Altered lower extremity joint mechanics occur during the star excursion balance test and single leg hop after ACL-reconstruction in a collegiate athlete

The effects of ACL-reconstruction on lower extremity joint mechanics during performance of the Star Excursion Balance Test (SEBT) and Single Leg Hop (SLH) are limited. The purpose of this study was to determine if altered lower extremity mechanics occur during the SEBT and SLH after ACL-reconstruction. One female Division I collegiate athlete performed the SEBT and SLH tasks, bilaterally, both before ACL injury and 27 months after ACL-reconstruction. Maximal reach, hop distances, lower extremity joint kinematics and moments were compared between both time points. Musculoskeletal simulations were used to assess muscle force production during the SEBT and SLH at both time points. Compared to the pre-injury time point, SEBT reach distances were similar in both limbs after ACL-reconstruction except for the max anterior reach distance in the ipsilateral limb. The athlete demonstrated similar hop distances, bilaterally, after ACL-reconstruction compared to the pre-injury time point. Despite normal functional performance during the SEBT and SLH, the athlete exhibited altered lower extremity joint mechanics during both of these tasks. These results suggest that measuring the maximal reach and hop distances for these tasks, in combination with an analysis of the lower extremity joint mechanics that occur after ACL-reconstruction, may help clinicians and researchers to better understand the effects of ACL-reconstruction on the neuromuscular system during the SEBT and SLH.     

High day-to-day repeatability of lower extremity muscle activation patterns and joint biomechanics of dual-belt treadmill gait: A reliability study in healthy young adults

PurposeThe reliability of lower extremity muscle activation patterns has not been clearly studied in a dual-belt instrumented treadmill environment. The primary study objective was to quantify the day-to-day reliability of quadriceps, hamstrings, gastrocnemius and gluteus medius activation patterns in healthy young adult gait. Secondarily, the reliability of spatiotemporal, and knee/hip motion and moment-based gait outcomes was assessed.Scope: 20 young adults were recruited and tested on two separate days. Using standardized procedures, participants were prepared for surface electromyography and lower extremity motion capture. All individuals walked on a dual-belt instrumented treadmill while muscle activation, segment motions and ground reaction forces were recorded. Sagittal plane motion and net external sagittal and frontal plane moments were calculated. Discrete biomechanical and muscle activation measures were calculated, and non-negative matrix factorization extracted amplitude and temporal muscle activation features. Intraclass Correlation Coefficients, Standard Error of Measurement and Minimum Detectable Change were calculated.ConclusionsHigh to excellent Intraclass correlation coefficients were found between visits for most primary and secondary outcomes. The absolute and relative reliability, including Minimum Detectable Change values, provided in this study support the use of dual-belt instrumented treadmill walking as an acceptable medium to collect biomechanical and lower extremity EMG outcomes for future studies.     

The effects of plyometric training of the posterior shoulder and elbow

The purpose of this research was to examine the effectiveness of a 6-week plyometric training period on power production of the posterior shoulder and elbow musculature. Twenty-eight normal college-aged volunteers (5 men, 23 women) were divided into control and plyometric training groups. Both groups were pre- and posttested using shoulder and elbow isokinetic tests and the Closed Kinetic Chain Upper Extremity Stability Test. The plyometric training group (n = 13) showed significant improvement in the power generated in the elbow extensor muscles; however, no other significant changes were observed within this group. The control group (n = 15) showed no significant changes in power output over the course of this study. It was concluded that plyometric training of the upper extremity enhances power production of the elbow extensor muscles. Therefore, plyometrics may help improve performance in overhead sports that require power.     

Lower and upper limb length of urban and rural 7-11 years old Turkish school children

This study was carried out on 779 male and 755 female 7-11 years old children, who are students of the primary schools in Diyarbakir city center and center connected areas. The average values of lower and upper extremity lengths of children in center and rural primary schools have been compared, and the results have been analyzed with the Student t-test. The relation between lower and upper extremity length averages and height is shown by correlation coefficients. It is observed that in the 11 years old boy's group and in the 9 years old girl's group of the center primary schools the total arm lengths are longer (p < 0.01). Upper and lower extremity lengths are increasing parallel to height. Iliospinal heights are obviously longer in the 11 year old group of boys and the 7, 9 and 11 year group of girls in the center primary school.     

