13

Form Considerations for Special Groups

Runners commonly believe that each person has his own unique running style, perfectly suited to his individual neuromuscular and anatomical characteristics—and thus that he should be left relatively unperturbed by the general form recommendations made by exercise scientists and coaches. Unfortunately, this popular maxim exists far outside the domain of truth, as the laws of physics apply to all runners and do not vary by individual. The problem of form is a matter of resolving how best to control the collision between body and ground during gait—a repeated encounter that is governed by immutable physical truths. In the end, the runner’s task is to develop form in a way that minimizes the risk of injury and—for those who are concerned with speed—improves the ability to run quickly. Expressed another way, the goal of running-form improvement is to optimize the production of propulsive force during running.

There may be 50 million everyday runners in the United States, but there are not 50 million ways to optimize form. Rather, there is a basic method for form that can be tweaked by unique groups of runners. For example, a runner who wants to be an elite sprinter may land on the ground with the same shank angle as the elite distance athlete (and even the non-elite, good-form distance runner). However, maximum shank angle (MSA) and reversal of swing (ROS) should be expanded significantly for the sprinter, compared with the distance-athlete’s efforts. In this chapter, we will take a closer look at how form varies across different groups of runners and how a runner must change her form if she wants to belong to a certain group of athletes (for example, if she has aspirations to be an injury-free runner or an elite competitor).

The Elite Distance Runner

While form varies tremendously among distance runners as a whole, there is much less variation in form among truly elite distance runners (for example, those who appear on the IAAF top-50 list at various distances). A recent study determined that top-level elite distance runners eschew heel-striking and use forefoot- to midfoot-striking patterns (1). Elite athletes also run with a very similar MSA, ROS, SAT, and thus ROS/MSA ratio.

Elite distance runners who set world records, win world championships, and garner Olympic medals at distances of 5 kilometers and longer share the following key form characteristics:

• During competitions they use an MSA of about 14 to 18 degrees.
• From MSA, each of their feet during sweep moves backward about eight to 12 degrees (their ROS) before striking the ground with an SAT of approximately six degrees.
• Their collision with the ground is accomplished by means of a midfoot- to forefoot-strike.
• Their ROS/MSA ratio is close to .7.

With very few exceptions, these are the form characteristics which—when combined with superior metabolic capacities during exercise—allow a runner to enter the club of world-class distance runners.

Form Differences Between International and American Elite Runners

International runners dominate American harriers in elite distance competitions. It is tempting and logical to suggest that running form disparities play a key role in creating these performance differences.

For example, American elites are less likely to run with a midfoot-strike pattern and are more likely to run with a heel-strike, thus increasing the duration and magnitude of braking (and breaking) forces and amplifying the rate of increase of vertical ground-reaction forces with every step. Notable American examples of such running include Desiree (Desi) Linden (figure 13.1) and Shalane Flanagan (figure 13.2).

Compared with international elites, American elites also tend to have diminished ROS. This causes less kinetic energy to reach the ground per step, higher SATs (thus producing greater braking and breaking forces), and smaller ROS/MSA ratios (a reflection and cause of their generally slower running speeds in international competitions).

Figure 13.1   Elite U.S. runner Desi Davila Linden has been a heel-striker throughout her career, with SATs as high as 16 degrees and ROS/MSA ratios as low as .27.

Figure 13.2   Elite U.S. runner Shalane Flanagan has also been a heel-striker throughout much of her career, with ROS/MSA ratios at .50 and below.

