How do we make our athletes lightning-fast?

Recommendations backed by science

Contents of Blog Post

1. Introduction
2. Biomechanics of Sprinting
3. Factors Affecting Sprint Performance
4. Sprint Training in Practice
5. Acceleration
6. Maximum Velocity
7. Example Program
8. Conclusion
9. References
10. About the Author
11. Comments

Introduction

Linear sprint speed is commonly perceived to be one of the key determinants of performance in many sporting endeavours. Faster athletes score more often (15), have a bigger impact in match-determining situations (12) and sign bigger professional contracts (33) than their slower peers. As such, it’s unsurprising that speed is such a desirable physical quality.

Speed refers to the displacement of an object or person over a given elapsed time. In sport, we often refer to speed in the context of maximal velocity sprinting. Another important component of sports speed is acceleration, defined as the rate of change in speed. Both aspects of sprinting speed form the foundational concept of speed for sports. These are very different measures and should not be discussed in the same context without a thorough explanation.

Making athletes faster can be a daunting project for strength & conditioning coaches or physical therapists looking for scientifically proven speed development methods to integrate into a thorough athletic development program or return to performance protocols.

Therefore, the aim of this article is to cut through the confusion and provide evidence-based recommendations to help you make your athletes lightning-fast.

Biomechanics of Sprinting

Sprint speed is a by-product of the relationship between stride length and stride frequency. Stride length is the distance covered during each cycle of running gait. Stride frequency refers to the cadence of the gait cycle. Positive or negative changes to stride length or stride frequency will affect sprinting performance.

Running gait consists of two key phases: stance and swing. The stance phase has three stages 1) touch down – in this stage, ground contact is initiated 2) mid-stance – this stage occurs when the centre of mass is directly above the base of support 3) toe-off stage. For male athletes, research suggests stride frequency (the number of strides taken per second) is a rather stable measure across individuals and performers, whereas better sprinters generally display longer stride length, covering more distance with each step taken in comparison to lower-level sprinters (29).

Interestingly, the opposite has been found for female athletes, with improved performance correlating with increased stride frequency (29). This perhaps indicates athletes with lower force-generating capacities may benefit from an increased rate of turnover. This has large implications for how we coach and train athletes with the aim of improving sprint speed, particularly across sexes. As a general rule, increasing athletes’ speeds requires greater force application to cover more distance with each stride and generally should not encourage them to take more steps over a given distance (34).

To do this, they must generate larger ground reaction forces (GRFs) during the stance phase and particularly the propulsion stage of each stride. Given elite sprinters typically display ground contact times of < 0.1 seconds, this places high demands on the elastic qualities of the force-producing muscles in the lower limbs. Generating a large impulse during the stance phase will demand greater degrees of stiffness and strength. In contrast, for female athletes, exercises that emphasize increased turnover are likely beneficial for improving performance. Therefore, developing improved swing phase mechanics for improved heel recovery efficiency and strength in the hip flexor muscles may prove beneficial for females.

Factors Affecting Sprint Performance

Sprint physiology is complex, with differing physical qualities more heavily associated with either acceleration or maximum velocity. Having said this, there is strong evidence, especially in field sports, that fast is fast, regardless of the sprint phase. Clark et al. (2019) demonstrated that athletes with greater acceleration qualities tended to also display higher maximum sprint velocities and vice-versa, perhaps dispelling the myth that an athlete is either good at accelerating or at top speed and that these qualities are independent (5).

Furthermore, Gabbett (2012) highlights the importance of all aspects of sprint performance in team and field sport athletes by identifying how more than 20 % of all sprints in professional rugby league matches are over 20 meters in length (14). This suggests that not only is acceleration critical to sports performance, but top speed may also play a crucial role, particularly when the nature of these longer sprints is considered (match-deciding plays, line-breaks, long chases, etc.). Given this knowledge, an appropriate speed program for team sports should aim to develop sprint ability at various phases—both short accelerations and maximum velocity, upright sprints.