Intraobserver reliability of posturography in patients with vestibular neuritis

The aim of the study was to establish the intraobserver reliability of a posturographic method in patients (n?=?34) with vestibular neuritis. Intraclass correlation coefficients (relative reliability) for all parameters and test positions (ALL_mean) ranged from 0.71 (95% CI: 0.41–0.85) to 0.92 (95% CI: 0.84–0.96). Absolute reliability (coefficient of variation) ranged between 3.1% (95% CI: 2.60–8.67) and 42.3% (95% CI: 40.7–74.5). Reliability of single test positions is much lower. The posturographic system showed good relative and satisfactory absolute intraobserver reliability for ALL_mean.     

Manual segmentation of DXA scan images results in reliable upper and lower extremity soft and rigid tissue mass estimates

Quantification of segment soft and rigid tissue masses in living people is important for a variety of clinical and biomechanical research applications including wobbling mass modeling. Although Dual-energy X-ray Absorptiometry (DXA) is widely accepted as a valid method for this purpose, the reliability of manual segmentation from DXA scans using custom regions of interest (ROIs) has not been evaluated to date. Upper and lower extremity images of 100 healthy adults who underwent a full body DXA scan in the supine position were manually segmented by 3 measurers independently using custom ROIs. Actual tissue masses (fat mass, lean mass, bone mineral content) of the arm, arm with shoulder, forearm, forearm and hand, thigh, leg, and leg and foot segments were quantified bilaterally from the ROIs. There were significant differences between-measurers, however, percentage errors were relatively small overall (<1–5.98%). Intraclass correlation coefficients (ICCs) were very high between and within-measurers, ranging from 0.990 to 0.999 and 0.990 to 1.00 for the upper and lower extremities, respectively, suggesting excellent reliability. Between and within-measurer errors were comparable in general, and differences between the tissue types were small on average (maximum of 42 and 53 g for upper and lower extremities, respectively). These results suggest that manual segmentation of DXA images using ROIs is a reliable method of estimating soft and rigid tissues in living people.     

Reliability and validity of three strength measures obtained from community-dwelling elderly persons

The purpose of this study was to describe the reliability and validity of 3 strength measures obtained from community-dwelling elderly individuals. The strength of 10 elders was tested initially and 6 and 12 weeks later using the MicroFET 2 hand-held dynamometer (knee extension strength), the Jamar dynamometer (grip strength), and the sit-to-stand (STS) test. Mobility was tested using the timed up-and-go (TUG) test and a timed walk test. Intraclass correlation coefficients, which were used to characterize the reliability of the strength tests, ranged from 0.807 to 0.981. Pearson correlations between the lower extremity strength measures and the TUG and gait speed ranged from 0.635 to -0.943. Our examination of the 3 measures for 12 weeks extends previous evidence of the stability of these strength measures and justifies the use of hand-held dynamometry and the STS test when investigating limitations in mobility.     

Between-session reliability of four hop tests and the agility T-test

The purposes of this study were firstly to investigate whether learning affects were present in the administration of 4 hop tests and the Agility T-test and secondly to assess the between-session reliability of these tests. Twenty-two recreational athletes (11 women: age 22.3 ± 3.7 years, height 167.7 ± 6.2 cm, weight 59.2 ± 6.9 kg and 11 men: age 22.8 ± 3.1 years, height 179.8 ± 4 cm, weight 79.6 ± 10 kg) took part in the study. The subjects performed 6 repetitions of each hop test and 4 repetitions of the Agility T-test once a week over a period of 3 weeks. Distances were normalized to leg length and presented as a percentage value for the single, triple and crossover hop. Results showed that there were significant differences in scores between genders and that learning affects were present in all tests. Intraclass correlation coefficients ranged from 0.76 to 0.92 for the hop tests and 0.82 to 0.96 for the Agility T-test. The results indicated that the hop and Agility T-tests are reliable tests for use with subjects in a clinical or team sport environment. The error measurement statistics presented could be of help to practitioners to determine whether changes in individuals' scores in the hop and Agility T-tests are because of a true change in performance or measurement error. Of most importance was the fact that all subjects achieved at least 90% limb symmetry index on all 4 hop tests. Therefore, we recommend that a minimum limb symmetry value of 90%, rather than previously recommended 85%, should be adopted during rehabilitation and conditioning.     