Elite U.S. female distance runners have highly unfavorable form characteristics, compared with their East-African competitors (table 13.1). Note that only one American runner (Jordan Hasay) has a “golden ratio” (ROS/MSA) greater than .5 on both legs. In fact, only one other American athlete (Molly Huddle) has a golden ratio above .5 on either leg. Also, notice that Molly Huddle is the only mid-foot striker with a negative FAT on each foot, while Jordan Hasay lands flat-footed. Amy Cragg is a slight heel-striker on her left foot (FAT = 1). Kara Goucher is a minimal heel striker on her right foot (FAT = 1), and otherwise all other contacts with the ground involve strong heel-striking with FAT at positive 6 and above (and as high as +20 for Kellyn Taylor). Given the disparities between right and left legs, the preference for heel-striking, and the very poor ROS/MSA ratios, it appears that elite U.S. female distance runners conduct very little form training.

The contrast in running-form metrics between the eight elite international women (including seven from East Africa) in table 13.2 and the elite American women could not be more stark. Please note that the international women have a “golden ratio” (ROS/MSA) greater than .5 in all cases except one (Caroline Kilel). This indicates the American elites are creating greater braking forces per step—and experiencing longer durations of braking forces during each “visit” to the ground (stance). Note also in particular the relative consistency of SAT values for the international women, with most SAT being in the five- to eight-degree range. Paula Radcliffe is an exception here, but note her exceptionally large golden ratios. Gelete Burka has rather large values for SAT, but compensates with expansive values for ROS and thus has very good golden ratios. Please examine in particular the values for the incredibly explosive Almaz Ayana (2015 World Champion at 5000 Meters, 2016 Olympic Games Gold Medalist at 10,000 Meters (29:12), and 2017 World Champion at 10,000 Meters): Almaz has superb values of ROS/MSA on her right (.85) and left (.70) legs. Her incredible speed comes from these long, high-powered sweeps (ROS values) leading to explosive “punches” of the ground.

TABLE 13.1 Running Form Metrics: Elite American Women
NAME	EVENT	LEG	MSA	ROS	SAT	FAT	ROS/MSA RATIO
Molly Huddle	Track training	Right	23	9	14	−12	0.39
		Left	26	14	12	−9	0.54
Shalane Flanagan	2016 U.S. Olympic Marathon Trials	Right	17	8	9	13	0.47
		Left	14	7	7	6	0.50
Amy Cragg	2016 U.S. Olympic Marathon Trials	Right	17	7	10	7	0.41
		Left	15	7	8	1	0.47
Sara Hall	Road training	Right	19	5	14	10	0.26
		Left	16	2	14	9	0.13
Desiree Linden (Davila)	2011 Boston Marathon	Right	22	6	16	11	0.27
		Left	21	10	11	11	0.48
Jordan Hasay	10K Race	Right	18	12	6	0	0.67
		Left	16	10	6	0	0.60
Kellyn Taylor	Road training	Right	16	4	12	20	0.25
		Left	10	2	8	8	0.20
Kara Goucher	2011 Boston Marathon	Right	18	5	13	1	0.28
		Left	20	3	17	10	0.15
Courtesy of Walt Reynolds, NovaSport Athlete Development.

TABLE 13.2 Running Form Metrics: Elite International Women
NAME	EVENT	LEG	MSA	ROS	SAT	FAT	ROS/MSA RATIO
Mary Keitany	2010 NYC Marathon	Right	10	5	5	5	0.53
		Left	10	5	5	0	0.54
Tirunesh Dibaba	2013 Tilburg Netherlands 10K Road Race	Right	16	10	6	−2	0.63
		Left	20	12	8	−4	0.60
Almaz Ayana	2015 Weltklasse Zurich DL 3K	Right	20	17	3	−5	0.85
		Left	20	14	6	−6	0.70
Genzebe Dibaba	2015 Carlsbad 5K Road Race	Right	17	12	5	−12	0.71
		Left	25	18	7	−4	0.72
Caroline Kilel	2011 Boston Marathon	Right	16	7	9	−2	0.44
		Left	8	3	5	−3	0.38
Paula Radcliffe	2008 NYC Marathon	Right	8	7	1	−1	0.88
		Left	2	3	−1	−5	1.50
Gelete Burka	2015 IAAF 10K World Champs Track	Right	24	14	10	0	0.58
		Left	24	13	11	0	0.54
Aberu Kebede	2013 Tokyo Marathon	Right	8	5	3	−5	0.63
		Left	12	7	5	−3	0.58
Courtesy of Walt Reynolds, NovaSport Athlete Development.

