A novel method for accurate division of the gait cycle into seven phases using shank angular velocity.

BACKGROUND: Accurate detection of gait events is crucial for gait analysis, enabling the assessment of gait patterns and abnormalities. Inertial measurement unit (IMU) sensors have gained traction for event detection, mainly focusing on initial contact (IC) and toe-off (TO) events. However, effective detection of other key events such as heel rise (HR), feet adjacent (FA), and tibia vertical (TBV) is essential for comprehensive gait analysis. RESEARCH QUESTION: Can a novel IMU-based method accurately detect HR, TO, FA, and TBV events, and how does its performance compare with existing methods? METHODS: We developed and validated an IMU-based method using cumulative mediolateral shank angular velocity (CSAV) for event detection. A dataset of nearly 25,000 gait cycles from healthy adults walking at varying speeds and footwear conditions was used for validation. The method's accuracy was assessed against force plate and motion capture data and compared with existing TO detection methods. RESULTS: The CSAV method demonstrated high accuracy in detecting TO, FA, and TBV events and moderate accuracy in HR event detection. Comparisons with existing TO detection methods showcased superior performance. The method's stability across speed and shoe variations underscored its robustness. SIGNIFICANCE: This study introduces a highly accurate IMU-based method for detecting gait events needed to divide the gait cycle into seven phases. The effectiveness of the CSAV method in capturing essential events across different scenarios emphasizes its potential applications. Although HR event detection can be further improved, the precision of the CSAV method in TO, FA, and TBV detection advance the field. This study bridges a critical gap in IMU-based gait event detection by introducing a method for subdividing the swing phase into its subphases. Further research can focus on refining HR detection and expanding the method's utility across diverse gait contexts, thereby enhancing its clinical and scientific significance.

Association between frontal plane knee control and lower extremity injuries: a prospective study on young team sport athletes.

BACKGROUND/AIM: Poor frontal plane knee control can manifest as increased dynamic knee valgus during athletic tasks. The purpose of this study was to investigate the association between frontal plane knee control and the risk of acute lower extremity injuries. In addition, we wanted to study if the single-leg squat (SLS) test can be used as a screening tool to identify athletes with an increased injury risk. METHODS: A total of 306 basketball and floorball players participated in the baseline SLS test and a 12-month injury registration follow-up. Acute lower extremity time-loss injuries were registered. Frontal plane knee projection angles (FPKPA) during the SLS were calculated using a two-dimensional video analysis. RESULTS: Athletes displaying a high FPKPA were 2.7 times more likely to sustain a lower extremity injury (adjusted OR 2.67, 95% CI 1.23 to 5.83) and 2.4 times more likely to sustain an ankle injury (OR 2.37, 95% CI 1.13 to 4.98). There was no statistically significant association between FPKPA and knee injury (OR 1.49, 95% CI 0.56 to 3.98). The receiver operating characteristic curve analyses indicated poor combined sensitivity and specificity when FPKPA was used as a screening test for lower extremity injuries (area under the curve of 0.59) and ankle injuries (area under the curve of 0.58). CONCLUSIONS: Athletes displaying a large FPKPA in the SLS test had an elevated risk of acute lower extremity and ankle injuries. However, the SLS test is not sensitive and specific enough to be used as a screening tool for future injury risk.

Sagittal Plane Hip, Knee, and Ankle Biomechanics and the Risk of Anterior Cruciate Ligament Injury: A Prospective Study.

BACKGROUND: Stiff landings with less knee flexion and high vertical ground-reaction forces have been shown to be associated with an increased risk of anterior cruciate ligament (ACL) injury. The literature on the association between other sagittal plane measures and the risk of ACL injuries with a prospective study design is lacking. PURPOSE: To investigate the relationship between selected sagittal plane hip, knee, and ankle biomechanics and the risk of ACL injury in young female team-sport athletes. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: A total of 171 female basketball and floorball athletes (age range, 12-21 years) participated in a vertical drop jump test using 3-dimensional motion analysis. All new ACL injuries, as well as match and training exposure data, were recorded for 1 to 3 years. Biomechanical variables, including hip and ankle flexion at initial contact (IC), hip and ankle ranges of motion (ROMs), and peak external knee and hip flexion moments, were selected for analysis. Cox regression models were used to calculate hazard ratios (HRs) with 95% CIs. The combined sensitivity and specificity of significant test variables were assessed using a receiver operating characteristic (ROC) curve analysis. RESULTS: A total of 15 noncontact ACL injuries were recorded during follow-up (0.2 injuries/1000 player-hours). Of the variables investigated, landing with less hip flexion ROM (HR for each 10° increase in hip ROM, 0.61 [95% CI, 0.38-0.99]; P < .05) and a greater knee flexion moment (HR for each 10-N·m increase in knee moment, 1.21 [95% CI, 1.04-1.40]; P = .01) was significantly associated with an increased risk of ACL injury. Hip flexion at IC, ankle flexion at IC, ankle flexion ROM, and peak external hip flexion moment were not significantly associated with the risk of ACL injury. ROC curve analysis for significant variables showed an area under the curve of 0.6, indicating a poor combined sensitivity and specificity of the test. CONCLUSION: Landing with less hip flexion ROM and a greater peak external knee flexion moment was associated with an increased risk of ACL injury in young female team-sport players. Studies with larger populations are needed to confirm these findings and to determine the role of ankle flexion ROM as a risk factor for ACL injury. Increasing knee and hip flexion ROMs to produce soft landings might reduce knee loading and risk of ACL injury in young female athletes.

