The Effects of a Heel Wedge on Hip, Pelvis and Trunk Biomechanics During Squatting in Resistance Trained Individuals.

Barbell back squats are a popular exercise for developing lower extremity strength and power. However, this exercise has potential injury risks, particularly to the lumbar spine, pelvis, and hip joint. Previous literature suggests heel wedges as a means of favorably adjusting trunk and pelvis kinematics with the intention of reducing such injury risks. Yet no direct biomechanical research exists to support these recommendations. Therefore, the purpose of this study was to examine the effects of heel wedges compared with barefoot on minimally loaded barbell back squats. Fourteen trained male participants performed a barbell back squat in bare feet or with their feet raised bilaterally with a 2.5-cm wooden block while 3-dimensional kinematics, kinetics, and electromyograms were collected. The heel wedge condition elicited significantly less forward trunk flexion angles at peak knee flexion, and peak external hip joint moments (p ≤ 0.05) compared with barefoot conditions. However, no significant differences were observed between conditions for trunk and pelvis angle differences at peak knee flexion (p > 0.05). Lastly, no peak or root mean square differences in muscle activity were elicited between conditions (p > 0.05). Our results lend support for the suggestions provided in literature aimed at using heel wedges as a means of reducing excessive forward trunk flexion. However, the maintenance of a neutral spine, another important safety factor, is not affected by the use of heel wedges. Therefore, heel wedges may be a viable modification for reduction of excessive forward trunk flexion but not for reduction in relative trunk-pelvis flexion during barbell back squats.

Trunk and lower limb biomechanics during stair climbing in people with and without symptomatic femoroacetabular impingement.

BACKGROUND: Femoroacetabular impingement is a pathomechanical hip condition leading to pain and impaired physical function. It has been shown that those with femoroacetabular impingement exhibit altered gait characteristics during level walking and stair climbing, and decreased muscle force production during isometric muscle contractions. However, no studies to-date have looked at trunk kinematics or muscle activation during dynamic movements such as stair climbing in this patient population. The purpose of this study was to compare biomechanical outcomes (trunk and lower limb kinematics as well as lower limb kinetics and muscle activation) during stair climbing in those with and without symptomatic femoroacetabular impingement. METHODS: Trunk, hip, knee and ankle kinematics, as well as hip, knee and ankle kinetics and muscle activity of nine lower limb muscles were collected during stair climbing for 20 people with clinical and radiographic femoroacetabular impingement and compared to 20 age- and sex-matched pain-free individuals. FINDINGS: Those with femoroacetabular impingement ascended the stairs slower (effect size=0.82), had significantly increased peak trunk forward flexion angles (effect size=0.99) and external hip flexion moments (effect size=0.94) and had decreased peak external knee flexion moments (effect size=0.90) compared to the control group. INTERPRETATION: Findings from this study indicate that while those with and without femoroacetabular impingement exhibit many biomechanical similarities when ascending stairs, differences in trunk forward flexion and joint kinetics indicate some important differences. Further longitudinal research is required to elucidate the cause of these differences as well as the clinical relevance.

The Biomechanical Demands on the Hip During Progressive Stepping Tasks.

Hatfield, GL, Charlton, JM, Cochrane, CK, Hammond, CA, Napier, C, Takacs, J, Krowchuk, NM, and Hunt, MA. The biomechanical demands on the hip during progressive stepping tasks. J Strength Cond Res 31(12): 3444-3453, 2017-Functional hip strengthening exercises are important components of lower extremity (LE) rehabilitation and include single-leg squats (SLS), step-downs (SD), and step-ups (SU). The biomechanical demand of these tasks is unclear. This repeated-measures study determined hip biomechanical demands in a healthy population. Twenty individuals (10 men, 26.6 ± 5.1 years, 22.1 ± 2.3 kg·m) participated. Three-dimensional motion, ground reaction force data, and surface electromyograms (EMG) were recorded during 4 randomly ordered tasks. Outcomes included frontal and sagittal plane hip moment impulses and muscle activity for each task. Repeated measures analysis of variance models (alpha = 0.05) determined between-task differences. Step-down and SLS were most biomechanically demanding, with significantly higher hip flexion and adduction moment impulses, and gluteus medius (GM) and quadriceps activity compared with half step-down (HSD) and SU. No significant difference was found between SD and SLS, indicating minimal difference in demand between the 2 tasks, likely due to kinematic similarities in performance; there were no significant differences in knee or hip sagittal plane angle excursion, or peak pelvic obliquity angle between the 2 tasks. Step-up was least demanding, with the lowest hip flexion and adduction moment impulses and GM, quadriceps, and hamstrings activity. Step-up was least demanding on the hip and would be a good starting task for hip strengthening protocols. Step-down and SLS were most demanding, requiring higher hip moments and muscle activity. These results provide evidence, which may be used in planning of progressive rehabilitation programs for patients with LE pathologies.

Clinical Tests of Standing Balance in the Knee Osteoarthritis Population: Systematic Review and Meta-analysis.

BACKGROUND: People with knee osteoarthritis (OA) have a high prevalence of falls. Poor standing balance is one risk factor, but the extent of standing balance deficits in people with knee OA is unknown. PURPOSE: The primary purpose of this study was to summarize available data on standing balance in people with knee OA compared with people without knee OA. A secondary purpose was to establish the extent of balance impairment across disease severity. DATA SOURCES: A literature search of the MEDLINE, EMBASE, CINAHL, and Web of Science databases through November 19, 2014, was conducted. STUDY SELECTION: Studies on individuals with knee OA containing clinical, quantifiable measures of standing balance were included. Methodological quality was assessed by 2 reviewers using a 16-item quality index developed for nonrandomized studies. Studies scoring >50% on the index were included. DATA EXTRACTION: Participant characteristics (age, sex, body mass index, OA severity, compartment involvement, unilateral versus bilateral disease) and balance outcomes were extracted by 2 reviewers. Standardized mean differences were pooled using a random-effects model. DATA SYNTHESIS: The search yielded 2,716 articles; 8 met selection and quality assessment criteria. The median score on the quality index was 13/17. People with knee OA consistently performed worse than healthy controls on the Step Test, Single-Leg Stance Test, Functional Reach Test, Tandem Stance Test, and Community Balance and Mobility Scale. The pooled standardized mean difference was -1.64 (95% confidence interval=-2.58, -0.69). No differences were observed between varying degrees of malalignment, or between unilateral versus bilateral disease. LIMITATIONS: No studies compared between-knee OA severities. Thus, expected changes in balance as the disease progresses remain unknown. CONCLUSIONS: Few studies compared people with knee OA and healthy controls, but those that did showed that people with knee OA performed significantly worse. More research is needed to understand the extent of balance impairments in people with knee OA using easy-to-administer, clinically available tests.