Abstract
ackground/Objectives: This study aimed to examine the post-activation performance enhancement effects of bilateral horizontal drop jumps (BHDJs) on 30 m sprint and coun- termovement jump (CMJ) performance, as well as in sprint mechanical and kinematics characteristics.Methods: Fourteen young sprinters (nine boys and five girls) completed both an experimental condition (EC) and a control condition (CC). The EC consisted of five BHDJs performed at each participant’s individually determined optimal drop height, whereas in the CC, no exercise has been performed.Results: The findings revealed no significant (p> 0.05) interactions for CMJ and time to 30 m. Significant increases in5 msplit times were observed across all segments in the CC, as well as in the initial 5 m segment in the EC. Regarding sprint mechanics, a significant interaction was found in the effectiveness of horizontal force application (−2.42% in CC vs.−0.33% in EC). Step frequency demon- strated significant interaction in the 5–10 m segment (−1.79% in CC vs. 1.20% in EC) and decreased significantly in the 15–20 m segment in the CC (−2.03% in CC vs.−1.85% in EC). Conclusions: In conclusion, performance parameters reduced under the CC, whereas the BHDJ intervention stabilized these parameters or exhibited smaller performance variations than in the CC. Keywords:post-activation potentiation enhancement; plyometric exercise; track and field; sprint running 1. Introduction A pre-conditioning activity performed before a competitive exercise session is a com- monly endorsed practice in training and athletic competitions, as it has been shown to enhance
parameters reduced under the CC, whereas the BHDJ intervention stabilized these parameters or exhibited smaller performance variations than in the CC. Keywords:post-activation potentiation enhancement; plyometric exercise; track and field; sprint running 1. Introduction A pre-conditioning activity performed before a competitive exercise session is a com- monly endorsed practice in training and athletic competitions, as it has been shown to enhance subsequent performance [1]. This improvement may be attributed to the enhance- ment of the contractile properties of muscle fibers, which enables the generation of greater force and power. The capacity of a muscle group to produce force has been shown to increase acutely following a post-activation potentiation enhancement (PAPE) stimulus, which refers to the short-term enhancement of performance in explosive movements elicited by a preceding maximal or near-maximal muscular effort, commonly termed a conditioning activity [1,2]. Resistance exercises have demonstrated significant effectiveness as PAPE interventions. Briefly, sled towing has been shown to acutely improve sprint performance over distances of 15–30 m by approximately 0.8–2.24% [3–6], while sled pushing can acutely Biomechanics2026,6, 10 https://doi.org/10.3390/biomechanics6010010
Biomechanics2026,6, 10 2 of 14 enhance 20 m sprint performance by about 0.95–1.8% [7]. Additionally, free-weight exer- cises performed at intensities between 60% and 80% of one-repetition maximum (1RM) have been shown to improve vertical jump height by approximately 2–10%, peak power output by 1.31–3.36%, and sprint performance by 1.5–1.9% [8–10]. Furthermore, the use of accommodating resistance, which combines free weights with resistance bands, has also been reported to elicit additional improvements in sprinting, horizontal, and vertical jump performance by 3.5%, 5.7%, and 8.5%, respectively [11–13]. Plyometric exercises as pre-conditioning activities are widely used to enhance running and jumping performance. In particular, alternate-leg horizontal bounding and squat jumps have been shown to improve 5 m, 10 m, and 20 m sprint performance following recovery intervals of 4 and 8 min [14–16]. Furthermore, combining bilateral Vertical Drop Jumps (VDJs) with additional plyometric exercises has been reported to enhance countermovement jump (CMJ) height and 20 m sprint performance [17,18]. Notably, bilateral VDJs have been found to improve 20 m running performance when assessed 15 s, 4 min, and 15 min after the intervention [19]. Conversely, some studies report no improvement in 20 m or 30 m sprint performance following the application of resisted squat jumps or knees-to-chest jumps [20,21]. Drop jumps (DJs) are widely implemented plyometric exercises and are regarded as an effective means of eliciting PAPE [22,23]. Previous research employing DJs as a pre-conditioning activity has demonstrated improvements in running [24], jumping [23], and throwing [25] performance. To maximize the potentiating effects of DJs, it is essential to select an appropriate drop height. Previous studies have shown that optimal drop height can be determined using the Reactive Strength Index (RSI), with an individual’s optimal height defined as the height that produces the lowest RSI value [19,26,27]. Additionally, determining the axis of jump execution is also a critical consideration. According to Hicks et al. [28] the specific “position” or, directionality, of strength or plyometric exercises induces distinct adaptations across different regions of the force–velocity spectrum. In line with this perspective, previous research has demonstrated that single-leg horizontal drop jumps (HDJs) acutely enhance
the lowest RSI value [19,26,27]. Additionally, determining the axis of jump execution is also a critical consideration. According to Hicks et al. [28] the specific “position” or, directionality, of strength or plyometric exercises induces distinct adaptations across different regions of the force–velocity spectrum. In line with this perspective, previous research has demonstrated that single-leg horizontal drop jumps (HDJs) acutely enhance change-of-direction performance to a greater extent than vertical drop jumps (VDJs) (−6.8% vs.−1.3%), likely because the movement trajectory in HDJs more closely corresponds to the directional demands of sprinting. Conversely, VDJs appear to produce superior improvements in vertical jump performance than HDJs (6.5 vs. 1%) [29]. Similarly, warm-up protocols incorporating PAPE through HDJs appear to enhance repeated-sprint performance greater than VDJs (3.35 vs. 2.65%), whereas PAPE induced via VDJs improves CMJ performance greater than HDJs (3.81 vs. 3.64%) [30]. By providing these direction-specific stimuli, it becomes particularly relevant, beyond examining sprinting and jumping performances, to investigate the acute influence of HDJs on the force–velocity spectrum. Accordingly, the present study incorporates HDJs along- side countermovement jump (CMJ) and sprint assessments to evaluate sprint mechanical variables associated with the force–velocity–power (FvP) profile [31,32]. To the authors’ knowledge, no studies have examined the acute effects of HDJs on sprint mechanical characteristics in young sprinters. Therefore, the present study aimed to evaluate the acute effects of bilateral horizontal drop jumps (BHDJs) on 30 m sprint and CMJ performance, and key mechanical and kinematic parameters. It was hypothesized that acceleration per- formance, running mechanics, and kinematics would be significantly enhanced following the BHDJ intervention, whereas CMJ height would remain unchanged. https://doi.org/10.3390/biomechanics6010010
Biomechanics2026,6, 10 3 of 14 2. Materials and Methods 2.1. Participants Fourteen young sprinters, nine boys and five girls (age: 16.86±1.70 years; body mass: 62.70±5.55 kg; height: 1.72±0.07 m; 100 m personal best ranging from 11.52 to 12.13 s for boys and 13.90 to 14.71 s for girls), participated in the study. All participants were physically active, engaging in a minimum of three training sessions per week, had at least two years of structured training experience, were familiar with plyometric jumping exercises, and were in good health, with no recent injuries. Participation was voluntary, and all athletes were fully informed of the study’s purpose, benefits, and potential risks. Written informed consent was obtained from each participant; for underage athletes, consent was additionally provided by a parent or legal guardian. All procedures conformed to the ethical standards of the Declaration of Helsinki and received approval from the University Ethics Committee (protocol number: 1271/17-3-2021). 