If this is the answer, what is the question: 100 billion. Any guesses? One answer is the number of stars in the Milky Way. It is also the number of neurons (brain cells) belonging to your average adult human. The brain typically shrinks with increasing age, at least in part due to death of neurons, leading to a decline in our mental abilities. However, we now know that new neurons, as well as new connections between them, can be generated throughout life. Exercise seems to slow or reverse the brain’s physical decay, much as it can with muscles. However, while exercise promotes the production of new neurons, learning a new skill helps to join them to the existing network of cells in the brain, without which the new brain cells would not survive.

Dancing combines the benefits of exercise with those of learning a new skill - dancers are constantly learning. This may be why a major study of the susceptibility of senior citizens to Alzheimer's disease found that dancing was the best method of reducing dementia risk. While a reduced risk of Alzheimer's disease was associated mental tasks such as reading (35%) and doing crossword puzzles (47%), frequent dancing was found to reduce the risk by a whopping 76 per cent. Other physical activities included in the study, such as cycling, swimming and golf were not found to have any beneficial effect on Alzheimer's risk. Dancing has also been found to be beneficial for people living with Parkinson's disease.

Psychologist Jean Piaget defined intelligence as "what you use when you don't know what to do". What better way to keep your mental acuity in top form by challenging yourself with new skills? In a dance environment, you are using several brain functions at once - kinesthetic, rational, musical, and emotional. You have to make rapid decisions about which way to turn, what speed to go, and which limbs to move. In a class environment, you are continually learning new and changing choreography. You are forced to use - and build - your intelligence as your teacher gives you new challenges. In partner-based dance you are constantly adapting to your partner's movements - you don't know what to do, you use your intelligence to respond accordingly.

While moving at a slower pace, and less involved in rapid decision making, Pilates also involves continual learning of new movements and choreography, combined with the benefits of mindfulness and correct breathing, which help to ease stress and calm the mind. 

Not that this is ultimately why you should dance. I would love you to dance for joy. The more the better - so dance, dance like noone is watching!

A challenge in any group exercise class is to pitch the exercises at the right level. Even in settings where I have divided the classes according to level, within each class there will be a range of abilities. I always offer different options, and I see my job as providing you with a challenge to make progress. Equally, each person needs to be honest with themselves about their own capabilities. It is unlikely that there will be one person who is 'the best at everything' and I encourage you to focus on your own journey rather than competing with the others.

How hard you work is strongly dependent on your personality and motivation. Some people are happy to tick over maintaining their current level of fitness, whereas others love 'feeling the burn' and will push themselves as hard as they can. So, how hard should you work?

One of my favourite sayings in this world of fad exercises is, "The best form of exercise is the one that you actually do." There is little point in exercising harder than you can maintain long term. For cardiovascular effort, there is a scale of perceived exertion (Borg Scale) which runs from 6 (no effort, eg. watching TV) to 20 (maximum exertion that you can only maintain for a short period, eg. sprinting to finish a race) and applies to adults under 65 years of age:

• For general low-impact exercise (eg. walking) try to reach 13-14, so that you are feeling warmer and your heart rate increases, but you are not short of breath, and you can enjoy taking in your surroundings while benefitting your heart.
• When doing vigorous aerobic exercise, you want to be working at about 16-18, close to the maximum effort that you can sustain. You might be able to say a sentence, but not carry on a conversation.
• When doing interval training, this is your opportunity to try to get up to 19 or 20 before your rest period. You would struggle to talk at this level.

As a very rough guide, you can multiply your Borg score by ten to get an idea of where your heart rate might be at each of these levels, bearing in mind that your maximum heart rate generally declines with age, and your resting heart rate declines with increasing fitness.

For muscular effort, you will get the quickest results by working to muscle failure. In doing so you risk suffering from sore muscles the next day - and stretching before or after your workout won't prevent it. It is important to recognise when your muscles have reached failure. Beyond this point, it is only possible to continue by executing the exercise with poor technique - using other muscles, poor alignment or momentum to do the work. This is where problem start, and the risk of injury increases.

Joseph Pilates is quoted as saying, "A few well-designed movements, properly performed in a balanced sequence, are worth hours of doing sloppy calisthenics or forced contortion." In Pilates, I don't encourage you to work to muscle failure. An important part of Pilates is practising healthy movement patterns, so that they become instinctive. If you reach muscle failure, your technique is likely to be starting to suffer, and you will start to reinforce poor alignment. 

Should you feel pain during exercise? It depends what you mean by pain. You should feel that your muscles are hot and working hard and this may reach the point of feeling painful, even. This is not a problem, and can be part of a good workout, as long as it doesn't spoil your enjoyment of the activity as a whole. Your muscles will strengthen and it will be more comfortable next time. Any pain in the joints, however, is an indication that you should stop and rest, and choose an easier version next time. If your joints get aggravated and inflamed it will serve no purpose in strengthening you, and will make your next workout feel harder, rather than easier. And here is where you risk long term injury. If your muscles hurt so much that you can no longer continue with good technique, then this is also an indication that you should stop, or choose an easier option that you can continue safely with.
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If you arrive in class with an injury or pain, let your instructor know - it may be wise to avoid even starting some exercises. Always let your instructor know if an exercise is causing you to feel pain and remember to keep each exercise within your own safe working level.