Comparison of intraobserver single-task reliabilities of the Interactive Balance System (IBS) and Vertiguard in asymptomatic subjects

The intraobserver reliabilities of the Interactive Balance System (IBS) and Vertiguard were compared in 30 asymptomatic volunteers. Relative reliability for all IBS single tasks and parameters in the IBS was excellent (intraclass correlation coefficient, ICC ≥0.75). The ICC values ranged from 0.78 to 0.89. The ICC values of the Vertiguard system ranged from 0 to 0.75. The cumulative measure of injury risk of the Vertiguard system was highly reliable.     

Quadriceps motor evoked torque is a reliable measure of corticospinal excitability in individuals with anterior cruciate ligament reconstruction

This study comprehensively evaluated the test–retest reliability of raw and normalized quadriceps motor evoked responses elicited by transcranial magnetic stimulation (TMS) in individuals with anterior cruciate ligament (ACL) reconstruction. Fifteen participants were tested on three different days that were separated at least by 24 h. Motor evoked responses were collected during a small background contraction on the reconstructed leg across a range of TMS intensities using torque (MEP_TORQUE) and electromyographic (MEP_EMG) responses. MEP_TORQUE and MEP_EMG were evaluated using different normalization procedures (raw, normalized to maximum voluntary isometric contraction [MVIC], peak MEP, and background contraction). MEP_TORQUE was also normalized to the magnetically-evoked peripheral resting twitch torque. The area under the recruitment curve was computed for both raw and normalized MEPs. Intraclass correlation coefficients (ICCs) were determined to assess test–retest reliability. Results indicated that MEP_TORQUE generally showed greater reliability than MEP_EMG for all normalization procedures. Vastus medialis MEP_EMG generally showed greater reliability than rectus femoris MEP_EMG. Finally, both MEP_TORQUE and MEP_EMG exhibited good reliability, even when not normalized. These findings indicate that MEP_TORQUE and MEP_EMG offer reliable measures of corticospinal function and suggest that MEP_TORQUE is a suitable alternative to MEP_EMG for measuring quadriceps corticospinal excitability in individuals with ACL reconstruction.     

The acute effects of dynamic and ballistic stretching on vertical jump height, force, and power

Stretching before performance is a common practice among athletes in hopes of increasing performance and reducing the risk of injury. However, cumulative results indicate a negative impact of static stretching and proprioceptive neuromuscular facilitation (PNF) on performance; thus, there is a need for evaluating other stretching strategies for effective warm-up. The purpose of this study was to compare the differences between two sets of ballistic stretching and two sets of a dynamic stretching routine on vertical jump performance. Twenty healthy male and female college students between the ages of 22 and 34 (24.8 +/- 3 years) volunteered to participate in this study. All subjects completed three individual testing sessions on three nonconsecutive days. On each day, the subjects completed one of three treatments (no stretch, ballistic stretch, and dynamic stretch). Intraclass reliability was determined using the data obtained from each subject. A paired samples t-test revealed no significant difference in jump height, force, or power when comparing no stretch with ballistic stretch. A significant difference was found on jump power when comparing no stretch with dynamic stretch, but no significant difference was found for jump height or force. Statistics showed a very high reliability when measuring jump height, force, and power using the Kistler Quattro Jump force plate. It seems that neither dynamic stretching nor ballistic stretching will result in an increase in vertical jump height or force. However, dynamic stretching elicited gains in jump power poststretch.     

