Introduction
Sprint ability is an important factor in a range of athletic activities and in many instances can define performance success. A specific example can be seen in the 100-m track and field sprint event, where the fastest sprinter will typically win the race (31 ). However, quicker athletes will have an advantage in team sports as well. For example, faster soccer players should be able to reposition themselves more quickly during crucial match situations, such as contests for the ball (80 ) and goal-scoring opportunities (28 ). Depending on the sport, the importance of speed can be affected by the distance traveled during a sprint effort. For strength and conditioning coaches, understanding the number of sprints and associated distances is important for sport-specific speed development.
Previous research has emphasized the value of acceleration (i.e., sprints of less than 20 m) for field sport athletes (27,54,88 ). For example, most (approximately 68%) sprint distances in professional rugby league were less than 20 m (30 ). To further illustrate the importance of short sprint speed, Gabbett (30 ) stated that the most common (approximately 46%) sprint distance for the positional grouping of hit-up forwards was 6–10 m, which emphasizes the ability to accelerate. Similar values for average sprinting distances were obtained for professional elite rugby union players (3 ), whereas Australian state-level cricket players cover between 10-17 m per sprint in 20-20 games (76 ). In professional soccer players, various researchers have reported that players sprint a total distance of between 200 and 1,100 m during a match (1,8,70,77 ). However, the mean duration of sprints completed during a soccer match is very short, tending to be between 2 and 4 seconds (90 ). This results in mean sprint distances of approximately 10–30 m (78 ), with most sprints being shorter than 20 m (26 ).
Although it is clear that speed over short distances is a requirement for most team sport athletes, a high maximal running velocity is also an important trait. Maximal velocity for team sport athletes is typically achieved during a longer sprint of 30–40 m (27,93,98 ). This has value to athletes, as maximal sprints in team sports can often be initiated from a moving start (27 ). Although sprints of these distances are less frequent in match play (26,46 ), athletes could have the opportunity to attain maximal velocity during a sprint effort if they begin the sprint while moving. This suggests that despite the importance of acceleration development for most athletes, speed over longer distance sprints (i.e., 30 m or greater) should also be developed. On the basis of these collective research findings, strength and conditioning coaches should therefore use distance-specific training for their athletes when looking to enhance speed.
To improve the speed qualities associated with various sports, coaches implement various types of training modalities (e.g., free, assisted, and resisted sprinting, resistance training, and plyometrics) (20,56 ). However, despite the widespread use of many training methods, there is limited information as to whether certain protocols are better used to induce speed improvements over specific distances (i.e., shorter or longer distance sprints). For this reason, it would be of great benefit for strength and conditioning coaches to have a resource that centralizes information regarding different speed training protocols and how they influence sprint performance over various distances.
Therefore, the purpose of this study was to perform a brief review and investigate the current scientific literature to quantify the effect of different training methods on sprint times over various sport-specific distances. The sprint distances investigated were 0–10, 0–20, 0–30, and 31+ m. As will be documented, these distances were investigated as they have been commonly used within the scientific literature and have application for team sport athletes. In this review, training studies were categorized into specific sprint training (free sprint, resisted, and assisted training methods); nonspecific training methods (strength, power, and plyometric training), and combined training methods, which is a mixture of specific and nonspecific methods. This brief review will document the speed training protocols established within the literature as being able to enhance sprint performance. More importantly, this study will highlight the protocols that could be used to improve speed over specific distances for athletes.
Methods
Study Selection
To obtain articles for the review, a database search of PubMed, Google Scholar, SPORTDiscus, and MEDLINE was conducted at the end of October 2014. The bibliographies of all reviewed articles were then searched and reviewed. Studies were chosen for inclusion if they fulfilled the following 7 selection criteria: (a) the study used a training method described earlier as nonspecific, specific, or combined; (b) the study detailed the duration of the training and the training frequency per week; (c) the study clearly detailed the outcome measures of interest (e.g., 10-m sprint time) measured with appropriate equipment (i.e., timing gates or radar gun); (d) the study provided detailed information about the male participants (e.g., age >18 years, height, body mass, and training status); (e) the study presented group mean and SD s for the dependent variable (sprint time or average velocity) of up to 100 m before and after training, or the effect sizes (ESs) and calculated percent changes; (f) the study was published before October 2014; and (g) the study was written in English and published as a full-text article in a peer-reviewed journal.