The Non-Elite Runner

While there can be significant variations among runners, form characteristics for the ordinary runner share a number of common points.

ROS and MSA

MSA tends to be greater in the average distance runner, compared to the elite competitor. Conversely, the non-elite distance runner has very little ROS and tends to simply drop the foot to the ground after attaining MSA, instead of sweeping the foot backward dramatically to make contact with the ground. Because the ROS/MSA ratio is much smaller in the non-elite runner, it sometimes descends to a speed-thwarting 0.1, instead of the 0.7 used by the elite runner. The average runner you see jogging down the street in your neighborhood usually has an MSA of 18 and SAT of 16, putting the ROS/MSA ratio at a miserable 2/16, or .125, a proportion that maximizes slowing and braking and minimizes forward propulsive forces and kinetic energy transferred to the ground.

ROS and SAT

Since ROS tends to be greatly reduced in the non-elite distance runner, it produces an SAT that is significantly greater in the non-elite runner, possibly as high as 16 degrees (figure 13.3).

This is a key reason why the ordinary runner experiences considerably greater braking forces, compared with the elite harrier. This is also why the non-elite runner produces the high vertical ground-reaction forces at exactly the wrong time (while the shank angle is still positive and before the shank has reached a position perpendicular with the ground). It is as though the non-elite runner is trying to pole-vault forward using his leg as a pole, instead of bouncing forward explosively after ground contact.

Heel-Strike Pattern and Braking Forces

The ordinary runner tends to land with a less-flexed knee and a straighter leg at touchdown, which augments the rate of transmission of braking forces through the leg, increases braking forces, and decreases the ability of the knee joint to act as a shock absorber and force dissipater after impact with the ground. In addition, the non-elite runner is much more likely to land on the ground with a heel-strike pattern. In fact, research reveals that up to 95 percent of all non-elite distance runners collide with the ground in this way (2).

Figure 13.3   The “runner on the street” is a very poor “sweeper”, reversing swing by just two degrees and hitting the ground with an SAT of ~16.

Time on the Ground

The average runner spends much more time on the ground per step, compared with the elite competitor. In fact, research reveals that ordinary distance runners may spend as much as 70 percent of their total running time on the ground during gait, versus less than 50 percent for elite runners. More time stuck on the ground means less time flying forward and therefore slower running speeds for non-elites. When running at 10-K race velocity, the elite runner may spend approximately 160 to 180 milliseconds on the ground per step, versus about 220 milliseconds for the common runner.

The Distance Runner Versus the Sprinter

High-quality sprinters share a few form characteristics with high-performance distance runners. For example, SAT tends to be quite similar—averaging about six to eight degrees—in both top sprinters and distance runners. ROS/MSA ratios also tend to be similar between the two groups, hovering near .7. For example, Usain Bolt (figure 13.4a), the world’s fastest man with a 100-meter world record time of 9:58, and Eliud Kipchoge (figure 13.4b), the worlds’ fastest marathon runner with a non-world-record time of 2:00:24, both have golden ratios (ROS/MSA) of .7.

However, there are also some key differences between sprinters and distance runners. For example, MSA is much greater in the elite sprinter, compared with the elite distance harrier (it is often twice as large). This is a reflection of the higher speeds obtained by the elite sprinter, which require that the “hammer” (leg) of the “pistol” (body) be cocked to a greater degree so that it can accelerate toward the ground for a longer period. This allows the leg to attain a higher velocity in the instant before ground contact, thus putting more kinetic energy into the ground. World-record holder Usain Bolt often attains an MSA of 28 degrees when he competes at 100 meters, whereas marathon world-record holder Dennis Kimetto ordinarily uses an MSA of around 14 degrees per step when he competes in the marathon (and Eliud Kipchoge used only 10 degrees when he ran his amazing 2:00:24). During competition, Kimetto does not run as fast as Bolt, so he can set his leg about half as far ahead of his body, compared with Usain. While Kipchoge does not cock his leg as far ahead as Kimetto, he has a better ROS, helping to account for his faster marathon pace.