Using force sensing insoles to predict kinetic knee symmetry during a stop jump

Knee kinetic asymmetries are present during jump-landings in athletes returning to sport following anterior cruciate ligament (ACL) reconstruction, and are associated with an increased risk for sustaining a second ACL injury. The loadsol® is a wireless load sensing insole that can be used in non-laboratory settings. The purpose of this study was to determine if the loadsol® could be used to predict knee extension moment and power symmetry during a bilateral stop jump task in healthy recreational athletes. Forty-two uninjured recreational athletes completed seven bilateral stop jumps. During each landing, the loadsol® (100 Hz) measured plantar load while 3D ground reaction forces (1920 Hz) and lower extremity kinematics (240 Hz) were collected simultaneously. Peak impact force, loading rate, and impulse were quantified using the loadsol® and peak knee extension moment, average knee extension moment, and total knee work was quantified using the laboratory instrumentation. Limb symmetry indices were quantified for each outcome measure. Multivariate backwards regressions were used to determine if loadsol® symmetry could predict knee kinetic symmetry. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to determine the agreement and error between predicted and actual knee kinetic symmetry. Loadsol® impulse and peak impact force symmetry significantly predicted kinetic knee symmetry and explained 42–61% of its variance. There was good agreement (ICCs = 0.742–0.862) between predicted and actual knee kinetic symmetry, and the error in the predicted outcomes range from ±18 to ±43. These results support using the loadsol® to screen for kinetic symmetries during landing in athletes following ACL reconstruction.     

Reliability of selected physical performance tests in young adult women

The purposes of this investigation were to establish the reliability of selected physical performance tests in women athletes and nonathletes and to determine performance differences between groups. Fifty women (25 athletes, 25 nonathletes) performed 5 tests in 2 sessions. The performance tests included the figure-eight hop test, up-and-down hop test, side-to-side hop test, hexagon hop test, and zigzag run test. Intraclass correlation coefficients (ICC [2, 1]) were calculated for trial-to-trial, intertester, and day-to-day reliability. Independent t-tests with Bonferroni adjustment (alpha = 0.01) were used for each individual test to compare differences between groups. All tests showed good reliability values (ICC > or = 0.76) in the nonathlete group for all conditions and varied reliability values (0.48-0.99) among conditions in the athlete group. The independent t-tests showed a statistically significant group effect (t > or = 3.041; p < or = 0.004) for all tests. The results showed that these physical performance tests are reliable measurement tools in the female population.     

Evaluation of a new anaerobic power testing system

The purpose of this study was to evaluate the reliability of a new anaerobic athletic performance system. This system is proposed to assess vertical jump height, anaerobic power through repetitive jumping, and reaction to both an auditory and visual stimulus. One hundred twenty-three subjects (92 men and 31 women; mean +/- SD: age, 20.5 +/- 2.1 years; body weight, 83.1 +/- 20.4 kg; height, 176.0 +/- 9.2 cm) volunteered to participate. To assess reliability of the new testing device, subjects were tested on 3 separate occasions (T1, T2, and T3). At least 72 hours but not more than 1 week separated each laboratory visit. During each testing session subjects performed a countermovement jump (CMJ), a 30 consecutive jumps anaerobic power test (30JT), and reaction to both an auditory and visual stimulus. Results showed no differences between T1, T2, and T3 in either CMJ height or 30JT assessments. However, reaction to an audible or visual stimulus significantly improved during each testing session. Intraclass reliability of the CMJ and the 30JT was greater than 0.96 across the 3 trials. Pearson correlation coefficients of r > 0.90 were seen for the CMJ and 30JT, indicating a high test-retest reliability. The test-retest reliability for the reaction tests were lower (r ranging from 0.72 to 0.83). A Bland-Altman plot showed limited agreement between methods of vertical jump height assessment. Results indicate that this new testing device shows high reliability to assess both CMJ height and anaerobic power. In addition, anaerobic power assessment in a jump test provides a specific measure of anaerobic power for many sports incorporating similar performance patterns.     