Data Acquisition and Analysis
The following characteristics were recorded for all articles: author, year, sample size, age, training status, training methods, total amount of training sessions, duration of training intervention, number of sessions per week, testing distances, and training effect in percent change or ES. This review used a methodological approach that quantified the changes associated with a training intervention (83,84 ). Training studies have been categorized into specific sprint training (free sprint, resisted, and assisted training methods); nonspecific sprint training (strength, power, and plyometric training methods); and combined training (combination of specific and nonspecific methods). To further the analysis, specific and nonspecific training methods were also analyzed within their subcategories of free sprinting, resisted sprinting, assisted sprinting, strength training, power training, and plyometrics. Studies using strength training were based on high-force or nonballistic training. Power training studies were characterized by high-velocity or ballistic training, including Olympic lifting.
Percent changes (%change), ESs, and training efficacy (TE) were used to quantify the changes with each training intervention and sprint distance of 0–10, 0–20, 0–30, and 31+ m (i.e., >30 m until the end of sprint distance). The qualitative inferences associated with the ES that were used in this review were in accordance with Hopkins (44 ). An ES less than 0.2 was considered a trivial effect; 0.2–0.6, a small effect; 0.6–1.2, a moderate effect; 1.2–2.0, a large effect; 2.0–4.0, a very large effect; and 4.0 and above, an extremely large effect. Training efficacy was defined as the change in sprint time per session and calculated for all cited studies (67 ).
It should be noted that an improvement in sprint performance (i.e., a decrease in sprint time) is denoted as a negative ES. This approach allows the reader to make decisions about the practicality and efficacy of certain training methods in relation to other samples for potential inclusion into strength and conditioning programs. After the literature search, 48 studies satisfied the inclusion criteria. The analysis included 1,485 subjects, with an average age of 22.2 ± 3.00 years, height of 1.79 ± 0.06 m, and mass of 80.2 ± 8.80 kg.
Results
Specific Sprint Training
Specific sprint training methods comprised all training forms in which the athlete sprinted either (a) without any loading on a flat surface (i.e., free sprinting); (b) resisted by sleds, bands, or an uphill incline; or (c) assisted with a towing device or a downhill slope. In summary, a total of 8 studies (13,23,49,56,61,81,89,100 ) were included for analysis in this section. Two hundred ten subjects with an average age of 22.3 ± 3.18 years, height of 1.79 ± 0.06 m, and body mass of 79.9 ± 7.34 kg were included in this analysis.
Table 1 displays the data from the specific sprint studies investigated. A summary of the distance interaction for each of the specific sprint training methods from Table 1 can be observed in Table 2 . The training effects associated with specific sprint training across all distances were generally classified as moderate (ES = ∼−1.10; %change = −3.40), with the greatest effect (ES = −1.12) observed for the 31+ m distance. Free sprinting had an average ES of −0.92 across all distances, and the greatest training effects were observed for the 31+ m distance. Training effects of resisted sprinting across all distances were classified as large, with an average ES of −1.39. The greatest ES for resisted sprinting was observed for the 0–20 m distance, and resisted sprinting tended to show the greatest training effects of all specific sprint training methods. Assisted sprint training was only investigated over the 31+ m distance and showed a small effect (ES = −0.31). Additionally, the greatest TE was observed for resisted sprint training across distances 0–10 and 0–20 m, with an average ES of −0.08. Free sprinting provided the greatest TE over the 0–30 and 31+ m distances, with an average ES of −0.07.
Table 1-a: Specific sprint training studies.
Table 1-b: Specific sprint training studies.