Figure 13.4   (a) World’s-best sprinter Usain Bolt and (b) world’s-best marathon runner Eliud Kipchoge share the same golden ratio.

Since SAT is similar between elite sprinters and elite distance runners, it seems obvious that ROS must be strikingly different. Bolt, for example, sweeps back from 28 degrees to about eight degrees of positive SAT (an ROS of 20 degrees); Kimetto starts at 14 degrees and comes back to six or seven degrees (an ROS of seven to eight degrees). Thus ROS/MSA is 20/28 = .71 for Bolt (figure 13.5) and 8/14 = .57 for Kimetto (figure 13.6).

Figure 13.5   Bolt has an MSA of around 28 and an SAT of about 7.

Figure 13.6   Dennis Kimetto (at far left) has an MSA of around 14 and an SAT of 6 to 7.

As mentioned, these form disparities help to produce the large differences in performance velocity between Bolt and Kimetto. Bolt’s more-expansive ROS imparts greater kinetic energy to the ground per step, compared with Kimetto’s less-bold reversal of foot movement. In addition, Bolt’s leg is moving much more quickly than Kimetto’s leg during ROS: Research suggests that Bolt’s leg may be clocking backward at about 300 to 350 degrees per second during ROS, while Kimetto’s leg moves at closer to 100 to 150 degrees per second (3).

The angular velocity of the shank during ground contact is also dramatically different between sprinters and distance runners, with sprinters reaching more than 1,000 degrees per second and elite distance runners reaching about 500 degrees per second. Non-elites will have slower angular velocities during stance, but the differences between sprinters and distance runners will still be present.

Ground-contact time (stance) is also quite different between elite sprinters and elite distance runners. Usain Bolt stays on the ground for no longer than 83 milliseconds per step when competing at 100 meters, while other notable sprinters such as Carl Lewis and Justin Gatlin have had their ground-contact times measured at between 83 and 100 milliseconds. By contrast, elite distance runners tend to be stuck on the ground for about 160 milliseconds per contact, and the ordinary runner remains lodged against the earth for a considerably longer 220 milliseconds or more per step.

The Sprinter’s “Air” Leg

Up to this point, this chapter has focused almost entirely on the “ground” leg—the lower leg that is immediately poised for contact with the ground or is actually on the ground. However, when it comes to measurements and comments about form, it is also important to mention the “air” leg—the leg that has just left the ground and is moving backward and then forward prior to reaching MSA, thus tracing the back and upper margins of the kidney bean path mentioned in chapter 1. Naturally, during running an air leg is always about to become a ground leg, and a ground leg is on the verge of becoming the air leg as a runner moves forward. The right and left legs repeatedly change roles during gait.

In sprinting, the air leg plays a particularly prominent role. The idea in sprinting is to maximize vertical ground reaction force when each foot is on the ground, and the air leg assists the ground leg in this task.

To understand this, weigh yourself on a bathroom scale. As you look down at the number, notice that your weight actually changes slightly as you move around during scale stance, even with subtle shifts in foot pressure and body position. Now swing your arms overhead while watching the scale reading. What happens? It is likely the swing of the arms upward instantly increased your “weight” by causing more force to be applied to the surface of the scale. This is the inevitable acting out of one of Newton’s original laws of motion: For every action, there is an equal and opposite reaction. The upward thrusting of your arms (resulting from a force directed overhead) created an equal and opposite reaction, with a force directed down into the scale.

