Marathon Running

Preparation

The London MarathonBefore embarking on this project, it would be wise to consult you doctor. You need to build cardiovascular fitness to run, going from brisk walks to short runs. The next stage is to have increasing lengths of runs increasing the weekly distance to enable you to run in the marathon.  Exercise programmes are readily available in any bookshop or on marathon running websites.  They typically consists of a tapering programme increasing from alternate days brisk walks in the first month, through to alternate day runs of 20-30 minutes for the next couple of months, through to increasing distance running, again on alternate days, accommodating runs of 20-30 miles per week. 

Do You Need To Change Insulin Regimes?

If you currently are on twice daily 30-70 biphasic insulin mix, this mixture will not enable you to have the flexibility for different levels of energy expenditure and food intake on rest days and training days. The Isophane component will also make you vulnerable to unpredicted hypoglycaemia when running.  So the answer is probably yes. You will need to change to at least a 3 times daily soluble insulin given before meals and Isophane insulin given at night time. If your diabetes seems well controlled, your total daily insulin dose is likely to be to that of your twice-daily regimen. This total daily dose is divided into four, with the first three doses given as soluble or analogue insulin, and the later as isophane insulin. This template regimen is then adjusted to take account of training and increased food. Additional insulin should be injected with the high-energy snacks taken after exercise.  A suggested dose of 2 units of insulin per 15 grams carbohydrate eaten is a useful starting point. Unfortunately there are no formulae or calculation for adjusting the insulin dose. Excellent education with a flexible response by the health care professional is required. Clearly more frequent blood glucose monitoring is essential, with tests before, during and following exercise.

Training and Rest Days

On training days, bolus insulin doses will increase to cope with increased carbohydrate load, and basal insulin levels will reduce.  By contrast, on rest days, there will be fewer snacks; with similar meal insulin doses to the template regimen, and an increased basal isophane dose. There is good evidence that the more rapid onset and shorter duration of action characteristic of the analogue Insulin Lispo or Insulin Aspart will assist in reducing hypoglycaemia and post-meal hyperglycaemia, and one of these is recommended as the bolus component. For some, the use of insulin infusion pumps may seem to offer potentially near-physiological insulin replacement, as the insulin infusion rates can be rapidly adjusted to meet requirements. The reported experience of such pump therapy in exercise is limited, but athletes may find the pump cumbersome, and current use is limited by cost.  However, which ever system of insulin replacement is chosen, a process of trial and error must individualize adjustments to the basic insulin regimen, although some guidelines can be set out. 

Insulin Doses

During the initial phase of training, the effect of low-level exercise may be to paradoxically increase blood glucose levels as glucose production from your liver is stimulated by the counter-regulatory hormones, and not checked by injected insulin exceeds muscle use. As the periods of exercise increase in length and intensity, a potential gap between glucose production and utilization appears. When it is apparent that your blood glucose falls during exercise, it is wise to reduce insulin prior to exercise, and to take an extra carbohydrate snack (30 grams) to keep starting blood glucose being 8-12 mmol per/l. At all levels of intensity of training, post-meal exercise following injection of the full pre-meal insulin dose may increase the risk of later hypoglycaemia. When the anticipated duration of moderate training is about an hour, a 50% reduction in pre-meal dose is required. When more intense exercise is planned to last over 30 or 60 minutes, a reduction of 50 and 75% of the pre-meal dose is needed, and for more prolonged exercise should be omitted. This vigorous pro-active reduction in pre-exercise insulin dose will substantially reduce the risk of hypoglycaemia during and following exercise by as much as 75%.  Furthermore, during prolonged training and the marathon event itself, low levels of insulin enable appropriate mobilization of fuel stores to support the exercise. On completing the training period, insulin should be given with the post-training snack or meal.  

