How far should we push ourselves to exercise vigorously?

Defining vigorous exercise is not so easy, since it depends on many factors, such as health status, fitness level and even perception of exertion.

To assess cardiovascular endurance, especially in elite sports, we use precise measurements such as VO2 max, referring to the maximum amount of oxygen our body can consume during vigorous exercise.

For public health, we prefer simpler, more accessible benchmarks such as resting metabolism (measured in METs, or metabolic equivalents). This system compares the energy used during exercise versus energy used at rest. Light exercise is less than 3 METs, whereas vigorous exercise is higher than 6 METs, meaning more than 6 times the energy expended when sitting [1]. In practice, it’s often our individual perception of the effort made that determines the level of intensity: very light, moderate, vigorous or maximum.

No need to run an ultramarathon, pedal your bike 100 kilometres or take part in an Ironman to reach, or exceed, a vigorous exercise level. Making a daily effort may be enough: running at a good pace, walking faster than 6.5 km/h, going uphill or upstairs briskly, shovelling snow or gardening. Even though these activities are less spectacular, they require significant cardiovascular effort and can absolutely be categorized as vigorous.

Heart rate can be one indicator for estimating exercise intensity [2]. It has to be measured at the right time, either during or right after exertion, using an electronic watch or gadget which logs pulse. It’s also simple to take it manually instead:

• Place two fingers on your wrist or neck (carotid artery);
• Count the beats for 15 seconds, using “a thousand and one, a thousand and two, ...”;

• Multiply that number by 4 to find out your heart rate in beats per minute (bpm).

  Pick up the pace... and reap the benefits

  Doing vigorous exercise provides us with many health benefits [4]. But be careful: overexerting ourselves can also have negative effects on our bodies. When we’re doing demanding exercise, we’re better off understanding what’s going on in our body, so we warm up properly, respect our limits and prevent the risks of overexertion.

There are two ways of estimating maximum heart rate (MHR):

• 220 - age
• 208 - (0.7 x age)

Heart rate reserve (HRR) is the difference between MHR and resting heart rate (RHR).

A rapid heartbeat and shortness of breath are obvious signs of vigorous physical activity. The heart beats faster, blood flow is directed to the muscles, and breathing gets heavier to meet the muscles’ increased need for oxygen.

Vigorous exercise is a stressor for our bodies. In response, our body releases stress hormones like adrenalin and cortisol, as well as endorphins – those so-called happy hormones – which help us tolerate pain better. However, those same endorphins can hide some signs of fatigue which should not be ignored.

The energy used by our muscles produces heat. To avoid overheating, our body triggers sweating, a key mechanism for regulating our body temperature.

Vigorous physical activity provides many benefits... but is not risk-free, especially if it is excessive or done without warming up. The physiological changes that occur during vigorous exercise can sometimes lead to serious outcomes:

• extreme fatigue, along with dizziness, caused by dehydration and an imbalance of electrolytes such as sodium;
• heat stroke and exhaustion, when our body can no longer cool itself down;
• torn muscles or tendons, if exercise is too vigorous, inappropriate or done without warming up enough;
• heart problems, which are rare but possible, in people who are at risk or did not warm up properly.

Overall health

According to the Montreal Heart Institute, many people are at risk, including:

• older people;
• smokers (past or present);
• people living with metabolic syndrome, diabetes or uncontrolled high blood pressure;
• very sedentary people;
• people with heart or lung problems [5].

Alcohol

Alcohol acts at multiple levels and affects our body’s ability to tolerate vigorous physical effort. It increases urine production, which worsens the dehydration associated with vigorous exercise. Alcohol increases heart rate and can cause uncomfortable palpitations, especially the day after a night of partying. It also slows down reflexes, increasing the risk of falls and injuries [6].

Medication

A number of medications can cause side effects such as fatigue, loss of appetite, dizziness or low blood sugar. These effects may increase the risk of complications during vigorous exercise [7]. Having said that, physical exercise is still one of the best “treatments” there is. Taking a medication (short-term or long-term) does not necessarily mean you cannot play sports. It’s important to adjust how vigorously you play and take advice from a healthcare professional.

Diet

Diet plays a key role in our bodies’ ability to support vigorous exercise. What we eat affects performance, recovery and exercise tolerance before, during and after vigorous activity.

There are many reliable resources offering suitable diet plans for different needs, based on goals and types of exertion.

Here are some simple tips for preventing complications associated with vigorous exercise:

• train progressively, with a program suitable for your physical condition and the planned type of effort;
• stay well hydrated before, during and after exercising;
• listen to your body: abnormal shortness of breath, unusual pain and nausea are warning signs which should be heeded;
• integrate periods of recovery and stretching;
• consult a healthcare professional if you have any questions about the safety of a fitness plan or to adapt exercise to a medical problem.

Vigorous physical activity is excellent for your health, provided you warm up properly. Knowing your body’s normal and abnormal reactions makes it easier to detect warning signs and work out without putting yourself in any danger.

Be active, yes, but always respect your limits: that’s the key to staying active and healthy for a long time!

For professional support, we’re here. Are you worried about any symptoms? We provide services which can help your doctor diagnose heart troubles and determine the right treatment. * Cardiac ultrasound * Doppler ultrasound Do you already have a prescription for one of these tests? Make an appointment online.