Wen Hua Wu

Gait in Pregnancy-related Pelvic girdle Pain: amplitudes, timing, and coordination of horizontal trunk rotations

Walking is impaired in Pregnancy-related Pelvic girdle Pain (PPP). Walking velocity is reduced, and in postpartum PPP relative phase between horizontal pelvis and thorax rotations was found to be lower at higher velocities, and rotational amplitudes tended to be larger. While attempting to confirm these findings for PPP during pregnancy, we wanted to identify underlying mechanisms. We compared gait kinematics of 12 healthy pregnant women and 12 pregnant women with PPP, focusing on the amplitudes of transverse segmental rotations, the timing and relative phase of these rotations, and the amplitude of spinal rotations. In PPP during pregnancy walking velocity was lower than in controls, and negatively correlated with fear of movement. While patients’ rotational amplitudes were larger, with large inter-individual differences, spinal rotations did not differ between groups. In the patients, peak thorax rotation occurred earlier in the stride cycle at higher velocities, and relative phase was lower. The earlier results on postpartum PPP were confirmed for PPP during pregnancy. Spinal rotations remained unaffected, while at higher velocities the peak of thorax rotations occurred earlier in the stride cycle. The latter change may serve to avoid excessive spine rotations caused by the larger segmental rotations.

Gait adaptations in low back pain patients with lumbar disc herniation: trunk coordination and arm swing

Patients with chronic non-specific low back pain (LBP) walk with more synchronous (in-phase) horizontal pelvis and thorax rotations than controls. Low thorax–pelvis relative phase in these patients appears to result from in-phase motion of the thorax with the legs, which was hypothesized to affect arm swing. In the present study, gait kinematics were compared between LBP patients with lumbar disc herniation and healthy controls during treadmill walking at different speeds and with different step lengths. Movements of legs, arms, and trunk were recorded. The patients walked with larger pelvis rotations than healthy controls, and with lower relative phase between pelvis and thorax horizontal rotations, specifically when taking large steps. They did so by rotating the thorax more in-phase with the pendular movements of the legs, thereby limiting the amplitudes of spine rotation. In the patients, arm swing was out-of phase with the leg, as in controls. Consequently, the phase relationship between thorax rotations and arm swing was altered in the patients.

Control of the lateral abdominal muscles during walking

Transversus abdominis (TA), obliquus internus (OI), and obliquus externus (OE) are involved in multiple functions: breathing, control of trunk orientation, and stabilization of the pelvis and spine. How these functions are coordinated has received limited attention. We studied electromyographic (EMG) activity of right-sided muscles and 3-dimensional moments during treadmill walking at six different speeds (1.4-5.4 km/h) in sixteen healthy young women. PCA revealed time series of trunk moments to be consistent across speeds and subjects though somewhat less in the sagittal plane. All three muscles were active during ≥75% of the stride cycle, indicative of a stabilizing function. Clear phasic modulations were observed, with TA more active during ipsilateral, and OE during contralateral swing, while OI activity was largely symmetrical. Fourier analysis revealed four main frequencies in muscle activity: respiration, stride frequency, step frequency, and a triphasic pattern. With increasing speed, the absolute power of all frequencies remained constant or increased; the relative power of respiration and stride-related activities decreased, while that of step-related activity and the triphasic pattern increased. Effects of speed were gradual, and EMG linear envelopes had considerable common variance (>70%) across speeds within subjects, suggesting that the same functions were performed at all speeds. Maximum cross-correlations between moments and muscle activity were 0.2-0.6, and further analyses in the time domain revealed both simultaneous and consecutive task execution. To deal with conflicting constraints, the activity of the three muscles was clearly coordinated, with co-contraction of antagonists to offset unwanted mechanical side-effects of each individual muscle.

Effects of experimentally increased trunk stiffness on thorax and pelvis rotations during walking

Patients with non-specific low back pain, or a similar disorder, may stiffen their trunk, which probably alters their walking coordination. To study the direct effects of increasing trunk stiffness, we experimentally increased trunk stiffness during walking, and compared the results with what is known from the literature about gait coordination with, e.g., low back pain. Healthy subjects walked on a treadmill at 3 speeds (0.5, 1.0 and 1.5m/s), in three conditions (normal, while contracting their abdominal muscles, or wearing an orthopedic brace that limits trunk motions). Kinematics of the legs, thorax and pelvis were recorded, and relative Fourier phases and amplitudes of segment motions were calculated. Increasing trunk stiffness led to a lower thorax-pelvis relative phase, with both a decrease in thorax-leg relative phase, and an increase in pelvis-leg relative phase, as well as reduced rotational amplitude of thorax relative to pelvis. While lower thorax-pelvis relative phase was also found in patients with low back pain, higher pelvis-leg relative phase has never been reported in patients with low back pain or related disorders. These results suggest that increasing trunk stiffness in healthy subjects causes short-term gait coordination changes which are different from those seen in patients with back pain.

“Movement of the sacroiliac joint during the active straight leg raise test in patients with long-lasting severe sacroiliac joint pain” : A letter to the editor

_Dear Editor of Clinical Biomechanics,_ We read with interest Kibsgard et al.s above Clinical Biomechanics paper. Radiostereometric Analysis was performed to measure sacroiliac movements during the Active Straight Leg Raise (ASLR) in 12 patients with chronic Pelvic Girdle Pain (PGP). Of the patients, 8 had been diagnosed with bilateral, and 4 with unilateral sacroiliac pain. All were about to undergo sacroiliac fusion surgery. We fully agree with Kibsgard et al. that this is an important field. About 5% of all pregnant women suffer from PGP that is sufficiently serious to warrant medical attention (Wu et al., 2004). Also athletes with groin pain may have PGP (Verrall et al., 2001), often in the form of osteitis pubis. Both groups of patients have difficulties performing the ASLR (Mens et al., 2006). Contralateral to the side of the raising leg, Kibsgard et al. observed 0.8° backward rotation of the ilium with respect to the sacrum (range−0.3° to −1.3°, ‘minus’ for backward), and ipsilaterally on average 0.0° (range −1.0° to +0.5°). We congratulate Kibsgard et al. with this contribution to the field. Still, there are some questions.