Dynamic stability during running gait termination: Differences in strategies between children and adults to control forward momentum

Lower extremity muscle activity during reactive balance differs between adults with chronic traumatic brain injury and controls

Background

Control of reactive balance is key to achieving safe independent walking and engagement in life activities. After traumatic brain injury (TBI), motor impairments and mobility challenges are persistent sequelae. To date, no studies have explored muscle activity of individuals with chronic TBI during a task that requires reactive control of balance.

Objective

To investigate lower extremity muscle activity during a reactive balance test performed by adults with chronic severe TBI and matched controls. We hypothesized that abnormal activity of lower extremity muscles would be related with poorer reactive balance performance. Also, we performed an exploratory analysis for those with TBI investigating the impact of unilateral versus bilateral lower extremity involvement in the control of reactive balance.

Methods

Ten adults with chronic severe TBI who were independent community ambulators and ten matched controls performed the computerized reactive balance test (Propriotest®) while lower extremity muscle activity was recorded. Electromyographic (EMG) activity was contrasted (Mann-Whitney U Test) between groups across each 10 s epoch of the 120 s test. Additionally, test scores were correlated (Spearman) with lower extremity composite EMG activity to distinguish muscle activity patterns related with reactive balance performance. Lastly, reactive balance test scores were correlated with reactive balance test scores and clinical functional measures only for the TBI group.

Results

Although the TBI group exhibited greater EMG activity across the entire test compared with the control group, significant differences were not observed. Greater composite EMG activity correlated significantly with poorer reactive balance performance across most of the 10 s windows of the test.

Conclusion

Greater muscle activity exhibited during the reactive balance test by individuals with chronic severe TBI compared to those without disabilities, particularly at small unexpected perturbations, highlights the greater physiologic effort required to control reactive balance even after independent ambulation is achieved.

Relationship of Knee Abduction Moment to Trunk and Lower Extremity Segment Acceleration during Sport-Specific Movements

The knee abduction moment (KAM) has been identified as a significant predictor of anterior cruciate ligament (ACL) injury risk; however, the cost and time demands associated with collecting three-dimensional (3D) kinetic data have prompted the need for alternative solutions. Wearable inertial measurement units (IMUs) have been explored as a potential solution for quantitative on-field assessment of injury risk. Most previous work has focused on angular velocity data, which are highly susceptible to bias and noise relative to acceleration data. The purpose of this pilot study was to assess the relationship between KAM and body segment acceleration during sport-specific movements. Three functional tasks were selected to analyze peak KAM using optical motion capture and force plates as well as peak triaxial segment accelerations using IMUs. Moderate correlations with peak KAM were observed for peak shank acceleration during single-leg hop; peak trunk, thigh, and shank accelerations during a deceleration task; and peak trunk, pelvis, and shank accelerations during a 45° cut. These findings provide preliminary support for the use of wearable IMUs to identify peak KAM during athletic tasks.

Assessing the reliability of biomechanical variables during a horizontal deceleration task in healthy adults

Horizontal deceleration technique is an underpinning factor to musculoskeletal injury risk and performance in multidirectional sport. This study primarily assessed within- and between-session reliability of biomechanical and performance-based aspects of a horizontal deceleration technique and secondarily investigated the effects of limb dominance on reliability. Fifteen participants completed four horizontal decelerations on each leg during test and retest sessions. A three-dimensional motion analysis system was used to collect kinetic and kinematic data. Completion time, ground contact time, rate of horizontal deceleration, minimum centre of mass height, peak eccentric force, impulse ratio, touchdown distance, sagittal plane foot and knee angles at initial contact, maximum sagittal plane thorax angle, and maximum knee flexion moment were assessed. Coefficients of variation (COV) and intraclass correlation coefficients (ICC) were used to assess within- and between-session reliability, respectively. Seven variables showed "great" within-session reliability bilaterally (COV ≤9.13%). ICC scores were 'excellent' (≥0.91; n = 4), or 'good' (0.76-0.89; n = 7), bilaterally. Limb dominance affected five variables; three were more reliable for the dominant leg. This horizontal deceleration task was reliable for most variables, with little effect of limb dominance on reliability. This deceleration task may be reliably used to assess and track changes in deceleration technique in healthy adults.

Biomechanical Analysis of Unplanned Gait Termination According to a Stop-Signal Task Performance: A Preliminary Study

There is a correlation between cognitive inhibition and compensatory balance response; however, the correlation between response inhibition and gait termination is not clear.

