Speed-work recruits different muscles than slow runs do: additionally, it strengthens the bones, ligaments and joints, so they can absorb and adapt to higher workloads.
This effect is similar to weight-training. The heavier the weight you lift, the stronger your muscle will become, because the muscle is having to resist more weight. With speed-work, the more you push the leg muscles to move faster, the more total muscle fibres you activate and the more explosively you contract them. This result is greater strength and injury resistance.
The bonus is, speed-work will boost your heart health, improve your skin health and your brain function.
Speed sessions evoke an increase in the maximal stroke volume of the heart: a greater stroke volume decreases the heart-rate and makes the heart more efficient.
At an easy pace, running a mile burns about 100 calories. However, the faster you run, the more calories you’ll burn during that mile. Plus, high-intensity training keeps your metabolism working hard even after the work-out is over. Research seems to suggest, that, the ‘after burn’ – the number of calories your body burns after your work-out, when your metabolism is ‘revved’ – lasts for longer when you have run faster.
Speed-work helps maintain efficiency by stimulating the central nervous system and activating more slow twitch muscle fibres. When you run at speed, your ground impact is lessened so reducing impact injuries.
Vorsprung advocates speed-work because it helps reduce injury. Many runners get injured when they try to run at speeds their muscles, tendons and ligaments aren’t ready for. Easy speed sessions help prepare those muscles.
Both science and practice support the clear benefits of speed-work for runners.
A study in Physiological Reports trained male and female runners to complete ten sessions of speed-training over the course of six weeks. By the end, their average 10K time improved by 3.2%: which would equate to a 50-minute 10K runner bringing their time down to 48:25.
During speed work-outs, you maximally activate your slow-twitch muscles and intermediate muscle fibres, which increases your aerobic capacity.
Speed work-outs, also, increase your production of myoglobin, which is a protein found in muscles. Myoglobin transports oxygen to the mitochondria in your muscles, which in-turn produce ATP to give your muscles energy. So, as you increase your myoglobin, you improve your body’s ability to quickly transport oxygen to the muscles for energy, making you able to run faster. Speed-work is uniquely beneficial in this aspect, as research indicates, that, high-intensity running is the best way to develop myoglobin.
While you may not significantly increase your VO2max (genetics can limit that), you will see clear benefits of speed-work. Your body will become more efficient at recruiting your fast-twitch muscles. Your running economy will improve, so that you expend less energy and can run faster at the same effort level, whether you are running a 5K or 50K.
Finally, there is the skill aspect. As Peter Coe once said, if you want to run faster, you have to practice running faster! Speed work-outs train you how to output more effort, maintain a higher cadence, and mentally cope with some physical discomfort while running. If you practice this skill once or twice a week consistently, you won’t just become faster, you will run faster with less effort.
Shorter is better when it comes to speed work-outs. A study published in the Journal of Strength and Conditioning Research confirmed what many top coaches practice shorter speed intervals: yielding more benefits to long-distance runners than long speed intervals. Shorter speed intervals develop more running economy and have less risk of injury than longer intervals.
All-in-all, from the casual to elite person speed-work is going to have a vast amount of benefits. Which is why it forms a cornerstone in Vorsprung's methodology.
References:
Runners Connect
Run Keeper
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