Cross your threshold and run fast
Ever wondered how fast you could run? Perhaps you are a closet speedster just waiting for the right moment to astound your clubmates on a time trial. If so, drop that chocolate cookie in the bin and read on ...
Acronyms abound in running and you’ve probably heard of VO2max and lactate thresholds.
VO2 max can be stated in a percentage and is an indication of how efficient your aerobic system is. If you have lungs like bellows to inhale and exhale vast quantities of oxygen, a strong heart, a good network of blood capillaries and a low body mass you probably have a high VO2 max. An elite young male runner can be expected to have a VO2max of at least 70. Our VO2 max declines by about 10% a decade as we get older.
Having a high VO2max is good news.
But how do you improve your VO2max? Firstly, by doing higher mileage and long runs as this increases the network of blood capillaries and makes the heart more powerful and efficient; and secondly by doing speed work at VO2 max effort which are sessions done at 5km race pace and faster. It is for this reason that one of the key sessions I use for runners is 1000m intervals done at 5km race pace. A third way is by shedding any excess weight. It has been calculated (The Cutting-Edge Runner; Matt Fitzgerald) that 1kg of extra body weight increases the energy cost of running by 3.5%. This means a runner who can do 10km in 40 minutes, but who then puts on a single kilogramme can be expected to slow down to 41min 28sec on 10km. But before you start a crash diet of lettuce and water, it is important to remember that we are talking about your ideal racing weight - going below your ideal racing weight will just weaken you and make you susceptible to illness.
However, there is a caveat, having a high VO2 max is not always the golden key which opens the door to great performances. It is only when a runner adds good running economy to this that we see great performances. Poor running economy wastes energy and nullifies some of the advantages of a high VO2 max. We can improve our running economy through increasing mileages, and by doing threshold and VO2 max sessions.
At the threshold
Lactate threshold is a key concept and for many years we were told that fatigue when running at high intensities was due to the build-up of lactic acid. The latest thinking is that muscle fatigue at higher intensities is due to neuromuscular fatigue caused by depolarisation of muscles resulting from a shift in the calcium/potassium balance. Fortunately, we don’t have to worry too much as to which of these is correct as they all occur at the same point. For the sake of brevity, I will simply call this your threshold. What we do know is that your threshold basically determines what speed you can maintain over race distances of 15 to 21km. The higher your threshold the faster you will run. Your threshold can be raised through training at tempo effort. Tempo effort corresponds to a pace between your 15km and 21km race pace, and a typical session would be a 5km or 8km tempo run at that pace.
Is it important to have good leg speed?
Absolutely! First the bad news for most of us - and good news for a select few - is that the faster you are over short distances, the faster you will be over longer distances right up to the Comrades marathon. Yup, now we’re talking on-your-toes 200m and 400m speed. But keep your day job if you are so slow that you use a calendar to mark your progress around a 400m track.
But there is a plan B
But having said this, most runners will benefit more from improving their threshold speed which is the percentage of their maximum speed they can maintain over the full race distance, than through trying to improve their maximum sprinting speed. This is simply because most runners have not trained to reach their full potential using VO2 max and lactate threshold sessions, and are racing slower than their times over 200m or 400m would predict, as they are unable to maintain a steady race pace.
So why do women beat me?
Have you ever wondered why some women can run the pants off you in road races? Yet you are sure that given half a chance to line up against them on the track you could probably whip them over 200m or 400m?
The secret lies in their ability to maintain a race pace at a high percentage of their maximum heart rate. In other word these runners have trained to do two things - to lift their VO2max and to lift their threshold level.
This can be illustrated by looking at what percentage of their maximum heart rates they can race at.
Well trained runners can race 10km at heart rates of around 95-98% of their max. Over the half marathon distance they can race at a heart rate of around 88-92% of max. There is obviously some variation in this as well from runner to runner. But a runner who has not trained to do this, will only be able to maintain a lower percentage of their maximum when racing.
Let’s say you have the same 400m speed as your female friend has, but you maintain a heart rate of 80-85% (compared to her 88-92%) of maximum over a half marathon. In this case you are about to be chicked. Guaranteed!
The good news is that you can gear up your training to include threshold and VO2 max sessions and improve your race times despite lacking good leg speed over a 200m or 400m. If you have not been doing threshold training, then you have not reached your potential and have plenty of room for improvement. Now that’s good news, isn’t it!