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Chapter 2: The Biomechanics of Distance Running
Brian Hanley
• Running speed is dictated by an athlete’s step length and cadence, although step length is
more important in differentiating between faster and slower runners, and reduces more with
fatigue. Being able to increase cadence, however, is often the deciding factor in sprint
finishes.
• Of the different components that make up step length, the distance the body travels during
flight is the most important. An athlete’s flight distance is determined by upward and forward
impulse in late stance, which usually decrease with fatigue because of reduced leg stiffness
and tolerance to repeated stretch loads.
• Middle-distance runners are more likely to land on the forefoot or midfoot at first contact,
whereas marathon runners tend to land on the heel. There are potential performance
benefits to landing near the front of the foot through the stretch-shortening cycle and shorter
contact times, although these apply less in longer events.
• There are small gains to be made from following rival runners in terms of air resistance,
although having air moving around the body for cooling is important in hot conditions.
Running uphill is unsurprisingly more energy costly than running on flat courses, but
running downhill can risk injury because of the increased load on the knee, hip, and shin
muscles.
• Running of soft surfaces, such as in cross country running, is more difficult than on roads
because the non-compliant nature of the surface reduces the effectiveness of the stretch-
shortening cycle, and is more energy costly because of an increase in leg stiffness to
accommodate a reduction in stability.
Introduction
A knowledge of the biomechanics of running is invaluable when describing an athlete’s
technique, explaining how they speed up or slow down, and understanding the external and
internal forces that cause their movements. As the outward expression of movement, an
athlete’s biomechanics translates their underlying physiological, nutritional and psychological
processes into running motion, and those who are biomechanically “better” are often those
who can manage this transfer more efficiently and economically while reducing injury risk. This
chapter provides a brief review of the important aspects of the running stride and its various
components, the effects of different footstrike patterns and fatigue on running technique, and
how racing conditions such as wind, hills and underfoot surface affect an athlete’s
biomechanics.
Step length and cadence
Running speed is the product of step length and cadence, the latter of which is often referred
to as step rate or step frequency. Step length is the distance between successive foot contacts
from a specific gait event on one foot to the equivalent event on the other foot, and is measured
in metres (m). The term ‘stride length’ is sometimes used interchangeably with ‘step length’
(Enomoto et al, 2008); however, stride length is most often used to refer to the distance
between a specific gait event on one foot to the equivalent event on the same foot (e.g.,
Cavanagh and Kram, 1989). Hence, a stride refers to two successive steps (Levine, Richards
and Whittle, 2012). Cadence measures how frequently the runner completes a step in a given
time, usually per second (measured in hertz, Hz). As speed is step length multiplied by
cadence, an athlete with a step length of 1.50 m and a cadence of 3.00 Hz runs at 4.5 metres
per second (ms-1). To convert ms-1 to kilometres per hour (kmh-1), we multiply by 3.6. Thus,
our runner’s speed of 4.5 ms-1 is equivalent to 16.2 kmh-1.
It is clear that both step length and cadence are important to running speed. However,
cadence tends to vary less between distance runners, ranging from about 2.75 to 3.25 Hz
(165 to 195 steps per minute). In middle-distance running, which includes fast starts and bursts
of speed (e.g., to reach the bend before other athletes, or avoid being boxed in), athletes have
to accelerate to ensure a good position. Increasing cadence in middle-distance races is
therefore a performance-determining factor because of these short phases of great
acceleration (Reiss, Ernest and Gohlitz, 1993). Over 800 m and 1500 m, individuals usually
change from sub-maximal to maximum speed by increasing cadence, as step length is already
close to its maximum at competition pace (Hunter, Marshall and McNair, 2004). Cadence also
increases during sprint finishes; for example, when Kenenisa Bekele won the 2007 World
Championship 10,000 m, his step length was relatively constant at approximately 1.95 m
throughout the race, and it was by increasing cadence during the last lap (from 3.2 Hz to 3.6
Hz) that he was able to achieve such a fast finish (Enomoto et al, 2008). At running speeds
outside of the sprint finish, increases in speed normally arise from increases in step length,
with an optimal step length and cadence unconsciously chosen by athletes to minimise energy
expenditure (Saunders et al, 2004).
Overall, most distance runners have techniques that optimise performance within their
physical and anthropometric builds where, ultimately, step length is limited by the athlete’s
stature and, more specifically, their leg length. Of course, this does not mean that short
athletes cannot succeed in distance running; indeed, many of the world’s best ever athletes
are shorter than average, e.g., the hugely successful Ethiopian distance runners, Haile
Gebrselassie and Kenenisa Bekele, are about 1.65 m tall (5’ 5”). Bushnell and Hunter (2007)
found that distance runners’ sprinting techniques differed from trained sprinters and suggested
that this might be because distance runners practise sprint technique less and are unable to
change technique greatly to increase cadence during sprint finishes. Coaches are therefore
advised to include sprint technique training into competitive distance runners’ schedules.
Components of step length
Step length is the sum of four distinct but interrelated components. At first contact, the athlete
strikes the ground with the foot, and the distance from the whole body centre of mass (CM) to
the foot centre of mass is the first of these components (here, I have termed this “foot ahead”).
The body then rolls forwards over the support foot until toe-off, in phases that can be most
easily summarised as early stance, midstance and late stance. The distance the foot moves
from its horizontal position at first contact until toe-off is the second component contributing to
step length (“foot movement”). Although this action is vital for correct running gait, foot
movement is a relatively small contributor to overall step length and does not differentiate
between faster and slower running. The distance from the CM to the foot centre of mass at
toe-off is the third of the four components, which I have termed “foot behind”. These three
components occur during the contact phase, which has a shorter duration in faster running
(because it leads to a higher cadence), and decreasing contact time is indeed one way by
which distance runners speed up (Bushnell and Hunter, 2007). After the contact phase, the
athlete has an airborne period during which the CM will experience a flight distance (the fourth
and final component) before first contact occurs on the other foot and the gait cycle is
repeated.
In effect, the three most important components of step length are the distance the foot lands
in front of the body, the distance the foot is behind the body at toe-off, and how far the athlete
travels during flight. To be successful, the athlete must cover sufficient distances during each
of these phases, but running faster is not a simple case of increasing any or all of these
components. First, the athlete needs to take care that the foot ahead distance is not too great
(sometimes termed “overstriding”) as the increased braking forces that occur slow the runner
more than necessary (Moore, 2016). However, it should be noted that braking at first contact
with the ground is normal and, although it often appears in fast-moving elite athletes that the
foot is landing directly under the body, it does not and to physically undertake such actions
would adversely reduce step length. Second, the foot behind distance occurs during late
stance when the hip, knee and ankle are extending to push the body forwards. However, as
with foot ahead distance, the athlete should take care not to deliberately overextend as the
increase in contact time not only decreases cadence, but also occurs when the lower limb
joints are no longer particularly effective. In general, there is little difference in foot ahead or
foot behind distances between elite standard athletes. Although the athlete cannot speed up
during flight in the absence of anything to push forwards against, and in fact slightly slows
down because of air resistance, flight distance contributes so much to step length that it is the
biggest differentiator between athletes. When running slowly, by contrast, flight distance can
be very small. Merely instructing an athlete to increase any of these distances is unlikely to be
productive; rather, it is through training, particularly at fast speeds and supplemented
appropriately with technical and resistance training, that the athlete learns to get the right
balance for their stature, strength and ability.
