Reliability and validity of the Kinect V2 for the assessment of lower extremity rehabilitation exercises

BackgroundBesides its initial use as a video gaming system the Kinect might also be suitable to capture human movements in the clinical context. However, the system’s reliability and validity to capture rehabilitation exercises is unclear.Research questionThe purpose of this study was to evaluate the test-retest reliability of lower extremity kinematics during squat, hip abduction and lunge exercises captured by the Kinect and to evaluate the agreement to a reference 3D camera-based motion system.MethodsTwenty-one healthy individuals performed five repetitions of each lower limb exercise on two different days. Movements were simultaneously assessed by the Kinect and the reference 3D motion system. Joint angles and positions of the lower limb were calculated for sagittal and frontal plane. For the inter-session reliability and the agreement between the two systems standard error of measurement (SEM), bias with limits of agreement (LoA) and Pearson Correlation Coefficient (r) were calculated.ResultsParameters indicated varying reliability for the assessed joint angles and positions and decreasing reliability with increasing task complexity. Across all exercises, measurement deviations were shown especially for small movement amplitudes. Variability was acceptable for joint angles and positions during the squat, partially acceptable during the hip abduction and predominately inacceptable during the lunge. The agreement between systems was characterized by systematic errors. Overestimations by the Kinect were apparent for hip flexion during the squat and hip abduction/adduction during the hip abduction exercise as well as for the knee positions during the lunge. Knee and hip flexion during hip abduction and lunge were underestimated by the Kinect.SignificanceThe Kinect system can reliably assess lower limb joint angles and positions during simple exercises. The validity of the system is however restricted. An application in the field of early orthopedic rehabilitation without further development of post-processing techniques seems so far limited.     

Reliability and comparability of the accelerometer as a measure of muscular power.

PURPOSE: The purpose of this study was to determine the effectiveness of using accelerometry as a reliable measure of upper body muscular power and its comparability with other conventional measurement tools. METHODS: Thirty men, aged 19 to 25 yr, gave informed written consent before performing a one-repetition maximum (1RM) bench press on a linear bench press apparatus. Three trials of 60% 1RM were then performed at 1-min intervals and the entire procedure was repeated the following day. Each trial was analyzed for average power (AP), average velocity (AV), and total displacement (TD) by three instruments: a uni-axial piezoresistive accelerometer (ICS Sensors Model 3145, Milpitas, CA) mounted on the Cybex Smith Press (Owatonna, MN) apparatus, a 17-mm video camera that recorded the lift, and an infrared photocell and timer system arranged to analyze a 20-cm segment of the lift. Acceleration data collected at 60 Hz obtained a direct measurement of force and an integrated measure of velocity to calculate muscular power. RESULTS: Repeated measures ANOVA and intraclass correlation coefficients indicated high trial to trial reliability (r = 0.99) for all measurement variables. Film AP was significantly greater (P < or = 0.05) than the accelerometer AP and the photocell AP in the 20-cm segment (356.6 +/- 94.8 W vs 335.5 +/- 97.7 W, and 342.0 +/- 97.2 W, respectively). Also, significant mean differences (P < or = 0.05) between the accelerometer and film measurements existed for AP (246.0 +/- 70.2 W vs 286.1 +/- 83.6 W), AV (44.4 +/- 9.2 cm x s(-1) vs 51.3 +/- 12.3 cm x s(-1)) and TD (43.2 +/- 7.9 cm vs 47.4 +/- 7.4 cm) when examined over the entire lift, but there were significant correlations between the two methods (AP, r = 0.95; AV, r = 0.98; TD, r = 0.93). CONCLUSIONS: These results suggest that although minor data acquisition errors were present, accelerometers can provide a reliable and versatile means to assess muscle power.     

Standard Scores for Women's Weight Training

In brief: The purpose of this study was to develop and determine the reliability of normative data for women by weight classification for one-repetition maximum (1-RM) for five weight-training exercises. Subjects were 221 female students enrolled in beginning coeducational classes for ten weeks. Standard scores were computed for seven body-weight classifications for bench press, half squat, dead lift, bent-arm pullover, and military press. The bootstrap procedure, which is a new computer-intensive technique, was used to estimate standard errors of the norms. This procedure aids in interpreting the stability of each standard score.     

