Correction: Neuromuscular adaptations to load-matched isometric vs. dynamic resistance training in Kho-Kho athletes: a pilot investigation
Year: 2026
Type: erratum
Abstract: There were mistakes in Table 3 as published. Several descriptive and inferential statistics for normalized isometric peak torque were incorrectly transcribed during table preparation. The original incorrect entries are quoted alongside the corrected entries below; unchanged cells are not repeated. The full corrected Table 3 ISO: change -0.33, SD 0.25, p < .05, d = -1.339, 95% CI [-2.236, -0.401]. Time: F(1,15)=1. 718,p=.210,η²p=.103;Group: F=3.836,p=.069,η²p=.204;Interaction: F=10.416,p=.006,η²p=.410. ISO: change -0.283, SD 0.315, p=.027, d_z=-0.900, 95% CI [-1.665, -0.097]. Time: F(1,15)=0. 794,p=.387,η²p=.050;Group: F=3.280,p=.090,η²p=.179;Interaction: F=6.874,p=.019,η²p=.314.ISO: change -0.25, SD 0.21, p < .05. ISO: change -0.252, SD 0.209, p=.007.ISO: change -0.20, SD 0.14, p < .05. DYN: change -0.17, SD 0.15, p < .05. There was a mistake in Figure 4 as published because the figure and caption did not accurately represent the corrected standardized within-group effects. The corrected Figure 4, based on the reanalyzed torque and sprint data and the available published jump-summary statistics, appears below.There was also a mistake in the caption of Figure 4 change; the magnitude of r is not directly comparable with d_z. The jump-height, RSI, FMax, and PMax effect estimates were retained from the published summary statistics because participant-level jump data were unavailable for re-estimation. The plot is descriptive; modality-specific differences should be judged from the Group × Time interaction tests."The published text reported incorrect descriptive and ANOVA values for selected isometric peak-torque outcomes.A correction has been made to the Results section, subsection "Isometric Peak Torque," paragraph 1:Original text: "For isometric testing, normalized peak torque (NPT) results are summarized in Table 3 and illustrated in Figure 2. For knee extension at 75°, the ISO group showed significant within-group improvements bilaterally (left: -0.33 ± 0.19, p < .05; right: ± 0.25, p < .05), whereas the DYN group did not show significant within-group improvement. Full repeated-measures ANOVA indicated a significant Time effect for PT 75° L EX, F(1,15) = 17.046, p < .001, η²p = .532, but the Time × Group interaction did not reach significance, F(1,15) = 3.350, p = .087, η²p = .183. In contrast, PT 75° R EX showed a significant Time × Group interaction, F(1,15) = 10.416, p = .006, η²p = .410, indicating a greater training-related change in ISO compared with DYN. At 45° knee extension, no significant Time effects, Group effects, or Time × Group interactions were observed."Corrected text: "For isometric testing, normalized peak torque (NPT) results are summarized in Table 3 and illustrated in Figure 2. At 75° knee extension, the ISO group improved on the left (-0.335 ± 0.189, p = .001, d_z = -1.769) and right (-0.283 ± 0.315, p = .027, d_z = -0.900), whereas the DYN group did not show significant withingroup changes. For PT 75° L EX, the main effect of Time was significant, F(1,15) = 17.132, p = .001, η²p = .533, whereas the Group × Time interaction was not significant, F(1,15) = 3.378, p = .086, η²p = .184. For PT 75° R EX, the Group × Time interaction was significant, F(1,15) = 6.874, p = .019, η²p = .314, indicating a larger change in ISO than DYN. At 45° knee extension, no significant Time, Group, or Group × Time effects were observed."The published subsection "Peak Torque Between Groups" contained the superseded interaction statistics from Table 3. A correction has been made to paragraph 1:Original text: "Between-group effects for isometric NPT outcomes are presented in Table 3. The only statistically significant Time × Group interaction was observed for PT 75° R EX, F(1,15) = 10.416, p = .006, η²p = .410, indicating that the magnitude of change differed between ISO and DYN for this outcome. PT 75° L EX showed a non-significant trend toward a Time × Group interaction, F(1,15) = 3.350, p = .087, η²p = .183. Similarly, PT 45° R Flex showed a large but non-significant interaction effect, F(1,15) = 3.718, p = .073, η²p = .199. Therefore, although several outcomes showed significant within-group or Time effects, clear modality-specific superiority was supported only for PT 75° R EX."Corrected text: "Between-group effects for isometric NPT outcomes are presented in Table 3. The only statistically significant Time × Group interaction was observed for PT 75° R EX, F(1,15) = 6.874, p = .019, η²p = .314, indicating that the magnitude of change differed between ISO and DYN for this outcome. PT 75° L EX showed a non-significant trend toward a Time × Group interaction, F(1,15) = 3.378, p = .086, η²p = .184. Similarly, PT 45° R Flex showed a large but non-significant interaction effect, F(1,15) = 3.718, p = .073, η²p = .199. Therefore, although several outcomes