The response of a skeletal muscle within a movement is dependent on its contractile history. After performing an exercise that causes contractile stimulation, fatigue and potentiation occur. The force that a muscle is able to produce after prior contractile activity is a result of the net balance between fatigue and potentiation (16,58). Fatigue causes an impaired or attenuated contractile response, which is generally demonstrated by a lower active force than otherwise expected (58). In contrast, postactivation potentiation (PAP) is a phenomenon in which muscular performance characteristics are enhanced after contractile stimulation (26,60,77). The enhancements in performance have been linked to an increase in the rate of force development in the muscles involved in a particular action (26,62). Although the exact mechanism responsible for the PAP response remains uncertain, most reviews have intimated that there are 2 main factors, and potentially a third factor, believed to be responsible for the PAP effect (26,60,62,77,82). The factors are namely phosphorylation of myosin regulatory light chains, increased recruitment of higher-order motor units, and potentially, changes in muscle pennation angle. Docherty and Hodgson (16) stated that PAP may be advantageous in voluntary force production, particularly in activities that require dynamic muscle contractions. As a result, many coaches will structure training programs in an attempt to invoke the PAP response in their athletes.
PAP can be achieved when a strength-based conditioning activity (CA), such as a resistance exercise with a load equal to or above 85% of an individual's 1 repetition maximum (1RM), is performed before a power- or velocity-based exercise (7,19–21,61). A power- or velocity-oriented exercise is one in which acceleration occurs through the full range of motion, resulting in a higher movement speed and power output (2,51). The traditional view of invoking the PAP response was to select biomechanically similar strength and power exercises (e.g., a back squat and a jump squat). More recently, however, there have been investigations as to whether sprinting speed over a variety of distances can be potentiated by a high-force (i.e., a strength or plyometric exercise) CA (4,8,10,22,23,34,35,46,56,66,76,79,81,86). In addition, there has been limited analysis as to change-of-direction (COD) speed and PAP (55,67). This article reviews the literature regarding whether the PAP response can be invoked in linear and COD speed. This will provide practical value to the strength and conditioning coach, in that potential benefits of PAP for linear and COD speed will be presented, as well as how this could be applied in athletes.
FACTORS INFLUENCING THE POSTACTIVATION POTENTIATION RESPONSE
There are several issues that a strength and conditioning coach must consider before implementing a CA to invoke a PAP response in an exercise. These issues can influence the extent and effectiveness of the PAP response invoked within an individual. The factors that will influence the fatigue and potentiation that may result from a previous exercise include the following: biomechanical similarities between the preload and power exercise (10,19–21,23); the athlete's training experience and level of strength (9,18,61,63,73,74); intensity of the CA performed (56,66,79); volume of the CA performed (82,86); and rest period length within the exercise pair (10,32,52,79). There has also been analysis on the influence of sex and PAP, which is an issue because there has been much less analysis of females compared with males (15,18,22,35,74,85). Coaches must have an understanding of these factors to successfully implement a CA for PAP in their athletes.
As previously stated, the original view for invoking a PAP response involved a strength-based CA, followed by a technically similar power exercise (7,19–21,61). This relates to not only the movement technique but also the magnitude and direction of force required within the task (12). Some examples include pairing a bench press with a medicine ball or bench throw for the upper body (2,20), or a back squat with a countermovement jump (CMJ) for the lower body (18,28,29). Despite the practical belief, some earlier studies were unable to find significant improvements in the power exercise after the CA. For example, Ebben et al. (20) found that ground reaction force and muscle activation of the pectoralis major and triceps did not significantly change during a medicine ball power drop exercise when it was preceded by a 5RM bench press in male collegiate basketball players. Jones and Lees (29) did not find that a CA of 1 × 5 repetitions at 85% 1RM back squats potentiated countermovement or drop jumps 3, 10, or 20 minutes after CA in strength-trained men. Nonetheless, Ebben et al. (20) and Jones and Lees (29) recognized the practical value of pairing exercises like this and also noted that there were not decreases in performance of the power exercise. Later research presented more promising results. In strength-trained rugby league players, Baker (2) documented approximately 4.5% increases in power output during a bench throw performed with a 50-kg resistance following 1 × 6 repetitions at 65% 1RM bench press. Duthie et al. (18) found a trend for enhanced squat jump height and power in female hockey and softball players after performing a set of 3RM half-squats. The trend was more pronounced in the relatively stronger subjects when compared with their weaker counterparts. These studies helped form the foundation for further investigation of PAP in athletic populations, and the training implications for such practices.