Reliability and validity of knee angles and moments in patients with osteoarthritis using a treadmill-based gait analysis system

BackgroundAlthough commonly used to study knee osteoarthritis (OA), relatively little is known about the reliability and validity of three-dimensional (3D) gait biomechanics derived from treadmill-based systems.Research questionUsing a treadmill-based gait analysis system, our objectives were to: 1) estimate the test-retest reliability of frontal and sagittal plane knee angles and moments in knee OA patients; 2) examine concurrent validity by estimating the associations between treadmill-based and overground (gold standard) measures; and 3) examine known-groups validity by comparing measures between knee OA patients and matched healthy controls.Methods34 patients and 16 controls completed 3D gait analyses using treadmill-based and overground systems. Treadmill walking speed was matched to self-selected overground speed. Marker set, knee angle and moment calculations were consistent for both systems. Patients completed a second test session using the treadmill-based system <24 h later but within 1 week of the first test session. Variables calculated from knee angle and moment gait waveforms during stance were evaluated using Bland and Altman plots, Intraclass Correlation Coefficients (ICC), Pearson correlations (r) and t-tests.ResultsVisual inspection of the Bland and Altman plots did not reveal any systematic differences between test and retest sessions; however, limits of agreement (LoA) were larger for the sagittal plane than the frontal plane. Mean differences between sessions for knee angles were <0.25 degrees and <0.18 %BW*ht for knee moments. ICCs ranged from 0.57-to-0.93 for test-retest reliability. Pearson correlations between treadmill and overground systems ranged from 0.56-to-0.97. Although highly associated, there were substantial differences in the moments, emphasizing they cannot be used interchangeably. Patients had greater first peak knee adduction moments (KAM) than controls [mean difference (95 %CI): 0.55 (−1.07, −0.04), p = 0.03].SignificanceResults suggest frontal and sagittal plane knee angles and moments in patients with knee OA evaluated using a treadmill-based system are reliable and valid.     

Comparison of electromyographic activity of the lower trapezius and serratus anterior muscle in different arm-lifting scapular posterior tilt exercises

ObjectiveTo determine the most effective exercise to specifically activate the scapular posterior tilting muscles by comparing muscle activity generated by different exercises (wall facing arm lift, prone arm lift, backward rocking arm lift, backward rocking diagonal arm lift).DesignRepeated-measure within-subject intervention.ParticipantsThe subjects were 20 healthy young men and women.Main outcome measuresLower trapezius (LT) and serratus anterior (SA) muscle activity was measured when subjects performed the four exercises.ResultsMuscle activity was significantly different among the four exercise positions (p < 0.05). The backward rocking diagonal arm lift elicited significantly greater activity in the LT muscle than did the other exercises (p < 0.05). The backward rocking arm lift showed significantly more activity in the SA muscle than did the other exercises (p < 0.05).ConclusionsClinicians can use these results to develop scapular posterior tilting exercises that specifically activate the target muscle.     

Validity and reliability of 2-dimensional trunk,hip, and knee frontal plane kinematics during single-leg squat,drop jump,and single-leg hop in females with patellofemoral pain

ObjectivesTo investigate validity and between-session reliability of frontal plane trunk, hip, and knee kinematics during three functional tasks in females with patellofemoral pain (PFP).DesignObservational.SettingResearch Laboratory.Participants20 females with PFP (22.7 ± 3.2 years, 69.9 ± 9.2 kg, 167.7 ± 9.6 cm).Main outcome measuresTrunk, hip, and knee frontal plane peak angles during the single leg squat (SLS), drop vertical jump (DVJ), and single leg hop (SLH) kinematics were evaluated using 2-dimensional (2D) and 3-dimensional (3D) motion capture. Participants returned to the lab one week later and competed a second 2D analysis of the functional tasks. Concurrent validity was assessed by evaluating relationship between 2D and 3D frontal plane kinematics with Pearson correlations. Between-session reliability was assessed by evaluating 2D kinematics with intraclass correlation coefficients by a single assessor.ResultsModerate to strong correlations (r = 0.55–0.76, p < .05) were found for frontal plane hip kinematics during all three tasks and the trunk during the SLH. Frontal plane kinematics demonstrated good to excellent test-retest reliability for each of the three tasks, (ICC _(2,1) = 0.70–0.90).Conclusion2D hip joint angles during the three functional tasks were the only valid frontal plane angles. Trunk, hip, and knee 2D frontal plane kinematics ranged between good-excellent reliability.     

