Heart rate is precisely how often your heart beats every minute and is a useful measure of intensity.

I would like to thank all of you who take the time to write in. I receive interesting comments and queries, some of which I enjoy replying to privately; others lend themselves nicely to being discussed publicly.

I get the feeling many of those asking questions already possess a degree of knowledge or experience in the field of exercise and fitness, which is encouraging and leads me to believe that awareness is on the rise.

If more people are reading and learning about fitness, then more people must ultimately be interested in improving their fitness and general health.

The query that struck me most this week was: “At what percentage of heart rate does one start to burn calories?” Losing weight is still perhaps the number one request fitness professionals receive throughout their daily business, but much confusion persists about the best ways to achieve it.

Heart rate is precisely how often your heart beats every minute and is a useful measure of intensity since the heart must beat more often during bouts of increased physical activity to meet the elevated demands of the muscles for oxygen and fuel-rich blood.

Losing weight is still perhaps the number one request fitness professionals receive throughout their daily business, but much confusion persists about the best ways to achieve it

Intensity of physical activity can therefore be measured and prescribed in this way, often as a percentage of maximum heart rate (MHR). MHR can be approximated by subtracting your age from 220: this number allegedly being the average MHR of a newborn baby in beats per minute before it begins to decline at a rate of roughly one beat per minute, per year.

Moderate physical activity is defined as 70 per cent of MHR, so technically any activity that elevates your heart rate to this level will constitute an effective workout. All physical activity at any intensity burns calories. However, if you are interested in burning enough calories to lose noticeable amounts of stored body fat, then 70 per cent is a good rule of thumb, maintained for at least half an hour at a time, three to four times per week.

If you are 20 years old, this would equate to 140 beats per minute, or if you are 50, it would be 120. You can calculate this without the need for fancy equipment; just take your pulse from your wrist or neck for a period of 15 seconds and multiply it by four, which is quicker than counting for a whole minute.

If you had any doubts you were working hard enough, then this will tell you. Aim for 70 per cent; anything over 80 per cent of your MHR is considered hard training, while anything over 90 is considered very, very hard.

During your workout, once all readily available sugars in your system are used up, your body will start to metabolise and burn stored body fat for fuel instead.

So, put simply, get your heart rate up and keep it there for at least 20 to 30 minutes each time you exercise. Now is there such a thing as too high?

This brings us to the second part of the question I was challenged with: “If I work out at too high an intensity, will my muscles grow excessively?” Traditional wisdom once said that low-to-moderate intensity is best for burning fat. However, we have recently come to appreciate that the higher the intensity, the more calories are burned overall.

Intense training also tends to kickstart a metabolic process of fat loss that lasts long after the actual workout has ceased, provided an effective healthy eating plan is also in place. Provided we are prepared and of the required level of fitness to pursue the activities we have chosen, then we need not shy away from the higher intensities based on traditional wisdom.

Growing excessive muscle mass is a separate issue, and is often a fear among females considering lifting weights. This one is much easier to answer: there really is nothing to fear. Muscles will only grow as a result of very specific types of stimuli, namely resistance training performed to momentarily muscular failure within the eight to 12 repetition range, spanning exercise that targets all the major muscle groups of the body.

Even if the training stimulus is correct, muscles will only grow in the presence of growth hormones. Growth hormones are naturally lower in women and decline with age too, so if you are affected by either of these factors, then muscle growth will not be easy.

Competitive bodybuilders sweat blood and tears to make their muscles grow. Now I’m no bodybuilder, but I would assume that suggesting muscles can grow almost by accident is probably actually quite offensive to them and their craft. Having said that, some of us may still be concerned about certain areas of our bodies we don’t want to get any bigger, but provided we are eating healthily and sticking to the above suggestions regarding losing body fat, rest assured body parts will not grow in girth.

By working the muscles that will eventually be visible through the declining body fat that sits on top will simply result in a more athletic shape, not a bulky one. Indeed, lifting weights and performing high-intensity workouts are a valuable addition to any fat-loss programme, as they raise basic metabolic rate, forcing your body to burn more calories not just while your training, but at rest too.

matthew.muscat.inglott@mcast.edu.mt