Concurrent Validity and Test-Retest Reliability of Pressure-Detecting Insoles for Static and Dynamic Movements in Healthy Young Adults.

Compared to force-plates, pressure-detecting insoles have the advantage that vertical ground reaction force (vGRF) can be estimated under field rather than laboratory conditions. However, the question arises whether insoles also provide valid and reliable results compared to a force-plate (i.e., the gold standard). The study aimed to investigate the concurrent validity and test-retest reliability of pressure-detecting insoles during static and dynamic movements. Twenty-two healthy young adults (12 females) performed standing, walking, running, and jumping movements while simultaneously collecting pressure (GP MobilData WiFi, GeBioM mbH, Münster, Germany) and force (Kistler®) data twice, 10 days apart. Concerning validity, ICC values showed excellent agreement (ICC > 0.75), irrespective of the test condition. Further, the insoles underestimated (mean bias: -4.41 to -37.15%) most of the vGRF variables. Concerning reliability, ICC values for nearly all test conditions also showed excellent agreement, and the SEM was rather low. Lastly, most of the MDC95% values were low (≤5%). The predominantly excellent ICC values for between-devices (i.e., concurrent validity) and between-visits (i.e., test-retest reliability) comparisons suggest that the tested pressure-detecting insoles can be used under field-based conditions for a valid and reliable estimation of relevant vGRF variables during standing, walking, running, and jumping.

Diverging Playing Positions do not Lead to Differences in YBT-UQ Performance in Youth Handball Players.

Handball playing positions can be differentiated between first line players who position themselves near the 6-m line and second line players who typically play outside the 9-m space. Handball is characterized by a high number of throwing actions that cause adaptations in the throwing shoulder. The objective of this cross-sectional study was to assess whether the specific physiological positional demands in handball lead to functional performance differences between the playing positions ( N =196; goalkeepers: n =25; backcourt: n =99; pivots: n =21; winger: n =51) in terms of shoulder mobility and stability in any reach direction as assessed through the Upper Quarter Y Balance Test (YBT-UQ). Contrary to our hypothesis, the results did not show significant differences between the playing positions in shoulder mobility and stability in youth handball players, irrespective of reach arm and reach direction. The obtained effect sizes ( η p 2 ) were solely small and ranged between 0.01 and 0.03. The adaptations following the demands of the diverging playing positions do not lead to significant differences in shoulder mobility and stability on the basis of the YBT-UQ. The overall training load of youth handball players may not be sufficient to lead to significant position-specific differences in shoulder mobility and stability.

Comparison of Lower and Upper Quarter Y Balance Test Performance in Adolescent Students with Borderline Intellectual Functioning Compared to Age- and Sex-Matched Controls.

The Lower (YBT-LQ) and Upper (YBT-UQ) Quarter Y Balance Test are well established assessment tools for the examination of dynamic balance and shoulder mobility/stability, respectively. However, investigations on YBT-LQ/UQ performance in students with borderline intellectual functioning (BIF) (i.e., intelligence quotient of 70-84 etc.) are lacking. Thus, the aim of the study was to compare YBT-LQ/UQ performance in students with and without BIF. Thirty students with BIF (age: 13.7 ± 1.2 years) and 30 age-/sex-matched students without BIF (age: 13.7 ± 1.3 years) performed the YBT-LQ and/or YBT-UQ. Normalized maximal reach distances (% leg/arm length) per reach direction and the composite score were used as outcome measures. A univariate analysis of variance was conducted to test for significant group differences. Irrespective of limb and reach direction, students with BIF compared to those without BIF showed significantly worse YBT-LQ (p ≤ 0.001-0.031; Cohen's d = 0.57-1.26) and YBT-UQ (p ≤ 0.001-0.015; Cohen's d = 0.68-1.52) performance with moderate to large effect sizes. Due to the poorer performance levels of students with BIF, specifically tailored interventions should be developed that have the potential to improve their dynamic balance and shoulder mobility/stability.

Effects of an Elastic Resistance Band Intervention in Adolescent Handball Players.