This means that in running, an upward thrust of the air leg (the so-called “high-knee” action) amplifies the force placed on the earth by the ground leg, increasing vertical propulsive force. This is why (at initial ground contact) the air leg of the sprinter is always further advanced through swing, compared with the air leg of the distance runner (figures 13.7 and 13.8). The air leg of the sprinter must be poised to drive upward at the moment of first contact with the earth by the ground leg, in order to maximize vertical ground reaction force. The air leg is helping the ground leg push into the running surface and thus is increasing velocity.

Figure 13.7   The sprinter’s “air thigh” must be higher during mid-stance of the ground leg, compared with the distance-runner’s air thigh, in order to increase the magnitude of propulsive force produced by the ground leg.

Figure 13.8   The distance runner’s “air thigh” must be lower during mid-stance of the ground leg, compared with the sprinter’s air thigh, because of the lower magnitudes of propulsive force required in the ground leg.

This reinforces the notion that sprinters should attempt to minimize “backside mechanics” during their training—that is, they should train in ways that increase the speed of movement of the leg after toe-off so that the swing leg can be in a position to drive upward as the other (ground) leg makes contact with earth.

Male Versus Female Runners

Popular articles often suggest that running form is somehow different in women compared with men, and they often place the focus on the angle made between the thigh and hip joint. This “Q angle” is often larger in women because of their generally wider hips in relation to their body size (figure 13.9). The implications of this difference are never made entirely clear, but one possibility is that women might tend to land on the ground with a slightly more supinated ankle, which then might cause them to go through a greater range of pronation during stance and perhaps spike the rate of injury. In other words, women might be more likely to land on the outsides (lateral edges) of their shoes compared with men, which would then lead to a greater inward rolling of the ankle (pronation) during stance.

However, new research indicates the pronation is not actually linked with a higher rate of injury (4). Furthermore, the laws of physics do not vary according to the gender of a runner. The form variables discussed in this book—foot-strike pattern, MSA, ROS, SAT, and ROS/MSA ratio—are optimized in the same way in male and female runners since the movements of their bodies are both subject to Newton’s Laws of Motion. A study of male and female world-record holders shows that the basic form metrics are identical for men and women at distances ranging from 200 meters up to the marathon (3). (There is one world-record-holding outlier—Florence Griffith Joyner—who, as she set the world record for 100 meters, had an unusually large MSA of around 34 degrees and an SAT of about 12 degrees.) This means that the overall process of training and optimizing the relevant form variables will be the same in male and female runners.

Figure 13.9   The greater Q angle of female runners might increase the risks of ankle-supinated landings, greater pronation during stance, and thus injury.

That being said, one might make the logical argument that form training could still be more important from an injury prevention standpoint for female runners. With the Q angle being greater in women, there is greater torque created at the hip compared with men, and thus foot-strike pattern would be especially critical. A heel-strike pattern would create dramatically greater torque forces at the hip in a shorter period of time, compared with a midfoot- strike, which is associated with a smaller VALR.

Older Versus Younger Runners

As is the case with the male-female contrast, masters and open runners experience the same forces during running and need to optimize the same form metrics. Form training will thus be very similar in runners, regardless of age.

That being said, masters runners tend to have more problems with backside mechanics, compared with younger runners. After toe-off, masters runners tend to have less hip extension compared with younger runners, and the movement of the swinging leg when it is behind the body tends to be more lethargic in older runners. Because the leg tends to move more slowly, it is prone to be late moving into proper position for the time-sensitive upward knee thrust of the air leg.

This can be corrected by training, using the drills in chapters 8 and 14. The lack of hip extension in masters runners is also a function of not only what happens during rearward-directed swing of the leg after toe-off, but also of a slower angular velocity of the ground leg during stance. Since the leg is generally moving more slowly during stance in the masters runner, the velocity of the foot at take-off is lower and thus hip extension is reduced. This situation can at least be partially rectified through the use of running-specific strengthening exercises, drills that emphasize minimization of ground-contact time, and dynamic mobility work to increase the flexibility of the hip flexors (which resist hip extension).