2.2. Procedures Participants completed five sessions (one familiarization session followed by four testing sessions), each separated by at least 48 h, to examine the acute effects of BHDJs on CMJ height; sprint performance (time to 30 m, and split times per 5 m); kinematic variables (step frequency, step length, contact time, and flight time); and sprint mechanical characteristics [theoretical maximal horizontal force (F0), theoretical maximal horizontal velocity (v0), maximal mechanical power output (Pmax), the mechanical effectiveness of horizontal force application (RFmax), and the rate of decline in RF (DRF)] [31]. At the beginning of every testing session, athletes completed a standardized warm- up consisting of 10 min of jogging, 5 min of dynamic stretching, 5 min of sprint drills, three 40 m sprintsof progressively increasing intensity, followed by 5 min of passive rest. During the first session, anthropometric data were collected and participants were familiar- ized with the BHDJ protocol. After familiarization, participants performed two BHDJs from 20, 30, 40, and 50 cm drop heights, with a 2 min recovery between trials [33] to determine their individual optimal height. The optimal height was defined as the height producing the highest RSI [19,34]. The RSI calculated as the ratio
data were collected and participants were familiar- ized with the BHDJ protocol. After familiarization, participants performed two BHDJs from 20, 30, 40, and 50 cm drop heights, with a 2 min recovery between trials [33] to determine their individual optimal height. The optimal height was defined as the height producing the highest RSI [19,34]. The RSI calculated as the ratio of BHDJ distance to ground contact time, expressed as RSI = Horizontal distance (m) to ground contact time (s) [35,36]. The BHDJ dis- tance was assessed using high-speed video recording at 300 Hz (Casio EX-F1,Tokyo, Japan) with reference markers placed at 1 m intervals, and contact time was measured using a ChronoJump platform (ChronoJump Boscosystem, Barcelona, Spain). Across sessions two to five, participants were randomly assigned to either the ex- perimental condition (EC) or the control condition (CC). The testing protocols for both conditions are illustrated in Figure. In the EC, participants performed five repetitions of BHDJs, with 10 s intervals between repetitions [30,37] followed by a 4 min period of passive recovery [19,37]. In the CC the participants sat for 7.5 min and did not perform any exercise. During all BHDJ trials, athletes were instructed to place their hands on their waists, stand at the edge of the drop box, and, upon ground contact, propel themselves forward as quickly and forcefully as possible using both legs. The 30 m sprint performance assessments were conducted in sessions two and three (Figurea), while the countermovement jump (CMJ) assessments were performed in sessions four and five (Figureb). https://doi.org/10.3390/biomechanics6010010
Biomechanics2026,6, 10 4 of 14 Figure 1.(a) 30 m PAPE protocol; (b) CMJ PAPE protocol. BHDJ = bilateral horizontal drop jump; CMJ = countermovement jump. Sprinting performance and kinematic parameters during the 30 m tests were evaluated using three high-speed cameras (Casio EX-F1, Tokyo, Japan) placed in the sagittal plane of motion at 5, 15, and 25 m, 10 m from the middle of the running lane, recording 10 m intervals. Eight marker poles were placed in adjusted spots to record 5 m intervals [38]. Reference markers were placed on both sides of the 30 m distance at 1 m intervals to evaluate kinematic characteristics (Figure). Each split time was calculated from the exact frame in which the athlete’s hip crossed the corresponding marker pole, and video parallax errors were corrected to achieve maximum accuracy in study results. The kinematic characteristics were calculated by analyzing each sprint step and averaging over 5 m splits. The instant when the first propulsive movement was detected was defined as the starting point (frame 0) [38,39]. Step length was defined as the distance from the take-off point of the toes of one foot until the touchdown point of the other lower limb, while step frequency was calculated by the ratio of running velocity divided by step length [16,40]. The frame where the athlete’s foot lost contact with the ground and the frame where the other foot touched the ground were used to calculate flight time. Contact time was calculated from the moment of the first touch on the ground until the moment the foot lost contact with the ground [16,40]. All the videos were analyzed using Quintic Biomechanics software v.31 (Quintic Consultancy Ltd., Birmingham, UK). The variables of the horizontal FvP profile were determined using Samozino’s method [32,41]. According to the applied method, F0 and v0were extrapolated from the linear sprint force–velocity relationship as the intercepts of the force and velocity axes of the linear regression, respectively. Pmaxwas calculated as Pmax= F0×v0/4. RFmaxwas determined as the proportion of total force directed in the horizontal direction, and DRF was computed as the slope of the