This included consideration of the strength levels of the athletes being trained, and how this could influence the CA intensity and recovery duration required for potentiation to manifest. Several studies have suggested that stronger individuals can experience a greater PAP response when compared with their weaker counterparts (9,18,61,63,73,74,82). Only Till and Cooke (76) and Batista et al. (3) have reported contrary findings. Till and Cooke (76) found that stronger (5RM deadlift = 72.5 ± 8.22 kg; relative strength = 1.001 ± 0.04 kg per kg body mass) or weaker (5RM deadlift = 62.5 ± 8.80 kg; relative strength = 0.874 ± 0.08 kg per kg body mass) academy soccer players responded no differently to a 5RM deadlift, tuck jumps, or maximal voluntary isometric contraction leg extension performed on an isokinetic dynamometer when used as a CA for a 20-m sprint or vertical jump. However, as the sample from Till and Cooke (76) was academy soccer players, and thus only in their late teens, the “stronger” players may not have actually been strong, which limits the application of conclusions drawn from this study. Batista et al. (3) demonstrated no significant differences in the PAP response in a CMJ after a maximal isometric contraction on a leg press in track and field athletes, recreational bodybuilders, and physically active individuals. The lack of biomechanical similarities (10,19–21,23) between the maximal isometric contraction leg press and dynamic CMJ could have influenced the findings of Batista et al. (3). Nevertheless, both Till and Cooke (76) and Batista et al. (3) did highlight the importance of monitoring individual responses to PAP exercises, which is an issue for all athletes regardless of strength levels.
Nonetheless, consensus among the literature seems to indicate the value of an athlete's strength training background for invoking PAP (9,18,61,63,73,74,82). For example, Chiu et al. (9) used a CA of 5 × 1 repetition back squats at 90% 1RM in collegiate athletes and recreationally trained individuals. When data were combined, the results indicated that there was no potentiation to the force or power generated during rebound or concentric-only jump squats with 30, 50, or 70% 1RM back squat performed either 5 or 18.5 minutes after CA.
When Chiu et al. (9) compared the PAP responses of the collegiate athletes and recreationally trained individuals separately, they found that the athletes enhanced their peak power generation in each of the jump conditions, whereas the recreationally trained individuals did not. Suchomel et al. (73) compared stronger (back squat greater than 2 × body mass) and weaker (back squatted approximately 1.6 × body mass) individuals when performing ballistic and nonballistic concentric-only half-squats as a CA. The results indicated that stronger subjects experienced significant increases in squat jump power after the nonballistic CA, and these enhancements occurred sooner (after 3 minutes and being maintained through 7 minutes) than for the weaker subjects. Seitz et al. (63) showed clear differences in the PAP responses for a squat jump after a CA involving 1 × 3 repetitions at 90% 1RM back squat in stronger subjects (back squat greater than 2 × body mass) compared with weaker subjects (back squat approximately 1.75 × body mass). Based on a meta-analysis of the literature and using magnitude-based inference analysis, Wilson et al. (82) documented that athletes (effect size [d] = 0.81) significantly respond better to CA designed to invoke PAP when compared with trained (d = 0.29) or untrained (d = 0.14) subjects. Taken together, these studies indicate that athletes with a history of strength training seem to be better positioned to use a CA to potentiate a power-based exercise than individuals without a strength training history.