The Right-Leg Versus Left-Leg Runner

Not only is there considerable variation among all runners when it comes to form characteristics and metrics, but there is also significant variation within an individual runner. That is, the action of a runner’s left or right leg may vary a bit from one encounter with the ground to the next. However, all runners have a distinct, signature pattern with each leg. The behavior of the right or left leg tends to converge around basic values of the form variables.

The biggest variation that occurs in an individual runner is from the right leg to the left leg. Somewhat surprisingly, the majority of runners have legs that function differently, with the right leg having different metrics (MSA, SAT, ROS, ROS/MSA, and even foot-strike pattern) compared with the left.

These disparities can be strikingly large. For example, my own work with an elite runner has revealed that, during competition, her left leg has an MSA of 18 degrees, an SAT of 6 degrees, an ROS of 12, an ROS/MSA ratio of 12/18 = .67, and a beautiful midfoot-strike pattern. On the right leg, however, the MSA is 17 degrees, the SAT is 10 degrees, the ROS is 7, the ROS/MSA ratio is only 7/17 = .41, and the foot-strike pattern is a disturbing heel-strike. Despite these large differences, this elite runner was unaware of the disparate behavior exhibited by her lower limbs. This disparity was fully corrected utilizing the drills outlined in this book.

This situation is actually a dream scenario for coaches. For the first time, we have real metrics regarding form and thus something specific we can really aim for as we coach our athletes. It is exciting to know that we can improve the speed and stamina of our athletes not only through long periods of challenging training, but also through the process of form optimization, which can take considerably less time to achieve. Form work is really the foundation of all running training and should be engaged in seriously from the outset of training. Otherwise, a runner may end up with one “victorious” leg and one “defeating” leg—or with generally poor form that negates all of the metabolic advances she makes through arduous training. With poor form, even a runner who has the strongest heart and muscles with the highest oxidative capacities will be, in effect, running with a Rolls-Royce engine and square wheels. Fortunately, we as coaches now have real numbers (for MSA, ROS, SAT, ROS/MSA, and FAT) that we can use as goals and guides as we teach optimal form to our runners.

Summary

When it comes to improving form, the task for every runner (male, female, sprinter, distance runner, young, and old) is the same: He or she must learn how to coordinate repetitive collisions with the ground in a way that optimizes MSA, SAT, ROS, ROS/MSA, and FAT. Doing so will simultaneously increase running speed and endurance while decreasing the risk of injury.

There are huge differences in these variables between the average runner and the elite distance runner, but the average runner should attempt to move his form numbers toward those achieved by the best elites. In doing so, he might not set a world record, but his performances will improve, and his risk of injury will decrease.

Sprinting and distance running do have striking form differences, with sprinters relying on forefoot-strikes, while distance runners who are interested in optimizing form go for midfoot-striking. Sprinters also exhibit greater MSA, an ROS that is greater in magnitude, higher angular velocity during ROS, greater angular velocity during ground sweep, shorter stance durations, and higher cadences.

References

1. Walter Reynolds, “Maximal Shank Angle, Reversal of Swing, and Shank Angle at Touchdown in World-Record Elite Distance Performances,” unpublished (2015).

2. H. Hasegawa et al., “Foot-Strike Patterns at the 15-km Point During an Elite-Level Half Marathon,” Journal of Strength and Conditioning Research 21, no. 3 (2007): 888–893.

3. Walt Reynolds, personal communication, February 7, 2017.

4. B.M. Nigg et al., “Running Shoes and Running Injuries: Mythbusting and a Proposal for Two New Paradigms: ‘Preferred Movement Path’ and ‘Comfort Filter,’ ” British Journal of Sports Medicine 49, no. 20 (2015): 1290–1294.