Validity and reliability of the medicine ball throw for kindergarten children

The purpose of this study was to establish validity and reliability evidence for the medicine ball throw test for kindergarten students, an underrepresented group in the literature. The subjects were 105 students, 5-7 years old, BMI 17.44 +/- 3.17 kg x m(-2), 43% female and 57% male. Intraclass correlation coefficients (ICCs) were used to examine reliability, and Pearson correlation coefficients and a paired t-test were used to examine validity. To accomplish this, the kindergarten students completed the medicine ball throw test on two different days and the modified pull-up test, the "criterion" measure, on another day. For the medicine ball throw, each student sat on the floor before throwing the medicine ball forward like a chest pass three times. The medicine ball throw was highly reliable both within 1 day (ICCs = 0.93 and 0.94 for day 1 and day 2, respectively) and across 2 days (ICC = 0.88), with all reliability estimates over the acceptable level of 0.80. The medicine ball throw scores were positively related with height (r = 0.34) and weight (r = 0.34), and there was a significant difference between the 5-year-old group (mean +/- SD; 111.78 +/- 34.93) and the 6-year-old group (135.60 +/- 39.77), t = -3.23, p = 0.002, which supports correlational and known-difference evidence of validity for the medicine ball throw test. Even though no correlation was found between the medicine ball throw test and the modified pull-up test, r = -0.04, other forms of validity evidence (i.e., known-difference and correlational) were apparent. In conclusion, the medicine ball throw test seems to be a valid and reliable measure of upper-body strength for kindergarten children.     

Effects of an individualized soccer match simulation on vertical stiffness and impedance

An observed relationship between soccer match duration and injury has led to research examining the changes in lower extremity mechanics and performance with fatiguing exercise. Because many fatigue protocols are designed to result in substantial muscular deficits, they may not reflect the fatigue associated with sport-specific demands that have been associated with the increasing incidence of injury as the match progresses. Thus, the aim of this study was to systematically analyze the progressive changes in lower extremity mechanics and performance during an individualized exercise protocol designed to simulate a 90-minute soccer match. Previous match analysis data were used to systematically develop a simulated soccer match exercise protocol that was individualized to the participant's fitness level. Twenty-four National Collegiate Athletic Association Division I soccer players (12 men, 12 women) participated in 2 testing sessions. In the first session, the participants completed the Yo-Yo Intermittent Recovery Test Level 1 to assess their fitness level and determine the 5 submaximal running intensities for their soccer match simulation. In the second test session, progressive changes in the rating of perceived exertion (RPE), lower extremity performance (vertical jump height, sprint speed, and cutting speed), and movement mechanics (jumping vertical stiffness and terminal landing impedance) were measured during the soccer match simulation. The average match simulation running distance was 10,165 ± 1,001 m, consistent with soccer match analysis research. Time-related increases in RPE, and decrements in sprinting, and cutting speed were observed, suggesting that fatigue increased as the simulation progressed. However, there were no time-related decreases in vertical jump height, changes in lower extremity vertical stiffness in jumping, or vertical impedance during landing. Secondary analyses indicated that the coordinative changes responsible for the maintenance of stiffness and impedance differed between the dominant and nondominant limbs. Despite an increase in RPE to near exhaustive levels, and decrements in sprint and cutting performance, the participants were able to maintain jump performance and movement mechanics. Interestingly, the coordinative changes that allowed for the maintenance of vertical stiffness and impedance varied between limbs. Thus, suggesting that unilateral training for performance and injury prevention in soccer-specific populations should be considered.     

A method for determining lower extremity muscle-tendon lengths during flexion/extension movements

A study was conducted to examine the relationship between muscle-tendon lengths of 16 lower extremity muscles and the flexion angle(s) of the joint(s) they cross. Anthropometric data from six subjects were obtained. Various lower extremity joint flexion angle combinations were simulated for each subject using computer software. For each simulated lower extremity position, muscle origin and insertion locations were determined based on averaged cadaveric origin/insertion information and individual anthropometric parameters. Corresponding muscle-tendon lengths were computed and normalized to segment lengths. Regression equations were derived which allow normalized muscle-tendon lengths to be estimated from known joint flexion angles. The regression equations obtained for biarticular muscles fit the data quite well giving correlation coefficients greater than 0.92. The correlation coefficients for the equations describing normalized single joint muscle-tendon lengths range from 0.77 to 0.97. The equations were then validated by comparing predicted lengths to those reported by previous investigations. Confirming the utility of the equations, the comparisons were excellent for both uniarticular and biarticular muscles. Used in conjunction with velocity data (obtained by differentiating the length data) and electromyogram recordings, these equations enable a detailed analysis of muscle function.     