Intensity of the CA is also an important consideration, as an intensity that is too low will generally not provide a PAP effect. For example, performing 8 front squats with dumbbells held at shoulder height equivalent to 20% of body mass (range = 12–18 kg) after a dynamic warm-up did not potentiate 10- or 20-m sprint performance in elite youth soccer players more than a dynamic warm-up alone (50). Therefore, strength and conditioning coaches must ensure that they use a load for the CA that provides the necessary intensity to enhance power output. The data from the meta-analysis conducted by Wilson et al. (82) suggested that moderate-intensity exercise (60–84% 1RM; d = 1.06) provided greater potentiating effects than heavy resistance (85–100% 1RM; d = 0.31). This was further discussed by Wilson et al. (82) that a moderate-intensity exercise could elicit PAP, without the degree of mechanical trauma associated with a higher resistance.
In addition, Yetter and Moir (86) stated that volume was more important than the actual load for eliciting a PAP response in maximal sprinting in strength-trained men. Wilson et al. (82) found some evidence in support of this, with the meta-analysis data indicating that a multiple-set CA protocol (d = 0.66) could elicit a greater PAP effect than single-set procedures (d = 0.24). However, a great range of loads have been used within the literature (82), and it is incumbent on coaches to select an appropriate one for their athletes.
The coach must also be aware of the time course for a PAP response in an athlete. The durations measured have ranged from immediately after a CA to extensive recovery periods closer to 20 minutes (82). Training background could also influence when peak potentiation occurs for an individual, with stronger subjects potentially invoking PAP sooner (63,73). Seitz et al. (63) noted that within their study, stronger subjects achieved the greatest potentiation 6 minutes after CA, whereas the weaker subjects' greatest potentiation occurred 9 minutes after CA. Wilson et al. (82) stated that rest period lengths of 7–10 minutes resulted in a greater effect (d = 0.70), when compared with shorter (3–7 minutes; d = 0.54) or longer (>10 minutes; d = 0.02) recovery durations. However, Nibali et al. (52) expressly stated that analysis and interpretation of mean data were not appropriate for determining the time course of a PAP response, and that it was more important for the coach to determine the individual response for each athlete. Nibali et al. (52) did state that investigating the time course of a PAP response within a training session is an appropriate way to ascertain the individual response of an athlete.
The current research suggests that when considering all the factors previously discussed, females should also be able to invoke a PAP response that is comparable to males (9,15,22,24,35,66,74). In addition, and similar to males, females can also experience great individual variation in response to a CA (74,85). Witmer et al. (85) found that 5/10 men and 4/10 women in their sample improved their vertical jump height following a CA protocol of 1 × 5 repetitions at 30% 1RM back squat, 1 × 4 repetitions at 50% 1RM back squat, and 1 × 3 repetitions at 70% 1RM back squat. Sygulla and Fountaine (74) investigated Division II collegiate female athletes from the sports of basketball, softball, and volleyball. When using a back squat CA of 1 × 5 repetitions at 50% 1RM, 1 × 5 repetitions at 60% 1RM, 1 × 3 repetitions at 75% 1RM, and 1 × 3 repetitions at 90%, the results indicated that there were no significant changes in squat jump height or power output 5 minutes after CA. When considering individual cases, however, Sygulla and Fountaine (74) stated that some of the stronger subjects were able to potentiate the squat jump. Additionally, any mechanisms responsible for the PAP response should be similar between the sexes (15). Coaches of female athletes should be confident that should they consider the general issues associated with PAP, they can effectively implement it into a training program.
DEFINITION OF LINEAR AND CHANGE-OF-DIRECTION SPEED
Before discussing the effects of PAP on linear and COD speed, it is important to define what these characteristics are. Linear speed is the ability to generate a high velocity in a straight line without any changes in direction, and is essential to performance success in many sports (17,39,45). Both acceleration (a sprint with increasing velocity, which occurs over distances from approximately 0–20 m in a linear sprint from a stationary start) and maximal velocity (top speed, which occurs between 30 and 60 m for most athletes in a linear sprint from a stationary start) are important components of speed for many field and court sport athletes (17,39,44,45). When discussing the PAP effects an exercise may have on linear speed, it is important to contextualize whether potentiation was seen for acceleration or maximal velocity sprinting.
