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Rapid dynamic training: challenging the limits to sprint performance
Jeremy Richmond
B.Sc- Physics, MExSpSc (candidate University of Sydney)
Fitness First Randwick Australia
Abstract
The search for more running speed had brought an
abundance of training methods and combinations
thereof. However, the benefit to sprint improvement of
these methods does not compare favourably against the
value of sprint training itself for which sprint running
has the exact specificity. The rapid dynamic training
exercise in this experiment is intended to isolate the
muscles that contract rapidly when sprinting. EMG
analysis of the vastus lateralis muscle during the
exercise revealed an average muscle activation time of
between 100 and 110 milliseconds. This method of
exercise allows those muscles that can activate in a
short time frame, as would be applicable to sprinting, to
be developed progressively. Therefore, the specific
muscles required for sprinting can be developed
preferentially.
Introduction
Athletes are always in search of more speed. Running
speed is an essential component of most major sports,
and can be the determining factor in the outcome of a
sporting event (Corn & Knudson 2003). It is for this
reason that athletes undertake training programs to
improve their individual speeds. In order to gain a
performance advantage, athletes are always in search of
newer methods. A number of researchers have found
that commonly used training methods such as high
resistance, over-speed, ballistics, plyometric training
and resisted running are not substantially better than
sprint training alone (Delecluse et al.1995, Rimmer &
Sleivert 2000, Majdell & Alexander 1991, McBride et
al. 2002, Kristensen et al.2006, Spinks et al.2007).
Rather than invest a great deal of time for little gain in
various methods, athletes would prefer a training
method that produces better results. The question is:
what are the reasons for these training methods not
being effective?
Are these methods specific enough in velocity and
movement produce a noticeable improvement?
Most strength improvements will occur when the
specific movement pattern is used in training, even
when different exercises involve identical muscle
Rapid Dynamic Training
groups (Weiss 1991). Also, the greatest strength gains
have been found by Behm & Sale (1993) to occur at or
near the training velocity. Wiemann & Tidow (1995)
say that the velocity in sprinting is directly related to
the movement of the legs for which the movement of
the joints that make up the legs are the functional result
of activating muscles (Kyrolainen et al.1999).
Therefore we need to make our muscles activate
quicker to move our legs faster, which would result in
higher running speed. However this principle will only
apply if the force produced by the leg remains the same.
How much force is needed to run fast?
Muscles need to produce 797N or 81kg of force in the
vertical direction, and 312N or 32kg of force in the
horizontal direction during the propulsive phase of
sprinting at 9.96 m/s (Mero et al.1992). The magnitude
of the force generated in sprinting seems small
compared to the weights that sprinters are known to lift.
Perhaps success in sprinting is related to power which
is equal to the product of force velocity.
How fast must my legs be moving to run fast?
The running action involves the leg moving rapidly
from the front of the body to the back. The backswing
velocity of the leg is directly related to the velocity of
the runner at full speed (Wiemann & Tidow 1995). At
9.9 m/s Kivi et al. (2001) measured the thigh moving
backward relative to the hip at a speed of 666 º/sec.
During the forward swing the thigh moves at 726 º/sec.
Furthermore, the knee extends at 1165 º/sec and flexes
at 1083 º/sec.
When running at 9.4 m/s, Kivi et al. (2001)
reported the thigh moving backward at 626 º/sec and
during forward swing moving at 727 º/sec. Other
measures around the knee joint at 9.4 m/s include
extension at 1156 º/sec and flexion at 1058 º/sec.
Therefore, to increase your speed from 9.4 to 9.9 m/s,
you will need to increase the speed at which you extend
your thigh by an extra 40 º/sec. In order to run at 9.9
m/s or faster, the thigh must be able to extend 89 º in
0.13 seconds at least. If the athlete cannot move their
thigh back at that speed, it seems fundamental that they
train to do so. Additionally, the athlete must develop a
fast extension of the knee, the fastest biomechanical
movement observed in sprinting.
1
How do I move my legs faster?
Can a better method be developed?
The muscles accelerating the body forward in sprint
running must contract at an increasing speed as the
sprint velocity increases according to Cavagna et al.
(1971). Sprinters running at 9.23 m/s do so with their
vastus lateralis (responsible for knee extension) muscle
activating within a time frame of approximately 145ms
(Nummela et al.1993). This activation occurs prior to
and during the ground contact time of 107ms. Similarly,
Kyrolainen et al. (1999) reported ground contact times
of 115ms at maximal speed with the vastus lateralis
activating over 142ms.
Kyrolainen et al. (1999) also reports the gluteus
maximus to be activated for 168ms (responsible in part
for thigh extension) and the biceps femoris to be
activated in two bursts totalling approximately 265ms,
once during stance and once prior to the leg making
contact with the ground in backswing. If the aim is to
run at speeds greater than this, the muscles that move
the legs must contract in less time, thereby moving the
joint quicker. By moving the legs quicker the sprinter
will run faster.
