## Heart Rate

Hi

Please tell me the formula for how to calculate correct heart rate. I think it has something to do with your age divided by 2 plus something? Also what is the correct range (i.e. resting and exercising), and what should your heart rate get to to burn fat? I am 37 years old, female and recently started going to gym. I have a lot of weight to lose, my body fat percentage is 45%. I am also hypertensive (130/90), but on medication and qymming with my doctor' s permission.

The other day I ran for 15 min on the treadmill (speed 4.2 so I did not strain), and after getting off, I felt a bit woozy? It was my first time on the treadmill. The heart rate monitor at one point reached 145, which I think was high and scared me a bit, especially in light of my hypertension. I felt fine after a few minutes and was very energised for the rest of the evening, taking a 30min walk later.

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###### Our expert says:
FitnessDoc

Hi Gym

heart rate is a useful training tool if used wisely, and it can help prevent overtraining and thus optimise performance. However, there are a few basics that are important.

First, maximum heart rate can't really be KNOWN using a formula. They're just estimates. There are a few of them. Most common is 215 minus your age (for women. It's 220 for men). The one you're referring to is known as the Karvonen formula, and it uses resting heart rate and maximum heart rate. I'd rather not go into detail on that one, because what I'm about to say doesn't use it anyway, so why bother with the number crunching? I'd say for you, you should use the equation as a guide (your max would be around 185, give your take a few percent). And then just use the watch to learn how YOUR body works, and not to base everything around that number.

When you train for general fitness and weight loss, it is best to train at an intensity that corresponds to between 70 and 90% of this maximum heart rate. This range is so wide because people are so different and that's why what works for one person does not necessarily work for another.

I get quite irritated by what is often written about heart rate training, because you will read that you have to keep your heart rate in a certain range otherwise you don't get the right benefits, or it's dangerous etc. This is just not true. I have come across very good runners, who, if they tried to obey this rule, would be walking just to make sure their heart rate did not get too high. You can't tell people like that that they must slow down because they are not getting fitter.

Similarly, I know people who have a naturally low heart rate, and for them to get their HR up to the 'ideal' range, they just about have to sprint until they collapse from exhaustion two minutes later. So the bottom line is that the actual value of your heart rate is not that important, it's ranges that you can use, but don't get too hung on the number. What you need to do instead is use your own heart rate from one day to the next to help you understand how your training is developing.

For example, you might do a 40 minute run at 75 to 80% of maximum, and this is a good session for weight loss and improved fitness. Generally, aim to train for between 30 and 45 minutes per session (at least) and on 4 to 5 days per week. The intensity, as mentioned, will range between 70 and 90% of maximum, depending on the exercise you do and the goals for that session. For improved performance, train at 85% of max and above. For weight loss and fitness, train at between 70 and 80% of maximum.

Do not get caught up in to believing the heart rate monitor as the final authority in your fitness level. The best way to use your heart rate monitor is to use it to compare training sessions from week to week. Therefore, if you train one day doing a particular session, take note of your heart rate. The next time you do the exact same session (say 30 minutes run at 12 km/hour), you should be able to compare your heart rate during the session. If it is lower, then it indicates that you are fitter than before, and your training is going well. If it is higher, then it shows that you are either tired, or training too hard or are possibly becoming ill. This is a sign that you are in need of a few easy training days.

Lastly, remember that heart rate depends on many factors - hydration, mood, stress levels, temperature and so on. Therefore, if your heart rate is not exactly what you think it should be, don't worry too much. Rather look at long term changes and patterns in heart rate, and try to interpret them as I explained above.

With respect to your woozines, I think there are a few thinsg that might have caused this. Low blood sugar is one. Low blood pressure is another. I know you're on meds for BP, but yours is not that high, so that is a good sign. Just monitor it, but don't panic about it too much as long as you exercise within boundaries of common sense.

Good luck

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