Object Although the area at the auricular surface defines the magnitude of weight transmission to the hip bones, this study proposes that the position of the auricular surfaces may also significantly influence load bearing patterns at the sacrum. This study attempts to investigate and classify variable positions of the auricular surfaces that may cause vertical shifts in weight-bearing patterns between the L-5 and S-1 segments, altering weight distribution at the lumbosacral and sacroiliac regions. Methods Three hundred human sacra were studied to determine the position and extent of their auricular surfaces in relation to the sacral segments. Specimens were grouped as “normal,” “high-up,” and “low-down” auricular surface-bearing sacra. All bones were also scrutinized for the presence of accessory articulating facets on the ala of the sacrum and sacralization of the L-5 segment or lumbarization of the S-1 segment. Seven dimensions and 5 articular areas were measured in all sacra. Nine indices were calculated to show proportional representation of dimensions and areas in the bones. Obtained data were analyzed for differences in groups of sacra bearing different auricular surface positions. Results Thirty-nine of the sacra (13%) showed auricular surfaces that occupied a high-up position (from upper S-1 to low S-2 segments). Forty-four of the sacra (15%) exhibited a low-down auricular surface (from the low S-1 to low S-3 sacral segments). The remaining bones demonstrated a normal position of the surface (from the S-1 to the middle of the S-3 segments). Twenty of the high-up sacra demonstrated unilateral or bilateral accessory articulating facets on the alae that articulated with extended transverse processes of the L-5 vertebrae. The low-down sacra transmitted load predominantly via lower (S2–3) segments and exhibited stouter, broader, and efficient weight-bearing lower sacral elements, and a prominent gap between the S-1 segment and the rest of the sacrum. The high-up sacra: 1) were shorter and broader in comparison with the normal sacra; 2) at times presented accessory articular facets on their alae; 3) had a smaller body span and a wider ala; 4) were found to have the plane of the facet joints nearer to the posterior aspect of the S-1 body; and 5) had the smallest of the facet areas. The low-down sacra were longer than they were broad, had a substantially broad body span at S-1, possessed the smallest interauricular distance, and showed considerable depth of the plane of the facet joints. Conclusions The position of the auricular surface varies in human sacra. These variations are associated with differential load bearing at the sacral joints. Only the high-up sacra demonstrated the presence of accessory articulating facets between L-5 and S-1. The position of the auricular surface can explain or possibly predict low-back pain situations.

We tested the hypothesis that the nervous system, and the cortex in particular, is a critical determinant of muscle strength/weakness and that a high level of corticospinal inhibition is an important neurophysiological factor regulating force generation. A group of healthy individuals underwent 4 wk of wrist-hand immobilization to induce weakness. Another group also underwent 4 wk of immobilization, but they also performed mental imagery of strong muscle contractions 5 days/wk. Mental imagery has been shown to activate several cortical areas that are involved with actual motor behaviors, including premotor and M1 regions. A control group, who underwent no interventions, also participated in this study. Before, immediately after, and 1 wk following immobilization, we measured wrist flexor strength, voluntary activation (VA), and the cortical silent period (SP; a measure that reflect corticospinal inhibition quantified via transcranial magnetic stimulation). Immobilization decreased strength 45.1 ± 5.0%, impaired VA 23.2 ± 5.8%, and prolonged the SP 13.5 ± 2.6%. Mental imagery training, however, attenuated the loss of strength and VA by ∼50% (23.8 ± 5.6% and 12.9 ± 3.2% reductions, respectively) and eliminated prolongation of the SP (4.8 ± 2.8% reduction). Significant associations were observed between the changes in muscle strength and VA (r = 0.56) and SP (r = -0.39). These findings suggest neurological mechanisms, most likely at the cortical level, contribute significantly to disuse-induced weakness, and that regular activation of the cortical regions via imagery attenuates weakness and VA by maintaining normal levels of inhibition.

L5-S1 transitions possess altered facet morphology. These alterations are possibly related to low back pain situations.

No abstract

No abstract

These preliminary findings suggest that anodal transcranial direct current stimulation enhances time to task failure of a sustained, submaximal contraction in older adults by potentially increasing cortical excitability and/or influencing the perception of exertion. These results raise the question of whether interventions that acutely increase cortical excitability could enhance physical function and/or exercise-induced adaptations in older adults.

No abstract

Object Low-back pain (LBP) has been associated with lumbar spines of normal morphology as well as those with L5–S1 “transitional” vertebrae. It is hard to find literature that quantifies the overall morphological changes in lumbar spines as related to transitional states. The object of this study was to investigate lumbar spine changes resulting from the presence of these transitional states. Methods The author quantified dimensions and angles and statistically compared the morphology of lumbar spines with or without L5–S1 transitions in the context of LBP. Anteroposterior and lateral radiographs were obtained from 50 patients suffering from LBP without transitional anomalies at the L5–S1 junction. These radiographs were compared with anteroposterior and lateral radiographs from patients suffering from LBP with L5–S1 transitional states involving accessory L5–S1 articulations, and with anteroposterior and lateral radiographs from patients with L5–S1 unilateral or bilateral fusions. Twelve linear dimensions from the anteroposterior views and 8 angles from the lateral radiographs were measured. Results The mean values of linear dimensions differed in 1) disc heights, 2) vertebral heights and widths, 3) pedicles and interpedicular distances, 4) angle values, and 5) overall configuration of the lumbar curvatures. Conclusions The L5–S1 accessory articulations led to increased lordotic curves, L-5 vertebral heights, and pedicle and angular dimensions. The L5–S1 fusions were related to smaller disc heights at all spaces, short and wide L-5 pedicles, taller and less wide transverse processes, and overall straighter spines with the least measures for all lumbar angles. Dimensional differences provided in this study may help in placing instrumentation at the lumbar vertebrae and working on intervertebral disc replacements in spines with specific L5–S1 transitional anomalies.