The Sprint Mechanics Assessment Score: A Qualitative Screening Tool for the In-field Assessment of Sprint Running Mechanics.

BACKGROUND: Qualitative movement screening tools provide a practical method of assessing mechanical patterns associated with potential injury development. Biomechanics play a role in hamstring strain injury and are recommended as a consideration within injury screening and rehabilitation programs. However, no methods are available for the in-field assessment of sprint running mechanics associated with hamstring strain injuries. PURPOSE: To investigate the intra- and interrater reliability of a novel screening tool assessing in-field sprint running mechanics titled the Sprint Mechanics Assessment Score (S-MAS) and present normative S-MAS data to facilitate the interpretation of performance standards for future assessment uses. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Maximal sprint running trials (35 m) were recorded from 136 elite soccer players using a slow-motion camera. All videos were scored using the S-MAS by a single assessor. Videos from 36 players (18 men and 18 women) were rated by 2 independent assessors blinded to each other's results to establish interrater reliability. One assessor scored all videos in a randomized order 1 week later to establish intrarater reliability. Intraclass correlation coefficients (ICCs) based on single measures using a 2-way mixed-effects model, with absolute agreement with 95% CI and kappa coefficients with percentage agreements, were used to assess the reliability of the overall score and individual score items, respectively. T-scores were calculated from the means and standard deviations of the male and female groups to present normative data values. The Mann-Whitney U test and the Wilcoxon signed-rank test were used to assess between-sex differences and between-limb differences, respectively. RESULTS: The S-MAS showed good intrarater (ICC, 0.828 [95% CI, 0.688-0.908]) and interrater (ICC, 0.799 [95% CI, 0.642-0.892]) reliability, with a standard error of measurement of 1 point. Kappa coefficients for individual score items demonstrated moderate to substantial intra- and interrater agreement for most parameters, with percentage agreements ranging from 75% to 88.8% for intrarater and 66.6% to 88.8% for interrater reliability. No significant sex differences were observed for overall scores, with mean values of 4.2 and 3.8 for men and women, respectively (P = .27). CONCLUSION: The S-MAS is a new tool developed for assessing sprint running mechanics associated with lower limb injuries in male and female soccer players. The reliable and easy-to-use nature of the S-MAS means that this method can be integrated into practice, potentially aiding future injury screening and research looking to identify athletes who may demonstrate mechanical patterns potentially associated with hamstring strain injuries.

Normalization of Early Isometric Force Production as a Percentage of Peak Force During Multijoint Isometric Assessment.

PURPOSE: To determine the reliability of early force production (50, 100, 150, 200, and 250 ms) relative to peak force (PF) during an isometric mid-thigh pull and to assess the relationships between these variables. METHODS: Male collegiate athletes (N = 29; age 21.1 [2.9] y, height 1.71 [0.07] m, body mass 71.3 [13.6] kg) performed isometric mid-thigh pulls during 2 separate testing sessions. Net PF and net force produced at each epoch were calculated. Within- and between-session reliabilities were determined using intraclass correlation coefficients and coefficient of variation percentages. In addition, Pearson correlation coefficients and coefficient of determination were calculated to examine the relationships between PF and time-specific force production. RESULTS: Net PF and time-specific force demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .82-.97; coefficient of variation percentages 0.35%-1.23%). Similarly, time-specific force expressed as a percentage of PF demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .76-.86; coefficient of variation percentages 0.32%-2.51%). Strong to nearly perfect relationships (r = .615-.881) exist between net PF and time-specific net force, with relationships improving over longer epochs. CONCLUSION: Based on the smallest detectable difference, a change in force at 50 milliseconds expressed relative to PF > 10% and early force production (100, 150, 200, and 250 ms) expressed relative to PF of >2% should be considered meaningful. Expressing early force production as a percentage of PF is reliable and may provide greater insight into the adaptations to the previous training phase than PF alone.

A qualitative screening tool to identify athletes with 'high-risk' movement mechanics during cutting: The cutting movement assessment score (CMAS).

OBJECTIVE: To assess the validity of the cutting movement assessment score (CMAS) to estimate the magnitude of peak knee abduction moments (KAM) against three-dimensional (3D) motion analysis, while comparing whole-body kinetics and kinematics between subjects of low (bottom 33%) and high CMASs (top 33%). DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Forty-one participants (soccer, rugby, netball, and cricket). MAIN OUTCOME MEASURES: Association between peak KAM and CMAS during a 90° cut. Comparison of 3D whole-body kinetics and kinematics between subjects with low (bottom 33%) and high CMASs (top 33%). RESULTS: A very large significant relationship (ρ = 0.796, p < 0.001) between CMAS and peak KAM was observed. Subjects with higher CMASs displayed higher-risk cutting postures, including greater peak knee abduction angles, internal foot progression angles, and lateral foot plant distances (p ≤ 0.032, effect size = 0.83-1.64). Additionally, greater cutting multiplanar knee joint loads (knee flexion, internal rotation, and abduction moments) were demonstrated by subjects with higher CMASs compared to lower (p ≤ 0.047, effect size = 0.77-2.24). CONCLUSION: The CMAS is a valid qualitative screening tool for evaluating cutting movement quality and is therefore a potential method to identify athletes who generate high KAMs and "high-risk" side-step cutting mechanics.