The terms agility and COD speed have been used interchangeably, but they are distinct. Sheppard and Young (65) define agility as the initiation of body movement, COD, or rapid acceleration or deceleration, often in response to a stimulus. COD speed is the physical component of agility and incorporates factors such as COD and sprint technique and leg muscle qualities (65). These factors could be arguably targeted by a CA for potentiation. A further consideration for potentiating COD speed is that the ability to effectively change direction can be directionally specific, as the required technique will change depending on the angle of the cut (57,69). This means that when discussing a particular COD speed test or exercise and any potential PAP effects, the actual structure and movements required within the test should be noted. There is crossover in the characteristics that are important for both linear and COD speed, including strength, power, and effective technique (11,14,25,39,54,71,72). This should lend itself to possible potentiation with an appropriate CA.
PAP AND LINEAR SPEED
If strength and conditioning coaches understand the science behind PAP, they could theoretically select appropriate exercises that could facilitate enhanced linear speed. There has been a recent increase in research that has investigated the relationship between PAP and linear speed (4,8,10,22,23,34,35,46,56,66,76,79,81,86). Table 1 displays a summary of the research analyzing PAP and linear speed. Where appropriate, percentage changes and magnitude-based inferences as shown by effect sizes (6,84) have been documented. Effect sizes were calculated for those data whose mean ± SD values were presented numerically within the manuscript. For the purpose of this review, a d 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 (27).
Much like established PAP research, studies have shown a large degree of individual variation as to whether linear sprint performance can be potentiated (4,10,22,34,76,79,81). This would clearly influence whether mean data can categorically show the effectiveness of select CA for potentiating linear speed. Nonetheless, there is still value in discussing the results of these studies. Several different loads have been found to potentiate sprint performance. Rahimi (56) found light (2 × 4 repetitions at 60% 1RM), moderate (2 × 4 repetitions at 70% 1RM), and heavy (2 × 4 repetitions at 85% 1RM) loads for the back squat potentiated 36.6-m sprint performance in experienced soccer players, with effects ranging from large (d = 1.44; moderate load) to extremely large (d = 4.35; heavy load). Yetter and Moir (86) compared front and back squats in strength-trained men, and found that back squats performed with 30–70% 1RM as a CA could potentiate the 10–20 and 30–40 m intervals of a 40-m sprint after 4 minutes. The improvements to maximal velocity sprinting were linked to the vertical impulses generated during a back squat (86), which are also an essential component of attaining peak speed (80).
Given that vertical force increases with load during a back squat (88), it is not surprising that heavier load back squats have also been found to potentially enhance linear speed. Chatzopoulos et al. (8) reported that 10 single repetitions at 90% 1RM of the back half-squat led to faster 0–10 m and 0–30 m sprint times after 5 minutes of recovery in recreational team sport athletes. Both of these changes had large effects (d = 1.96 and 1.23, respectively). Back squats performed with 90–91% of 1RM (4,22,35,46) have also been found to improve the best 0–5 and 0–10 m sprint times when recovery periods were individualized in professional rugby players (4), 36.6-m sprint performance in Division II football players (22), 40-m sprint time in division III football players (46), and 100-m sprint performance in strength-trained, college-aged women (35). In the study by Bevan et al. (4), the change in the most potentiated 0–5 m sprint elicited a moderate effect (d = 0.72), whereas the 0–10 m change was small (d = 0.50). Evetovich et al. (22) found a small effect for the change in 36.6-m time that occurred 8 minutes after CA (d = 0.29). The significant improvement in 100-m sprint performance in college-aged women documented by Linder et al. (35) resulted in an improvement of 0.19 seconds 9 minutes after CA, which also had a small effect (d = 0.41). Although McBride et al. (46) did find a significant improvement in maximal velocity sprinting over 0–40 m, there was only a trivial effect (d = 0.15).
