running form | biomechanics | running style
Running form: How you can become a better runner without increased fitness - with the right form.
Is there really such a thing as 'good running form'? Coaches preach relentlessly about proper form, and runners classify other competitors as having 'good' or 'bad' mechanics, yet scientific research has shown that first-class form is an extremely elusive quality.
With that caveat in mind, what should you do about your form? Isn't there a biomechanical adjustment you could make which would carry little risk of making you less efficient - and which could shave time from your 5-K or 10-K PBs without the need to devote months of training to the process of upgrading physiological variables like lactate threshold, VO2max, and specific endurance? Well, Peak Performance surveyed the scientific literature on form improvement dating back to 1980, searching for information which might help your running. We found several 'gold nuggets' which could revamp your running style in a positive way.
Our first stop along the running-form pathway was to study the work of one of the most tireless and practical investigators of optimal running mechanics - Dr. Nancy Hamilton at the University of Northern Iowa. Hamilton has approached the form problem from a unique angle - by linking it with the process of ageing. In fact, the impetus for her research came from her observation that running performances and overall running form change rather dramatically as a result of getting older.
Although most investigators have linked age-related performance fall-offs with declines in cardiac power and losses in muscle mass and strength, Hamilton wondered whether changes in form might also account for a significant fraction of the performance downturn. It was an exciting idea, because it meant that it might be possible to identify those specific aspects of form which must be preserved in order to sustain fast and efficient running velocities.
The Hamilton tapes
So, at the World Games in Eugene and the National Championships in San Diego in 1989, Hamilton spent hour after hour videotaping 162 competitive runners (83 males and 79 females). She then digitised the runners' performances into a computer and literally spent hundreds of hours analysing the runners' biomechanics. Fast runners were compared with slow ones, older runners with young upstarts. As she watched the tapes unwind, Hamilton became convinced that performance differences between runners of the same age and also age-linked declines in velocity might be caused to a very large extent by mechanical factors such as range of motion at the hips, knees, and ankles.
Her theory was that range of motion was bound to influence stride length and stride frequency, two key components of running economy and the two elemental aspects of running which must change if you're to become a faster runner. After all, you can make all the improvements you want in VO2max, economy, lactate threshold, and form, and such upgrades might allow you to run for a longer period of time at your current, familiar speeds without any change in stride length or frequency, but the improvements will only help you move more quickly if they actually lead to quicker and/or longer strides.
It's the length - or the frequency
For example, if you currently run a 5K at a steady pace in around 18:30, you cannot improve your time unless you change your stride length or frequency. If you currently take 180 steps per minute (90 strides) and your stride length is 3 metres (1.5 metres per step), you're automatically locked into approximately a 1667-stride (3334-step) race, since 5000 divided by 3 equals about 1667 strides. Now 3334 steps divided by 180 steps per minute gives you a finishing time of around 18.5 minutes, or 18:30.
If you improve yourself physiologically or ameliorate your form and transfer that nice change into a 1-per cent increase in stride rate (without any decrease in stride length), you'll run your 5Ks in around 18:20, a 10-second improvement. If your transformation produces a 1-per cent increase in stride length instead of rate (without any loss in rate), your 5-K time will slide down by the same amount - to that nice 18:20. Of course, simultaneously upgrading stride length and rate by 1-per cent each will bring you home in about 18:10.
Do stride patterns change with ageing? Of course, but Hamilton was startled to learn that stride rate dropped off to only a small extent (and the change wasn't statistically significant). In fact, there was actually a trend for stride rate to increase slightly between the ages of 35 and 55, after which it began to decline a bit. The stride rates of runners in their 80s were only about 4- to 5-per cent slower than those of the 35-year-old whippersnappers.