Ground reaction forces in running
The importance of the stance phase during running is obvious given it is during ground contact
that the body applies an external force to generate forward momentum. In simple terms, a
force causes a change in velocity and, when running, different external forces are
experienced. These include ground reaction forces in late stance that accelerate the athlete
upwards and forwards, air resistance that causes slowing down, and frictional forces that
provide grip. A force is a vector, which means that it has a magnitude (measured in newtons,
N) and a direction (Winter et al, 2016). It can be quite difficult to analyse forces as single
vectors so, in biomechanics, the ground reaction forces between the body and running surface
are very often resolved into three directions: vertical (the only direction affected by gravity),
forwards-backwards, and side-to-side. When a person stands still on a weighing scale, the
value on the display is their vertical ground reaction force (i.e., their weight), although it is
normally displayed in the technically incorrect but more familiar units of kilograms or pounds.
Because people’s weights vary considerably, it is quite normal in biomechanics to present
force magnitudes in bodyweights (BW), whereby the forces measured are divided by the
athlete’s weight. For example, if a runner who weighs 600 N (approximately 61 kg / 135 lb)
experiences a landing force of 900 N, we could express this as 1.5 BW.
At first contact with the ground, the runner experiences a large impact force of between 2 and
3 BW (Cavanagh, 1990). Because the impact force occurs very early in the gait cycle, the
muscles are often unprepared for it and respond through passive deformation of body tissues
(Watkins, 2010). This “muscle latency” period lasts about 70 milliseconds, and the combination
of relatively large impact forces and the inability of the body to respond fully mean that there
is more variability within limbs, and asymmetry between them, than during the rest of the gait
cycle (Hanley and Tucker, 2018). Vertical forces during running tend to increase during early
stance with a peak at midstance, associated with controlling the downwards movement of the
CM, and preventing any vertical collapse during this weight acceptance phase (Winter and
Bishop, 1992); lower limb joint stiffness is therefore a key factor in maintaining posture during
this phase (Serpell et al, 2012). Note here that “stiffness”, the relationship between the
deformation of a body and a given force (Butler, Crowell III and McClay Davis, 2003), is used
to explain in simple terms how much or how little the lower extremity joints bend during stance,
rather than tightness or soreness in the muscles after exercise.
Although vertical forces, and probably more so side-to-side forces, are difficult to link with
performance (Cavanagh, 1990), the role of forwards-backwards forces are easier to
understand in terms of running speed. Both the braking and propulsive forces that occur in
this force direction have peak magnitudes of between 0.3 and 0.5 BW (Cavanagh and
Lafortune, 1980; Munro, Miller and Fuglevand, 1987), although what is more important is not
the peak force but the total force applied during each phase. The product of force and time is
impulse, defined as the change in momentum (Winter et al, 2016). Put simply, the larger the
negative impulse during braking in early stance, the more the athlete will decelerate, which
requires a similarly large positive impulse during late stance to speed up enough to maintain
an overall constant speed (Chang and Kram, 1999). Maintaining a constant pace is therefore
easier when the braking impulses are kept low, which theoretically occurs with a shorter foot
ahead distance (Moore, 2016) and emphasises the biomechanical advantage of avoiding
overstriding.
Movements and muscles involved in running
We have already noted that there are effectively two phases that contribute to step length and
cadence during running: a contact phase and a flight phase. These arise because each leg
goes through a period where it is in stance (the contact phase) and a period in swing,
comprising early swing, midswing and late swing. In normal running, each leg’s swing phase
is longer than the stance phase, and it is during the short time when both legs are in swing
that flight time occurs, whereby one leg is in early swing, just after toe-off, and the other leg is
in late swing, just before first contact (Novacheck, 1998). This of course means that during
normal running, there is no occasion when both feet are in contact with the ground at the same
time. For ease of explanation, the following sections will describe joint and body segment
movements during the stance and swing phases, although it should be remembered that these
are, in reality, interdependent parts of a continuous movement. In addition, as there are
hundreds of muscles involved in running, only the activity of large muscle groups will be
considered.
Muscle moments and powers
Before discussing the movements of the body’s joints and segments, it is useful to understand
a little about the internal forces produced by muscles. Muscles act on bones to create
movements at joints via tendons; for example, the soleus muscle in the calf pulls on the
calcaneus (heel bone) via the Achilles tendon to plantarflex the ankle. It is often helpful to
consider the muscle and tendon as part of one unit, rather than separate, and refer to it as the
muscle-tendon unit (MTU). Most of the movements in running are rotational, such as knee
flexion, and joint moments (or torques) indicate the amount and direction of rotational force
about a joint. These are useful because they describe the relative contributions of different
muscle groups during certain movement phases (Enoka, 2008). Calculations of mechanical
power are used to complement the joint moment information by measuring the rate of work
done by MTUs across a joint (White and Winter, 1985). MTUs that shorten when activated
(often described as “concentric”) generate power, whereas those that lengthen (“eccentric”)
absorb it (Vardaxis and Hoshizaki, 1989). Power that has been absorbed in MTUs stores
elastic energy that can be later converted to kinetic energy with resulting power generation
(Cavagna, Dusman, and Margaria, 1968) through the stretch-shortening cycle mechanism that
increases running efficiency (Cavagna, Saibene, and Margaria, 1964). The stretch-shortening
cycle is a complicated phenomenon, but in essence refers to the rapid lengthening and
subsequent shortening of an MTU, whereby the early stretch absorbs energy that enhances
performance during the concentric phase of activity (Komi, 2000).
In distance running, some joint stiffness is required for optimal usage of the stretch-shortening
cycle, although too much or too little can lead to reduced performances and injury (Butler,
Crowell III and McClay Davis, 2003). Greater running economy has been associated with
greater lower limb stiffness (Dutto and Smith, 2002) because of a better use of elastic energy,
and Arampatzis et al (2006) found that runners with better economy had a more compliant
quadriceps femoris tendon and higher triceps surae (gastrocnemius and soleus) tendon
stiffness. It is also possible that less economical athletes have techniques that lead to
unnecessary and wasteful vertical motion (Nummela, Keränen, and Mikkelsson, 2007).