Power versus strength-power jump squat training: influence on the load-power relationship

PURPOSE: The purpose of this investigation was to compare the impact of power training and strength-power training on the load-power relationship in the jump squat. METHODS: Twenty-six recreationally trained male subjects were randomly assigned to either a power training group (P; N=10), a strength-power training group (SP; N=8), or a control group (C; N=8). The P group trained for 12 wk, performing seven sets of six jump squats with the optimal load for maximal power output (body mass only, no external load), whereas the SP group performed five sets of six jump squats with the optimal load for maximal power output (body mass only, no external load) and three sets of three squats with 90% of their one-repetition maximum (1RM). Work performed by the P and SP subjects was equivalent throughout the 12 wk of training. Peak power relative to body mass (PP), jump height (JH), peak force relative to body mass (PF), and peak velocity (PV) during the jump squat were examined across loads of body mass (BM) and 20, 40, 60, and 80 kg at week 0 (baseline) and after weeks 6 (midtest) and 12 (posttest). RESULTS: After training, the P group significantly increased PP at BM and 20 kg, whereas the SP group significantly increased PP output across all loading conditions. Similarly, jump height was significantly increased by the P group at the lighter loads (BM, 20 kg, and 40 kg) and by the SP group at all loads. Whereas significant improvements in maximal power output and jump height at BM were observed in both P and SP groups, no difference in maximal power output or maximal jump height existed between the training groups. CONCLUSION: Combined lower-body strength-power training is effective as power training for improving maximum jump height and maximum power output in the jump squat, and it is more effective than power training at producing all-around (i.e., from BM to 80 kg) improvements in the load-power relationship of the jump squat.     

Validity of various portable devices to measure sit-to-stand velocity and power in older adults

BackgroundMovement velocity and power in a single STS are related to functional performance in older adults. Identifying accessible tools that provide valid measures of STS velocity/power would allow practitioners to evaluate physical function in clinical settings where time, space and finances are limited.Research questionDoes a linear position transducer (LPT), iPhone application (App), and inertial measurement unit (IMU) obtain valid measurements of velocity and power during a single STS compared with 3D motion capture?MethodsTwenty-seven community-dwelling older adults aged ≥60 years completed a single STS test with mean velocity and power simultaneously measured with 3D motion capture, an LPT, IMU and App. Acceptable validity was established if the Pearson correlation coefficient (r) was very high (≥0.7) and bias as a standardised effect size (ES) was small (<0.6). The relationship between STS velocity/power and 30s chair STS performance was also evaluated.ResultsMeasures of STS velocity obtained by the LPT (r = 0.94, ES = −0.21) and App (r = 0.89, ES = −0.19) were very highly valid when compared to 3D motion capture, and were very strongly related to 30s STS performance (r ≥0.74). The LPT (r = 0.87, ES = 0.13) and App (r = 0.74, ES = −0.12) also showed very high correlations and negligible bias for measuring STS power. Data collected by the IMU failed to meet our pre-determined threshold of acceptable validity for STS velocity (r = 0.72, ES = 1.00) or power (r = 0.61, ES = 0.34).SignificanceThe LPT and iPhone App, but not the IMU, are valid tools for measuring STS velocity and power in community-dwelling older adults. Clinicians can use STS velocity obtained by either the LPT or App as a simple and valid proxy for functional status, which could help identify patients at high-risk of incident disability.     