Table 2: Specific sprint training and its effect on different distances.*
Nonspecific Sprint Training
Strength and power-based training, in addition to plyometric training, were included as nonspecific forms of sprint training in this review. A total of 28 studies were included, in which 1,062 subjects (age = 22.1 ± 3.04 years, height = 1.79 ± 0.06 m, and body mass = 79.5 ± 8.93 kg) were included in the analysis. The data for all studies are presented in Table 3 . Table 4 provides a summary of the distance interactions from the pooled and averaged data for the nonspecific sprint training methods. The combined nonspecific training effects across all distances were classified as small (average ES = −0.32; %change = −2.63). Although there was a tendency for the ES to decrease with distance (i.e., from 0–10 to 0–30 m), the greatest effect (ES = −0.43), although small, was observed for the 31+ m distance.
Table 3-a: Nonspecific sprint training studies.
Table 3-b: Nonspecific sprint training studies.
Table 3-c: Nonspecific sprint training studies.
Table 3-d: Nonspecific sprint training studies.
Table 3-e: Nonspecific sprint training studies.
Table 4: Nonspecific sprint training and its effect on different distances.*
Similarly, the ES for strength training was classified as small (ES = 0.34) and tended to decrease as the sprint distance increased. However, the greatest ES (−0.55) was observed for the 31+ m distance. Power training had the lowest overall average effect (ES = −0.17) out of the nonspecific sprint training methods. Unlike strength training, the ES for power training increased with distance, with the greatest effect (ES = −0.33) observed for the 31+ m distance. Plyometric training had an average small ES of −0.29 over all distances. The greatest effect for plyometric training was observed for the 0–10 m distance (ES = −0.35; %change = −2.39).
Nonspecific sprint TE was −0.02 across all distances, and the greatest value was observed for strength training for the 31+ m distance. Average strength TE was −0.02 per session for all distances, whereas power training was most efficient for the 0–30 and 31+ m distance. The TE for plyometric training was −0.01 per training session, with a maximum value of −0.02 for the 31+ m distance.
Combined Sprint Training
Several investigations used a combination of specific and nonspecific training, which have been categorized as combined sprint training in this review. Eleven studies were included in this section. The training consisted of 4–10 weeks of strength and power (29 ), assisted and resisted sprint training (61 ), strength and plyometric training (40,60,82,85,92 ), different strength and resistance training (43 ), sprint plus resistance training (89 ) and resisted sprinting (94 ), or sprint plus endurance or power training (47 ). The subjects (n = 211) in the included studies had an average age of 22.2 ± 2.41 years, height of 1.81 ± 0.06 m, and body mass of 82.3 ± 9.51 kg. The data for all combined training studies are shown in Table 5 . Table 6 provides a summary of the pooled and averaged ES, %change, and TE across all distances. Combined training methods showed a small effect, with an average ES of −0.51 across all distances. The largest training effects (ES = −0.59; %change = −2.81) for this training method were observed for the 0–10 m distance, although training effects seemed to diminish with distance. Training efficacy equaled approximately −0.03 to −0.04 ES across all distances.
Table 5: Combined training studies.
Table 6: Combined sprint training and its effect on different distances.*
Training Efficacy
To clearly document the TE data for each of the individual protocols, they have been included again in Figure 1 . From the data displayed in Figure 1 , the results indicated that specific training methods seemed to be the most efficient method across all distances, followed by the combined methods of sprint training. More specifically, resisted sprinting provided the highest TE for the 0–10 and 0–20 m distances. Free sprinting had the highest TE for the 0–30 and 31+ m distances.
Figure 1: Training efficacy of each training method in different distances.
Discussion
This study provided a brief review of the effects of specific, nonspecific, and combined sprint training methods and their TE on sprint times over different distances. This information is important for the strength and conditioning coach, as coaches must attempt to use the most appropriate protocols for developing speed over specific distances (i.e., 0–10, 0–20, 0–30, and 31+ m) for their athletes. Collectively, the results from the reviewed articles demonstrated that each specific (sprint, resisted, and assisted training methods), nonspecific (strength, power, and plyometric training), and combined (mixture of specific and nonspecific protocols) training method could improve sprint performance. However, as will be discussed, there seem to be specific adaptations to the distances investigated.