Similarly, these authors found that shorter contact times were associated with better running
economy at several speeds typical of elite 5000 and 10,000 m runners, and reasoned that this
was because shorter contact times tend to feature shorter braking phases.
The swing phase
The function of the swing phase is to allow the foot to clear the ground after toe-off and be
repositioned in front of the CM ready for first contact (Levine, Richards and Whittle, 2012).
During early swing, the hip flexes so that the thigh moves from a position slightly behind the
body to one in front of the body, with considerable activity by the rectus femoris and iliopsoas
muscles. Because of the mass of the thigh and its location as the nearest joint to the trunk,
this movement of the hip is important to the whole leg’s contribution to overall running speed,
with Bushnell and Hunter (2007) reporting that distance runners sped up by flexing the hip 14°
more during midswing. The knee moves from a straightened angle of about 160° at toe-off to
a very flexed position during midswing (55-60°) by concentric activity of the hamstrings, and
then straightens again to about 150° in preparation for landing. The main knee extensors on
the front of the thigh, the quadriceps femoris group, are mostly responsible for this movement,
although runners should note that the hamstrings are often under considerable stress during
late swing because of how they act to control knee extension (Chumanov, Heiderscheit, and
Thelen, 2011). As well as helping the foot to clear the ground, the decrease in knee angle
during swing acts to reduce the leg’s moment of inertia (its resistance to rotation), and
enhances the flight phase because the recovery leg’s energy requirements are lowered (Kong
and de Heer, 2008; Smith and Hanley, 2013). Some of the necessary actions taken to clear
the ground are made by the ankle, which is plantarflexed at toe-off and moves to a more
dorsiflexed position at landing, caused by activity of the tibialis anterior and other shin muscles.
Along with the knee extensors, a key role of the ankle plantarflexors is to create high joint
stiffness before and after first contact (Hanon, Thépaut-Mathieu and Vandewalle, 2005) to
enhance the stretch-shortening cycle.
The stance phase
The purpose of the stance phase is to generate the impulse the body needs to move forwards.
At first contact with the ground, the hip is flexed so that the thigh is ahead of the body and
then extends to a position behind the body (usually a small amount of hyperextension). The
main muscles involved are the hip extensors, comprising gluteus maximus and the three
hamstring muscles, which mostly act concentrically during this motion and provide the “drive”
for moving forwards. The knee flexes about 15-20° from its more straightened position at first
contact until midstance and is associated with enabling a more level path of the CM (Saunders
et al, 1953), although it has been found that elite runners flex their knees less and have shorter
durations of knee flexion during stance (Leskinen et al, 2009). These differences in knee
motion mean elite runners have greater knee stiffness (Heise, Smith and Martin, 2011), and
are thus able to use elasticity better, allowing them to achieve faster times in competition and
withstand tiredness for longer (Leskinen et al, 2009). This elasticity occurs because the
decrease in knee angle at midstance results in energy absorption through the lengthening of
the quadriceps femoris, which subsequently shortens to extend the knee and propel the body
forwards and upwards.
The ankle lands in a slightly dorsiflexed position at first contact (Buczek and Cavanagh, 1990)
and dorsiflexes more in midstance largely because of knee flexion (as the tibia moves forwards
relative to the foot). The plantarflexors, such as gastrocnemius and soleus, are an important
energy generator as they act concentrically in late stance to create positive impulse. During
the stance phase, there are also important foot movements, such as pronation and supination,
which are each effectively a combination of rotational movements. These are often described
as ankle motions, but actually occur at the subtalar joint, which is between the talus bone and
heel bone (calcaneus), located under it. In general, the runner lands on the outside of the foot
(hence the wearing down of this part of the shoe first), pronate during the early, loading part
of stance so that the foot is placed flat on the ground, and then supinate (moves the weight
back to the foot’s outside) during late stance. The function of the pronation and supination
movements is to place the foot so that it is in the best position to provide support and guide
correct movement, for example as a shock absorber (Novacheck, 1998).
Upper body movements
The movements of the upper limbs generally act in opposition to the ipsilateral (same-side)
lower limbs to counteract moments of the swinging legs around the vertical axis (Hinrichs,
1987; Pontzer et al, 2009). Furthermore, Hinrichs (1987) stated that the arm swing provides a
meaningful contribution to lift and subsequently flight, and although the arms do not provide
forward propulsion of the CM, they minimise changes in horizontal velocity during stance.
However, it is debated as to whether the shoulder muscles are primarily responsible for the
swinging motion of the arms or whether their movement is mostly a passive response to the
legs’ movements (Pontzer et al, 2009). Regardless of the exact contribution of the upper limbs,
and as elbow angles are generally more variable between runners than lower limb angles
(Hanley, Smith and Bissas, 2011), the ungainly arm movements often adopted even by elite
athletes should be avoided in providing balance and propulsion to the body, and are frequently
an indicator of a problem elsewhere in the body.
The movements of the arms complement those of the torso, where the upper part of the trunk
can be seen to act in opposite and counterbalancing motion to the lower part (Novacheck,
1998), and indeed trunk rotation in running has been associated with increased efficiency
(Bramble and Lieberman, 2004). Pelvic rotation is the way in which the pelvis twists about a
vertical axis, moving each hip joint forwards as that hip flexes, and backwards as the hip
extends (Levine, Richards and Whittle, 2012), meaning that less hip flexion and extension are
required because a portion of step length is achieved by the forwards-backwards movements
of the pelvis instead (Inman, Ralston and Todd, 1981). Another important movement at the
lower end of the torso is pelvic obliquity, where one side of the pelvis drops below the other
(Levine, Richards and Whittle, 2012). This occurs during midstance, where the gluteus medius
muscle on the outside of the hip acts to stabilise the pelvis whilst allowing a small drop to occur
on the opposite side so that the overall path of the CM does not fluctuate too greatly
(Saunders, Inman and Eberhart, 1953).
Footstrike patterns
Distance runners make first contact with the rearfoot (heel-striking), midfoot or forefoot
(Stearne et al, 2014). Middle-distance runners are more likely to land with an anterior footstrike
pattern (either midfoot or forefoot) (Hayes and Caplan, 2012), with the percentage of athletes
making first contact with the rearfoot increasing as the race distance gets longer (Hanley et
al, 2019; Hasegawa, Yamauchi and Kraemer, 2007). When grouped across sex and race
distance, forefoot and midfoot strikers had shorter ground contact times and faster finishing
times in 800 m and 1500 m races (Hayes and Caplan, 2012). Similarly, at the 15-km distance
of a half-marathon, rearfoot strikers had longer contact times than forefoot and midfoot strikers
(Hasegawa, Yamauchi and Kraemer, 2007) and these shorter contact times could be seen as
a performance benefit from landing more forwards on the foot, possibly because footstrike
pattern is a factor that affects the stretch-shortening cycle (Cavagna, Saibene and Margaria,
1964; Cavagna and Kaneko, 1977). As faster distance runners are more likely to be mid- or
forefoot strikers (Stearne et al, 2014), it has been suggested that running economy is positively
influenced by effective exploitation of this elastic energy (Di Michele and Merni, 2014).
