Muscle mass declines by 3-5% per decade after 30 years of age in physically inactive people. This can lead to weakness, loss of stamina, and difficulties with weight management. The good news is that weight bearing exercise can help to maintain and even increase muscle mass at any age. A sufficient intake of protein - in conjunction with strength training - is needed to sustain muscle mass. However, don't go overboard, as you use calcium to help digest protein, so too much may increase osteoporosis risk (see below).

From your mid-thirties onwards, bone density drop can drop by about one-percent per year, potentially leading to osteopenia or osteoporosis. In the early years following the menopause there can be a rapid decline of 20 percent, with an associated risk of bone fractures. Strength training and impact exercises will help to minimise the loss of bone density, as will ensuring an adequate supply of calcium and vitamin-D. Daily short bursts of sunshine in the summer - not enough to burn - will provide all the vitamin D you need in the spring and summer. Public Health England also recommends taking a daily 10 microgram vitamin-D supplement in the autumn and winter.  Calcium can come not just from milk - other great sources include leafy greens and baked beans. Also, there is emerging evidence that Vitamin K is necessary for bone health - present in meat, eggs, dairy and natto (fermented soy).

​With a good lifestyle, age shouldn't hold you back at all. Some of my oldest clients are also some of my most capable. I'm reaching half the age of body builder Ernestine Shepherd (pictured - unfortunately not one my clients), so I reckon I'm just getting started. 

My Dad ran his first marathon when I was a small child. His training took him away from home so much, that my Mum threatened to leave him if he ever ran another. He went on to run another five marathons. One or other of them never took the hint, and they are still married. During his last marathon, my Dad injured his hip, around 18 miles in. Given that he was 'nearly there', he carried on, in agony for the final eight miles. That's right, he ran EIGHT MILES in agony. Fortunately, he recovered fully and didn't suffer a recurring injury as a result. As a child, I didn't see the grief; I saw the heroism of his running and thought that running a marathon was the ultimate proof of being superfit and determined. From a personal challenge point of view, I think all runners dream of the marathon, but in terms of fitness, the 5k race is a superb distance to run. Not only is it a metric distance - what era are we in, the 1950s? - it is also offers benefits for your health, wealth and sanity.
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Here are my five favourite reasons for loving 5k:

1. It's motivating. By timing your runs, you can keep track of your progress, and quickly see improvements in your 5 km time. You are racing against yourself. Apps such as Runkeeper, Strava and MapMyRun make this job easier. You can adjust your time by your age and sex using the WAVA age grading system - to make a fair comparison with your differently aged, opposite sex running partner.
2. It's realistic. You can have a normal life while training for the 5 km race. I have a particular loop, a little over 3.5 km that I like to run on a weekend morning before showering, which keeps me just fit enough to know I can always do 5 km. It takes 20 minutes, give or take, and then I get on with my day. 
3. Parkrun! It's a free, weekly timed run. If you go often enough, you'll start to get to know the regulars - my motto is that running is the new pub - and you will always be welcome as a Parkrun tourist in a new city. Every now and then, you volunteer at an event and get a warm glow of smugisfaction.
4. It's sustainable. My ethos is always about sustaining exercise for life, and the 5 km run offers just that. It is perfectly reasonable to continue to run this distance for many decades. Any flat surface running will put some repetitive strain on the joints, but with good technique and adequate recovery time, it is possible to enjoy a long running career without ill effects - provided you do not train through injury. In fact, runners have been found to experience less pain as they age than non-runners.
5. You can work at higher intensity. High intensity training is now thought to offer greater fitness benefits than longer exercise bouts at lower intensity. Or you can walk it, if you need to.

Dedication and superhuman fitness are seen in the 5 km race too. Mo Farah set a British 5,000 m record of just 12:53:11. Mind you, even Mo had to give a marathon a try, so perhaps the call of the marathon is just too strong to resist.