*** many thanks to Neil Rooney for this blog post ***

In my last blog post Running Faster I outlined the mechanism behind making yourself run faster by training below your lactate threshold. There is another golden reason why running below you lactate threshold is vitally important and it's got nothing to do with speed but keeping yourself healthy and injury free.

I'm sure you've all met people like myself who never get injured and claims to feel energised after exercise. Most people I know who are training for a specific event will feel tired or worn out a couple of weeks into a program. It's not uncommon to hear marathon runners and triathlete wishing race day away so they can have "time off training" or "get their lives back" and are complaining about being worn out. These people are also the individuals who are going to complain of these running or exercise related injuries. The injuries in question are; joint pain, ligament strain, Achilles tendinitis, compartment syndrome, shin splints, stress fracture, knee bursitis, meniscus or cartilage damage/tear, runners knee, IlioTibial band pain, low back pain, shoulder capsule pain and rotator cuff injuries (in swimmers).

So why are these injuries so common and why are the occurring?

Let me begin by giving my views on a quote that gets thrown around all too often. I'm not 100% certain who the quote came from so I won't suggest but it was definitely from somebody in the "barefoot" movement. The quote goes to the tune off "Running is one of the most dangerous exercises you can choose with over 70% participants getting injured" they proceeded to suggest running barefoot would save you from this dooming percentage. Well even if you run barefoot with picture perfect posture your risk of injury will be up around 70% if you continuously train above lactate threshold. So once again physiology reins through and regardless of what you do or don't put on your feet you must obey the physiology and biochemistry if you are to avoid these injuries.

When you exercise (and let's take running as the example: although this applies to all exercise, running is a good example because of the impact - cycling and swimming are virtually impact free so these injuries are less likely, however the rules still apply) you are breaking your body down in an attempt to rebuild it and make it stronger and perform better. Every single workout should have a purpose and that purpose should be fresh in your head during that work out. Differing workouts during the week will have varying purposes but all workouts are aimed at getting you to the same place.

In the last post I gave an example of a female runner training above and below her lactate threshold. I explained that once you go above your lactate threshold you will be burning sugars as a primary fuel source. This means you will be generating lactic acid at a rate quicker than you can process it, to be reused as energy. This lactic acid will build up in your muscle and connective tissues and this is not a good idea. Let me explain!

When exercising a waste product spills out from the power stations in your muscle cells called lactic acid. Lactic acid is collected and brought to the liver where it is processed and manufactured back into a fuel source to be reused. You might remember this from school, it's called the Kreb's cycle. Above your lactate threshold lactic acid will accumulate and eventually make your muscles feel so sore that you have to stop. Below the lactate threshold you will be able to process this lactic acid and continue exercising for a long period. If you stay below lactate threshold and exercise for a few hours eventually lactic acid will build up and you will lose the battle to process it quicker than you develop it. When lactic acid builds up is tissues they will feel sore and you will have to stop.

Along with lactic acid build up during training above lactate threshold you will also accumulate carbon dioxide in your tissues as you develop breathlessness. This will push the body into a more acid state. As you push on the glycogen stores run low and your body starts looking for protein to use as fuel.

Since the muscles have a huge blood supply they are not at huge risk of the ill effects of these metabolic products. However in the connective tissues; fascia, bone, ligaments, tendons, joint capsule, joints, meniscus, cartilage and bursa there is very little blood turn over. As a result of poor blood turn over metabolic waste can build up really easily and very quickly in these tissues, especially if you are always training in a zone that produces lactic acid faster than you can recycle it, above your lactate threshold.

When you keep running above the lactate threshold and repeatedly beat your body up you will accumulate enough waste and acid by products to cause severe pain (free nerve endings or pain receptors don't like acidic environments) and eventually injury. Once a connective tissue becomes injured by tearing or spraining it is very difficult to repair. These tissue don't have a huge blood supply so the process will take time (far longer than a muscle strain), it will also require rest which is usually the last thing a marathon runner will do if a race date is approaching.

The general story of a person with one of these injuries is; take a few days rest until pain subsides, since you're not running the acid accumulation is less and therefore pain is less. Then the person will go for a light jog and they feel good, most people are worried and this light jog is under the lactate threshold so no acid accumulation. Then the person feels cured so goes out the for the next run all guns blazing, training way above lactate threshold and to their utter surprise the injury returns.

Does any of this sound familiar? If so try experimenting with a heart rate monitor. I've been using Garmin for the past 6 years before that I had a Polar. Personally I think the Garmin brand is best. I use a forerunner 310XT, which meets all my swimming, biking and running needs.

I commute on average 140km per week around London on a single speed bike, the vast majority of this is below my lactate threshold. Also all of my long runs are performed 1-2bpm below my lactate threshold. It is these factors alone that prevent me getting injured no matter how many kilometres I run each week. I measure my lactate threshold roughly every 6 weeks. It's essential to monitor the lactate threshold (it will vary with fitness) so that you can be just under it on a long run pushing the fat burning system to its limit.

Remember you can't run a marathon or ironman on sugar, so train your body to fuel on fats.

In the next post I will describe how you go about finding your lactate threshold without using any equipment other than a heart rate monitor. That seems like a logical step since I've been explaining its importance so much.