However, Stearne et al (2014) found no differences for total lower limb mechanical work or
mean power between foot-strike patterns when running at 4.5 ms-1. This might be because
whereas forefoot striking has been associated with greater stiffness at the knee, rearfoot
striking has been associated with greater stiffness at the ankle (Butler, Crowell III and McClay
Davis, 2003). Indeed, the lower prevalence of midfoot and forefoot striking over longer
distances amongst both recreational and world-class marathon runners (Hanley et al, 2019;
Larson et al, 2011) could be because carbohydrate oxidation rates are greater during forefoot
striking (Gruber et al, 2013).
Landing on the front of the foot has been proposed as less likely to lead to injury (Kulmala et
al, 2013) as it reduces peak impact forces (Cavanagh and Lafortune, 1980; Lieberman et al,
2010). This is because the wider forefoot allows impact forces to be distributed over a larger
area (Rooney and Derrick, 2013), although these forces are also reduced during heel-strike
in appropriate footwear (Whittle, 1999). However, it is not conclusive that vertical loading
forces are directly responsible for lower limb injury (Nigg, 1997), especially given the
multiplanar and complicated movements involved in running. Furthermore, whereas rearfoot
striking might be associated with certain injuries (e.g., at the knee), forefoot striking is
associated with injury to other areas (e.g., ankle) (Kulmala et al, 2013). Higher loads to the
gastrocnemius were found in forefoot striking (Shih, Lin and Shiang, 2013), and Stearne et al
(2014) stated that forefoot striking thus might actually increase the risk of Achilles tendinopathy
and triceps surae injury. It is therefore inadvisable for habitual rearfoot strikers to switch
footstrike pattern as it can increase the injury risk to untrained muscles (Stearne et al, 2014).
Effects of fatigue
It is well understood that one of the main limits on performance in distance running is fatigue,
characterised by a reduction in power output and a decline in performance (Kellis and Liassou,
2009). There are three potential sites of failure: those within the central nervous system; those
concerned with neural transmission from the central nervous system to muscle; and those
within the individual muscle fibres (Bigland-Ritchie and Woods, 1984). Local muscular fatigue
occurs because of intensive activity in that muscle (Mizrahi, Verbitsky and Isakov, 2000), and
is one of many forms of fatigue that affect distance runners. Even though the competitive
distances are shorter, middle-distance runners are more susceptible to fatigue in some ways
than long-distance runners, possibly because those who specialise over shorter distances
have a greater proportion of fast-twitch muscle fibres (Nummela, Keränen, and Mikkelsson,
2008) and because their pacing profiles in championship competition feature several bursts of
great acceleration (Hettinga, Edwards and Hanley, 2019).
Change in running speed is the most obvious outcome of fatigue, resulting from decreases in
either step length and cadence, or both (Buckalew et al, 1985; Elliott and Ackland, 1981).
However, athletes racing over different distances sometimes suffer decreases in only one of
these two factors; for example, in a 5 km road race, Hanley, Smith and Bissas (2011) found
that the men had reduced cadence only, whereas in a men’s 10,000 m track race, Elliot and
Ackland (1981) found decreases in step length (from 1.76 m on the second lap to 1.66 in the
second-last lap), whereas cadence did not change. In a high-quality women’s marathon,
Buckalew et al (1985) found that, as faster finishers had longer step lengths, maintenance of
step length over the full distance was the deciding factor in the outcome of the race. This
means the marathon differs from shorter distance races (i.e., changes in cadence are not as
important for race success) because the physiological changes that occur in the second half
mean that maintaining step length is the key to avoiding great reductions in speed to the finish.
Dutto and Smith (2002) reported that during running to exhaustion, leg stiffness decreased
with fatigue and this might have caused step length to increase (rather than because of a
conscious decision by the athletes), with a resulting increase in energy cost. A similar
decrease in leg stiffness, found during exhaustive running by Hayes and Caplan (2014), was
believed to be more likely due to changes in ankle stiffness, rather than at the knee. A
decrease in leg stiffness results in a failure to fully use the stretch-shortening cycle (Chan-
Roper et al, 2012), such as during the push-off phase in running. Repeated stretch-shortening
cycle exercise itself induces fatigue, leading to increased lower leg stiffness to protect passive
biological structures (Debenham et al, 2016), and which affects force production as there is a
reduction in the amount of storage of elastic energy (Nicol, Komi and Marconnet, 1991a). It is
possible that this reduction is caused by an increase in transition time from stretch to
shortening (e.g., between braking and push-off phases) (Nicol, Komi and Marconnet, 1991a).
Indeed, Hayes and Caplan (2012) found that contact times in high-calibre club athletes
increased from the first lap to the last lap of both 800 m and 1500 m races, and given its
association with cadence, the ability to maintain or decrease contact time in the later stages
might be crucial for success. Nicol, Komi and Marconnet (1991b) found that longer contact
times occurred after a marathon because of increased maximal knee flexion that suggested a
reduction in tolerance to repeated stretch loads, which led to increased muscular work when
the knee extended during a longer push-off phase to maintain a constant running speed. As
this increased work requirement in itself increases the rate of fatigue, the most common
outcome of stretch-shortening cycle fatigue is simply for the athlete to slow. In treadmill tests
where runners exercised to exhaustion, those athletes who ran for longer were those who had
more stable running styles (Gazeau, Koralsztein and Billat, 1997), and it is possible that
detrimental changes in stride mechanics can be avoided to some extent through the
development of local muscular endurance of key lower limb muscles, particularly the knee
flexors and hip extensors (notably, the hamstrings fulfil both of these roles) (Hayes, Bowen
and Davies, 2004). The changes that occur from running to exhaustion (or considerable
fatigue) could lead to overuse injuries (Riazati et al, 2020), and indeed changes often occur to
reduce pain in those already suffering patellofemoral pain syndrome (Bazett-Jones et al,
2013). Many of these gait alterations relate to muscle strength before and after high-intensity
exercise; by contrast, with regard to changes in joint angles with fatigue over short race
distances, Hanley, Smith and Bissas (2011) found that hip, knee, ankle and shoulder angles
at both first contact and toe-off did not alter throughout a 5 km road race, and Elliot and
Ackland (1981) reported very small or no changes in lower limb joint angles with fatigue in
10,000 m track running. Thus, even when fatigued, many athletes maintain their usual
technique and coaches should note that running form, whether “good” or “bad”, is not
necessarily a robust guide as to whether an athlete is tiring.
