Sprint mechanics evaluation using inertial sensor-based technology: A laboratory validation study.

Advances in micro-electromechanical systems have turned magnetic inertial measurement units (MIMUs) into a suitable tool for vertical jumping biomechanical evaluation. Thus, this study aimed to determine whether appropriate reliability and agreement reports could also be obtained when analyzing 20-m sprint mechanics. Four bouts of 20-m sprints were evaluated to determine whether the data provided by a MIMU placed at the lumbar spine could reliably assess sprint mechanics and to examine the validity of the MIMU sensor compared to force plate recordings. Maximal power (P0 ), force (F0 ), and velocity (V0 ), as well as other mechanical determinants of sprint performance associated with the force-velocity, power-velocity, and ratio of forces-velocity, such as applied horizontal force loss (Sfv ) and decrease in ratio of forces (Drf ), were calculated and compared between instrumentations. Extremely large-to-very large correlation levels between MIMU sensor-based sprint mechanics variables and force plate recordings were obtained (mean±SD, force plate vs MIMU; V0, 8.61±0.85 vs 8.42±0.69; F0 , 383±110 vs 391±103; P0 , 873±246 vs 799±241; Sfv, -44.6±12.7 vs -46.2±10.7), ranging from 0.88 to 0.94, except for Drf, which showed weak-to-moderate correlation level (r=.45; -6.32±1.08 vs -5.76±0.68). Step-averaged force values measured with both systems were highly correlated (r=.88), with a regression slope close to the identity (1.01). Bland and Altman graphical representation showed a no random distribution of measured force values. Finally, very large-to-extremely large retest correlation coefficients were found for the intertrial reliability of MIMU measurements of sprint performance variables (r value ranging from .72 to .96). Therefore, MIMUs showed appropriate validity and reliability values for 20-m sprint performance variables.

Vertical jumping biomechanical evaluation through the use of an inertial sensor-based technology.

Progress in micro-electromechanical systems has turned inertial sensor units (IUs) into a suitable tool for vertical jumping evaluation. In total, 9 men and 8 women were recruited for this study. Three types of vertical jumping tests were evaluated in order to determine if the data provided by an IU placed at the lumbar spine could reliably assess jumping biomechanics and to examine the validity of the IU compared with force plate platform recordings. Robust correlation levels of the IU-based jumping biomechanical evaluation with respect to the force plate across the entire analysed jumping battery were found. In this sense, significant and extremely large correlations were found when raw data of both IU and force plate-derived normalised force-time curves were compared. Furthermore, significant and mainly moderate correlation levels were also found between both instruments when isolated resultant forces' peak values of predefined jumping phases of each manoeuvre were analysed. However, Bland and Altman graphical representation demonstrated a systematic error in the distribution of the data points within the mean ±1.96 SD intervals. Using IUs, several biomechanical variables such as the resultant force-time curve patterns of the three different vertical jumps analysed were reliably measured.

Jumping performance differences among elite professional handball players with or without previous ACL reconstruction.

AIM: Handball is one of the most challenging sports for the knee joint. Persistent strength and jumping capacity alterations may be observed among athletes who have suffered anterior cruciate ligament (ACL) injury. The aim of this study was to examine unilateral and bilateral jumping ability differences between previously ACL-reconstructed rehabilitated elite handball athletes and sex, age and uninjured sport activity level-pairs of control players. METHODS: It was a Cross-sectional study with one factor: previous ACL injury. We recruited 22 male (6 ACL-reconstructed and 16 uninjured control players) and 21 female (6 ACL-reconstructed and 15 uninjured control players) elite handball players who were evaluated 6.2±3.4 years after surgical ACL reconstruction. A battery of jump tests, including both bilateral and unilateral maneuvers, was performed. Two-tailed unpaired (intergroup comparison) and paired (intragroup comparison) t-tests were performed for mean comparisons. The P-value cut-off for significance was set at <0.05. RESULTS: The previously ACL-reconstructed female athletes showed a lower bilateral drop jump contact time (0.429±179.9 vs. 0.349±151 s, P<0.05) and less distance reached (3.820±0.54 vs. 4.428±0.44 m, P<0.05) in the unilateral triple hop for distance (UTHD) on their reconstructed leg compared with the dominant legs of the uninjured control athletes. No significant differences were observed for any other recorded variable. Among the male athletes, no significant differences between groups were found for the studied jumping variables. CONCLUSION: Previously ACL-reconstructed elite female handball athletes demonstrated both lower vertical bilateral drop jump (VBDJ) contact times and lower UTHD scores for the injured leg several years after injury. These deficits could contribute to an increase in ACL re-injury risk.