Although stride rate didn't change much, stride length did decline by rather massive amounts. Looking at the most extreme comparison possible - the stride lengths of 35- to 39-year-old runners versus those of 90-year-old competitors, Hamilton found that stride length during sprinting declined from 4.72 metres per stride (2.36 meters per step) to 2.84 metres per stride (just 1.42 metres per step), a whopping 40-per cent decline! As Hamilton put it concisely, 'Even though the legs of older runners were still moving quickly, they were not gaining as much distance per step'.
Although Hamilton was somewhat surprised by her results, her findings reinforced exactly what other researchers had noticed about walking patterns. Basically, at least six different studies published since 1980 have shown that walking speed declines with ageing, even though 'gait timing' (the number of steps per minute) remains constant. The key change is the same one Hamilton observed - a rather remarkable plummeting of step length.
Why does it happen?
Stride length shortened progressively and predictably once runners passed the age of 40, but what was actually causing the negative change? For one thing, Hamilton found that ageing increased the amount of time each foot remained in contact with the ground during running. In other words, older runners weren't 'exploding' from one foot to the other as they ran; instead they were spending more time with their feet 'planted' to the ground. This increase in the amount of time spent in the 'stance phase' of running produced greater deceleration (the longer your foot is on the ground, the more speed you lose) and thus accounted for some of the stride-length dip. Older runners simply weren't moving as fast when they 'toed off.' Thus, they crossed more meagre amounts of territory before the next footstrike occurred.
However, stride-length fall-offs turned out to be most closely related not to stance-phase lethargy but to changes in range of motion at the hips and knees. For example, range of motion at the knees during running (basically, knee flexion) decreased by 33 per cent - from 123 degrees to just 95 degrees - between the ages of 35 and 90. This shift basically put the lower part of the leg at a right angle with the thigh at the point of maximum flexion (during the swing phase of the gait cycle) - rather than crooked back upward toward the buttocks.
Why is this important? Well, keeping the knee less flexed and the foot down at the level of the knee rather than perched up by the buttock during the swing phase of running (when the leg is brought forward to make the next contact with the ground) would mean that in effect you were creating an extra-long lever with a heavy foot dangling out at its end. That's bad, because long levers are harder to move than short levers. Plus, that size-11 foot tends to weigh a lot, and once you put weight on the end of a lever it loves to resist motion (that's why the heavier person on a see-saw tends to remain planted on the ground). As your leg begins to swing forward, it's best to have that knee tucked up by the buttock, cutting your lever almost in half by making the knee - rather than the foot - the endpoint of your limb.
Picture it this way: as you are running along, your left foot has just initiated contact with the ground. Your right leg is flexed at the knee, and as your left foot rocks forward toward toe-off, you swing your right leg forward. As you swing your right leg forward, it's most economical to have your knee flexed so that your right foot has moved well up toward your buttock. If your leg stays straight, or flexes only moderately at the knee, too much weight will be at the end of your right 'lever', which has its pivot point at your right hip. As a result, that leg will be very difficult to accelerate. Once you've shortened that lever by flexing the knee, you can zing your right leg forward at high speed, and you've solved part of the problem of achieving a more expansive stride length.
That blasted hip
Although movement at the knee declined with ageing, Hamilton found that the loss of range of motion at the hip was even greater - dropping by 38 per cent between the ages of 35 and 90. There was a slight age-related difference between the two different types of range-of-motion decline, with knee 'stiffness' striking with greatest force after the age of 50 and hip problems waiting until the age of 60 or so. However, Hamilton's research suggested that preservation of hip flexibility was more important for maintaining speed, compared with the maintenance of knee suppleness.
Specifically, Hamilton found that the key to optimal hip range of motion was the conservation of hip mobility in the kick or drive phase of running - when the foot becomes a rigid lever for toe-off, the gluteal and hamstring muscles recoil and contract to propel the leg backward, and the quads also activate themselves to help straighten the leg for the backward push. We can call this basic motion hip extension - the backward movement of the leg at the hip.