OBJECTIVES

The purpose of this study was to investigate the gait parameters of the lower extremity that occurred during unplanned gait termination (UGT) in two groups classified by the stop-signal reaction time (SSRT).

METHODS

Twenty young adults performed a stop-signal task and an unplanned gait termination separately. UGT required subjects to stop on hearing an auditory cue during randomly selected trials. The spatiotemporal and kinematic gait parameters were compared between the groups during UGT.

RESULTS

In phase one, the fast group had a significantly greater angle and angular velocity of knee flexion and ankle plantar flexion than the slow group (p < 0.05). Phase two showed that the fast group had a significantly greater angle and angular velocity of knee extension than the slow group (p < 0.05). Concerning the correlation analysis, the angle and angular velocity of knee flexion and ankle plantar flexion showed a negative correlation with the SSRT during UGT in phase one (p < 0.05). Phase two showed that the angle and angular velocity of knee extension was negatively correlated with the SSRT during UGT (p < 0.05).

CONCLUSION

The shorter the SSRT, the greater the angle and joint angular velocity of the ankle or knee joint that were prepared and adjusted for gait termination. The correlation between the SSRT and UGT suggests that a participant's capacity to inhibit an incipient finger response is associated with their ability to make a corrective gait pattern in a choice-demanding environment.

Biomechanical and Neuromuscular Performance Requirements of Horizontal Deceleration: A Review with Implications for Random Intermittent Multi-Directional Sports

Rapid horizontal accelerations and decelerations are crucial events enabling the changes of velocity and direction integral to sports involving random intermittent multi-directional movements. However, relative to horizontal acceleration, there have been considerably fewer scientific investigations into the biomechanical and neuromuscular demands of horizontal deceleration and the qualities underpinning horizontal deceleration performance. Accordingly, the aims of this review article are to: (1) conduct an evidence-based review of the biomechanical demands of horizontal deceleration and (2) identify biomechanical and neuromuscular performance determinants of horizontal deceleration, with the aim of outlining relevant performance implications for random intermittent multi-directional sports. We highlight that horizontal decelerations have a unique ground reaction force profile, characterised by high-impact peak forces and loading rates. The highest magnitude of these forces occurs during the early stance phase (< 50 ms) and is shown to be up to 2.7 times greater than those seen during the first steps of a maximal horizontal acceleration. As such, inability for either limb to tolerate these forces may result in a diminished ability to brake, subsequently reducing deceleration capacity, and increasing vulnerability to excessive forces that could heighten injury risk and severity of muscle damage. Two factors are highlighted as especially important for enhancing horizontal deceleration ability: (1) braking force control and (2) braking force attenuation. Whilst various eccentric strength qualities have been reported to be important for achieving these purposes, the potential importance of concentric, isometric and reactive strength, in addition to an enhanced technical ability to apply braking force is also highlighted. Last, the review provides recommended research directions to enhance future understanding of horizontal deceleration ability.

Relationships Between Eccentric and Concentric Knee Strength Capacities and Maximal Linear Deceleration Ability in Male Academy Soccer Players

ABSTRACT

Harper, DJ, Jordan, AR, and Kiely, J. Relationships between eccentric and concentric knee strength capacities and maximal linear deceleration ability in male academy soccer players. J Strength Cond Res 35(2): 465-472, 2021-The purpose of this study was to investigate the relationships between maximal linear deceleration ability, and knee flexor (KF) and knee extensor (KE) strength. Fourteen male academy soccer players completed a 30-m linear sprint, a maximal linear deceleration test, and eccentric and concentric KF and KE contractions in both dominant leg (DL) and nondominant leg (NDL) at slower (60°·s-1) and faster (180°·s-1) angular velocities on an isokinetic dynamometer. Maximal linear deceleration ability was evaluated using distance-to-stop (DEC-DTS) and time-to-stop (DEC-TTS), with isokinetic peak torque representing KF and KE strength capacity. Relationships were established using Pearson's correlation coefficients (r) with magnitude-based inferences used to describe the uncertainty in the correlation. Both concentric KE and KF strength at 180°·s-1 in the NDL had the highest correlations with deceleration ability (r = -0.76 and r = -0.78, respectively). In the DL, concentric KE and KF strength at 180°·s-1 also had very likely large correlations with deceleration ability (r = -0.54 and -0.55, respectively). All correlations between eccentric KF strength and deceleration ability were unclear. At 180°·s-1, correlations between eccentric KE strength and deceleration ability were also unclear; however, at 60°·s-1, both DL (r = -0.63 to -0.64) and NDL (r = -0.54 to -0.55) had very likely large correlations with deceleration ability. These findings provide novel insights into the unilateral KF and KE strength capacities underpinning the ability to decelerate rapidly from high-sprint velocities.