One of the key factors associated with high-level sprinting, particularly during acceleration, is the efficiency of force application during the stance phase (24). Horizontal GRF relative to body weight is likely a key to improved speed during the initial strides of a sprint. One method proposed for improving horizontal force production is through horizontally orientated strength training. Exercises such as the barbell hip thrust have been hypothesized to generate greater transfer for sprinting (6) due to the force-vector theory which classifies sports skills on the basis of the direction of force expression relative to the global coordinate frame (13).

However, some coaches and more recent research suggest this may not be the case, particularly in acceleration, whereby the untrained eye may ignore the trunk/shank angles displayed by athletes resulting in vertical force production intra-individually, while global force production is horizontal in nature (18). This is not to say an exercise like the hip thrust cannot contribute to improved sprint performance, merely that transfer of training is a complicated topic and is multi-factorial in nature.

Another heavily researched training method for increasing horizontal force application during sprinting is resisted sprints. Resisted sprints come in several forms; resistance band sprints, sled sprints, prowler pushes and although not resisted, incline sprints All these methods work through the same principle of overloading the horizontal component of force application by artificially slowing the athlete down. These methods allow athletes to maintain acceleration posture for far longer than traditional free sprints and can result in far more training density being directed towards peak power production along with reinforcing horizontal GRF orientation (34).

To improve acceleration performance using resisted sprints most effectively, an athlete’s horizontal velocity should be reduced to ~50% of top speed (7, 8). The loads when applied to a sled to create such a decrement in velocity appear to be far greater than what was traditionally believed to be acceptable by coaches who were concerned about alterations to sprint mechanics when using heavy resistance. However, recent literature has demonstrated these concerns are likely misplaced and that a range of light, moderate and heavy sled pushes may be useful at various stages of a properly periodized speed development program (25).

Weyand et al. (2000) and Nagahara et al. (2018) demonstrated that larger GRFs produced during each step were particularly important to sprinting speed during the maximal velocity phase (33, 26). Athletes wanting to run at higher maximum velocities are therefore required to express more force, in a shorter period. Furthermore, lower body strength has also been shown to correlate with sprint performance. McBride et al. (2009) (r = -0.61, p = 0.01), Trajano, et al. (2014) (r = -0.57, p = 0.04) and Baker et al. (1999) (r = -0.66, p<0.05) have all demonstrated strong correlations between 1-RM back squat strength and sprint performance in elite athletes (21, 32, 2).

This should come as little surprise given the gluteal muscles, quadriceps, hamstrings and calves are the prime movers of the force-producing actions shown in sprinting. The strong relationship between lower-body strength and sprint speed may be attributed to the fact that those athletes demonstrating greater force-producing capabilities are able to produce higher peak GRFs, impulse, and increased rate of force development (30).

Perhaps more important than strength, muscle-tendon unit (MTU) stiffness has been shown to correlate strongly with sprint performance in athletes (9). MTU stiffness describes the efficiency with which energy can be transferred from the force-producing muscles into force-receiving surfaces (i.e. the ground). For example, a stiffer ankle complex will reduce energy leakages between the calves and the foot when striking the ground. MTU stiffness can be assessed through tests such as the incremental drop jump test, where jump height or flight time and ground contact times are used to generate a reactive strength index (RSI).

The reactive strength index helps athletes and coaches better understand the quality of forces and speed of application when assessing vertically orientated interactions with the ground. RSI could be considered a key performance indicator for sprint performance due to its high correlation with sprint speed in both acceleration and at maximum velocity (9) and thus can serve as a useful assessment tool for coaches and athletes.

Sprint Training in Practice

The greatest improvements in sprint performance following training interventions have been shown to come from combined/mixed method training programs that include sprints, plyometric exercises and weights training with both heavy loads (maximal strength training) and moderate loads at high movement velocities (ballistic training) (10). For the best transfer of training, plyometric exercises should be prescribed with the direction of force application in mind. To best develop horizontal power for sprinting, skips, horizontal jumps and bounds have been proposed as the most effective training tools (10), ultimately, and perhaps most importantly, the most potent sprint training stimulus available is sprinting itself (19).