Hip torques and the effect of posture in side-stepping with elastic resistance

BackgroundThe way movement-based exercises affect targeted muscles is not always obvious. Side stepping with an elastic band around the forefeet is aimed at strengthening hip abductors and lateral rotator muscles, with the premise that it creates an external torque of adduction and medial rotation of the femur around the pelvis that needs to be counteracted by hip muscles. However, hip torques during this exercise have not been previously quantified.Research questionIs the premise that the side-stepping exercise creates an external torque of adduction and medial rotation of the femur around the pelvis correct?MethodsThirty-six adults performed the exercise in an upright and a squat posture while 3D kinetic and kinematic data were collected. Hip muscle torques were calculated using inverse dynamics. The effect of posture and potential interactions with sex, side-stepping phases, and trailing/leading directions were analyzed using Pearson correlation and mixed-model ANOVAs.ResultA hip net muscle torque of extension, abduction and medial rotation was required to perform the exercise, regardless of phase and direction. The net muscle torque towards medial rotation required during the exercise was smaller (P < 0.001) in the upright (0.05–0.12 N m kg^-1 m^-1 across phases) compared to the squat posture (0.10–0.24 N m kg^-1 m^-1). In contrast, hip abductor torque was not affected by posture. When averaged across phases and directions, the normalized hip medial rotator muscle torque was highly correlated with knee flexion (r = 0.93, P < 0.001).SignificanceThe assumption that the side-stepping with the elastic band on the forefeet creates an external hip torque of medial rotation is erroneous. The resistance imposed to the hip during this exercise is consistent with the goal of strengthening the muscles that contribute to hip abduction and hip medial (not lateral) rotation. Changing the knee flexion angle is an effective way to manipulate hip rotator torque when prescribing this exercise in strength training and rehabilitation programs.     

Reliability and validity of a new device to measure isometric strength in polyarticular exercises.

BACKGROUND: The purpose of this study was to assess the validity of a new device to evaluate isometric strength during multi-joint exercise such as the squat or bench press. METHODS: The device used an electric motor-driven bar to simultaneously generate and measure forces during weight lifting exercises. This new device and a force platform measured the forces generated by either the motor on a fixed telescopic steel girder (passive condition) or a subject pushing vertically against the bar from three squat positions (active condition). In the passive condition, 252 measurements were made, with 3 trials for 6 bar heights and 14 bar loads. In the active condition, 8 young physically active students (age, height and body mass were 25.1 +/- 2.6 years, 179.3 +/- 7.2 cm and 82.0 +/- 9.9 kg, respectively) performed 3 maximal isometric strength (MIS) trials in each of the 3 squat exercise positions (parallel, half and quarter squat), and 3 additional MIS trials in one position randomly assigned two weeks later to test inter-day reliability. RESULTS: In the passive condition, no differences were observed between the forces measured by the force platform and the new device. The coefficient of linear regression (r) and the coefficient of variation (CV) were 1 and below 0.23%, respectively. In the active condition, the peak MIS measured was 2828 N and the values of r and CV were above 0.982 and below 5.96%, respectively. The assessment of inter-day reliability showed an r value of 0.984 and a CV of 3.98%. CONCLUSIONS: This study demonstrated that the new electric motor-driven exerciser provides valid and reliable data when used to generate forces and measure isometric strength throughout the load and motion ranges commonly used in squat exercise.     

Isokinetic resistance training combined with eccentric overload improves athletic performance and induces muscle hypertrophy in young ice hockey players

ObjectivesTo determine the combined effects of slow isokinetic resistance training and eccentric overload and compare it to traditional resistance training on strength, power, body composition and muscle hypertrophy in young ice hockey players.DesignExperimental, randomized trial.MethodsTwenty-two resistance-trained ice hockey players (18 ± 1 year) were assigned to either isokinetic resistance training and eccentric overload (ISO/ECC; n = 11) or traditional resistance training (TRAD; n = 11). Participants underwent supervised progressive resistance training for 8 weeks (2–3 sessions/week) involving lower body multiple-joint exercises (heavy squats and explosive jump squats). The ISO/ECC group performed their training using a computerized robotic engine system (1080 Quantum synchro, Sweden), whereas the TRAD group performed the same resistance exercises with isotonic loading. Before and after the intervention, participants were evaluated in 1RM back squat, loaded jump squats, sprint- and jump performance, body composition and muscle thickness using ultrasound measurement.ResultsSimilar moderate increases in 1RM back squat and power output in the jump squats were found in both the ISO/ECC and TRAD groups (11–17%, P < 0.01), whereas only the ISO/ECC group showed improvements in drop jump performance (9.8%, P = 0.01). Moreover, similar trivial changes in body composition were observed in both groups, while only the ISO/ECC training group increased muscle thickness in the vastus intermedius (P = 0.01) and rectus femoris muscles (P = 0.03).ConclusionsBoth modalities effectively increased maximal strength and power output, whereas isokinetic resistance training, combined with eccentric overload, improved drop jump performance and induced greater muscle hypertrophy than traditional training in young ice hockey players.     