Air resistance
Air resistance occurs when an athlete runs overground and, as noted above for external
forces, causes a change in the athlete’s speed. An athlete running in still air (wind speed of
0.0 ms-1) experiences a headwind equal to their running speed (Davies, 1980); compared with
no wind conditions, headwinds increase total energy consumption, whereas tailwinds
decrease it. Very strong tailwinds can cancel out the effects of running through the air,
although they can also have a negative effect on the ability to maintain correct running posture
(Davies, 1980). Running closely behind rivals is a very common tactic as it allows less
physiologically capable athletes to maintain the pace of faster, front-running athletes
(Brisswalter and Hausswirth, 2008), and is one of the principles behind pre-arranged
pacemakers. Davies (1980) found that the energy cost of overcoming air resistance on a calm
day was approximately 4% for middle-distance running (at 6 ms-1), and 2% for marathon
running (5 ms-1). He recommended athletes shield behind a front runner until the closing
stages of a race, although they need to be in very close proximity. However, many athletes
deliberately choose to avoid following others too closely as it can eliminate the cooling effects
of moving air, especially in hot conditions (Noakes, 2003). Additionally, Kyle (1979) calculated
that middle- and long-distance runners reduced energy consumption by only 2 – 4% by
shielding from the wind, and Trenchard, Renfree and Peters (2016) calculated that distance
runners in competitive situations actually gain little from drafting. Ultimately, air resistance is
very small at speeds below 4.44 ms-1 (Léger and Mercier, 1984), and might be of great
importance for the distance runner only in strong headwinds. In weather conditions where the
relative humidity is high (at or close to 100% saturation), rainfall can negatively affect
performance, particularly in the marathon (Ito et al, 2013). However, as with wearing loose
clothing, some athletes might benefit from light rain because of a cooling effect. Overall, the
best conditions for distance running are generally a combination of sea-level elevation, little
or no wind, cool but dry conditions, and athletes of similar ability to act as pacemakers.
Effects of gradient
Changes in gradient frequently occur in road racing, and are a common feature of cross
country and other off-road running. Even though running downhill is generally faster because
of gravitational forces contributing to propulsion (Paradisis and Cooke, 2001), it can also have
negative consequences. These effects can be exacerbated because athletes are unfamiliar
with running downhill and alter their gait to accommodate the slope, including applying more
braking impulse than necessary (Gottschall and Kram, 2005). Although it has a lower
metabolic cost than running on a level surface (Minetti, Ardigò and Saibene, 1994), running
downhill on shallow slopes still requires some positive mechanical energy generation because
elastic energy storage is insufficient to meet all energy demands (Snyder, Kram and
Gottschall, 2012).
Aside from the risk of falling, the mechanics of running downhill can also increase the risk of
injury. Although not necessarily direct causes of injury, greater vertical impact peak forces
were found during downhill running (Gottschall and Kram, 2005; Telhan et al, 2010), and peak
tibial impact accelerations increased on downhill gradients because of higher vertical
velocities at impact (Chu and Caldwell, 2004). Because of the greater loading in early stance,
running downhill increases the load on the knee extensors, hip extensors, and anterior and
posterior shin muscles (Eston et al, 1995). Appell, Soares and Duarte (1992) stated that this
mechanical stress during downhill running causes disruption of the myofibrils in the affected
muscles, and the accrued muscle damage can affect running form and muscle function for up
to three days afterwards (Chen, Nosaka and Tu, 2007). The loss of strength in the quadriceps
femoris is caused by morphological damage during exercise (Lieber and Friedén, 1993) and
is associated with the relative length of the muscle; for example, the quadriceps femoris does
more work at its longer length during downhill running than during uphill running (Eston et al,
1995). Small uphill sections (of 1% gradient or less) often have little effect on the maintenance
of running speed (Angus and Waterhouse, 2011). However, anyone who has run uphill knows
intuitively that it is more difficult than running on level surfaces because energy cost increases
with greater inclines (Minetti, Ardigò and Saibene, 1994), with a more forward lean of the trunk
and shorter step lengths. Of course, some athletes deliberately choose hilly courses because
of the challenge involved, or because hill running suits their abilities. Training to run downhill
before competition can help prevent muscle damage (Eston et al, 1995) and coaches are thus
advised to include it in their athletes’ training regimens.
Cross country and off-road running
Running on natural terrain in the form of cross country running, trail running, orienteering and
fell running are popular with athletes of all abilities. On soft ground, the surface absorbs energy
and returns little, which can be particularly detrimental to those distance athletes who rely to
a greater extent on lower limb muscle elasticity (Canova, 1998). In general, running on
surfaces such as sand, grass and trails requires greater metabolic energy expenditure than
running on smooth, flat, hard surfaces (Voloshina and Ferris, 2015). Increases in energy cost
of between 26% and 72% have been estimated when running in forests (typical of orienteering
and trail running), dependent on the underfoot conditions (Creagh and Reilly, 1997). The
energy cost of running through long grass on rough terrain is increased because of decreased
step lengths, greater hip flexion during swing, and larger vertical displacements of the CM
(Creagh and Reilly, 1997). Pinnington and Dawson (2001) found that running on sand had a
greater energy cost than running on grass and proposed that this was because of a reduction
in elastic energy potentiation, caused partly by an increase in contact time. They also
suggested that the increase in energy cost could be because sand’s compliant nature requires
increased leg stiffness that increases muscle activity to stabilise the lower limb joints
(Pinnington and Dawson, 2001). Although running on such surfaces might reduce
performance (e.g., time to complete a particular distance compared with athletics tracks or
roads), they can provide a beneficial training stimulus, and can suit some athletes’ running
styles better than more stable, harder surfaces.
Conclusion
Running is a highly complex movement, requiring years of refinement to become automated
and efficient, and a good understanding of biomechanics is indispensable in trying to improve
performance. Although the running stride has been broken down into its various components,
a holistic view of an athlete’s biomechanics is essential in good coaching so, for example,
understanding that increasing step length is beneficial to performance should be tempered
with the risk of overstriding or decreasing cadence. Training improvements in technique take
time and are best viewed as part of a whole-body exercise, where what occurs during swing
in one leg is seen as complementing what happens during stance in the other. Distance
running is, of course, an endurance activity and external factors such as the effects of wind,
hills, surface and rival athletes’ tactics can influence the rate of fatigue. Indeed, the manner in
which an athlete accommodates these potential challenges can be affected by tiredness, and
coaches are recommended to incorporate technically sound practice in training to prepare the
body biomechanically for these race elements.