Shorter ground force production times would save the
runner time on the ground, resulting in improved sprint
performance provided the same velocity was achieved
after each step. Murphy et al. (2003) suggests that ground
force production times may be the difference between fast
and slow runners over 10m. Kunz & Kaufmann (1981)
related shorter ground force production times with elite
sprint performance. They attributed this to a greater
average backswing acceleration of the thigh. If shorter
ground force production time is the mechanism that will
enable faster running speeds, then this must be achieved
through faster moving limbs either during or prior to the
foot making contact with the ground.
The theory of rapid dynamic training is based on the
notion that in order to increase the movement velocity of
a particular limb, in this case the legs for sprinting, the
muscles that move the limb must be trained to activate in
less time but with the same or greater amount of force.
Therefore, the exercises are designed to activate the
muscle within the time frame needed to produce quicker
action.
Does a method exist to benefit sprint performance?
How can we activate our muscles quicker?
Training with plyometric methods improves the initial
phase of sprinting within the first 10m although beyond
that distance Delecluse et al. (1995) and Rimmer &
Sleivert (2000) find it to be no more effective than
sprint training itself.
The most specific of the plyometric exercises to
sprinting is said by Young (1992) to be maximal
bounding. Mero & Komi (1994) found the speed of
maximal bounding to be slower than in maximal
sprinting, although still faster than the speed measured
by Hunter et al. (2005) in the early acceleration phase
of sprinting. In addition, Mero & Komi (1994) found
the ground force production times of maximal bounding
to be longer than that of maximal sprinting although
shorter than that reported by Mero (1988) and Murphy
et al. (2003) in the early acceleration phase of sprinting.
Taking this into account, the velocity specificity
principle (Behm & Sale 1993) suggests that bounding
would impose demands on the same muscles used
during the early acceleration phase of sprinting. If these
demands caused an adaptation of those muscles,
sprinting performance would be enhanced in the early
acceleration phase.
Rimmer & Sleivert (2000) found that plyometric
training was able to reduce the ground contact time by 7
milliseconds in the early acceleration phase with this
reduction being maintained near maximal speeds. The
result is improved sprint performance through
decreasing the amount of time touching the ground.
Muscles move our limbs. In order to move our limbs
faster, such as our legs to make us run faster, we need
to speed up and strengthen the muscles that will be
recruited for the movement. For example, only the
muscles in the vastus lateralis that can be activated in
145
milliseconds
when
sprinting
maximally
(Kyrolainen et al.1999, Nummela et al.1993) need to be
developed. This may require those particular muscles to
be taught to contract faster through practice. It is the
objective of this paper to verify the muscle activation
times of a fast repetitive movement belonging to the
rapid dynamic training method so that this technique
can be used as a method to speed up and strengthen the
muscles recruited in the movement that may be
applicable for sprinting.
Rapid Dynamic Training
Where did the idea come from?
The idea is based on studies of animal behaviour.
Studies on cats show the recruitment of slow ankle
extensors is maintained during locomotion and jumping
(Smith et al.1977). During a medium paced walk of
0.8m/s muscular contractions lasted 300-400ms,
whereas during a slow-paced gallop of 2.5m/s they
lasted 100-125ms. Activity during ballistic jumping
tasks consisted of bursts of muscular activity of 100150ms for the lowest jumps and 150-200 ms for the
highest jumps (Smith et al.1977). In contrast during
rapid paw shakes, elicited by the attaching of masking
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tape to the paw of the cat plus the immersion of the
cat’s paw in shallow water, Smith et al. (1980) found
the slow ankle extensor is silent whilst the fast ankle
extensor is selectively recruited. The muscle
contractions lasted an average of 88ms during rapid
paw shakes (a reflexive action by the cat in an attempt
to discard the tape and/or water from its paw) which is
considerably shorter than that during locomotion and
jumping tasks. For such a rapid activation rate in
humans, recruitment of fast twitch fibres would be
essential.
It would be of interest to athletes and coaches to
reproduce a similar response in human locomotive
muscle in terms of time of muscle activation as a rapid
paw shake in a cat, because of the association with fast
twitch fibres and athletic performance (Potteiger et
al.1999, Mero 1985). Unfortunately unlike cats, most
humans do not have an aversion to water and tape on
the foot. Therefore an alternate method must be
invented. If our goal is to run faster, we need to isolate
the muscles that will be required to contract within the
145 milliseconds that the vastus lateralis contracts at
maximal speed (Kyrolainen et al.1999, Nummela et
al.1993) and impose demands on the isolated muscle.
This should result in an adaptation by the isolated
muscle to whatever stimulus is provided, such as
progressive resistance.