Stiff Landings Are Associated With Increased ACL Injury Risk in Young Female Basketball and Floorball Players.

BACKGROUND: Few prospective studies have investigated the biomechanical risk factors of anterior cruciate ligament (ACL) injury. PURPOSE: To investigate the relationship between biomechanical characteristics of vertical drop jump (VDJ) performance and the risk of ACL injury in young female basketball and floorball players. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: At baseline, a total of 171 female basketball and floorball players (age range, 12-21 years) participated in a VDJ test using 3-dimensional motion analysis. The following biomechanical variables were analyzed: (1) knee valgus angle at initial contact (IC), (2) peak knee abduction moment, (3) knee flexion angle at IC, (4) peak knee flexion angle, (5) peak vertical ground-reaction force (vGRF), and (6) medial knee displacement. All new ACL injuries, as well as match and training exposure, were then recorded for 1 to 3 years. Cox regression models were used to calculate hazard ratios (HRs) and 95% CIs. RESULTS: Fifteen new ACL injuries occurred during the study period (0.2 injuries/1000 player-hours). Of the 6 factors considered, lower peak knee flexion angle (HR for each 10° increase in knee flexion angle, 0.55; 95% CI, 0.34-0.88) and higher peak vGRF (HR for each 100-N increase in vGRF, 1.26; 95% CI, 1.09-1.45) were the only factors associated with increased risk of ACL injury. A receiver operating characteristic (ROC) curve analysis showed an area under the curve of 0.6 for peak knee flexion and 0.7 for vGRF, indicating a failed-to-fair combined sensitivity and specificity of the test. CONCLUSIONS: Stiff landings, with less knee flexion and greater vGRF, in a VDJ test were associated with increased risk of ACL injury among young female basketball and floorball players. However, although 2 factors (decreased peak knee flexion and increased vGRF) had significant associations with ACL injury risk, the ROC curve analyses revealed that these variables cannot be used for screening of athletes.

Single-Leg Squat as a Tool to Evaluate Young Athletes' Frontal Plane Knee Control.

OBJECTIVE: To determine the agreement between 2-dimensional video analysis and subjective visual assessment by a physiotherapist in evaluating young athletes' knee control, and to determine the intrarater reliability and inter-rater reliability of the single-leg squat test. DESIGN: Frontal plane knee control was assessed by a physiotherapist on a 3-point scale. Frontal plane projection angles were calculated from video images. To determine the intrarater reliability, a physiotherapist reassessed 60 subjects' performances from a video. For the inter-rater reliability, 20 subjects were assessed by both the physiotherapist and a nonexperienced tester. The study continued for 3 test years. SETTING: Research institute. PARTICIPANTS: Three hundred and seventy-eight floorball, basketball, ice hockey, and volleyball players. ASSESSMENT OF VARIABLES: Knee control was assessed to be good, reduced, or poor. MAIN OUTCOME MEASURES: Agreement between the video analysis and subjectively assessed frontal plane knee control. Intrarater reliability and inter-rater reliability. RESULTS: There were statistically significant differences in the mean frontal plane knee angles between subjects rated as having "good," "reduced," or "poor" knee control. Intrarater reliability was fair for the assessments in the first year, moderate (dominant leg) and good (nondominant leg) for the second year, and very good (dominant leg) and good (nondominant leg) for the third year. Inter-rater reliability was fair/poor. CONCLUSIONS: This study suggests that by using the subjective assessment of the single-leg squat task, it is possible to detect differences in frontal plane knee control in young team sport athletes. The assessment can be considered to be reliable for clinical use when performed by an experienced tester.

Predictors of lower extremity injuries in team sports (PROFITS-study): a study protocol.