using Samozino’s method [32,41]. According to the applied method, F0 and v0were extrapolated from the linear sprint force–velocity relationship as the intercepts of the force and velocity axes of the linear regression, respectively. Pmaxwas calculated as Pmax= F0×v0/4. RFmaxwas determined as the proportion of total force directed in the horizontal direction, and DRF was computed as the slope of the linear RF–velocity relationship across the acceleration phase [31]. The intraclass correlation coefficient (ICC) assessing the consistency between baseline trials, as derived from 30 m sprint performance, was notably high (0.994, 95% confidence interval (CI) from 0.978 to 0.998). Finally, the participants performed CMJs on a ChronoJump platform, with their hands at their waist, and the best trial of the three jumps was used in the analysis [37]. https://doi.org/10.3390/biomechanics6010010
Biomechanics2026,6, 10 5 of 14 Figure 2.Cameras placement during 30 m tests. 2.3. Statistical Analysis The Shapiro–Wilk and Levene’s tests were used to assess normality and homogeneity of the data. A 2×2 repeated-measures ANOVA (time: Pre and Post×conditions: CC and EC) was conducted for all dependent variables. Sphericity was evaluated employing Mauchly’s test, and, when necessary, the Greenhouse-Geisser correction was applied. Interactions and main effects of time and condition were examined. In case of significant ANOVA, Bonferroni post hoc analysis was used. All data are presented as mean±standard deviation (SD), and Cohen’s d is used to display the magnitude of the within-subjects effect. Cohen’s d was calculated as the mean difference between conditions divided by the standard deviation of the differences, and interpreted using conventional thresholds as small (d = 0.2), medium (d = 0.5), and large (d = 0.8) [42]. Significance level was set atp≤0.05. All analyses were conducted using the statistical program SPSS (IBM SPSS version 25.0, Chicago, IL, USA). 3. Results The results of the statistical analysis for the sprinting and jumping performance for both conditions are displayed in Table. A significant main effect of time for the 5 m (F = 12.07,p= 0.004,η 2= 0.48, Observed power (OP) = 0.89), 10 m (F = 5.53p= 0.035, η 2 = 0.30, OP = 0.59), 15 m (F = 5.59p= 0.034,η 2= 0.30, OP = 0.59), 20 m (F = 7.43 p= 0.017,η 2 = 0.36, OP = 0.71), 25 m (F = 6.98p= 0.020,η 2= 0.35, OP = 0.69), and 30 m (F = 7.39p= 0.018,η 2= 0.36, OP = 0.71) sprint time. Bonferroni’s post hoc anal- ysis revealed that both conditions significantly decreased the 5 m performance (CC: Mean Difference (MD) =−0.03 s ,p= 0.025; EC: MD =−0.02 s,p= 0.006). Furthermore, Post hoc main effect of time analysis indicated a significant decrease in the 10 m (MD =−0.03 s , p= 0.017), 15 m (MD =−0.04 s,p= 0.010), 20 m (MD =−0.05 s,p= 0.003), 25 m (MD =−0.04 s ,p= 0.003), and 30 m (MD =−0.05 s,p= 0.002) sprint performance only for the CC. No significant
MD =−0.02 s,p= 0.006). Furthermore, Post hoc main effect of time analysis indicated a significant decrease in the 10 m (MD =−0.03 s , p= 0.017), 15 m (MD =−0.04 s,p= 0.010), 20 m (MD =−0.05 s,p= 0.003), 25 m (MD =−0.04 s ,p= 0.003), and 30 m (MD =−0.05 s,p= 0.002) sprint performance only for the CC. No significant (p> 0.05) interaction or main effect of time and condition was observed for the CMJ for both conditions. The results of the ANOVA indicated a significant interaction effect (condition×time) for RFmax(F = 5.43p= 0.037,η 2= 0.29, OP = 0.58). Post hoc analysis showed that only the CC significantly reduced the RFmaxpost intervention (MD =−1.07%,p= 0.008). No significant (p> 0.05) interaction or main effect of time and condition was found for the F0, v0, Pmax, SFv, and DRF for both the EC and CC (Table). The results of the analysis of variance for kinematics variables indicated a significant interaction effect in step frequency at 5–10 m distance interval (F = 6.36p= 0.025,η 2 = 0.33, OP = 0.65). Post hoc interaction effect analysis showed that only the CC significantly decreased the step frequency at 5–10 m (MD =−0.08 Hz,p= 0.026). A main effect of time https://doi.org/10.3390/biomechanics6010010