Method
The experiment was conducted with only subject, a
male aged 37 years of 172 cm in height and weighing
79 kg. The subject was familiar with the procedures and
any risks of the test. In the experiment the subject was
required to perform a fast repetitive exercise with an
external load resistance of 20 kg equivalent to 971N of
force including body weight.
Surface EMG recordings were collected using
Noraxon MyoResearch (Noraxon U.S.A. Inc.)
telemetric EMG system. Bipolar electrodes were placed
over each muscle belly, with a reference electrode
placed at the ankle. Signals were sampled at
1500Hz. EMG skin preparation procedures of shaving,
abrasion and cleaning were completed and electrode
placement was performed on 10 muscles of the
subjects’ right leg including the vastus lateralis, gluteus
maximus, biceps femoris, and tibialis anterior.
The data was analysed using an Excel spreadsheet
(Microsoft Office Professional Edition 2003). In the
absence of force platforms to verify movement, the
activation of the tibialis anterior was taken as indication
of movement of the right leg away from the ground.
EMG data was rectified and displayed. Data referring to
the vastus lateralis (VL) muscle was separated for
analysis.
Rapid Dynamic Training
Raw EMG from Rapid Dynam ic
Training Exercise
17000
Gluteus
Maximus
12000
Biceps
Femoris
7000
Vastus
Lateralis
2000
Tibialis
anterior
-3000
0.5 0.9 1.2 1.5 1.9 2.2 2.5 2.9 3.2 3.5 3.9 4.2 4.5
Tim e (s)
Figure 1: EMG data of these muscle groups in the rapid
dynamic training exercise.
Static levels were calculated from the first 500
milliseconds of the analysis as this time frame
represented quiet standing. The average static level was
subtracted from the entire length of the experiment.
Each step was identified from the time display of EMG
peaks referring to the VL muscle. Determination of the
start of each peak was enabled using a formula that
recognized the change in EMG over time. The software
was programmed to recognize the beginning of each
peak through the identifying of a change of 50uV and
100uV.The data representing 16 separate steps was
combined to form one average waveform.
Statistical analysis
Each data point from the beginning of the waveform
representing a step was combined to form one average.
The standard deviation of each average was calculated.
Results
Frequency of alternating movement
The EMG measurements displayed of the gluteus
maximus, biceps femoris, vastus lateralis and tibialis
anterior show the rate of steps (figure 1). From this the
number of steps per second with the right leg is
approximately 7.5 per second. This equates to an
equivalent step cycle of 450 steps per minute.
3
Rapid Dynam ic Exercise versus Hop
Average Rectified EMG of VL
2400
1600
2200
2000
1800
Rapid dynamic
exercise
1200
Poly. (EMG of
Vastus Lateralis
1600
2
R = 0.920
1400
EMG (uV)
EMG (uV)
Hop
EMG of Vastus
Lateralis
1200
1000
800
800
400
600
400
200
0
0
0
50
100
150
200
250
300
350
400
Tim e (m s)
-200
0
20
40
60
80
100
120
Tim e (m s)
Figure 2: Display of the average EMG from the vastus
lateralis collected over 16 steps including standard
deviation.
Muscle activation time
The experimental evidence shows the average muscle
activation time of the vastus lateralis to be less than 110
milliseconds (figure 2). Peak averaged raw EMG occurs
approximately 15ms from the beginning of muscle
contraction. This value differs slightly from the
polynomial trend-line of best fit (R=0.92) where the
peak occurs around 20ms from the beginning.
Peak EMG
The averaged rectified EMG peak for the VL muscle
during the rapid dynamic exercise was 1330uV
compared to the peak EMG of the VL during the
hopping task, which was 439uV (figure 3). Also, the
activation time during the rapid dynamic exercise
(110ms) is observed to be shorter than that during the
hopping task (400ms).
Discussion
Observations seen in the EMG of the vastus lateralis
include:
Muscle activation time of approximately
110ms
The greatest amplitude at the beginning of the
EMG waveform
Peak EMG during the rapid dynamic exercise
is 3 times greater than during the hopping task.
Rapid Dynamic Training
Figure 3: Comparison of EMG from the vastus lateralis
during the rapid dynamic exercise and a hop executed
prior to the rapid dynamic exercise.
The muscle activation time, consisting of recruitment
and relaxation, of 110ms for the VL in this experiment
is less than that recorded by Kyrolainen et al. (1999)
and Nummela et al. (1993) of 145ms during maximal
sprinting. This may suggest that the muscle fibres
recruited during this exercise would be recruited during
sprinting. If we have isolated the muscles used for
sprinting during the exercise, by then subjecting them
to increasing load those muscles will be strengthened.
