This study investigated the reliability and validity of linear sprint tests (LS) and curvilinear sprint tests (CS) using a GPS device (GPEXE lt). Twenty-one (21) student athletes completed a 40 m LS as well as a left and right CS. Maximum sprint speed (MSS) and split times at short (0–10 m), intermediate (0–20 m), and long (0–30 m) distances were determined using the GPEXE lt and single-beam timing gates (TG). Intrasession reliability and concurrent validity of GPEXE lt were assessed. The GPEXE lt consistently showed high reliability for MSS (ICC ≥ 0.95; CV ≤ 1.8%), despite underestimation compared to TG (bias = −2.57 to −0.95%; ICC ≥ 0.87). Acceptable reliability was observed for CS and LS intermediate and long distance split times (ICC ≥ 0.91; CV ≤ 2.1%), with lower reliability for short distances (ICC ≥ 0.70; CV ≤ 3.6%). The GPEXE lt split times for CS and LS showed good agreement with TG (ICC ≥ 0.66), but were overestimated at long distances (5.5–9.7%) and short distances (11.1–14.6%). Although the MSS was found to be the most reliable and valid variable to assess LS and CS speed performance with GPEXE lt, caution is needed due to limited validity.

This study aimed to evaluate the ability of a hydraulic resistance device (HRD) to assess the force and power output and force–velocity–power profile of short sprints, while examining the effects of hydraulic overload on these outcomes. Twenty-eight amateur athletes performed 20 m sprints under minimal (MiL), moderate (MoL), and high (HiL) overloads. Sprint velocity was measured with the HRD, while resistance force (F_r) was assessed from the pressure via the HRD and from the reaction force via the force plate (FP). Using velocity and F_r during the sprints, maximal velocity (v_max), average horizontal force (F_avg), average power (P_avg), and FvP profile variables (F₀, v₀, and P_max) were calculated. A two-way ANOVA analysed the effects of overload and calculation method. In addition, a correlation between the HRD and FP measurements was evaluated. For all variables, very high to excellent correlation between the HRD and FP was observed (r ≥ 0.96). However, the F_avg, P_avg, F₀, and P_max calculated by the HRD were lower than the FP across all overloads (η² ≥ 0.51; p < 0.001). Regardless of the method used, F_avg, P_avg, and F₀ were highest at HiL (η² ≥ 0.38; p < 0.001), and v₀ was highest at MiL (η² = 0.35; p < 0.001), whereas overload had no significant effect on P_max (η² = 0.01; p = 0.770). The HRD is a feasible means for monitoring force and power output during hydraulic resisted sprints but should not be directly compared to other resistance devices. HiL produced the highest F_avg, P_avg, and F₀ and may be optimal for increasing power output and improving acceleration performance.

This study investigated how the acceleration-speed profile (ASP) of the weaker and stronger side changes at different radii. Twenty male youth soccer players completed 30 m linear and curvilinear sprints (12.15, 11.15, 9.15, 7.15, and 6.15 m radius) in three training sessions. Sprint speed and acceleration over time and distance were recorded using a GNSS device. The maximum theoretical speed (S₀), the acceleration (A₀), slope of the ASP (AS_slope), the area under the AS_slope (ASP_area), the acceleration at a sprint speed of 3 m/s (A₃), and the curvilinear sprint deficit (ASP_deficit) of the individual sprints were analyzed. The effects of side, radius, and their interaction were evaluated with 2 × 5 ANOVA and the post hoc tests. A significant effect of radius and side was observed for all variables (F ≥ 3.50, p ≤ 0.037, η² ≥ 0.15). The ASP_area and S₀ decreased at tighter radii. The A₃ and A₀ remained relatively unchanged, resulting in a steeper AS_slope, and a larger ASP_deficit. At the same radius, the weaker side CS had a smaller ASP_area, S₀, A₃, and a larger ASP_deficit. The ASP of the curvilinear sprint in youth soccer players is side-dependent at both ends (acceleration and top speed), while radii mainly affect late acceleration and top speed performance. These observations should be considered when adapting soccer players' sprint training and monitoring external load based on acceleration.