showed significant within-group or Time effects, clear modality-specific superiority was supported only for PT 75° R EX."The published text incorrectly reported a significant Group × Time interaction for initial squat-start speed and duplicated several ANOVA values across effect columns. Corrections have been made to the Results section, subsection "Squat Linear Sprint," paragraphs 1-2:Original text:"Sprint performance results are presented in Table 6. Both groups demonstrated significant within-group improvements in initial speed from the squat-start position (ISO: -0.75 ± 0.60 m/s, p < .05, d = -1.27; DYN: -0.45 ± 0.49 m/s, p < .05, d = -0.92). Full repeated-measures ANOVA showed a significant main effect of Time for initial speed, F(1,15) = 12.838, p = .003, η²p = .461, indicating an overall pre-post improvement. A significant Time × Group interaction was also observed for initial speed, F(1,15) = 12.838, p = .003, η²p = .461, suggesting that the magnitude of change differed between ISO and DYN. The main effect of Group approached significance, F(1,15) = 4.042, p = .063, η²p = .212.""No significant Time, Group, or Time × Group effects were observed for average sprint speed, specific energy, or average contact time. Specifically, average speed showed no significant Time effect, F(1,15) = 2.295, p = .151, η²p = .133, or Time × Group interaction, F(1,15) = 2.295, p = .151, η²p = .133. Specific energy and average contact time also showed non-significant effects. Therefore, the sprint-related findings suggest that the intervention primarily affected initial acceleration from the squat-start position, whereas average sprint speed, energy expenditure, and contact time were not significantly altered.""Sprint performance results are presented in Table 6. Both groups demonstrated significant within-group improvements in initial speed from the squat-start position (ISO: -0.721 ± 0.567 m/s, p = .005, d_z = -1.271; DYN: -0.451 ± 0.493 m/s, p = .036, d_z = -0.916). The main effect of Time was significant, F(1,15) = 20.435, p < .001, η²p = .577, indicating an overall pre-post improvement. However, neither the main effect of Group, F(1,15) = 0.961, p = .342, η²p = .060, nor the Group × Time interaction, F(1,15) = 1.083, p = .315, η²p = .067, was significant. Therefore, the data support improvement in both groups but do not support a modality-specific advantage for initial squatstart speed.""No significant Time, Group, or Group × Time effects were observed for average sprint speed, specific energy, or average contact time. For average speed, the Time effect was F(1,15) = 1.170, p = .296, η²p = .072, and the Group × Time interaction was F(1,15) = 2.129, p = .165, η²p = .124. For specific energy, the Group × Time interaction was F(1,15) = 0.493, p = .493, η²p = .032; for average contact time, it was F(1,15) = 1.321, p = .268, η²p = .081. Thus, the sprint findings indicate a general improvement in initial speed across groups, whereas average speed, specific energy, and contact time were not significantly altered."The published interpretation of Figure 4 incorporated the incorrect sprint interaction and treated the plotted effects as a single metric. The original and corrected text are quoted below:"Figure 4 presents the standardized mean difference (SMD) magnitude plot, which provides a descriptive visualization of within-group effect sizes across torque, jump, and sprint outcomes. The plot displays the magnitude and direction of training-related changes for ISO and DYN, with 95% confidence intervals used to indicate the precision of each effect estimate. In general, the DYN group showed mostly small-to-moderate effects across several outcomes, although a large effect was observed for 75° flexion torque. The ISO group showed large withingroup effects for selected outcomes, including 75° knee-extension torque, jump height, and initial squat-start sprint speed.""However, the SMD plot should be interpreted together with the updated ANOVA results. Large within-group effect sizes alone do not confirm modality-specific superiority unless supported by a significant Time × Group interaction.Based on the updated analyses, the clearest differential responses between ISO and DYN were observed for PT 75° R EX and initial squat-start sprint speed. In contrast, vertical jump improvements reflected a significant Time effect without a significant Time × Group interaction. Therefore, Figure 4 "The plot is descriptive and must be interpreted together with the Group × Time interaction tests. The corrected analyses support a differential response for PT 75° R EX. Initial squat-start speed improved in both groups without a significant Group × Time interaction, and vertical jump improvement likewise did not show a significant Group × Time interaction. Therefore, Figure 4 does not establish modality-specific superiority for sprint or jump performance."The published discussion incorrectly interpreted the sprint result as evidence of a differential