Diet

The dietary requirements of a marathon runner who is diabetic or non-diabetic are the same, but diabetic foods of low glycaemic index are not suitable during and following running, although should remain an important part of the diet on rest days. As he is of normal body weight, reducing carbohydrate is not appropriate, as this will lead to early fatigability.  The increase in energy expenditure of training will need to be supported.  During the training programme, as the length of training increase, the carbohydrate intake should also increase, so that typically during exercise 60 grams of carbohydrate are consumed per hour of exercise.  This can be taken as a glucose polymer drink, which may reduce hypoglycaemia whilst running. After exercise carbohydrate again needs to be taken to replenish muscle and liver stores of glucose.  Again, typically 60-120 grams in the post exercise period.  This is taken with further bolus insulin.  With adequate replacement on training days, there is no need to take extra carbohydrate on rest days, as this can impair overall glycaemic control without improving muscle glycogen stores.

Marathon Day

On the morning of the marathon, a carbohydrate meal needs to be taken 2-3 hours prior to the event with a much-reduced dose of short acting insulin. He should aim to start the event with a blood glucose value of between 10-15 mmol per/l, and 30 grams of glucose taken every half hour throughout the marathon. This can be taken as a glucose or glucose polymer drink or in sweet form. On completing the event, 60-120 grams should be taken in association with further bolus analogue insulin. Your normal insulin template can be followed for the rest of the day, but with reduced isophane insulin at night to reduce the risk of nocturnal hypoglycaemia.

Will I Do Myself Harm?

Exercise produces periods of hypertension and there is a theoretical risk of deterioration in diabetic retinopathy.  There appears to be no increased risk of progression to proliferative retinopathy with regular exercise, and for some this risk may be reduced.  If you have background retinopathy, without pre-proliferative retinopathy, it should be quite safe for you to run the marathon.

Marathon running is a feasible possibility for people with type I diabetes who do not have cardiovascular disease or other significant diabetic complication.  The energy requirements for marathon running are the same in diabetics as other people.  It is necessary to have multiple daily injection regimens to allow for variations in training schedules and rest days, and ideally analogue insulin should be the bolus component to allow for high-glycaemic index carbohydrate intake.  Close co-operation between the athlete and the health care provider are required with regular reviews of blood glucose results, food intake and training schedules to reduce the risk of hypoglycaemia.

Marathon Running

By Richard Hudson

I have participated in a number of endurance sports events since being diagnosed with type 1 diabetes in June 1999 at the age of 36.

Marathons

2 months prior to my diagnosis I had run my first ever marathon in a time of 3hrs 37mins and one of my first thoughts when planning life as a diabetic was wondering whether it would be possible to run another marathon.  Later as that appeared to be achievable the objective became - can I run faster than I did pre diagnosis.

More recently I have come across many very helpful books and websites that provide detailed advice to diabetics taking on endurance type activities but 5 years ago it felt more like a process of trial and error.  I would go to my local park which helpfully had a 1 mile circuit measured out.  Leaving my blood testing kit at the start I would simply run ever increasing numbers of miles, testing every few laps to see what my blood sugars did in response to the exercise, amounts of insulin I took before running and numbers of dextrose tablets consumed during running.

The experience of running 3 marathons as a diabetic, each one faster (best to date 3hrs 3mins) has also added to the process.  The regime that seems to work for me is:

Running the Marathon

Skip normal breakfast shot of fast acting insulin (in my case Novorapid) and inject 8 to10 units slow acting insulin instead (in my case insulatard).  This is about 3 hours before the start.  About 2 hours before the start eat bowl of porridge or similar low GI carbohydrate.  10 to 15 mins pre start test blood and if below 10 mmol/l take a couple of dextrose tablets with water or equivalent of glucose sports drink – aiming to be around 12 mmol/l at the start.  I try not to be much higher than this due to the potentially dehydrating impact of your body trying to get rid of excess sugar through your urine.

During the first 16 miles stick to 1 dextrose tablet per mile plus occasional water to keep hydrated.  If my legs feel unusually leaden I know that this is probably a sign of low sugar levels and I will take an extra dextrose to adjust the balance.  If at all possible I avoid testing during the race as I find it very disruptive and difficult to get going again – but clearly testing is better than falling over !