Effects of fatigue on bilateral ground reaction force asymmetries during the squat exercise

Physical performance and injury risk have been related to functional asymmetries of the lower extremity. The effect of fatigue on asymmetries is not well understood. The goal of this investigation was to examine asymmetries during fatiguing repetitions and sets of the free-weight barbell back squat exercise. Seventeen healthy recreationally trained men and women (age = 22.3 ± 2.5 years; body mass = 73.4 ± 13.8 kg; squat 8 repetition maximum [8RM] = 113 ± 35% body mass [mean ± SD]) performed 5 sets of 8 repetitions with 90% 8RM while recording bilateral vertical ground reaction force (GRFv). The GRFv asymmetry during the first 2 (R1 and R2) and the last 2 (R7 and R8) repetitions of each set was calculated by subtracting the % load on the right foot from that of the left foot. Most subjects placed more load on their left foot (also their preferred non-kicking foot). Average absolute asymmetry level across all sets was 4.3 ± 2.5 and 3.6 ± 2.3% for R1 and R2 and R7 and R8, respectively. There were no effects of fatigue on GRFv asymmetries in whole-group analysis (n = 17). However, when initially highly symmetric subjects (±1.7% Left-Right) were removed, average absolute GRFv asymmetry dropped from the beginning to the end of a set (n = 12, p = 0.044) as did peak instantaneous GRFv asymmetry when exploring general shifts toward the left or right leg (n = 12, p = 0.042). The GRFv asymmetries were highly repeatable for 8 subjects that repeated the protocol (Cronbach's α ≥ 0.733, p ≤ 0.056). These results suggest that functional asymmetries, though low, are present in healthy people during the squat exercise and remain consistent. Asymmetries do not increase with fatigue, potentially even decreasing, suggesting that healthy subjects load limbs similarly as fatigue increases, exposing each to similar training stimuli.     

Preseason and midseason balance ability of professional Australian footballers

Balance ability has been shown to be important for sports performance and injury prevention. It is unclear whether balance ability changes due to sports participation and regular training without specific balance training. It has not been shown whether certain sports such as the various football codes that often involve single limb stance and balance as part of kicking, running, rapid changes of direction, jumping, and landing actually influence balance ability. The aim of this study was to determine whether there was a difference in balance ability measured at preseason and during the competitive season for elite footballer. Twenty-eight professional Australian footballers who did not undertake any specific balance training took part in this study. Postural sway from single limb balance on a force platform was measured for both limbs 1 week before the start and midway through a 22-week competitive season. The subjects were required to step onto a balance mat on top of the force platform and maintain balance for 20 seconds. The maximum sway of the center of pressure in the mediolateral direction was used as the balance score. It was found that there was not a significant difference in the balance ability measurement at the start and during the competitive season. Sports participation and regular training did not influence balance ability in this cohort of athletes.     

The validity and reliability of the 1RM bench press using chain-loaded resistance

The purposes of this study were to determine the validity and test-retest reliability of the 1 repetition maximum (1RM) chain-loaded, free-weight bench press (CBP) and to examine possible learning effects that may occur between the test-retest measurements. Nine resistance-trained men (20.58 +/- 1.31 years, 188.24 +/- 9.29 cm, 92.07 +/- 16.94 kg) and seven resistance-trained women (20.42 +/- 0.98 years, 175.61 +/- 9.32 cm, 73.61 +/- 10.80 kg) participating in Division II college basketball completed this study. Two familiarization sessions took place using light to moderate loads to learn proper technique. The subjects completed a 1RM test on the traditional plate-loaded bench press 4 days before completion of the CBP 1RM, which was followed by 4 days of rest before completing the retest. Intraclass correlation coefficients (ICC) and the percent coefficients of variation (CV) were used to determine relative and absolute test-retest reliability. Concurrent validity was determined from the Pearson correlation coefficients between the CBP and the plate-loaded bench press. Test-retest differences were analyzed with the paired t-test. ICC and CV for the men (r = 0.99, 1.4%) and women (r = 0.93, 3.5%), respectively indicate that highly reproducible 1RM scores can be found with the CBP. High validity was also found with high correlations between the CBP and plate-loaded bench press for the men (r = 0.95) and women (r = 0.80). A statistically significant (p = 0.04) but clinically small (2.57 kg) shift in the mean occurred between the CBP test and retest for the men, whereas no change occurred for the women. The data indicate that valid and reliable 1RM scores can be found after two familiarization sessions in men and women athletes who have previous resistance training experience.