Measuring maximal horizontal deceleration ability using radar technology: reliability and sensitivity of kinematic and kinetic variables

Radar technology has the potential for providing new insights into maximal horizontal deceleration ability. This study aimed to investigate the intra- and inter-day reliability and sensitivity of kinematic and kinetic variables obtained from a novel, maximal horizontal deceleration test, using radar technology. Thirty-eight university sport athletes completed testing for intra-day analysis. Twelve of these participants also completed the deceleration test on a second day for inter-day analysis. The maximal horizontal deceleration test required participants to decelerate maximally following 20 m maximal horizontal sprint acceleration. Reliability was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV%). Sensitivity was evaluated by comparing typical error (TE) to the smallest worthwhile change (SWC). A number of kinematic and kinetic variables had good (ICC > 0.75, CV < 10%) overall intra-day reliability, and were sensitive to detect small-to-moderate changes in deceleration performance after a single familiarisation session. Only kinetic variables had good overall inter-day reliability and were sensitive to detect moderate changes in deceleration performance. The utilisation of this test protocol to assess maximal horizontal deceleration can provide new insights into individual maximal horizontal deceleration capabilities. Future work using this or similar approaches may provide insights into the neuromuscular performance qualities needed to decelerate maximally.

Can Countermovement Jump Neuromuscular Performance Qualities Differentiate Maximal Horizontal Deceleration Ability in Team Sport Athletes?

This investigation aimed to determine the countermovement jump (CMJ) neuromuscular performance (NMP) qualities that differentiate between athletes with high or low horizontal deceleration ability. Twenty-seven male university team sport athletes performed a CMJ on vertical axis force plates and a maximal horizontal deceleration following a 20 m maximal horizontal sprint acceleration. The instantaneous velocity throughout the maximal horizontal deceleration test was measured using a radar device. The deceleration ability was evaluated using the average deceleration (HDEC, m·s-2) and change in momentum-referred to as the horizontal braking impulse (HBI, N·s·kg-1). Participants were dichotomised into high and low HDEC and HBI according to a median-split analysis, and CMJ variables calculated for the overall eccentric, eccentric-deceleration and concentric phases. When horizontal deceleration ability was defined by HDEC, the CMJ concentric (effect size (ES) = 0.95) and eccentric (ES = 0.72) peak forces were the variables with the largest difference between groups. However, when defined using HBI, the largest difference was the concentric (ES = 1.15) and eccentric (ES = -1.00) peak velocities. Only the concentric mean power was significantly different between the high and low groups for both HDEC (ES = 0.85) and HBI (ES = 0.96). These findings show that specific eccentric and concentric NMP qualities may underpin the horizontal deceleration abilities characterised by HDEC and HBI. Specific NMP training interventions may be beneficial to target improvements in either of these measures of horizontal deceleration abilities.

Effects of Practice on the Control of Whole-Body Momentum in Active Children and Adults

The purpose of this study was to determine the effects of practice on performance of a running task requiring maximal speed and accurate termination. Physically active pre-pubertal boys and men ran as fast as possible and stopped at a pre-determined target location. Twenty-five trials were collected and comparisons made between first five (early) and last five (late) trials. Approach velocity, normalized approach velocity (percent of maximal sprint velocity, %Vmax), stopping distance from target, and success rate were calculated. Self-efficacy for task performance and fatigue reports were collected prior to trials. Children ran more slowly than adults in absolute terms but performed at higher relative velocity. Both groups displayed similar accuracy and percentages of successful trials across early and late practice. Adults increased approach velocity and %Vmax from early to late; children, already higher in relative maximal velocity, did not change. Self-efficacy paralleled performance findings and correlated with %Vmax and success rate; both groups reported higher self-efficacy for late compared with early. With practice, adults increased approach velocity and children did not; however, children appeared to be performing at a higher relative level from the beginning, perhaps reflecting their more substantial recent histories of similar physical activity and limiting further effects of practice.