Validating two systems for estimating force and power

This study examined the validity of 2 kinematic systems for estimating force and power during squat jumps. 12 weight-trained males each performed single repetition squat jumps with a 20-kg, 40-kg, 60-kg and 80-kg load on a Kistler portable force plate. A commercial linear position transducer (Gymaware [GYM]) and accelerometer (Myotest? [MYO]) were attached to the bar to assess concentric peak force (PF) and peak power (PP). Across all loads tested, the GYM and MYO estimates of PF and PP were moderately to strongly correlated ( P≤0.05-0.001) with the force plate measurements ( R=0.59-0.87 and R=0.66-0.97), respectively. The mean PF and PP values were not significantly different between the 2 kinematic systems and the force plate, but the estimates did produce some systematic bias and relatively large random errors, especially with the 20-kg load (PF bias >170 N, PF error >335 N, PP bias >400 W, PP error >878 W). Some proportional bias was also identified. In summary, the estimation of PF and PP by a linear position transducer and accelerometer showed moderate to strong relative validity and equivalent absolute validity, but these estimates are limited by the presence of bias and large random errors.     

Femoral medial deviation angle during a one-leg squat test in individuals with patellofemoral pain syndrome

ObjectivesPatients with patellofemoral pain syndrome (PFPS) often demonstrate a collapse of the knee in the medial direction during a one-leg squat. This study investigated the medial displacement magnitude of the knee during a one-leg squat test in females with PFPS.DesignThe study design was a cross sectional comparative investigation.ParticipantsThirteen healthy females and 12 females with PFPS.Main measuresParticipants were tested during a one-leg squat test using a single camera. The thigh segment alignment in the frontal plane was measured by the angle projected between the long axis of the thigh and the foot (femoral frontal angle) and the horizontal deviation (femoral deviation) of the distal thigh relative to the foot.ResultsA one-way ANOVA showed that the femoral frontal angle was significantly larger (p=0.019) for the PFPS group with no significant differences for the femoral deviation (p=0.288). Both measurements showed good trial-to-trial reliability while the femoral frontal angle showed good test–retest reliability.ConclusionThe increased femoral frontal angle magnitude during the one-leg squat demonstrates that the one-leg squat may be a useful clinical tool for the evaluation process of PFPS.     

Combining higher-load and lower-load resistance training exercises: A systematic review and meta-analysis of findings from complex training studies

ObjectivesThe aim of the present meta-analytical review was to determine the effectiveness of training programmes combining higher-load and lower-load exercises in one workout (i.e. complex training [CT]) on lower-body performance.DesignSystematic review and meta-analysis.MethodsA search of five electronic databases (PubMed, Web of Science, SportDiscus, CINAHL and Scopus) was conducted to identify all publications up to 7 March 2018. Meta-analyses were performed using a random-effects model with the dependent variables countermovement jump (CMJ) height, squat jump (SJ) height, one-repetition maximum (1-RM) squat performance and sprint time for 5 m, 10 m, 20 m, 30 m and 40 m, respectively.ResultsThe analysis comprised 33 studies and a total of 1064 healthy participants. The meta-analysis revealed that CT is effective in improving CMJ (95% confidence interval [CI] 5.6%–12.3%), SJ (95% CI 8.0%–17.4%), 1-RM squat (95% CI 16.4%–30.7%) and sprint performance (5 m = 95% CI −14.8% to −0.9%, 10 m = 95% CI −6.0% to −2.1%, 20 m = 95% CI −7.4% to −1.4%, 30 m = 95% CI −8.0% to −0.6%). However, when directly compared to traditional training methods, only 1-RM squat strength performance and 20 m sprint time were superior following CT interventions (95% CI 0.2%–13.7% and 95% CI −1.6% to −0.1%, respectively)ConclusionsCT is an acceptable method for improving jump, strength and sprint performance in athletes. Compared to traditional training methods, CT seems to produce superior training effects only for 1-RM squat and 20 m sprint performance; however, these findings were influenced by single studies and should be therefore interpreted with circumspection.     