Background: According to human-centered design principles, user experience and user satisfaction are key aspects when developing or providing patients and clients with assistive, rehabilitation, or training technologies. Existing tools for assessing user experience and satisfaction are often either too narrow (developed for specific technologies) or too broad, failing to capture all relevant aspects of the technology being evaluated. Objective: The main objective of this study was to present the development process and content validation of a questionnaire that, following further validation steps, could be useful for researchers and developers in assessing the satisfaction of direct end users with assistive, rehabilitation, and training technologies. Methods: The development of the User Satisfaction Questionnaire for Assistive, Rehabilitation, and Training Technologies (U-ART-Q) followed a multistep process: (1) literature review, (2) domain definition and item generation, (3) expert consultation, (4) linguistic validation, and (5) content validation. Initially, 72 items were generated and organized into 7 domains. After expert review and linguistic validation, the questionnaire underwent content validation by 8 experts in physiotherapy, kinesiology, and ergonomics. Each item was rated for relevance using a 4-point Likert-type scale. The content validity ratio (CVR) and item-level content validity index (I-CVI) were calculated, and items below the accepted thresholds were removed or further revised. Results: Expert consultation resulted in the removal or merging of 20 items to improve clarity and reduce redundancy. Of the 52 items evaluated during content validation, 44 met the CVR and I-CVI criteria (CVR >0.75 and I-CVI >0.78). Eight items required additional review, and 2 items were ultimately removed. The final questionnaire comprises 10 initial screening questions and 50 content-valid items across 7 domains: design, comfort, effectiveness and usefulness, service, treatment or exercise, overall impressions, and safety. The overall average content validity index was 0.915, providing evidence of strong content validity. A macro-enabled Excel tool was developed to automate item selection and generate a PDF version of the questionnaire based on initial screening responses. Conclusions: The U-ART-Q is a newly developed instrument for assessing user satisfaction with assistive, rehabilitation, and training technologies. Further research will focus on psychometric evaluation, reliability testing, and multilingual validation to determine whether the U-ART-Q can provide a standardized method for assessing user satisfaction. Once fully evaluated, the questionnaire could support both developmental usability testing and postmarket evaluation, facilitating evidence-based decision-making and guiding future product improvement.

Background and purpose The hiking position is a fundamental technique in International Laser Class Association dinghy sailing that requires prolonged trunk muscle activation to counteract external heeling forces. However, the influence of hip angle on trunk muscle activation during hiking has not been sufficiently investigated. From an applied perspective, clarifying this relationship could help coaches and strength and conditioning specialists use hip-angle adjustments to target different trunk-loading demands during simulator-based training. Therefore, the purpose of this pilot study was to determine how different hip angles in the hiking position on a sailing simulator affect trunk muscle activation in Slovenian sailors competing in International Laser Class Association classes. Material and methods Ten competitive International Laser Class Association sailors participated in the study. Maximal voluntary contractions of selected trunk muscles were recorded before testing. Participants then performed two trials on a sailing simulator at three hip angles (extended, semi-flexed, and flexed). Surface electromyography was used to assess rectus abdominis, external oblique, internal oblique, and erector spinae activation, with values normalized to each participant’s maximal voluntary contraction. Results Hip angle had a significant effect on rectus abdominis activation (59.3 ± 18.5%, 30.8 ± 14.2%, and 14.9 ± 10.7% of maximal voluntary contraction for the extended, semi-flexed, and flexed positions, respectively; p < 0.001), external oblique activation (46.2 ± 17.2%, 31.9 ± 8.9%, and 21.7 ± 8.5% of maximal voluntary contraction; p = 0.002), and internal oblique activation (24.9 ± 7.6%, 15.5 ± 6.7%, and 13.8 ± 8.4% of maximal voluntary contraction; p = 0.002). Erector spinae activation remained low across all conditions (5.4 ± 4.2%, 3.6 ± 2.0%, and 3.2 ± 2.0% of maximal voluntary contraction) and did not differ significantly between hip angles (p = 0.082). Conclusions Greater hip extension during a simulated hiking position was associated with increased activation of the rectus abdominis, external oblique, and internal oblique muscles, whereas erector spinae activation remained low. These acute responses indicate that hip angle can be used as a practical loading variable when planning hiking-simulator technique and conditioning sessions.