Sprint training and sprinting, in general, come with some inherent risks. Hamstring strain injury (HSI) is the most common injury found during sprinting actions (28), accounting for up to a quarter of all soft-tissue injuries in sports (27). Thus, mitigating this risk of HSI with appropriate programming and complementary training methods is an essential component of a well-developed speed training program. Rather than avoid sprinting through fear of exposure to injury (11), researchers suggest for positive effects from an injury prevention perspective, team and field sport athletes should perform sprint training on a weekly basis (20).

Oakley et al. (2018) go further and suggest team and field-sport athletes should be exposed to 6-10 bouts of sprinting per week with a total volume of 90-120 metres completed at greater than 95 % of maximal sprint speed (27). Furthermore, Carey et al. (2017) suggest athletes should be required to ‘earn the right’ to sprint by appropriately building sprint volumes in alignment with an ACWR (acute: chronic workload ratio) that remains below 1.4:1 (4). This ensures athletes build the necessary fitness required to tolerate increasing training demands appropriately and reduces the likelihood of injury. However, recently scholars have questioned the legitimacy of the ACWR model’s validity due to statistical artefacts and a lack of conceptual integrity, raising further doubts about the ideal progression of training volumes (17).

A commonly cited risk factor for HSI during sprinting is hamstring muscle fascicle length (3). Recent research indicates that the most effective stimulus for improving hamstring fascicle adaptations is sprint training itself (23) once more supporting the importance of actually exposing athletes to sprinting itself. In addition, to complement a sprint training program, hamstring fascicle length can be improved through heavy, supramaximal eccentric training with many research papers citing the Nordic hamstring curl exercise as a useful tool in achieving this goal (1).

Acceleration

During the acceleration phase of a sprint, the athlete’s trunk and shin should assume a positive lean in relation to the ground. Many coaches suggest the legs should work in more of a ‘piston-like’ action during the early strides of a sprint. This is posited to lead to greater horizontal force production with GRFs orientated more negatively, leading to improved propulsion. In order to optimize this technique, the athlete should rise gradually with each stride, rather than abruptly standing tall as soon as possible.

A common error seen during the acceleration phase of a sprint is cueing or intention to maximize stride frequency—being displayed through many short, choppy steps leading to reduced force application and dampening of the centre of mass displacement. That is, the athlete is failing to protect themselves far enough with each stride to create a positive effect on performance. This appears to come from the false assumption, as mentioned earlier, that stride frequency is the common limiting factor in sprint performance. Therefore, a useful cue for many athletes is to instruct them to take ‘big, long powerful strides’ as they initiate the sprint.

During the acceleration phase, the arms should work through an increased range of motion with visual observation of elite performers demonstrating the use of an accentuated ‘arm-split’ in the first few strides. Additionally, as shown in Figure 1, it’s not uncommon to see high-level sprinters harnessing hip internal rotation torques during block starts and therefore this should not be coached out of athletes through the misguided idea that arm and leg action should remain exclusively linear in nature.

Maximum Velocity

Posture
Most coaches agree that during the maximum velocity phase of a sprint, the athlete should assume a tall, upright posture with at most a small or gradual positive lean in the direction being travelled. Additionally, Hansen (2014) suggests that for optimal sprinting technique, the athlete should emphasize hip displacement from the ground, or increase ‘hip height’. (16) In effect, this enables athletes to better access the full extent of their hip extension capacity during the stance phase and translates to improved force application during the sprinting action.

Alignment
Based on visual observation of elite performers, it’s suggested that the limbs should avoid traversing the midline of the body to create excessive rotational force. Furthermore, athletes should also retain a rhythmical arm and leg action and avoid a mechanical or robotic technique that works exclusively in the sagittal plane. The arms and legs ought to trace a curvilinear path with the hands closer to the mid-line at the front and wider at the back during all phases of the sprint and the legs mostly linear through the sagittal plane during upright maximum velocity sprinting.