The fast rate of activation in this experiment is the
result of training with the rapid dynamic method. At the
beginning of the rapid dynamic training program the
step rate was approximately 4 per second. At the time
of this experiment, approximately 16 weeks later, the
step rate had increased to 7.5 per second. This
measurement of the muscle activation during the
exercise is from one subject, therefore it may not be
within the capability of another subject. A pilot study
revealed that beginners with a step rate of 4.25 per
second improved their step rate to 5.4 per second after
four training sessions (unpublished data). Therefore it
seems that the muscles can be trained to activate faster.
However, this fact needs more comprehensive research.
What does this fast activation rate suggest?
A muscle activation time of 110ms may suggest that
fast-twitch muscle fibre is preferentially recruited.
Smith et al. (1980) showed in experiments with rapid
paw shakes in cats, that fast muscle is recruited whilst
the slow muscle remains silent. In humans, Linnamo
(2000) said that during rapid movements an increased
4
activation of fast motor units or decreased activation of
the slow ones may occur. This is also the conclusion of
Citterio & Agostoni (1984) who evaluated the fast
fibres of quadriceps muscle to be selectively activated
as cycling speed increased from 50 to 100 cycles per
minute. By comparison, the movement speed in our
experiment is closer to 450 cycles per minute. At such a
high speed of movement as in our experiment, the
preferential recruitment of fast-twitch fibre seems more
probable. If fast twitch fibre has been selectively
recruited in the rapid dynamic exercise then this rapid
dynamic exercise could be a method of isolating those
fibres, enabling the strengthening of those fibres
exclusively by subjecting them to increasing load.
Why is fast twitch fibre important for sprinting?
People having predominantly fast twitch fibres are able
to achieve higher force and power output at relatively
higher speed than those who have a predominance of
slow twitch fibres (Tihanyi et al.1982). Researchers
have found that a greater percentage of fast twitch fibre
in the legs correlates with faster sprint performance
(Mero 1985). Therefore finding a training method that
develops these particular fibres is essential to
improving sprint performance. One such method is
sprint cycle training where Jansson et al. (1990)
reported an increase in proportion of type IIa muscle
fibre and a concomitant decrease in type I fibres.
Looking at results of training by sprint running,
Dawson et al. (1998) found that type II fibre percentage
in the vastus lateralis increased relative to type I, and
area of type II increased whilst area of type I decreased.
This correlated with significant improvements to sprint
performance. From this, it is reasonable to assume that
training methods designed to develop type II muscle
fibre will improve sprint performance.
The evidence shows that heavy resistance training
methods which increase the proportion of fast twitch
fibres do not benefit sprint performance to the same
extent as explosive training methods that are more
velocity specific and produce neuromuscular
adaptations (Delecluse et al.1995, Kotzamanidis et
al.2005, Harris et al.2000). Neither heavy resistance
training nor explosive power training are significantly
better than sprint training itself in terms of improving
sprint performance, even though these methods have
been found to produce an increase in type II fibres
(Staron et al.1989, Hakkinen et al.1985, Hickson et
al.1994, Dawson et al.1998, Potteiger et al.1999).
According to Mero et al. (1992), a logical explanation
for sprinters having greater type II than type I fibre
areas in their leg extensor muscles, and therefore being
faster, is that their training consists of fast repetitive
movements similar to the rapid dynamic exercise in this
Rapid Dynamic Training
experiment. If specific development of type II muscle
fibre is required for improving sprint performance, then
it is logical that in training, these fibres be recruited and
relaxed quickly, as would be seen in fast repetitive
movements. Therefore, the time of muscle activation in
training would be specific to the task of sprinting.
Conclusion
The ability to develop a relatively high proportion of
maximal strength is not a prerequisite to superior sprint
performance at fast contractile velocities (Farrar &
Thorland 1987). Instead, it is the ability to contract and
relax muscles rapidly in a dynamic movement that is
fundamental for the production of sufficient speed of
the legs. Additionally, what is needed is greater average
backswing acceleration of the thigh, as the backswing
velocity of the leg relates directly to the velocity of the
runner at full speed (Kunz & Kaufmann 1981,
Wiemann & Tidow 1995). Furthermore, greater thigh
acceleration results in shorter ground force production
time thereby reducing time on the ground. The ability to
accelerate the legs faster, or produce force quicker
against the ground when sprinting requires the
activating muscles to be recruited and relaxed in a
shorter time, providing the force produced by the
muscle remains the same or higher.
In this experiment, it was observed that the vastus
lateralis muscle activated and relaxed in less time than
that needed during maximal sprinting. The high
frequency of movement and the short duration of
muscle activation suggest a selective activation of fast
twitch muscle fibre. Athletes are always in search of
more speed for which they would benefit from the
preferential development of their fast twitch fibres.
Therefore, the rapid dynamic training exercise
demonstrated in this experiment provides a facility
through which those particular muscles can be isolated
and subjected to progressive resistance. If the muscles
that can be isolated are indeed fast twitch fibres then the
rapid dynamic training method can also be applied to
many more athletic activities.
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