INTRODUCTION: Several intrinsic risk factors for lower extremity injuries have been proposed, including lack of proper knee and body control during landings and cutting manoeuvres, low muscular strength, reduced balance and increased ligament laxity, but there are still many unanswered questions. The overall aim of this research project is to investigate anatomical, biomechanical, neuromuscular, genetic and demographic risk factors for traumatic non-contact lower extremity injuries in young team sport athletes. Furthermore, the research project aims to develop clinically oriented screening tools for predicting future injury risk. METHODS: Young female and male players (n=508) from nine basketball teams, nine floorball teams, three ice hockey teams, and one volleyball team accepted the invitation to participate in this four-and-half-year prospective follow-up study. The players entered the study either in 2011, 2012 or 2013, and gave blood samples, performed physical tests and completed the baseline questionnaires. Following the start of screening tests, the players will be followed for sports injuries through December 2015. The primary outcome is a traumatic non-contact lower extremity injury. The secondary outcomes are other sports-related injuries. Injury risk is examined on the basis of anatomical, biomechanical, neuromuscular, genetic and other baseline factors. Univariate and multivariate regression models will be used to investigate association between investigated parameters and injury risk.

Improvements in functional capacity from Nordic walking: a randomized-controlled trial among elderly people.

This study examined the effects of an instructed structured Nordic walking (NW) exercise program on the functional capacity of older sedentary people. Volunteers were randomly assigned to an NW group (68.2 ± 3.8 yr old) or control group (69.9 ± 3.0 yr old). Before and at the end of the 9-wk intervention, functional tests and 2-dimensional ground-reaction-force (GRF) patterns of normal (1.40 m/s) and fast (1.94 m/s) walking speeds were measured. The intervention included a 60-min supervised NW session on an inside track twice a week for 9 wk. The mean changes in functional tests differed between groups significantly. Gait analyses showed no significant differences between the groups on any GRF parameters for walking speed either before or after the intervention. The study showed that NW has favorable effects on functional capacity in older people and is a suitable form of exercise for them.

Loading and gait symmetry during level and stair walking in asymptomatic subjects with knee osteoarthritis: importance of quadriceps femoris in reducing impact force during heel strike?

Repetitive impulsive forces during walking are claimed to result in joint osteoarthritis (OA). The aim of this study was to investigate impact loading and gait symmetry during level and stair walking in asymptomatic elderly subjects with knee OA. It was hypothesised that pre-activity of the quadriceps femoris muscle (QF) would be an important factor reducing impulsive loading when walking on level ground. Subjects [21 female, six men, 66.2 (7.6) years] were studied. The subjects had no knee pain or diminished functional capacity, but showed radiographically light or moderate bilateral knee OA changes. Ground reaction forces (GRFs), plantar pressure distribution, muscle activation pattern [vastus medialis (VM), vastus lateralis, biceps femoris and gastrocnemius medialis] and asymmetry during level walking and stair walking were evaluated. Almost 20% of subjects had a distinct heel-strike transient at maximal speed with lower pre-activity of VM (P<0.05). The most forceful maximum vertical GRF in the braking phase occurred in stair descent [1.52 (0.21) BW]. This was 32.5% (P<0.001) higher than seen when walking on the level at normal speed. The loading rate of stair descent [10.87 (2.96) BW/s] was significantly stronger (P<0.05) than in level walking at normal speed [8.55 (1.93) BW/s]. There was no asymmetry in kinematic or kinetic variables in level walking. However, asymmetry increased during stair walking. The control of quadriceps femoris prior to heel-strike is possibly an important factor that reduces impulsive loading during walking in asymptomatic OA subjects. Stair walking is a demanding motor task and the musculoskeletal system is loaded more during stair descent than level walking at normal speed.

Effect of intramedullary gradual elongation of the shorter limb on gait patterns.

BACKGROUND: Seven young patients were followed 52 weeks after intramedullary lengthening for limb length discrepancy (LLD). The mean LLD before surgery was 3.0 +/- 1.1 cm and 1 year after surgery at the time of the nail-removal it was 0.3 +/- 0.3 cm. METHODS: The plantar pressures and the ground reaction forces (GRF) were recorded simultaneously with electromyographic (EMG) activities at normal and fast walking speeds. RESULTS: Bilateral comparison indicated that the uncorrected LLD resulted in asymmetrical gait patterns. The peak pressures were higher in the lateral heel and in the medial forefoot in the longer limb as compared to the shorter limb at normal walking speed. At fast walking speed, the peak pressures of the longer limb were higher in the forefoot area but lower in the central midfoot. One year after surgery, a clear improvement in the gait symmetry was observed compared to preoperative condition. Significantly, foot loading models were quite similar 52 weeks after surgery. However, during the follow-up period of 52 weeks, the maximal isometric knee extensor torque still remained at lower levels on the operated side until week 52 postoperatively, but reached the same level with non-operated side within 2 years. CONCLUSIONS: The improved walking symmetry obtained after surgical treatment may diminish possible pathologic loading of the lower extremity and may prevent the early appearance of arthritis in the lower extremities.