References
Angus, S.D. and Waterhouse, B.J. (2011) ‘Pacing strategy from high-frequency field data:
More evidence for neural regulation?’, Medicine and Science in Sports and Exercise, 43(12),
pp.2405-2411.
Appell, H.-J., Soares, J.M.C., and Duarte, J.A.R. (1992) ‘Exercise, muscle damage and
fatigue’, Sports Medicine, 13(2), pp.108-115.
Arampatzis, A., De Monte, G., Karamanidis, K., Morley-Klapsing, G., Stafilidis, S., and
Brüggemann, G.-P. (2006) ‘Influence of the muscle-tendon unit’s mechanical and
morphological properties on running economy’, The Journal of Experimental Biology, 209(17),
pp.3345-3357.
Bazett-Jones, D.M., Cobb, S.C., Huddleston, W.E., O’Connor, K.M., Armstrong, B.S.R., and
Earl-Boehm, J.E. (2013) ‘Effect of patellofemoral pain on strength and mechanics after an
exhaustive run’, Medicine and Science in Sports and Exercise, 45(7), pp.1331-1339.
Bigland-Ritchie, B. and Woods, J.J. (1984) ‘Changes in muscle contractile properties and
neural control during human muscular fatigue’, Muscle and Nerve, 7(9), pp.691-699.
Bramble, D.M. and Lieberman, D.E. (2004) ‘Endurance running and the evolution of Homo’,
Nature, 432(7015), pp.345-352.
Brisswalter, J. and Hausswirth, C. (2008) ‘Consequences of drafting on human locomotion:
benefits on sports performance’, International Journal of Sports Physiology and Performance,
3(1), pp.3-15.
Buckalew, D.P., Barlow, D.A., Fischer, J.W., and Richards, J.G. (1985) ‘Biomechanical profile
of elite women marathoners’, International Journal of Sport Biomechanics, 1(4), pp.330-347.
Buczek, F.L. and Cavanagh, P.R. (1990) ‘Stance phase knee and ankle kinematics and
kinetics during level and downhill running’, Medicine and Science in Sports and Exercise,
22(5), pp.669-677.
Bushnell, T. and Hunter, I. (2007) ‘Differences in technique between sprinters and distance
runners at equal and maximal speeds’, Sports Biomechanics, 6(3), pp.261-268.
Butler, R.J., Crowell III, H.P., and McClay Davis, I. (2003) ‘Lower extremity stiffness:
Implications for performance and injury’, Clinical Biomechanics, 18(6), pp.511-517.
Canova, R. (1998) ‘Can cross-country running be considered an athletics event in its own
right?’, New Studies in Athletics, 13(4), pp.13-19.
Cavagna, G.A., Saibene, F.P., and Margaria, R. (1964) ‘Mechanical work in running’, Journal
of Applied Physiology, 19(2), pp.249-256.
Cavagna, G.A. and Kaneko, M. (1977) ‘Mechanical work and efficiency in level walking and
running’, The Journal of Physiology, 268(2), pp.467-481.
Cavanagh, P.R. (ed.) (1990) Biomechanics of distance running. Champaign, IL: Human
Kinetics.
Cavanagh, P.R. and Kram, R. (1989) ‘Stride length in distance running: velocity, body
dimensions, and added mass effects’, Medicine and Science in Sports and Exercise, 21(4),
pp.467-479.
Cavanagh, P.R. and Lafortune, M.A. (1980) ‘Ground reaction forces in distance running’,
Journal of Biomechanics, 13(5), pp.397-406.
Chang, Y.-H. and Kram, R. (1999) ‘Metabolic cost of generating horizontal forces during
human running’, Journal of Applied Physiology, 86(5), pp.1657-1662.
Chan-Roper, M., Hunter, I., Myrer, J.W., Eggett, D.L., and Seeley, M.K. (2012) ‘Kinematic
changes during a marathon for fast and slow runners’, Journal of Sport Science and Medicine,
11(1), pp.77-82.
Chen, T. C., Nosaka, K., and Tu, J.-H. (2007) ‘Changes in running economy following downhill
running’, Journal of Sports Sciences, 25(1), pp.55-63.
Chu, J.J. and Caldwell, G.E. (2004) ‘Stiffness and damping response associated with shock
attenuation in downhill running’, Journal of Applied Biomechanics, 20(3), pp.291-308.
Chumanov, E.S., Heiderscheit, B.C., and Thelen D.G. (2011) ‘Hamstring musculotendon
dynamics during stance and swing phases of high-speed running’, Medicine and Science in
Sports and Exercise, 43(3), pp.525-532.
Creagh, U. and Reilly, T. (1997) ‘Physiological and biomechanical aspects of orienteering’,
Sports Medicine, 24(6), pp.409-418.
Davies, C.T.M. (1980) ‘Effects of wind assistance and resistance on the forward motion of a
runner’, Journal of Applied Physiology, 48(4), pp.702-709.
Debenham, J., Travers, M., Gibson, W., Campbell, A., and Allison, G. (2016) ‘Eccentric fatigue
modulates stretch-shortening cycle effectiveness – a possible role in lower limb overuse
injuries’, International Journal of Sports Medicine, 37(1), pp.50-55.
Di Michele, R. and Merni, F. (2014) ‘The concurrent effects of strike pattern and ground-
contact time on running economy’, Journal of Science and Medicine in Sport, 17(4), pp.414-
418.
Dutto, D.J. and Smith, G.A. (2002) ‘Changes in spring-mass characteristics during treadmill
running to exhaustion’, Medicine and Science in Sports and Exercise, 34(8), pp.1324-1331.
Elliot, B. and Ackland, T. (1981) ‘Biomechanical effects of fatigue on 10,000 meter running
technique’, Research Quarterly for Exercise and Sport, 52(2), pp.160-166.
Enoka, R.M. (2008) Neuromechanics of human movement. 4th edn. Champaign, IL: Human
Kinetics.
Enomoto, Y., Kadono, H., Suzuki, Y., Chiba, T., and Koyama, K. (2008) ‘Biomechanical
analysis of the medalists in the 10,000 metres at the 2007 World Championship in Athletics’,
New Studies in Athletics, 23(3), pp.61-66.
Eston, R.G., Lemmey, A.B., McHugh, P., Byrne, C., and Walsh, S.E. (2000) ‘Effect of stride
length on symptoms of exercise-induced muscle damage during a repeated bout of downhill
running’, Scandinavian Journal of Medicine and Science in Sports, 10(4), pp.199-204.