Biomechanics2026,6, 10 6 of 14 occurred in step frequency at 20–25 m interval (F = 8.09p= 0.014,η 2= 0.38, OP = 0.75). Bonferroni’s post hoc analysis revealed that the step frequency at the 15–20 m distance interval reduced only for the CC (MD =−0.09 Hz,p= 0.015). Table 1.Mean±SD, 95% CI, % change, and effect size for sprinting and CMJ performance variables between pre- and post-measurements for both conditions. Condition 5 m 10 m 15 m 20 m 25 m 30 m CMJ PerformanceCC Pre 1.37 ±0.09 2.14 ±0.14 2.82 ±0.18 3.47±0.22 4.08±0.27 4.70±0.32 30.92±6.50 Post 1.40 ±0.10 * 2.18±0.14 * 2.86±0.18 * 3.51±0.23 * 4.14±0.27 * 4.77±0.33 * 30.22±6.37 95%CI −0.05–−0.01 −0.06–−0.01 −0.07–0.01 −0.08–0.02 −0.09–0.02 −0.09–0.03 −0.18–1.58 %∆ 2.03% 1.53% 1.37% 1.4% 1.33% 1.29% −2.27% ES 0.68 0.73 0.81 0.98 0.96 1.05 0.46 EC Pre 1.39 ±0.10 2.16 ±0.15 2.84 ±0.18 3.48±0.23 4.09±0.27 4.71±0.32 31.09±6.11 Post 1.40 ±0.09 2.17 ±0.14 2.85 ±0.18 3.50±0.23 4.12±0.27 4.74±0.27 * 30.81±4.84 95%CI −0.02–−0.01 −0.04–0.01 −0.04–0.01 −0.06–0.01 −0.07–0.02 −0.08–0.02 −2.27–2.83 %∆ 1.08% 0.53% 0.45% 0.72% 0.66% 0.68% −0.90% ES 0.88 0.26 0.28 0.38 0.37 0.40 0.06 CC = control condition; EC = experimental condition; 95%CI = 95% Confidence Intervals; %∆= percent change; ES = effect size; CMJ = countermovement jump. * significantly different from baseline trial (p< 0.05). Table 2.Mean±SD, 95% CI, % change, and effect size for sprint mechanical variables between pre- and post-measurements for both conditions. Condition F 0(N·kg −1 ) v0(m·s −1 ) Pmax (W·kg −1 ) SFv (N·s·m −1 · kg −1 ) RFmax(%) DRF (% ·s·m) Mechanical ProfileCC Pre 7.68 ±1.00 8.60±0.77 16.60±3.05−0.89±0.11 44.29±3.47−8.37±0.8 Post 7.41 ±1.04 8.66±0.94 15.91±2.77−0.87±0.16 43.21±3.40 *−8.16±1.38 95%CI −0.02–0.57−0.25–0.14 0.18–1.19 −0.07–0.04 0.34–1.80 −0.62–0.20 %∆ −3.60% 0.62% −4.14% −1.61% −2.42% −2.51% ES 0.54 0.16 0.78 0.15 0.84 0.30 EC Pre 7.47 ±1.03 8.72±0.75 16.07±2.72−0.86±0.13 43.64±3.50−8.01±1.12 Post 7.41 ±0.90 8.60±0.74 16.00±2.71−0.86±0.11 43.50±3.20 *−8.10±0.98 95%CI −0.11–0.24−0.05–0.29−0.47–0.62 −0.03–0.03 −0.53–0.82−0.18–0.36 %∆ −0.83% −1.42% −0.47% 0% −0.33% −1.14% ES 0.20 0.42 0.08 0 0.12 0.20 CC = control condition; EC = experimental condition; 95%CI = 95% Confidence Intervals; %∆= percent change; ES = effect size; F0= theoretical maximal horizontal force; v0= theoretical
0.30 EC Pre 7.47 ±1.03 8.72±0.75 16.07±2.72−0.86±0.13 43.64±3.50−8.01±1.12 Post 7.41 ±0.90 8.60±0.74 16.00±2.71−0.86±0.11 43.50±3.20 *−8.10±0.98 95%CI −0.11–0.24−0.05–0.29−0.47–0.62 −0.03–0.03 −0.53–0.82−0.18–0.36 %∆ −0.83% −1.42% −0.47% 0% −0.33% −1.14% ES 0.20 0.42 0.08 0 0.12 0.20 CC = control condition; EC = experimental condition; 95%CI = 95% Confidence Intervals; %∆= percent change; ES = effect size; F0= theoretical maximal horizontal force; v0= theoretical maximal horizontal velocity;Pmax= theoreticalmaximal horizontal power; SFv= slope of the linear force–velocity relationship; RFmax= maximal ratio of horizontal-to-resultant force; DRF = rate of decrease in the ratio of horizontal force. * significantly different from baseline trial (p< 0.05). A main effect of time was noticed in running velocity at 0–5 m (F = 12.04p= 0.004, η 2 = 0.48, OP = 0.89), 15–20 m (F = 5.75p= 0.032,η 2= 0.31, OP = 0.60), and 20–25 m (F = 5.97 p= 0.030,η 2= 0.32, OP = 0.62). Post hoc analysis of the main effect of time revealed that both conditions significantly reduced the running velocity at 0–5 m distance interval (CC: MD =−0.07 m·s −1 ,p= 0.021; EC: MD =−0.04 m·s −1 ,p= 0.005). Moreover, for the15–20 m and 25–30 m intervals, the Post hoc analysis indicated a significant decrease in running velocity only for the CC (MD =−0.01 m·s −1 ,p= 0.025 and MD =−0.01 m·s −1 ,p= 0.005, respectively). No significant interaction effects or main effects of time or condition were observed for step length or contact and flight time. Furthermore, running velocity and step frequency showed no significant interaction or main effects across the remaining distance intervals (Table). https://doi.org/10.3390/biomechanics6010010
Description
The study investigates the effects of BHDJs on sprint and jump performance.