With regard to the 0–10 and 0–20 m sprint distances, the largest percent changes (∼4.1%) and effects (ES = −1.11) were observed for specific sprint training methods (i.e., free and resisted sprinting) (Tables 1 and 2 ; Figure 1 ). With regard to free sprint training, this modality typically forms the basis for most speed development programs (56 ). Indeed, previous research has documented that free sprint training can induce positive technical adaptations, such as increased step length (52,53,56 ) and reduced contact time (89 ) during acceleration . Taken together, this provides evidence as to why free sprint training is a popular method used to improve speed over 20 m in athletes.
In recent years, modalities that overload an athlete (i.e., resisted sprinting), or allow an athlete to reach supramaximal velocities (i.e., assisted sprinting), have increased in popularity (10,20,25,56 ). Of these 2 specific modalities, resisted sprint training is more commonly used in an attempt to improve speed over distances up to 20 m (49,56,100 ). Certainly, of the reviewed articles, only 1 used assisted methods (61 ), and speed was not measured over the acceleration period. In contrast to assisted methods, resisted sprint training has been typically used to improve the acceleration phase of sprinting (4,20,57,89 ). Resisted sprint training has value as it can overload an athlete within the specific movements of sprint acceleration (57 ), and the results from this review indicated that this method seemed to be the most efficient for improving speed over distances less than 20 m (Figure 1 ). Indeed, relatively greater resisted sprint training loads (>10% body weight or a weight that caused more than a 10% decrease in sprint time) can not only improve linear sprinting speed (4 ) but also increase horizontal force production (48 ). Resisted sprint training methods, in this instance sled towing, can also increase step length (56 ) and reduce contact time (89 ), which illustrates the positive influence this training method can have on sprint kinematics. The data from this brief review highlight the need for specific training to optimize early sprint speed, which likely could be linked to movement specificity. To this end, both free and resisted sprint training methods can be used.
To an extent, this study also supports the use of nonspecific methods (i.e., strength, power, and plyometric training) for improving speed over distances up to 20 m (Tables 3 and 4 ; Figure 1 ). The training effects for the nonspecific methods were, however, generally less than those of the specific methods. Nonetheless, strength and conditioning coaches should be cognizant of how these methods could still influence sprint acceleration . Force production is clearly important while accelerating (72,88 ), in addition to generating the necessary power for sprinting (5,36 ). Furthermore, several studies have indicated strong relationships between maximal strength and sprint acceleration performance (6,22,64,97 ), and strength training by itself can improve short sprint speed (56 ). This underscores the importance of strength to the initial phase of sprinting. Furthermore, although strength and power training may not have a pronounced and direct transfer of training effect to running speed in trained athletes (7,75 ), it can positively influence changes in muscle architecture (75 ) and aspects of technique, such as step length during acceleration (7 ).
Nevertheless, the nonspecific protocols investigated in this brief review typically form the foundation for an athlete's training program, to influence other aspects of sport-specific performance. Some examples include increases in general strength (11,17,34,50 ), body mass (14,33 ), movement velocity (21 ), and intermuscular coordination (26 ), which can ultimately benefit sports performance. Further to this, plyometrics can improve leg power (19,59,91 ), even if the direct influence on speed may not be as pronounced when compared to specific training methods. Athletes should incorporate multiple training modalities within their training programs (40,82,85 ), several of which could provide some impact on speed over short distances by enhancing strength and lower-body power. Furthermore, strength and conditioning coaches must ensure that their athletes can express their strength and power within the sprint step, and this can be encouraged by using more specific methods of training.