Eston, R.G., Mickleborough, J., and Baltzopoulos, V. (1995) ‘Eccentric activation and muscle
damage: biomechanical and physiological considerations during downhill running’, British
Journal of Sports Medicine, 29(2), pp.89-94.
Gazeau, F., Koralsztein, J.P., and Billat, V. (1997) ‘Biomechanical events in the time to
exhaustion at maximum aerobic speed’, Archives of Physiology and Biochemistry, 105(6),
pp.583-590.
Gottschall, J.S. and Kram, R. (2005) ‘Ground reaction forces during downhill and uphill
running’, Journal of Biomechanics, 38(3), pp.445-452.
Gruber, A.H., Umberger, B.R., Braun, B., and Hamill, J. (2013) ‘Economy and rate of
carbohydrate oxidation during running with rearfoot and forefoot running patterns’, Journal of
Applied Physiology, 115(2), pp.194-201.
Hanley, B., Bissas, A., Merlino, S., and Gruber, A.H. (2019) ‘Most marathon runners at the
2017 IAAF World Championships were rearfoot strikers, and most did not change footstrike
pattern’, Journal of Biomechanics, 92, pp.54-60.
Hanley, B., Smith, L.C., and Bissas, A. (2011) ‘Kinematic variations due to changes in pace
during men’s and women’s 5 km road running’, International Journal of Sports Science and
Coaching, 6(2), pp.243-252.
Hanley, B. and Tucker, C.B. (2018) ‘Gait variability and symmetry remain consistent during
10,000 m treadmill running’, Journal of Biomechanics, 79, pp.129-134.
Hanon, C., Thépaut-Mathieu, C., and Vandewalle, H. (2005) ‘Determination of muscular
fatigue in elite runners’, European Journal of Applied Physiology, 94, pp.118-125.
Hasegawa, H., Yamauchi, T., and Kraemer, W. J. (2007) ‘Foot strike patterns of runners at
the 15-km point during an elite-level half marathon’, The Journal of Strength and Conditioning
Research, 21(3), pp.888-893.
Hayes, P.R., Bowen, S.J., and Davies, E.J. (2004) ‘The relationships between local muscular
endurance and kinematic changes during a run to exhaustion at vV
O2 max’, The Journal of
Strength and Conditioning Research, 18(4), pp.898-903.
Hayes, P.R. and Caplan, N. (2014). Leg stiffness decreases during a run to exhaustion at the
speed at V
O2 max’, European Journal of Sport Science, 14(6), pp.556-562.
Hayes, P. and Caplan, N. (2012) ‘Foot strike patterns and ground contact times during high-
calibre middle-distance races’, Journal of Sports Sciences, 30(12), pp.1275-1283.
Heise, G.D., Smith, J.D., and Martin, P.E. (2011) ‘Lower extremity mechanical work during
stance phase of running partially explains interindividual variability of metabolic power’,
European Journal of Applied Physiology, 111, pp.1777-1785.
Hettinga, F.J., Edwards, A.M. and Hanley, B. (2019) ‘The science behind competition and
winning in athletics: using world-level competition data to explore pacing and tactics’, Frontiers
in Sports and Active Living, 1, 11.
Hinrichs, R.N. (1987) ‘Upper extremity function in running. II: angular momentum
considerations’, International Journal of Sports Biomechanics, 3(3), pp.242-263.
Hunter, J.P., Marshall, R.N., and McNair, P.J. (2004) ‘Interaction of step length and cadence
during sprint running’, Medicine and Science in Sport and Exercise, 36(2), pp.261-271.
Inman, V.T., Ralston, H.J., and Todd, F. (1981) Human walking. Baltimore, MD: Williams &
Wilkins.
Ito, R., Nakano, M., Yamane, M., Amano, M., and Matsumoto, T. (2013) ‘Effects of rain on
energy metabolism while running in a cold environment’, International Journal of Sports
Medicine, 34(8), pp.707-711.
Kellis, E. and Liassou, C. (2009) ‘The effect of selective muscle fatigue on sagittal lower limb
kinematics and muscle activity during level running’, Journal of Orthopaedic and Sports
Physical Therapy, 39(3), pp.210-220.
Komi, P.V. (2000) ‘Stretch-shortening cycle: a powerful model to study normal and fatigued
muscle’, Journal of Biomechanics, 33(10), pp.1197-1206.
Kong, P.W. and de Heer, H. (2008) ‘Anthropometric, gait and strength characteristics of
Kenyan distance runners’, Journal of Sports Science and Medicine, 7(4), pp.499-504.
Kulmala, J.-P., Avela, J., Pasanen, K., and Parkkari, J. (2013) ‘Forefoot strikers exhibit lower
running-induced knee loading than rearfoot strikers’, Medicine and Science in Sports and
Exercise, 45(12), pp.2306-2313.
Kyle, C.R. (1979) ‘Reduction of wind resistance and power output of racing cyclists and
runners travelling in groups’, Ergonomics, 22(4), pp.387-397.
Larson, P., Higgins, E., Kaminski, J., Decker, T., Preble, J., Lyons, D., McIntyre, K., and
Normile, A. (2011) ‘Foot strike patterns of recreational and sub-elite runners in a long-distance
road race’, Journal of Sports Sciences, 29(15), pp.1665-1673.
Léger, L. and Mercier, D. (1984) ‘Gross energy cost of horizontal treadmill and track running’,
Sports Medicine, 1, pp.270-277.
Leskinen, A., Häkkinen, K., Virmavirta, M., Isolehto, J., and Kyröläinen, H. (2009) ‘Comparison
of running kinematics between elite and national-standard 1500-m runners’, Sports
Biomechanics, 8(1), pp.1-9.
Levine, D., Richards, J., and Whittle, M.W. (2012) Whittle’s gait analysis. 5th edn. Edinburgh:
Churchill Livingstone.
Lieber, R.I. and Fridén, J. (1993) ‘Muscle damage is not a function of muscle force but active
muscle strain’, Journal of Applied Physiology, 74(2), pp.520-526.
Lieberman, D.E., Venkadesan, M., Werber, W.A., Daoud, A.I., D’Andrea, S., Davis, I.S.,
Mang’Eni, R.O., and Pitsiladis, Y. (2010) ‘Foot strike patterns and collision forces in habitually
barefoot versus shod runners’, Nature, 463(7280), pp.531-535.
Minetti, A.E., Ardigò, L.P., and Saibene, F. (1994) ‘Mechanical determinants of the minimum
energy cost of gradient running in humans’, The Journal of Experimental Biology, 195(1),
pp.211-225.
Mizrahi, J., Verbitsky, O., and Isakov, E. (2000) ‘Fatigue-related loading imbalance on the
shank in running: a possible factor in the stress fractures’, Annals of Biomedical Engineering,
28, pp.463-469.