Achilles tendon loading during weight bearing exercises

ObjectiveCompare the estimated Achilles tendon (AT) loading using a musculoskeletal model during commonly performed weight bearing therapeutic exercises.DesignControlled laboratory study.SettingUniversity biomechanics laboratory.ParticipantsEighteen healthy males (Age:22.1 ± 1.8 years, height:177.7 ± 8.4 cm, weight = 74.29 ± 11.3 kg).Main outcome measure(s)AT loading was estimated during eleven exercises: tandem, Romberg, and unilateral standing, unilateral and bilateral heel raising, unilateral and bilateral jump landing, squat, lunge, walking, and running. Kinematic and kinetic data were recorded at 180 Hz and 1800 Hz respectively. These data were then used in a musculoskeletal model to estimate force in the triceps surae. AT cross-sectional images were measured by ultrasound to determine AT stress. A repeated measure multivariate analysis of variance (α = 0.05) was used on AT loading variables.ResultsSquat and unilateral jump landing were the most different in AT stress. Peak AT stress variables were generally greater during more dynamic, unilateral exercises compared to more static, bilateral exercises.ConclusionsBilateral, more static exercises resulted in less AT loading and may serve as a progression during the rehabilitation compared to more dynamic, unilateral exercises.     

The inter-device reliability of global navigation satellite systems during team sport movement across multiple days

Objectives(1) Determine the inter-device and inter-manufacturer reliability; and (2) investigate the variation in reliability over time for common global navigation satellite systems.DesignRepeated measures.MethodsA total of twenty 10-Hz devices manufactured by StatSports (n = 10, Apex Pro; StatSports, Newry, Ireland) and Catapult Sports (n = 10, Vector S7; Catapult Sports, Melbourne, Australia) were towed on a sprint sled during 8 × 40-minute team sport movement protocol over a 4-week period. The coefficient of variations for distance, velocity and acceleration/deceleration metrics were calculated to show dispersion of the data relative to the mean or median for each manufacturer and interpreted as good, ≤5%; moderate, <10%; and poor, coefficient of variation ≥10%. The coefficient of variation range described the variation in reliability and was interpreted as small, ≤5%; moderate, <10% and large, ≥10%. Inter-manufacturer agreement was represented as a Cohen d (±95% confidence interval) standardised effect size.ResultsInter-device reliability for distance, peak velocity and average acceleration was good (coefficient of variation = 0.1 to 3.9%) for both manufacturers, with small variation across sessions. For most threshold-based acceleration and deceleration counts, StatSports devices showed good to moderate reliability, with moderate variation across sessions; Catapult showed good to poor reliability, with large variation across sessions. Inter-manufacturer agreement demonstrated moderate to very large effect sizes reported for most metrics.ConclusionsReliability was suitable and consistent for measures of distance, velocity, and average acceleration. StatSports devices generally possessed suitable reliability and consistency for threshold-based accelerations and decelerations, though Catapult devices did not. Most metrics should not be compared between manufacturers.     

A comparison of electromyography of gluteus medius and maximus in subjects with and without chronic ankle instability during two functional exercises

ObjectiveTo determine how gluteus medius (Gmed) and maximus (Gmax) activate during closed-chain functional rehabilitative exercises in those with and without chronic ankle instability (CAI).DesignCohort study. Subjects performed ten repetitions of a rotational lunge and single-leg rotational squat while surface electromyography was used to collect mean muscle activity of the Gmed and Gmax.Main outcome measuresMean electromyography activity of the Gmed and Gmax at maximum excursion was compared between Groups and Exercises using a separate 2-way repeated measures analysis of variance design for each muscle.SettingUniversity biomechanics lab.ParticipantsNine healthy (8F, 1M) and nine CAI subjects (8F, 1M)ResultsFor Gmax activation, there was a statistically significant Group by Exercise interaction (F_3,48 = 4.84, p = 0.043). A Scheffe's post-hoc test revealed that during the rotational squat, the CAI group had significantly lower Gmax activation (51.1 ± 31.0%) than the healthy group (78.6 ± 44.8%). There were no statistically significant findings for the Gmed. In the healthy group, the Gmax produced significantly higher activation during rotational squat (78.6 ± 44.8%) compared to the rotational lunge (57.6 ± 31.9%).ConclusionBecause the CAI group had significantly less Gmax activation than the healthy group during the rotational squat at the point of maximum excursion, and because the rotational squat showed significantly higher Gmax activation compared to the rotational lunge, it may be important for clinicians to implement the rotational squat during rehabilitation for those with CAI. Future prospective and intervention research involving hip musculature in those with CAI is recommended.     