For the longer sprint distances (0–30 and 31+ m), which is characterized as the maximum velocity phase of sprinting for most athletes (10 ), specific training was again found to be more beneficial than other methods. Further to this, from the reviewed research, no studies that investigated resisted methods measured sprint performance over distances greater than 30 m. In contrast, 4 studies documented the effects of free sprint training on maximum velocity sprinting (13,23,61,81 ), whereas 1 study analyzed assisted sprinting (61 ). The benefits of free sprint training are not surprising, given the importance of an effective technique for generating a high maximum running speed (62,69 ). Indeed, there are specific technical characteristics that can distinguish between skill levels (12,16,87 ) and contribute to faster sprinting performance (16,55 ). For example, short ground contact times (16 ), smaller touchdown distances (69 ), higher angular velocities of the stance-limb hip joint (63 ), a greater step frequency (16,99 ), and greater extension of the hip, knee, and ankle joints of the stance limb at takeoff (38 ) will all contribute to a higher maximal velocity when sprinting. Unfortunately, to the investigator's knowledge, there has been no scientific research that has documented the technique adaptations to maximal velocity sprinting, which result from any of the specific training methods analyzed in this study. Although it could be surmised that, similar to acceleration , there could be increases in step length (52,53,56 ) and decreases in contact time (89 ) during maximum velocity sprinting, this must be confirmed through further analysis.
Although not as pronounced as for specific training, the results from this brief review also provided evidence for the positive effect nonspecific speed training can have on 0–30 and 31+ m sprint performance. Once again, however, even though the effect on speed may not be as great as that for specific training, the findings from this brief review do not discount the value of strength, power, and plyometric training. As previously stated, there are many other benefits for an athlete that can be attained from these training protocols (18,19,32 ). Furthermore, the effects of plyometric training, which places an emphasis on the development of the stretch-shortening capacities of the muscles such that improvements in a dynamic athletic action such as jumping can be achieved (92,96 ), could be more impactful on the maximal velocity phase of sprinting. This is because the stretch-shortening capacities of the lower-body muscles contribute more to maximal velocity sprinting than acceleration (51 ), and a recent meta-analysis also concluded that plyometric training can positively influence sprint performance (68 ). Collectively, the results from this study and those of previous research suggest that strength and conditioning coaches should use nonspecific training modes to supplement the use of specific methods, as this could potentially enhance maximal sprinting speed in athletes.
The greatest limitation of this brief review of different speed training methods on sprint performance over different distances is the grouping of subjects across a range of studies. As a result, the training status of subjects across the different investigations was likely different. Indeed, highly trained athletes will adapt differently to the same stimulus when compared to healthy, untrained participants (5 ). In the context of this study, however, all populations were grouped into 1 pool to increase sample size for the analysis of each sprint distance. Additionally, the specific and the nonspecific training methods each combined 3 different subcategories. For some of these categories, there was limited research for protocols (i.e., assisted sprint training) or training effects over certain distances (i.e., the effects of plyometric and power training on sprint performance over the 31+ m distance). Therefore, some of the guidelines with regard to these training methods and distances should be considered with the correct context by the reader.
Nevertheless, this review provides the strength and conditioning coach with insight into the effects of various speed training methods related to distance traveled when sprinting. The overall effects of training tended to decrease with distance. This suggests that larger improvements in speed can be made over the initial few strides of a sprint, perhaps implying that sprint acceleration may be more trainable than maximum velocity in many athletes. However, such a contention needs validation through empirical means. For all distances, specific sprint training was found to be the most beneficial in decreasing sprint times. However, nonspecific training should also be used to supplement speed development for all distances.
Practical Applications
There are several practical implications for the strength and conditioning coach that can be drawn from this brief review. To improve sprint performance, distance-specific training should be implemented. For speed over short distances (i.e., a sprint distance up to 20 m), coaches should focus on specific sprint training, especially free and resisted sprinting protocols. For example, free sprinting with a focus on technique and also resisted sprinting using a moderate load (>10% body weight or weight that cause more than 10% decrease in time) seem to elicit the greatest gains in sprint performance. This type of training adheres to principles of specificity in that the primary goal is to improve technique specific to sprinting, hence the increased likelihood of transference to running speed.
The practical applications that can be drawn from this brief review also do not discount the benefits of nonspecific training. Nonspecific speed training modalities, such as strength, power, and plyometric training, would benefit other physical performance characteristics, such as increased strength and power production, which would still influence sprinting speed. Strength and conditioning coaches can use nonspecific training methods to support specific speed training . However, if a coach wishes to improve the speed of their athletes, they must use specific sprint training to ensure optimal performance improvements for all distances.
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