and you are able to hold a conversation at the same time!


How much time should you spend being physically active in one session? According to the research conducted over the past 20 years and guidelines from a range of expert bodies, you need to be active for 30 minutes, five days a week for health benefits. That’s only 1.5 per cent of the total time in one week. At first this may sound too much but you have to begin slowly, building up stamina over a period of weeks. Start with simple exercise such as walking. Walk for just five and then increase the timing. If you are worried about any health problems, talk to your physician.

The Department of Health and Human Services (HHS), USA has released guidelines that advise adults in the age group 18 to 60 to exercise daily.

Tips before you begin exercising:

• Choose an exercise that fits your fitness and lifestyle
• Set realistic goals. Give your body time to adjust to your new routine
• Do not give up; if you miss, get back the next day
• Include rest days in your schedule
• Motivation and socialization are necessary to pull on

Breathing properly

Air enters the lungs and the oxygen in the air is passed through the lining of the lungs. The oxygen is taken up by the red blood cells. The red blood cells enter the circulating blood carrying the oxygen. The blood goes to the heart and is circulated throughout the entire body. The muscles use this oxygen for the needed energy. Its being used will give off carbon dioxide (CO2), which is in turn released into the blood stream and returned to the lungs to be exhaled. It is important therefore to breathe properly.

equipment on gym floor

Time to Check with Your Doctor

It is best to check with your doctor before you start with any exercise programme. For most people physical activity is safe. However, if you are aging or have any chronic disease, or if you are on any medication for an ailment, it is safer to check with your doctor about your exercise regimen.

Check this list before you begin your fitness programme:

• Pregnancy.
• Previous heart attack.
• Asthma or lung disease.
• Diabetes, heart, liver or kidney disease.
• Arthritis, osteoporosis.
• Previous joint replacement surgery.
• Feeling of pain in the chest, joints, or muscles during physical activity.
• Loss of balance, dizziness or loss of consciousness.
• Joint or muscle injury.
• Not feeling too well.

The American College of Sports Medicine recommends that you seek medical advice if two or more of the following points apply

• You are a man older than 45 years or a woman older than 55 years.
• You have a family history of heart disease before the age of 55.
• You have high blood pressure or high cholesterol.
• You smoke or you quit smoking in the past six months.
• You are overweight or obese.

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