Carrying asymmetric loads during different walking conditions

The purpose of this dissertation was to investigate how asymmetric load carriage affects joint kinetics and postural control during walking and stair negotiation. In the first two studies, frontal plane joint moments were analyzed when carrying unilateral versus bilateral loads during stair negotiation. Peak L5/S1 contralateral bending moments were significantly higher when carrying a 20% body weight (BW) unilateral load for both stair ascent and descent. In addition, peak external knee varus and hip abduction moments were significantly higher in unloaded limb stance as compared to loaded limb stance. Based on our findings, we suggest that the low back and lower extremity play different roles in adjusting to asymmetric loads and recommend splitting loads bilaterally in order to decrease the frontal plane joint moments. In the last dissertation study, we assessed postural control when carrying unilateral versus bilateral loads during walking on even and uneven surfaces. Carrying 20% BW bilateral or unilateral loads resulted in a significantly higher double stance ratio than unloaded walking. Carrying a 20% BW unilateral load or walking on an uneven surface resulted in a significantly increased coefficient of variation (CV) of double stance ratio. Unloaded limb stance had a significantly higher double stance ratio and mean medial-lateral (ML) center of pressure (COP) velocity, although the loaded limb had a significantly higher CV of ML COP velocity. We suggest that load carriage and unloaded limb stance require more conservative postural control, while asymmetric loads and uneven surfaces require more step-by-step postural adjustments

Mediolateral postural stability when carrying asymmetric loads during stair negotiation

The purpose of this study was to assess postural stability in the medial-lateral (ML) direction when carrying unilateral and bilateral loads during stair negotiation. Twenty-four healthy young adults were instructed to ascend and descend a three step staircase under three load conditions: no load, 20% body mass (BM) bilateral load, and 20% BM unilateral load. A modified time-to-contact (TTC) method was proposed to evaluate postural stability during stair negotiation. Carrying unilateral loads required more rapid postural adjustments as evidenced by lower minimum ML TTC and ML TTC percentage as compared bilateral loads and no load during stair descent. In addition, lower ML TTC and TTC percentage were found for loaded limb stance for stair descent. Taken together, unilateral loads and the loaded leg during stair descent are of concern when considering postural stability during load carriage. These results illustrate differing postural control challenges for stair ascent and descent during load carriage

Carrying asymmetric loads during different walking conditions

The purpose of this dissertation was to investigate how asymmetric load carriage affects joint kinetics and postural control during walking and stair negotiation. In the first two studies, frontal plane joint moments were analyzed when carrying unilateral versus bilateral loads during stair negotiation. Peak L5/S1 contralateral bending moments were significantly higher when carrying a 20% body weight (BW) unilateral load for both stair ascent and descent. In addition, peak external knee varus and hip abduction moments were significantly higher in unloaded limb stance as compared to loaded limb stance. Based on our findings, we suggest that the low back and lower extremity play different roles in adjusting to asymmetric loads and recommend splitting loads bilaterally in order to decrease the frontal plane joint moments. In the last dissertation study, we assessed postural control when carrying unilateral versus bilateral loads during walking on even and uneven surfaces. Carrying 20% BW bilateral or unilateral loads resulted in a significantly higher double stance ratio than unloaded walking. Carrying a 20% BW unilateral load or walking on an uneven surface resulted in a significantly increased coefficient of variation (CV) of double stance ratio. Unloaded limb stance had a significantly higher double stance ratio and mean medial-lateral (ML) center of pressure (COP) velocity, although the loaded limb had a significantly higher CV of ML COP velocity. We suggest that load carriage and unloaded limb stance require more conservative postural control, while asymmetric loads and uneven surfaces require more step-by-step postural adjustments.</p

Mediolateral postural stability when carrying asymmetric loads during stair negotiation