The results from these studies seem to indicate the challenge of making interpretations on the mean data for a sample, as any large individual variations will impact the strength of magnitude-based inference (6). There is context as to why a bilateral strength exercise such as the back squat could influence both acceleration and maximal velocity sprinting. As previously noted, the generation of vertical force is essential for maximal velocity sprinting (80), as this will assist with flight and turning over the steps. In addition, although the horizontal component of ground reaction force is more pronounced during acceleration (49), vertical force is still needed for flight and augmentation of step kinematics during acceleration (40). Therefore, an exercise such as the loaded back squat, which requires the generation of high vertical ground reaction forces (88), could be used to potentiate both acceleration and maximal velocity (4,8,22,35,46,56,86).
There are also studies that have shown certain strength exercises did not potentiate sprint performance. Performing a set of 5RM deadlifts did not enhance 0–10 m or 0–20 m sprint times after 4, 5, or 6 minutes of recovery in young, professional soccer players (76). However, the actual strength of the teenage soccer players investigated by Till and Cooke (76) could have been the limiting factor in attaining PAP, given the importance of this capacity (9,18,61,63,73,74,82). Indeed, the “strong” subjects from Till and Cooke (76) lifted a load of 72.5 ± 8.22 kg, which is well below 5RM deadlift loads that have been lifted by strength-trained men (129.7 ± 23.5 kg) (1).
Division I collegiate male track and field athletes did not experience improvements in 40-m sprint times 1 minute after performing 3 power cleans with 90% 1RM (23). The power clean can be a technically difficult lift (83), so athletes' experience with an exercise such as this could influence how much loading they can use, and thus the resulting intensity of the exercise could be compromised. Additionally, the short recovery time of 1 minute may also have meant that fatigue was predominant over potentiation within the 40-m sprint (16,58). Guggenheimer et al. (23) also investigated high knee running on a vibration platform within their study, but using this as a CA had no effect on 40-m sprint performance. Lim and Kong (34) found that performing 1 × 3 repetitions at 90% 1RM back squat did not improve 30-m sprint performance after 4 minutes in well-trained track and field athletes. McBride et al. (46) and Crewther et al. (10) used a 3RM back squat for Division III football players and rugby players, respectively, and found that the CA did not enhance 0–5 (10), 0–10 (10,46), or 0–30 m times (46).
One of the potential limiting factors in these studies that did not find that sprint performance could be potentiated was that the strength exercises used were bilateral (i.e., squats, deadlifts, power cleans) (10,23,34,46,76). As previously noted, a bilateral exercise such as the back squat has been shown to potentiate sprint performance in certain studies (4,8,22,35,46,56,86), as this exercise can allow for an appropriate intensity and load to invoke a PAP response. However, given the great individual variations that occur with PAP responses (4,10,22,34,76,79,81), certain subjects may not respond to a bilateral movement that produces a technique dissimilar to maximal running. Sprinting is a cyclic unilateral action in which the athlete alternates between single-limb support and flight (40,80). A key issue for an athlete in transferring general strength to the sprint step is ensuring that the nervous system can control the augmented muscle mass and strength to recruit the appropriate motor units for the running task (78). This is why unilateral strength exercises (e.g., split-squats, lunges) have been recommended for speed training (13,41,68), as they hold true to the ideal of specificity. Furthermore, Yetter and Moir (86) stated that a back squat may not provide a movement-specific stimulation to the muscles required for sprint acceleration because of the different mechanical demands of acceleration versus maximal velocity sprinting (40,48,49,80). If coaches find that an athlete does not respond to a bilateral exercise as a CA, whether this is for a short acceleration sprint or a maximal velocity effort, they could potentially adopt something more sprint-specific (e.g., unilateral exercises such as a Bulgarian split-squat, stationary lunge, or walking lunge). Indeed, an exercise such as the walking lunge places a greater emphasis on horizontal force production (31,33), which could benefit sprinting given the importance of horizontal force for increasing running speed (5,48,49). At this stage, there is currently no research that has investigated unilateral strength exercises to potentiate linear speed, so this is an avenue for future research.
