Gait phase normalization resolves the problem of different phases being compared in gait cycle normalization.

For time-continuous analysis of gait, the problem of variations in cycle durations is resolved by normalizing to the gait cycle, but results depend on the definition of the cycle start. Gait cycle normalization ignores variations in gait phase durations, which results in averaging and comparing data across different phases. We propose gait phase normalization as part of a comprehensive method for independently analyzing magnitude and timing differences. First, gait phases are identified and differences in absolute and/or relative timing of phase durations or any point of interest between conditions or groups are analyzed using standard statistics. Next, time-continuous gait data is normalized to gait phases, and statistical parametric mapping (SPM) is used to assess magnitude differences in gait data. This approach is demonstrated on data recorded from ten young healthy adults walking on a treadmill at five different speeds. Sagittal knee angle was normalized to gait cycle or gait phase using five different gait cycle start events. Walking at different speeds resulted in significant changes in gait phase durations, highlighting a problem ignored by gait cycle normalization. SPM results for knee angle normalized to gait cycle varied from normalization to gait phases. Gait phase normalized SPM results were robust to the definition of the cycle start, in contrast to gait cycle normalized data. The approach of analyzing phase durations and normalizing data to gait phases overcomes previous limitations and enables a comprehensive analysis of magnitude and timing differences in time-continuous gait data and could be readily adapted to other tasks.

Effects of A Single Balance Training Session on Neural Excitability in Individuals With Chronic Ankle Instability.

CONTEXT: Individuals with chronic ankle instability (CAI) demonstrate reduced spinal reflex modulation and corticospinal excitability of the soleus, which may contribute to decreased balance performance. OBJECTIVE: To determine the effects of a single session of balance training on Spinal-reflexive excitability modulation and corticospinal excitability in those with CAI. DESIGN: Randomized controlled trials. SETTING: Research laboratory. PARTICIPANTS: Thirty participants with CAI were randomly assigned to the balance training (BAL) or control (CON) group. MAIN OUTCOME MEASURES: Modulation of soleus spinal-reflexive excitability was measured by calculating relative change in normalized Hoffmann reflexes (ratio of the H-reflex to the M-wave) from prone to single-leg standing. Corticospinal excitability was assessed during single-leg stance using transcranial magnetic stimulation, outcomes of which included active motor threshold (AMT), motor evoked potential, and cortical silent period (CSP). Balance performance was measured with center of pressure velocity in anterior to posterior and medial to lateral directions. Separate 2 × 2 repeated-measures analyses of variance were employed to determine the effect of group (BAL and CON) and time (baseline and posttraining) on each dependent variable. RESULTS: There were significant group by time interactions in the modulation of soleus spinal-reflexive excitability (F1,27 = 4.763, P = .04); CSP at 100% AMT (F1,27 = 4.727, P = .04); and CSP at 120% AMT (F1,27 = 16.057, P < .01). A large effect size suggests increased modulation of spinal-reflexive excitability (d = 0.81 [0.03 to 1.54]) of the soleus in BAL compared with CON at posttest, while CSP at 100% (d = 0.95 [0.17 to 1.70]) and 120% AMT (d = 1.10 [0.29 to 1.84]) was reduced in BAL when compared with CON at posttest. CONCLUSION: After a single session of balance training, individuals with CAI initiated increases in spinal reflex modulation and corticospinal excitability of the soleus. Thus, individuals with CAI who undergo balance training exhibit positive neural adaptations that are linked to improvements in balance performance.

Spine and pelvis coordination variability in rowers with and without chronic low back pain during rowing.

The aim of this study was to compare the spine-pelvis coordination and coordination variability (CV) during rowing in elite rowers with and without chronic low back pain (CLBP). Fourteen professional rowers (6 healthy and 8 with CLBP) participated in this study. 3D kinematic of upper trunk (UT), lower trunk (LT), lower back (LB), and pelvis segments during ergometer rowing at 70% and 100% of peak power were captured. The adjacent segments' coordination and CV were calculated using modified vector coding method. The results showed that segments' range of motion increased in both groups with increasing intensity, especially in CLBP rowers. CLBP rowers showed significantly lower: LT dominancy in LT/LB coordination at both intensities; anti-phase pattern in LB/Pelvis coordination at 100% intensity; UT/LT CV in early recovery, and significantly higher LB/Pelvis CV in final recovery and catch position (p < 0.05). Moreover, both groups showed significantly lower UT dominancy for UT/LT coordination in sagittal plane; higher anti-phase pattern in frontal plane; lower UT/LT CV in sagittal plane, lower LT/LB CV in sagittal and transverse plane, lower LB/Pelvis CV in frontal plane in trunk preparation phase, and a lower UT/LT CV in frontal plane for acceleration phase at 100% versus 70% intensity. In conclusion rowers with CLBP cannot adapt their coordination pattern and its variability with increase in intensity, and the movement in the kinematic chain from pelvis to UT stops in spine-pelvic junction. These findings have practical implications in designing coaching and rehabilitation strategies to facilitate performance and prevent injuries.