training response. A correction has been made to the Discussion section, subsection "Jump and Sprint Performance," paragraph 2:Original text: "Both groups improved SLS initial sprint speed, with a significant Time × Group interaction indicating that the magnitude of change differed between ISO and DYN. This supports the potential value of isometric training for enhancing force production from static or low-velocity starting positions, which is relevant to Kho-Kho actions that begin from crouched or semi-static positions and aligns with recent evidence linking isometric strength and sprint-speed characteristics in field-sport athletes (39). However, average sprint speed did not improve significantly, suggesting that the intervention influenced initial acceleration rather than sustained sprint velocity. These findings support the use of targeted speed-development training alongside strength training for broader sprint performance enhancement."Corrected text: "Both groups improved SLS initial sprint speed, but the Group × Time interaction was not significant.Accordingly, the sprint result should be interpreted as a general pre-post improvement rather than evidence that ISO produced a greater acceleration response than DYN. Average sprint speed also did not improve significantly. These findings support the inclusion of targeted speed-development training alongside strength training when broader sprint-performance enhancement is the goal."The published discussion also attributed the initial-acceleration result specifically to isometric training. A correction has been made to the Discussion section, subsection "Kho-Kho Performance Implications," paragraph 1:Original text: "For Kho-Kho athletes, rapid acceleration from static positions, efficient directional changes, and explosive low-stance movements are critical. The present study provides preliminary evidence that RPE-regulated isometric training may support selected performance attributes relevant to these demands, particularly joint-anglespecific force production and initial acceleration from low or semi-static positions. These adaptations may be useful for actions requiring rapid transition from static to dynamic movement, although the present findings should not be interpreted as definitive evidence that isometric training is broadly superior to dynamic training."Corrected text: "For Kho-Kho athletes, rapid acceleration from static positions, efficient directional changes, and explosive low-stance movements are critical. The present study provides preliminary evidence that RPE-regulated resistance training may support selected performance attributes relevant to these demands. The modality-specific finding was limited to normalized 75° right knee-extension peak torque, whereas initial squat-start speed improved across both groups without a significant Group × Time interaction. Accordingly, initial acceleration should not be attributed specifically to the isometric intervention. These findings remain exploratory and should not be interpreted as evidence that isometric training is broadly superior to dynamic training."The conclusion was revised to remove the unsupported claim of a modality-specific advantage for initial sprint acceleration. The original and corrected first paragraphs are quoted below:Original text: "This pilot study suggests that both isometric and dynamic resistance training, when regulated using perceived exertion, may improve selected neuromuscular and sport-related performance outcomes in collegiate Kho-Kho athletes over a 5week period. The ISO group showed promising short-term improvements in selected outcomes, particularly joint-angle-specific kneeextension torque and initial squat-start acceleration. However, not all outcomes demonstrated significant between-group effects, and vertical jump improvements should be interpreted as within-group changes rather than clear evidence of ISO superiority. Therefore, definitive superiority of isometric training over dynamic resistance training cannot be concluded from the present pilot study." Corrected text: "This pilot study suggests that both isometric and dynamic resistance training, when regulated using perceived exertion, may improve selected neuromuscular and sport-related outcomes in collegiate Kho-Kho athletes over five weeks. A significant modality-specific difference was observed for normalized 75° right knee-extension peak torque, with a larger change in ISO. Initial squat-start speed improved in both groups, but the between-group difference in change was not significant. Vertical jump improvements also did not demonstrate a significant Group × Time interaction. Therefore, definitive superiority of isometric training over dynamic resistance training cannot be concluded from this exploratory pilot study."The original version of this article has been updated.
Institution: Gdansk University of Physical Education and Sport
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,353
OpenAlex ID: W7204152002