Moore. I.S. (2016) ‘Is there an economical running technique? A review of modifiable
biomechanical factors affecting running economy’, Sports Medicine, 46, pp.793-807.
Munro, C.F., Miller, D.I., and Fuglevand, A.J. (1987) ‘Ground reaction forces in running: a
reexamination’, Journal of Biomechanics, 20(2), pp.147-155.
Nicol, C., Komi, P.V., and Marconnet, P. (1991a) ‘Fatigue effects of marathon running on
neuromuscular performance’, Scandinavian Journal of Medicine and Science in Sports, 1(1),
pp.10-17.
Nicol, C., Komi, P.V., and Marconnet, P. (1991b) ‘Effects of marathon fatigue on running
kinematics and economy’, Scandinavian Journal of Medicine and Science in Sports, 1(4),
pp.195-204.
Nigg, B.M. (1997) ‘Impact forces in running’, Current Opinion in Orthopedics, 8(6), pp.43-47.
Noakes, T. (2003) ‘Fluid replacement during marathon running’, Clinical Journal of Sport
Medicine, 13(5), pp.309-318.
Novacheck, T.F. (1998) ‘The biomechanics of running’, Gait and Posture, 7(1), pp.77-95.
Nummela, A., Keränen, T., and Mikkelsson, L.O. (2007) ‘Factors related to top running speed
and economy’, International Journal of Sports Medicine, 28(8), pp.655-661.
Nummela, A., Heath, K.A., Paavolainen, L.M., Lambert, M.I., St Clair Gibson, A., Rusko, H.K.,
and Noakes, T.D. (2008) ‘Fatigue during a 5-km running time trial’, International Journal of
Sports Medicine, 29(9), pp.738-745.
Paradisis, G.P. and Cooke, C.B. (2001) ‘Kinematic and postural characteristics of sprint
running on sloping surfaces’, Journal of Sports Sciences, 19(2), pp.149-159.
Pinnington, H.C. and Dawson, B. (2001) ‘The energy cost of running on grass compared to
soft dry beach sand’, Journal of Science and Medicine in Sport, 4(4), pp.416-430.
Pontzer, H., Holloway III, J.H.H., Raichlen, D.A., and Lieberman, D.E. (2009) ‘Control and
function of arm swing in human walking and running’, The Journal of Experimental Biology,
212(4), pp.523-534.
Reiss, M., Ernest, O., and Gohlitz, D. (1993) ‘Analysis of the 1989 - 1992 Olympic cycle with
conclusions for coaching distance running and walking events’, New Studies in Athletics, 8(4),
pp.7-18.
Riazati, S., Caplan, N., Matabuena, M., and Hayes, P.R. (2020) ‘Fatigue induced changes in
muscle strength and gait following two different intensity, energy expenditure matches runs’,
Frontiers in Bioengineering and Biotechnology, 8, 360.
Rooney, B.D. and Derrick, T.R. (2013) ‘Joint contact loading in forefoot and rearfoot strike
patterns during running’, Journal of Biomechanics, 46(13), pp.2201-2206.
Saunders, J.B., Inman, V.T., and Eberhart, H.D. (1953) ‘The major determinants in normal
and pathological gait’, The Journal of Bone and Joint Surgery, 35(3), pp.543-558.
Saunders, P.U., Pyne, D.B., Telford, R.D., and Hawley, J.A. (2004) ‘Factors affecting running
economy in trained distance runners’, Sports Medicine, 34, pp.465-485.
Serpell, B.G., Ball, N.B., Scarvell, J.M., and Smith, P.N. (2012) ‘A review of models of vertical,
leg, and knee stiffness in adults for running, jumping or hopping tasks’, Journal of Sports
Sciences, 30(13), pp.1347-1363.
Shih, Y., Lin, K.-L., and Shiang, T.-Y. (2013) ‘Is the foot striking pattern more important than
barefoot or shod conditions in running?’, Gait and Posture, 38(3), pp.490-494.
Smith, L.C. and Hanley, B. (2013) ‘Comparisons between swing phase characteristics of race
walkers and distance runners’, International Journal of Exercise Science, 6(4), pp.269-277.
Snyder, K.L., Kram, R., and Gottschall, J.S. (2012) ‘The role of elastic energy storage and
recovery in downhill and uphill running’, The Journal of Experimental Biology, 215(13),
pp.2283-2287.
Stearne, S.M., Alderson, J.A., Green, B.A., Donnelly, C.J., and Rubenson, J. (2014) ‘Joint
kinetics in rearfoot versus forefoot running: implications of switching technique’, Medicine and
Science in Sports and Exercise, 46(8), pp.1578-1587.
Telhan, G., Franz, J.R., Dicharry, J., Wilder, R.P., Riley, P.O., and Kerrigan, D.C. (2010)
‘Lower limb joint kinetics during moderately sloped running’, Journal of Athletic Training, 45(1),
pp.16-21.
Trenchard, H., Renfree, A., and Peters, D.M. (2016) ‘A computer model of drafting effects on
collective behavior in elite 10,000 m runners’, International Journal of Sports Physiology and
Performance, 12(3), pp.345-350.
Vardaxis, V. and Hoshizaki, T.B. (1989) ‘Power patterns of the leg during the recovery phase
of the sprinting stride for advanced and intermediate sprinters’, International Journal of Sports
Biomechanics, 5(3), pp.332-349.
Voloshina, A.S. and Ferris, D.P. (2015) ‘Biomechanics and energetics of running on uneven
terrain’, The Journal of Experimental Biology, 218(5), pp.711-719.
Watkins, J. (2010) Structure and function of the musculoskeletal system. 2nd edn. Champaign,
IL: Human Kinetics.
White, S.C. and Winter, D. (1985) ‘Mechanical power analysis of the lower limb musculature
in race walking’, International Journal of Sport Biomechanics, 1(1), pp.15-24.
Whittle, M.W. (1999) ‘Generation and attenuation of transient impulsive forces beneath the
foot: A review’, Gait and Posture, 10(3), pp.264-275.
Winter, D.A. and Bishop, P.J. (2012) ‘Lower extremity injury: Biomechanical factors associated
with chronic injury to the lower extremity’, Sports Medicine, 14, pp.149-156.
Winter, E.M., Abt, G., Brookes, F.B.C., Challis, J.H., Fowler, N.E., Knudson, D.V., Knuttgen,
H.G., Kraemer, W.J., Lane, A.M., van Mechelen, W., Morton, R.H., Newton, R.U., Williams,
C., and Yeadon, M.R. (2016) ‘Misuse of “power” and other mechanical terms in sport and
exercise science research’, The Journal of Strength and Conditioning Research, 30(1),
pp.292-300.