From about 16 miles (and as your body’s stores of energy near depletion) I find that I need to steadily increase my sugar in take – normally this would be adding glucose sports drinks on top of the dextrose per mile – around one 330ml pouch per 4 miles.  By mile 26 I am probably taking the equivalent of 2 dextrose tablets per mile rather than 1.   As earlier, if my legs feel very leaden I will take an extra tablet – though as everything feels leaden at this stage it makes it a bit more difficult !
Despite what feels like the vast amounts of sugar eaten by the end, my post finish blood sugars have to date been in the 5-10mmol/l range.  I have not been particularly scientific about what I eat post race.  However I have found that I probably only need 50% of normal insulin levels the rest of that day (if eating normally) and 75% of normal levels the day after to stay balanced.

One other experience not to be recommended:

Don’t be tempted to skip your morning insulin altogether as a means of removing the risk of low blood sugars.  The most probable impact (as I found) is that your body runs out of insulin altogether later in the race and therefore has no means of bringing in sugar to replace depleted muscle stores.  You find it almost impossible to run as your body resorts to converting fat and muscle into energy.  Then when you have finished your body takes far longer to recover and unexpectedly needs greater than normal levels of insulin to help repair the damage you have done to your muscles.

Globe Trotting Fundraiser Sets Sights on Great North Run

Fundraising superstar Mark Golding has set a target of raising thousands of pounds for charities Diabetes UK and the Juvenile Diabetes Research Foundation over the coming years. He is currently working hard to prepare for the Great North Run in October this year, but will also be taking part in the Western Australia Iron man contest in 2008.

Big-hearted Mark was diagnosed with Type 1 Diabetes in June 2005 at the age of 29. After the initial shock of diagnosis, Mark pledged to prove that diabetes is no bar to leading an active and healthy life and decided to raise as much money as possible for charity Diabetes UK.  Mark has been joined on his fundraising journey by dad Arthur Golding 58 and little brother Sebastian, 8 years old, who will be running the Junior Great North Run. Marks mates Howard Bowmer and Paul Eldon, who have helped since Marks diagnosis, will also run the Great North Run later in the year. 

Fundraiser Mark Golding trains this way
On a Half marathon  training day, I will decrease the bolus (Novorapid) dose taken prior to a workout by approximately 20%.

This greatly reduces the risk of hypoglycemia during exercise. In fact I have never suffered a hypo whilst half marathon training or racing.

I will always test my blood glucose about half an hour before beginning any activity. If it is below 6mmol/l, I will eat one or two slices of bread.

This is normally enough to keep my blood glucose balanced during training. I don't normally eat anything further.

On a half marathon day, I will have decreased the previous nights basal (Lantus Glargine) dose by a couple of units.

I will eat a breakfast consisting of a bowl of Bran Flakes and two slices of toast approximately two hours prior to the event. This is taken with a bolus insulin dose approx 20% less than usual.

Once the race starts, I take two dextrose/glucose tablets every mile. I have found that this works extremely well for me in a half marathon.

I will test my blood glucose at the end of the race. It has always been between 4.5mmol/l and 5.5mmol/l and as I have stated above, I have never experienced a hypo during half marathon training or a race.

My marathon training has required me to take a little bit more care. I initially found that very long runs 15+ miles would cause my blood glucose to drop. This would sometimes happen the day after the run. In order to counteract this, I have increased my CHO (carb) intake. As my training requires me to run at least four times a week, I have found that consumption of pasta, potatoes and thick wholemeal bread has eliminated my risk of low blood glucose.

Prior to a run, I will check my blood glucose and if it is below 6-7mmol/l, I will have snack. In my case, this always consists of a couple of slices of bread or a roll/bun.

The reduction in insulin, that works for me in a half marathon seems to be working during my marathon training. I have never run out of insulin during training and therefore high blood glucose or the risk of DKA (diabetic ketoacidosis) has not been an issue for me.

I prefer my blood gluscose to be between 8-9mmol/l at the start of my run. Although this is high, it doesn't last. I always finish with levels at between 5-6mmol/l. I will also consume two dextrose tablets every mile. However I do not start to use dextrose tablets until mile three. This appears to work.If people wish to know more about Mark’s activities or make a donation they can check his website at http://www.justgiving.com/endurancefordiabetes