Several studies have also investigated whether plyometric exercises can potentiate sprint performance (46,76,79). The concept of applying plyometrics as a CA for sprint performance relates to the idea of the specificity of overload provided by a jump, and the resulting magnitude and direction of force required (12). Exercises such as maximal hopping and bounding produce similar patterns of braking and propulsion when compared with maximal sprinting, with an increase in force production due to the nature of jumping (47). However, the need to be specific when applying plyometrics as a CA is highlighted by McBride et al. (46) and Till and Cooke (76). McBride et al. (46) investigated jump squats (1 × 3 repetitions at 30% 1RM) as a PAP protocol in Division III football players, but found that no changes to 0–10, 0–30, or 0–40 m sprint resulted 4 minutes after CA. Till and Cooke (76) used a set of 5 tuck jumps as a CA in academy soccer players, which only had a trivial influence on 0–10 and 0–20 m sprint performance. In both studies, the magnitude and direction of the force application required may not have been great or specific enough to potentiate linear speed. In contrast, Turner et al. (79) found more promising results when using alternate leg bounds as a CA in strength-trained males. Performing alternate leg bounds with body mass only, or with an additional load of 10% body mass, was found to enhance 0–10 and 0–20 m sprint performance at select time points after the CA, with moderate to large effects for the significant changes (d = 0.86–1.41). Turner et al. (79) linked the positive PAP results to the explosive nature of bounding, which again asserts the importance for magnitude and direction of force application for potentiation in sprinting (12,47).
Of all the studies considered in this review for PAP and sprinting, only 2 involved samples that were not classically defined in their study as being “strength-trained” (66,81). Whelan et al. (81) used recreational athletes (hurling, Gaelic football, soccer, rowing, and triathlon), whereas the subjects from Smith et al. (66) were classified as anaerobically trained (as opposed to strength-trained). Interestingly, both studies analyzed whether resisted sprinting could be adopted as a CA for PAP. Whelan et al. (81) explored whether towing a sled with 25–30% of body mass could potentiate 0–10 and 0–30 m sprint performance 3 and 5 minutes after CA, and their results indicated that there were no changes to sprint performance. Smith et al. (66) investigated using 18.28-m sprints while towing 0–30% body mass loads as a CA for a 36.6-m sprint, but found only trivial-to-small effects on linear speed (d = 0.14–0.28). However, the subjects from both studies (66,81) may not have had the requisite strength to obtain potentiation from sled towing (9,18,61,63,73,74,82). In addition, towing a load of approximately 30% body mass can alter an athlete's sprint technique (30,42), and this could have impacted any potentiation that could have resulted from resisted sprinting. For example, Lockie et al. (42) found that when towing a load equivalent to 32.2% of body mass, male field sport athletes experienced significant decreases in step length, step frequency, and flight time, and significant increases in contact time, within the first 2 steps of a 15-m sprint. Nonetheless, given that biomechanical specificity has been recommended for invoking a PAP response (10,19–21,23), and resisted sled towing provides an overload specific to sprinting (42), future research should investigate whether resisted sprinting can be used to potentiate linear speed in more strength-trained subjects.
POSTACTIVATION POTENTIATION AND CHANGE-OF-DIRECTION SPEED
There is much less research on the effects of a CA on COD speed performance, especially when compared with linear speed. Indeed, there were only 2 PAP studies that used a speed test involving a direction change (55,67), and the focus of one of these studies was actually on repeated-sprint ability (RSA) (55). A summary of the research investigating PAP and COD speed is shown in Table 2. Percentage changes and magnitude-based inferences (6,84) have again been documented where appropriate, and the parameters set by Hopkins (27) were adopted.