The objective was to investigate the effects of a 9-week elastic resistance band training within the regular handball training sessions compared to regular handball training only. Participants were randomly assigned to an intervention (INT: n=16; age: 17.0 ± 0.7 years) or a control (CON: n=16; age: 16.9 ± 0.9 years) group. The INT-group performed elastic resistance band exercises (3/week) for 20-30 minutes while the CON-group conducted regular handball training only. Pre- and post-training assessments included measures of strength endurance (Closed Kinetic Chain Upper Extremity Stability Test [CKCUEST]), maximal isometric strength (MIS), and throwing velocity. Significant main effects of Test (i.e. pre- to post-training enhancements) were detected for the CKCUEST (p < 0.001, 0.54 ≤ η p 2 ≤ 0.57) and throwing velocity (p = 0.001, η p 2 = 0.34). We found a significant (throwing velocity: p = 0.004, η p 2 = 0.25) and a tendency toward (MIS of the internal rotators, non-throwing arm: p = 0.068, η p 2 = 0.12) a significant Test × Group interaction, both in favour of the INT-group. A 9-week strengthening program using elastic resistance bands combined with regular handball training is effective to improve upper extremity strength endurance, throwing velocity, and MIS of the internal rotators of the non-throwing arm.

Upper Quarter Y Balance test performance: Normative values for healthy youth aged 10 to 17 years.

BACKGROUND: The Upper Quarter Y Balance test (YBT-UQ) is a field test for measuring shoulder mobility/stability. However, there is a lack of information regarding age- and sex-specific reference values for classifying the YBT-UQ performance of children and adolescents. OBJECTIVE: The aim was to investigate YBT-UQ performance in youth and to provide age- and sex-specific normative values. METHOD: Six hundred and sixty-five persons (325 girls, 340 boys) aged between 10 and 17 years carried out the YBT-UQ test. Following this, maximum reach values, normalised in terms of arm length, were calculated for each arm (i.e., left and right) and reach direction (i.e., medial [MD], inferolateral [IL], superolateral [SL]), and the composite score (CS) per arm. Additionally, percentiles were displayed graphically and in tabular form, distinguished according to age and gender. RESULTS: In boys, those aged 14-15 years showed a higher achievement (e.g., MD direction) compared with both younger (12-13-year-olds) and older (16-17-year-olds) persons. In girls, differences related to age could only be observed for the IL direction and the CS, where the youngest age group (10-11-year-olds) achieved better results than the older groups. Sex-specific differences to the girls' advantage could be observed in 12-13-year-olds (i.e., SL and CS), and to the boys' advantage in 14-15-year-olds (i.e., for all reach directions) and 16-17-year-olds (i.e., IL and SL direction and CS). Further, curvilinear developments were observed with regard to the 10th, 50th, and 90th percentiles, and were more strongly marked in boys than in girls. CONCLUSIONS: The obtained age- and sex-specific normative values for the YBT-UQ can be used by teachers, coaches, and therapists to classify the level of shoulder mobility/stability among 10-17 year-old children and adolescents.

Discriminative validity of the lower and upper quarter Y balance test performance: a comparison between healthy trained and untrained youth.

BACKGROUND: The Lower (YBT-LQ) and Upper (YBT-UQ) Quarter Y Balance Test have been widely used for the assessment of dynamic balance and shoulder mobility/stability, respectively. However, investigations on the validity of the two tests in youth are lacking. Therefore, we performed two studies to determine discriminative validity of the YBT-LQ (study 1) and the YBT-UQ (study 2) in healthy youth. METHODS: Sixty-nine male soccer players (age: 14.4 ± 1.9 yrs) and 69 age-matched untrained male subjects (14.3 ± 1.6 yrs) participated in study 1 and 37 young swimmers (age: 12.3 ± 2.1 yrs) as well as 37 age-/sex-matched individuals (age: 12.5 ± 2.0 yrs) took part in study 2. Absolute (cm) and relative (% leg/arm length) maximal reach distances per reach direction and the composite score of the YBT-LQ/UQ were used as outcome measures. One-way analysis of variance and the receiver operator characteristic curve analysis (i.e., calculating the area under the curve [AUC]) were conducted to assess discriminative validity. RESULTS: Concerning the relative values, youth athletes showed significantly better YBT-LQ (study 1: p < 0.001, d = 0.86-1.21) and YBT-UQ (study 2: p < 0.001, d = 0.88-1.48) test performances compared to age- and sex-matched untrained subjects. Further, AUC-values indicated a chance of ≥74% (YBT-LQ) and ≥ 71% (YBT-UQ) to discriminate between youth athletes and controls. These findings were confirmed when using the absolute data for analysis. CONCLUSIONS: According to our results, the YBT-LQ and the YBT-UQ seem to be useful test instruments to discriminate trained and untrained healthy youth performance for dynamic balance and shoulder mobility/stability, respectively.

Lower Quarter Y Balance Test performance: Reference values for healthy youth aged 10 to 17 years.