Quantification of the validity and reliability of sprint performance metrics computed using inertial sensors: A systematic review

BackgroundWearable inertial sensors enable sprinting to be biomechanically evaluated in a simple and time efficient manner outside of a laboratory setting.Research Question: Are wearable inertial sensors a valid and reliable method for collecting and measuring sprint performance variables compared to referenced systems?MethodsPubMed, SPORTDiscus, and Web of Science were searched using the Boolean phrases: ((run* OR sprinting OR sprint*) AND (IMU OR inertial sensor OR wearable sensor OR accelerometer OR gyroscope) AND (valid* OR reliabil*)). Articles with injury-free subjects of any age, sex or activity level were included.ResultsFifteen studies met the inclusion criteria and were retained for analysis. In summary, higher Intra-class correlation [ICC] or Pearson correlation coefficients (r) were observed for contact time (ICC ≥ 0.80, r ≥ 0.99), trunk angular displacement (r ≥ 0.99), vertical and horizontal force (ICC ≥ 0.88), and theoretical measures of force, velocity and power (r ≥ 0.81). Low coefficient of variation (CV) were found in peak velocity (≤ 1%), average velocity (≤ 3%), and contact time (≤ 3%,). Average and peak velocity, and resultant forces, were found to have a wide range of r (0.32-0.92) and CVs (0.78–20.2%). The lowest r (-0.24 to 0.49) and highest CVs (15–22.4%) were noted for average acceleration, crania-caudal force, instantaneous forces, medio-lateral ground reaction forces, and rate of decrease in ratio of forces.SignificanceDue to a wide range of methodological differences, a clear understanding of the validity and reliability of different inertial sensors for the analysis of sprinting has yet to be established. Future research into the sensor’s placement, attachment method and sampling frequency are among several factors that need further investigation.     

The effects of hip- and ankle-focused exercise intervention on lower limb mechanics during single leg squat among physically active females

ObjectivesThere are two types of kinetic chain in dynamic knee valgus (DKV) namely top-down (proximal origins) and bottom-up (distal origins). This study compared the influence of four-week hip- and ankle-focused exercises on lower limb mechanics during single-leg squat (SLS) among physically active females.MethodsThirty-six physically active females with excessive DKV were divided into either HIP, ANKLE, or control groups. The intervention groups completed exercises that focused either on the hip or ankle musculature for 12 sessions over four weeks. The SLS test protocol was performed with 3D motion capture at pre- and post-intervention. Data were analyzed with two-way ANOVA test.ResultsHIP group showed increased dominant knee (F (2.66) = 9.437, P = .001) and ankle (F(2.66) = 16.465, P = .001) sagittal moment during 45° SLS at post-intervention compared to ANKLE and Control groups. HIP group also showed increased hip flexion angle for dominant (F(2.66) = 12.032, P = .001) and non-dominant leg (F(2.66) = 3.618, P = .032) compared to other groups during 60° SLS. No other significant differences were observed on other variables.ConclusionDKV did not show any significant changes during SLS after a four-week exercise intervention focusing on hip and ankle joints.     

Development of a short and effective shoulder external rotation strength program in handball: A delphi study

BackgroundWeakness of the shoulder external rotators (ER) is one of the main risk factors for shoulder pain in handball. Short, effective shoulder ER strength programs the players will adhere to are lacking.Objectivesto develop a short and effective shoulder ER strength program, handball players will adhere to.MethodsWe conducted a modified Delphi study, including experts in the field of shoulder, strength training and handball. In the first round, the experts were asked to rate eight pre-defined shoulder ER exercises on efficacy and adherence and to suggest other preferred exercises. In round two, they were asked to rate the new exercises from round one. In round three, they received a statistical summary of the panels scores, their own score and a summary of the suggestions. Based on the feedback, the experts were asked to revise their response.ResultsSixteen experts completed three rounds with 100% response rate. Twenty-eight exercises were rated. We reached consensus for both efficacy and adherence for two exercises, ER in 90° abduction in a bent-over squat position and ER in 90° abduction combined with horizontal abduction and trunk rotation in a push-up position.ConclusionWe reached consensus for both efficacy and adherence for two exercises.