Sole et al. (67) used a 10-m shuttle test to investigate the PAP response after the use of the back squat as a CA (1 × 3 repetitions at 90% 1RM) in Division II male and female athletes. The COD required was a 180°, up-and-back cut. Although there were no significant changes to shuttle test performance after the 4-, 8-, and 12-minute time points, Sole et al. (67) suggested that there was a trend toward an enhancement of COD speed, although the overall effect across subjects and time periods was trivial (d = 0.18). Sole et al. (67) did imply that a heavy resistance exercise such as the 90% 1RM back squat could be used to potentiate COD speed, but this was within the context of the highly individualized responses to the CA. Previous research has established the importance of vertical and horizontal force production during the braking phase of a COD, as this allows for a more effective deceleration before a cut (69,71). An exercise such as the loaded back squat may provide the vertical force production required to potentiate a 180° cut, as manipulation of these force components during stance is necessary for a fast direction change (25,69,71).
Okuno et al. (55) investigated the effects of a CA on RSA in elite male handball players. The RSA test used six 30-m shuttle sprints, in which there was a 180°, up-and-back COD after 15 m (i.e., 15-m sprint, COD, followed by another 15 m sprint). Okuno et al. (55) acknowledged that the results of their study were also influenced by the fact that their RSA test featured a direction change. Thus, the results from this research were considered for this article. The CA was a back half-squat that progressed to a load of 90% 1RM lifted for 5 sets of 1 repetition, with 2 minutes of recovery between lifts. The best sprint from the RSA test, as well as the mean sprint, was potentiated by the CA, with moderate (d = 0.54) and small (d = 0.41) effects, respectively. However, Okuno et al. (55) also correlated the back half-squat 1RM load with the magnitude of change for the RSA variables, and although the correlation with RSA mean time was moderate (r = 0.50), the relationship with the best RSA time was low (r = 0.03). Okuno et al. (55) suggested that this related to the fact that COD speed was dependent not only on strength but also on technique. The complexities of a direction change could have an influence of whether a bilateral CA such as a back squat could be used to potentiate COD speed.
In addition, the direction changes from both Sole et al. (67) and Okuno et al. (55) were 180°, up-and-back cuts. Although this type of COD is often trained and assessed in different sports (14,36,53,54), this is not the only type of direction change required of many athletes. Many sports require an athlete to make sharp, diagonal direction changes while running forward (44). There are many studies that have used planned and reactive versions of tests and potential training drills that involved direction changes from 30 to 45° (37,70–72), and several studies have linked COD performance through these directions to measures of strength and power (43,69,71,72). Quicker performance in 30–45° direction changes has been related to higher levels of lower-body strength as measured by the isometric midthigh pull in male and female recreational athletes (69) and female basketball players (71,72). Lockie et al. (43) associated enhancement in lower-body power as shown through jump tests (vertical CMJ, standing broad jump, and lateral jump) with a quicker performance of the change-of-direction and acceleration test, which features 45° cuts (44), in college-aged men and women. Collectively, the results from these studies may suggest that a COD drill involving diagonal cuts could theoretically be potentiated by a strength- or power-based CA, although this needs to be confirmed by research. Furthermore, the coach should also ensure that any performance enhancements in COD ability that result from a CA then transfer into the actual match performance of the athlete.
There is also currently no research that has documented whether a CA can potentiate reactive agility. This is notable given that numerous sources have stated that planned COD and reactive agility tasks are distinct (37,64,65,87). Sole et al. (67) recommended investigation of whether a heavy resistance exercise could potentiate agility performance that incorporates perceptual demands. Given that agility is not purely limited by COD speed (which has a foundation in strength, power, and technique) but also decision-making (65), it may be more difficult to ascertain whether a reactive task was potentiated by a CA. However, given the importance of perception and decision-making for team sports (64,65,87), it would be worth determining whether specific reactive training drills can be potentiated by a strength- or power-based CA.