BACKGROUND: The Lower Quarter Y Balance Test (YBT-LQ) has been widely used to register dynamic balance performance in children and adolescents. However, studies evaluating age- and sex-specific normative data to assess and classify YBT-LQ performance for these age-cohorts are missing. OBJECTIVE: Thus, we investigated YBT-LQ performance in healthy youth to provide age- and sex-specific reference values. METHODS: Six-hundred and sixty-nine individuals (286 female, 383 male) aged 10-17 years performed the YBT-LQ with their left and right leg. Normalized maximal reach distances (% leg length) for all three directions (i.e., anterior, posterolateral, posteromedial) and the composite score were calculated. Further, age- and sex-specific percentile values (i.e., 10th to 90th percentile) were computed and plotted. RESULTS: In boys, the oldest age group (16-17 years) performed better than the younger ones (14-15, 12-13, and 10-11 years). In girls, the youngest age group (10-11 years) often achieved better values compared to the 12-13-year olds. Further, 16-17-year old boys compared to the same aged girls showed better YBT-LQ performance in all but one measure (except left leg reach in posterolateral direction). For both sexes, curvilinear shaped curves were detected for percentile values across the reach directions. CONCLUSIONS: The generated age- and sex-specific reference values for the YBT-LQ can be used by practitioners to evaluate dynamic balance performance in healthy youth aged 10-17 years.

RELIABILITY AND MINIMAL DETECTABLE CHANGE OF THE UPPER QUARTER Y-BALANCE TEST IN HEALTHY ADOLESCENTS AGED 12 TO 17 YEARS.

PURPOSE/BACKGROUND: There are a few studies investigating the reproducibility of the Upper Quarter Y Balance Test (YBT-UQ) in adults. However, no study has determined test-retest reliability and the minimal detectable change of the YBT-UQ in adolescents from different age cohorts. The aim of the present study was to establish test-retest reliability and minimal detectable change of the YBT-UQ in a sample of healthy adolescents. METHODS: In a school setting, 111 students (59 female, 52 male) aged 12-17 years performed the YBT-UQ twice, separated by one week. Normalized maximal reach distances (% arm length) for all three directions (i.e., medial, inferolateral, superolateral) and the composite score were used as outcome measures. Intraclass correlation coefficient (ICC3,1) and standard error of measurement (SEM) were calculated to assess both relative and absolute test-retest reliability. In addition, the minimal detectable change (MDC95%), an index that is defined as the minimal amount of change in performance that falls outside the measurement error or performance changes due to variability was determined. RESULTS: Irrespective of age cohort, reach arm, and reach direction, the measure of relative reliability ranged from "moderate-to-good" to "excellent" ICC values and the proxy of absolute reliability was rather small (i.e., SEM ≤ 7.6%). The MDC95% needed to identify relevant effects in repeated measurements of the YBT-UQ performance ranged between 4.8% and 21.1%, depending on age, reach arm, and reach direction. CONCLUSIONS: The detected values imply that the YBT-UQ is a reliable field test that can be used to detect changes of upper quarter mobility/stability in healthy adolescents aged 12-17 years. LEVEL OF EVIDENCE: 2b.

Effects of a blocked versus an alternated sequence of balance and plyometric training on physical performance in youth soccer players.

BACKGROUND: The sequence of blocked balance training (BT) followed by blocked plyometric training (PT) showed greater improvements in physical performance than vice versa and is explained by a preconditioning effect of BT-related adaptations on subsequent adaptations induced by PT. However, it remains unclear whether beneficial effects can also be induced using alternating instead of blocked BT and PT exercise sequences. Thus, we examined the effects of a blocked versus an alternated sequence of BT and PT on physical performance in trained individuals. METHODS: Twenty young soccer players (13 years) were randomly assigned to a blocked (n = 10) or an alternated (n = 10) intervention group. Both groups trained balance and plyometric exercises for six weeks (two sessions/week). The exercises were conducted in a blocked (three weeks of BT followed by three weeks of PT) or an alternated sequence (weekly change of BT and PT). Assessment of pre- and post-training performance included measures of balance, muscle power, speed, and agility. RESULTS: Mainly significant main effects of Test (i.e., pre- to post-test improvements) were observed for the Y-balance test (p ≤ 0.014, 1.3 ≤ Cohen's d ≤ 1.81), the squat jump (p = 0.029, d = 1.36), the countermovement jump (p = 0.002, d = 2.21), the drop jump (p = 0.004, d = 1.96), the split times/total time over 15-m sprinting (p ≤ 0.001, 2.02 ≤ d ≤ 3.08), and the figure-T agility run (p < 0.001, d = 3.80). Further, tendencies toward significant Test x Group interactions were found for several items of the Y-balance test and for SJ height in favor of the blocked BTPT group. CONCLUSIONS: Our results indicate that the combined training of balance and plyometric exercises is effective to improve proxies of physical performance in youth soccer players. In addition, there is a limited advantage in some parameters of balance and muscle power for the blocked as compared to the alternated sequence of BT and PT.