Range of motion
Hansen (2014) suggests during sprinting, athletes should emphasise ‘front-side dominant’ mechanics, particularly in the lower body (16). This means that the cyclical leg action works predominantly in front of the athlete’s centre of mass (COM). This can be developed through a high knee drive action and rapid heel recovery whereby the trailing leg avoids kicking up high and too far behind the COM. These positions can be seen in Figure 2 at toe-off (knee drive), maximal vertical projection and strike (heel recovery).

Furthermore, the arm action during upright sprinting should be relaxed yet powerful. The elbows will typically be observed in an acutely flexed position at the front side, with the hand close to the mouth or cheek, and then in an obtuse position at the backside with the hand clearing the hip behind the body. A common misnomer is that the elbows should remain in a rigidly fixed right angle during sprinting.

Foot strike
A critical aspect of sprinting technique appears to be the minimization of horizontal braking forces (26). These forces are typically generated during an ‘over-striding’ or ‘heel-striking’ pattern and cause the athlete to decelerate before propulsive forces can be applied during the stance phase, thus creating a net reduction in horizontal velocity. Therefore, foot strike should be initiated as close to directly under the athlete’s COM as possible – without compromising other elements of technical efficiency.

Athletes should be instructed to aim to initiate their ground contact through the ball of the foot, with a dorsiflexed ankle beneath their hips to improve horizontal force orientation and to better prepare the ankle complex to harness its stretch-shortening cycle qualities. A constraints-based drill that may help an athlete with this are mini-hurdle wicket sprints, as seen in the video clip above. When the hurdles are spaced appropriately, stride length can be guided, and foot strike can be orientated more efficiently as the athlete self-organizes their limbs during the exercise. A suggested starting point for mini hurdle spacing is for each hurdle to be spaced at the athletes standing height apart.

Once the athlete completes a few repetitions of the drill, the coach can reassess the spacings through trial and error to modify spacings on an individual basis. As mentioned in the range of motion section above, in order to optimize knee drive, a stiff and powerful foot strike during ground contact is essential. Athletes should be reminded to apply large and abrupt GRFs with each step with cues ranging from ‘hammer the ground’ to audible feedback such as ‘make the ground pop’.

Example Program

Example speed program for field or team sport athletes during an in-season phase, playing one game per week on Saturday.

Tuesday: Acceleration
Warm-up: Walking lunge, hamstring ground sweeps, lateral lunges and side-to-side sumo squats
Technical drills: A-march, A-skip, B-skip, A-run, straight leg bounding
Constraints-based exercise: Hill or sled sprints
Sprinting: 8 x 30 m sprints starting chest to ground with 90 seconds rest between reps
Thursday: Maximum velocity
Warm-up: Walking lunge, hamstring ground sweeps, lateral lunges, side-to-side sumo squats
Technical drills: A-march, A-skip, B-skip, A-run, straight leg bounding
Constraints-based exercise: Mini hurdle wicket sprints
Sprinting: 4 x 60 m walk-in start sprints with 3 mins rest between reps

Conclusion

Making athletes lightning-fast can seem daunting at first. However, as this article has outlined, there are simple components of training, that if programmed with appropriate intensity and volume, and completed consistently, serve as the underlying ingredients in a speed training program that can make athletes lightning fast. Understanding the basic biomechanical principles of speed along with visual examples of how these can be developed in practice is a great place for young coaches and therapists to get started. The pillars of any good speed development program are sound technique, a well-rounded training program consisting of appropriate strength, power and plyometric exercises and emphasis on the act of sprinting itself. With this article, it is my hope you now have fewer doubts about the key aspects of sprint training and can begin to make meaningful differences to your athlete’s health and performance on the field.

References