PRACTICAL APPLICATION OF THE POSTACTIVATION POTENTIATION RESPONSE FOR SPEED TRAINING
Taken together, there are several practical applications that can be taken from the analyzed research studies investigating the PAP response in linear and COD speed (4,8,10,22,23,34,35,46,55,56,66,67,76,79,81,86). In addition, strength and conditioning coaches should also follow the traditional recommendations for strength, power, and sprint training prescription when using a CA to potentiate speed. Some guidelines for linear and COD speed potentiation include the following:
- Ensuring that the individual has an appropriate training history, especially regarding strength training, to fully take advantage of PAP after a resistance CA (9,18,61,63,73,74).
- Ensuring sufficient recovery periods between sessions that involve PAP exercise pairs (i.e., at least 48 hours), while also making sure that the recovery periods are not too long (i.e., 96 hours or greater) to limit the risk of detraining (7).
- Set and repetition ranges can follow the traditional guidelines for strength, power, and speed development, which are 3–6 sets of up to 5–6 repetitions for each exercise pair (18,38,41,43,59,75).
- The back squat can be used to potentiate sprint performance, with loads of 60–90% of 1RM shown to be effective in enhancing linear speed over a variety of distances (4,8,22,35,46,56,86), whereas a 90% of 1RM load could be used to potentiate COD speed (55,67). Stronger individuals should be able to tolerate a heavier load when using the back squat as a CA, which could have greater benefits for invoking the PAP effect (9,18,61,63,73,74). Although the technique required for the back squat may not be movement-specific when compared with sprinting, it does allow for the requisite intensity needed to invoke a PAP response.
- Alternate leg bounds can also be used to potentiate linear speed (79), so the coach could also consider using plyometric exercises to potentiate sprinting.
- Monitoring the time response to a CA for each individual is essential when attempting to optimize a PAP response (52). The coach should use this information to govern the training design for the individual within a squad.
- Regardless of the exercise used for the CA, the coach must monitor whether the individual responds to the stimulus. If one does not, the coach should consider other exercises (e.g., unilateral strength exercises such as the Bulgarian split-squat, stationary lunge, or walking lunge, as opposed to the bilateral back squat) to potentiate linear and COD speed.
The research suggests that linear sprint performance can be potentiated by strength CA such as a back squat, or a plyometric CA such as alternate leg bounding. Some preliminary investigations of PAP and COD speed seem promising, but more research is needed before definitive conclusions and practical applications can be provided. However, as noted, the current research provided some suggestions for strength and conditioning coaches to consider for their programs that attempt to use the PAP response for training. The coach should first be aware of the large variation in individual responses to PAP. The variation in response can take form in the amount of rest time an individual requires for the PAP response to show to the type of CA that elicits a PAP response. Strength levels of the individual can also affect the PAP response. Coaches must therefore make sure that they are attempting to program for the individual, rather than a blanket program for an entire squad.
Regarding the type of CA used to elicit the response, considerations need to be made regarding the proper loading to elicit the response and the specificity of force application. For the back squat, a wide range of loads have been used across all of the studies, with loading from 60% of 1RM to 90% of 1RM showing potentiating effects. The largest effects for linear speed were found for moderate (60% 1RM) and heavy (≥85% 1RM) loading, but this conclusion is a suggestion rather than an absolute guideline. Acceleration and maximal velocity sprinting have been potentiated through a strength CA, possibly due to the importance of vertical force that is generated during the strength CA and sprinting itself. This could also be applied to COD speed, as large vertical and horizontal forces are required during deceleration, and this could be potentiated by a CA such as a back squat.
The concept of specificity of force application also seems to hold true for alternate leg bounds as well, as this exercise has been used successfully to potentiate linear sprinting. Despite this, certain athletes may not be potentiated by a bilateral exercise such as a back squat. The coach could experiment with unilateral exercises, but this requires more scientific research before definitive recommendations can be provided. Strength and conditioning coaches must also be aware that there will be variations in the time required for potentiation of linear or COD speed between athletes. As a result, coaches should monitor the time course of potentiation for their athletes to determine the best “window” for potentiation for each individual, regardless of the exercise used as a CA for linear or COD speed.
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