Limb Differences in Unipedal Balance Performance in Young Male Soccer Players with Different Ages.

In soccer, the dominant leg is frequently used for passing and kicking while standing on the non-dominant leg. Consequently, postural control in the standing leg might be superior compared to the kicking leg and is further enhanced with increasing age (i.e., level of playing experience). Unfortunately, leg differences in postural control are associated with an increased risk of injuries. Thus, we examined differences between limbs in unipedal balance performance in young soccer players at different ages. Performance in the Lower Quarter Y Balance Test (YBT-LQ) of the dominant and non-dominant leg and anthropometry was assessed in 76 young male soccer players (under-13 years [U13]: n = 19, U15: n = 14, U17: n = 21, U19: n = 22). Maximal reach distances (% leg length) and the composite scores were used for further analyses. Statistical analyses yielded no statistically significant main effects of leg or significant Leg × Age interactions, irrespective of the measure investigated. However, limb differences in the anterior reach direction were above the proposed cut-off value of >4 cm, which is indicative of increased injury risk. Further, statistically significant main effects of age were found for all investigated parameters, indicating larger reach distances in older (U19) compared to younger (U13) players (except for U15 players). Although reach differences between legs were non-significant, the value in the anterior reach direction was higher than the cut-off value of >4 cm in all age groups. This is indicative of an increased injury risk, and thus injury prevention programs should be part of the training of young soccer players.

Performance and reliability of the Lower Quarter Y Balance Test in healthy adolescents from grade 6 to 11.

BACKGROUND: The Lower Quarter Y Balance Test (YBT-LQ) has been widely used in the field to assess dynamic balance performance in various populations. However, no study has demonstrated test-retest reliability of the YBT-LQ in adolescents including several age cohorts, even though reliability is necessary to provide repeatable performance data. OBJECTIVE: Thus, we examined test-retest reliability of the YBT-LQ in healthy adolescents. METHODS: In a school setting, 178 secondary school students (93 female, 85 male) in sixth to eleventh grades (11-19 years) performed the YBT-LQ twice, 7 days apart. Normalized maximal reach distances (% leg length) for all three directions (i.e., anterior, posterolateral, posteromedial) and both legs and the composite score were used as outcome measures. Intraclass correlation coefficient (ICC3,1) and standard error of measurement (SEM) were calculated to assess relative and absolute test-retest reliability, respectively. Practical relevance of the YBT-LQ was determined by calculating the minimal detectable change (MDC95%). RESULTS: Irrespective of grade, test-retest reliability for all distances reached was predominately "excellent" (i.e., ICC3,1 > 0.75) and the rather small SEM values ranged from 1.77 to 5.81%. Depending on grade and reach direction, MDC values of 4.90 to 16.10% represent the minimum amount of change needed to identify clinically relevant effects in repeated measurements of the YBT-LQ performance. CONCLUSIONS: The observed values suggest that the YBT-LQ is a reliable test and suitable to detect changes of dynamic balance performance in healthy adolescents from grade six to eleven (i.e., aged 11-19 years).

Selective activation of lower leg muscles during maximum voluntary isometric contractions.

The pronators and supinators play a key role in the medio-lateral stability of the ankle joint complex (i.e. talo-crural and subtalar joints). We hypothesized that each shank muscle has a specific activation pattern determined by its anatomical course around the axes of the subtalar and talo-crural joints. A secondary objective was to examine the effect of foot posture on these activation patterns. Forty-nine young adults (25 normal-arched feet, 24 flat-arched feet) performed maximum voluntary isometric contractions against manual resistance in four movement directions: plantarflexion (PF), dorsiflexion (DF), pronation (PRO) and supination (SUP). Electromyographic activity was recorded from tibialis posterior (TP) and peroneus longus (PL) with intramuscular electrodes, and gastrocnemius medialis (GM) and tibialis anterior (TA) with surface electrodes. When compared to their agonist function, all muscles were co-activated at significantly lower levels in their synergistic function (GM: 23% during SUP, TA: 72% during SUP; TP: 42% during PF, PL: 52% during PF) (p<0.001). A significant interaction between foot posture and contraction type was evident for TA. During isometric contractions, the electromyographic activity of the shank muscles is geared to their biomechanical advantage according to their position relative to the subtalar and talo-crural joint axes.