But how can older runners preserve adequate hip extension and thus stride length - and younger harriers improve on the extension they already have? Certainly, flexibility of the quadriceps muscles is one key, since over-tight quads will resist backward leg movements. Consistent and thorough stretching routines for the quads - carried out only after a thorough warm-up - can certainly help make the quads and their associated connective tissues more supple.
However, Hamilton points out that another key is to deliberately alter the way you run, eg, to focus more on using the muscles around the buttocks to push backward on each step.
As she puts it, 'Rather than reaching out with the foreleg to get maximum distance forward during a stride, think about pushing back as hard as you can on each step. Use the buttocks and hamstrings to do so, very much the way you might push out hard from a set of starting blocks. Run from your hips - not from your knees'. Make sure you do this only after your quads are warmed up and loose, however, to avoid overstressing them with your new-found form.
So those are three great ideas for form transformation - better quadriceps flexibility, increased knee flexion during the swing phase, and heightened backward pushes with the hams and glutes, the goal being the natural advancement of stride length. What else does the highly respected Hamilton recommend? 'Paradoxically, while knee flexion is good during the 'swing' phase of running, it's not so good during the stance phase - when the foot is on the ground. Excessive ankle flexion is also bad. The problem that occurs when you flex your ankle and knee too much at impact is that you have to straighten those joints back out again at toe-off. So, the more they are flexed, the greater the amount of time spent in footstrike,' says the excellent UNI researcher. Of course, that's bad, because during footstrike the foot is essentially screwed into the ground and there can be no horizontal movement. Movement only occurs when you are leaping from one foot to the other, so the goal is to make footstrike very brief yet very explosive in terms of force production.
As we've mentioned before in PP, improvements in performance associated with decreased footstrike time can be rather phenomenal. For example, take the case of the elite female road racer who has been finishing her 5-K races in about 16 minutes. Figuring that she takes about 190 steps per minute, that is a 3,040-step (16 X 190) race for her. Snip just one-thousandth of a second from her footstrike, and she'll be home three seconds sooner, perhaps enough of a saving to help her pass another runner or two. Trim 1/300th of a second, and she'll arrive 10 seconds more quickly, perhaps enough to finish among the top five runners. Shear off just 1/100th, still a very small change, and she'll cross the finish line 30 seconds sooner, enough to win the race.
Of course, the absolute time improvements are even greater for 'back-of-the-pack' competitors. Someone running a 5K in 30 minutes (or about 5400 steps) would improve overall race time by almost a minute if the stance phase were condensed by 1/100th of a second.
True, footstrike time should not be made too brief, because an overly abbreviated stance phase might not allow enough time to generate maximal force - and thus could curtail stride length. However, can you actually think of any distance runners who are too explosive? The usual problem is the reverse - a rather sad collapse of the foot against the ground, poor stability, modest force development, and mediocre acceleration over to the other foot.
Strangely enough, although Hamilton found that excess knee flexion during the stance phase was bad because it fattened total footstrike time, increased knee flexion during stance is often recommended by form experts because 'it helps to absorb shock'. Although this proposition has a certain appeal, there is absolutely nothing in the scientific literature to suggest that people who flex more at the knees actually experience lower impact forces at the hips and spine - or have lower rates of injury.
The bottom lines? Expanded knee flexion during the swing phase of running is good; during the stance phase it's bad. Quad flexibility upgrades stride lengths, and so does better buttock-muscle pushing. For now, those are four fine ways to begin renovating your form. Is there a danger of 'overstriding' with these fine-tunes? Not if you avoid 'reaching out' with your swing leg, and not if you let your leading foot land just slightly ahead or just under your centre of gravity. Your body will almost catch up with your lead foot just before impact with the ground, which will avoid any 'braking action' and will put you in great position to move powerfully forward.
In the next issue of Peak Performance, we'll continue our quest for good form by exploring the fantastic running-mechanics work carried out by the celebrated researchers Peter Cavanagh and Keith Williams.
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