Acceleration Training

Sprint based training with team sports has become a main stay in the training week. This is partly due to the increasing demands of field-based sports, its ability to deliver an injury preventative exposure and to help athletes prepare. There is no doubt that training and developing this facet of an athletes game can give a performance advantage, of which teams strive for. However, if a player can get up to maximum velocity quickly this poses another performance treat through acceleration. A positive acceleration effort over 5 to 10m can give advantage during high intensity tasks (Harper et al., 2019). 

The Acceleration phase is regarded as a primary sprint related activity. (Gronwald et al., 2022). However, it is considered that acceleration is mechanically different when compared to other phases of running (Higashihara et al., 2018). Footballers can be exposed up to 46 high intensity accelerations in game (Harper et al., 2019). It’s fair to state that average in game exposure to this action are high in number and intensive in nature. Given that high-speed running preparation is pivotal for most team sports a new consideration of understanding acceleration and how this is best trained must be addressed. 

To be able to quantify this action a study established this as a running effort above 3m.s-2 (Tierney at al., 2016); with acceleration phases in field-based sports is between 5 to 15m, depending on the task at hand. Mechanically speaking, to produce this over ground force the shape of accelerative running requires the hip angle to remain high with a shortened step length combined with a small knee momentum arm (Astrell et al., 2024). This finding agrees with previous studies that reported an increased truck lean coupled with end range hip flexion, which are optimal for maximal horizontal forces (Morin et al., 2015). 

Hunter, Marshall & McNair looked at the ground reaction forces (GRF) within the acceleration phase of sprinting, over 15m. Using 40 pre-trained individuals and assessing through video analysis GRF data was collected. The results reported that not only did the faster athletes displayed a greater horizontal force than vertical one but also had the ability to implement these in a faster capacity. Meaning that individuals that can project body mass forward, over ground rather than upwards were able to achieve faster acceleration times. The research suggested that although longer ground contact times are required to overcome inertia when compared to up right running but a higher acceleration performance is driven from quick ground contacts. 

This can be interpreted in one of two way by the athlete, either they increase step frequency to decrease ground contact or put force down through a decrease step frequency. The former is an easier to adopt when coaching however, is inefficient in nature. The latter is harder to adopt but significantly more optimal. This suggests that a degree of acceleration training is required to reach the desired technique to efficiently and effectively accelerate. 

When thinking about acceleration training it would be thought that completing this activity or similar activities in nature, such as plyometrics is the way forward. However, this is not the case with the ability to produce concentric force seen as key (Sleivert & Taingahue., 2004). Firstly, it is important to identify that the first two to four steps of acceleration where the athlete is taking the body from a near stationary, static position a concentric muscle contraction is required (Sleivert & Taingahue., 2004). The researcher looked at the relationship between acceleration times over 5m, concentric muscle strength and power output. Thirty athletes completed sprints over 10m from a static start with force-time data collected from the first step using force plates. 72 hours later athletes completed a loaded split squat jump between 30-70% of one repetition max. Completing the jump with a pause at the bottom, like that of the squat jump. This technique was used to ensure a concentric contraction was primarily used rather than a plyometric action. The results demonstrated that athletes that were better at performing the loaded split squat jumps held the better 10m acceleration times. Demonstrating that the ability to produce concentric force is fundamental to effectively accelerate. 

Gaining the ability to produce this force creates a good foundation but it is no good if the athlete does not know how to express this in a positive and effective manor. Therefore putting this into practice is the next steps in acceleration training. There is a plethora of equipment that can be used to progress this on and to facilitate acceleration ability. With the advancement of technology, the equipment choice is varied, with Run Rockets, Exer-Genie, 1080 Sprint Trainer, parachutes, bungies, sleds and prowlers all available. The use of weighted sleds has been widely researched as they are mostly used and ease of use within team sports. 

A comparison between resisted runs versus unresisted runs was completed in a untrained student population. Two equal groups of 22 were devised, a resisted run group (RS group) using 5kg weighted sleds with others being in the unresisted run group (US group). Each group followed the same sprint training program three times a week of eight weeks with a 50m sprint effort at the start and end of the testing period. Both groups were asked to perform 4 x 20m and 4 x 50m maximum effort runs. Running velocity was measure at 20m, 40m and 50m in addition to stride length and frequency. 

The study found that the RS group improved over 20m but did not significantly improve the maximum speed. Whereas, the US group improved performance over 40m and 50m. The conclusion was that weighted sled or resisted acceleration training did improve acceleration performance but had little to no effect after 20m. However, the study failed to take times at each interval and only looked at velocity max. If time had been used as a performance outcome it could be hypothesised that if athletes can improve acceleration performance that times to reach 20, 40 and 50m would decrease but not improve top end speed. 

If sleds are to be used to facilitate acceleration performance an optimum weight must be found. Lockie, Murphy & Spinks (2003) studied this among 20 field-based athletes with differing loads of 12 and 35% body mass of an individual. It was reported that stride length was the most effected through a decrease of 10% in the lighter load and 25% in the heavier loads. This was mirrored in step frequency between the two loads but at a lower rate of 6% between the two loads. More critically, sled runs increased ground contact time, trunk lean and hip flexion. As more load is added an increase in shapes with a longer time spend on the ground is seen as the athlete overcomes the increased inertia. However, the team found that with heavier loads a greater disruption is seen to the normal acceleration kinematics. Therefore, caution must be taken when using heavier loads to increase acceleration performance. 

To increase acceleration performance a detailed and structured approach must be adopted to ensure the needs of the athlete are taken care of. Acceleration training can aid the performance of sprint efforts up to 20m but does not have an impact on maximum velocity. Therefore, acceleration and up-right running should be viewed differently and trained for separately within a concurrent program. The foundations of adequate acceleration training come from concentric muscle contraction to create a sound foundation before layering on more advanced technical training. The utilisation of equipment is varied and is dependent on availability, athlete and practionor competencies. The use of weighted sleds is most widely researched with the use of lighter loads being recommended to encourage acceleration performance.