The purpose of this study was to assess postural stability in the medial-lateral (ML) direction when carrying unilateral and bilateral loads during stair negotiation. Twenty-four healthy young adults were instructed to ascend and descend a three step staircase under three load conditions: no load, 20% body mass (BM) bilateral load, and 20% BM unilateral load. A modified time-to-contact (TTC) method was proposed to evaluate postural stability during stair negotiation. Carrying unilateral loads required more rapid postural adjustments as evidenced by lower minimum ML TTC and ML TTC percentage as compared bilateral loads and no load during stair descent. In addition, lower ML TTC and TTC percentage were found for loaded limb stance for stair descent. Taken together, unilateral loads and the loaded leg during stair descent are of concern when considering postural stability during load carriage. These results illustrate differing postural control challenges for stair ascent and descent during load carriage.This accepted article is published as Wang, J., Gillette, J.C., Mediolateral postural stability when carrying asymmetric loads during stair negotiation., Applied Ergonomics, 85(May 2020); 103057. Doi: 10.1016/j.apergo.2020.103057. Posted with permission. </p

Carrying asymmetric loads while walking on an uneven surface.

Background Individuals often carry asymmetric loads over challenging surfaces such as uneven or irregular terrain, which may require a higher demand for postural control than walking on an even surface. Research Question The purpose of this study was to assess postural stability in the medial-lateral (ML) direction while carrying unilateral versus bilateral loads when walking on even versus uneven surfaces. Methods Nineteen healthy young adults walked on even and uneven surface treadmills under three load conditions: no load, 20% body weight (BW) bilateral load, and 20% BW unilateral load. A Pedar in-shoe pressure system (Novel, Munich, Germany) was used to evaluate center of pressure (COP)-based parameters. Results Carrying 20% BW bilateral or unilateral loads significantly increased double support ratio. In addition, carrying a 20% BW unilateral load significantly increased coefficient of variation (CV) of double support ratio, CV of ML COP excursion, and CV of ML COP velocity. Walking on an uneven surface significantly increased double support ratio, ML COP excursion, ML COP velocity, and CV of double support ratio. When carrying a 20% BW unilateral load, unloaded limb stance had significantly increased double support ratio and ML COP velocity, although it appears that the loaded limb may be used to make step-by-step adjustments as evidenced by the higher CV of ML COP velocity. Significance Unilateral load carriage, walking on uneven surfaces, and unloaded leg stance are of particular concern when considering postural stability.This article is published as Wang, J., Gillette, J.C., Carrying asymmetric loads while walking on an uneven surface. Gait & Posture. 65(2018); 39-44. Doi: 10.1016/j.gaitpost.2018.06.173. Posted with permission.</p

Carrying asymmetric loads during stair negotiation

Individuals often carry items in one hand instead of both hands during activities of daily living. The combined effects of carrying asymmetric loads and stair negotiation may create even higher demands on the low back and lower extremity. The purpose of this study was to investigate the effect of symmetric and asymmetric loading conditions on L5/S1 and lower extremity moments during stair negotiation. Twenty-two college students performed stair ascent and stair descent on a three-step staircase (step height 18.5 cm, tread depth 29.5 cm) at preferred pace under five load conditions: no load, 10% body weight (BW) unilateral load, 20% BW unilateral load, 10% BW bilateral load, and 20% BW bilateral load. Video cameras and force platforms were used to collect kinematic and kinetic data. Inverse dynamics was used to calculate frontal plane moments for the L5/S1 and lower extremity. A 20% BW unilateral load resulted in significantly higher peak L5/S1 lateral bending, hip abduction, and external knee varus moments than nearly all other loading conditions during stair ascent and stair descent. Therefore, we suggest potential benefits when carrying symmetrical loads as compared to an asymmetric load in order to decrease the frontal joint moments, particularly at 20% BW load.This is a manuscript of an article from Gait & Posture, 53 (2017); 67-72. DOI: 10.1016/j.gaitpost.2017.01.006. Posted with permission. </p

Carrying asymmetric loads during stair negotiation: Loaded limb stance vs. unloaded limb stance

Background Individuals often carry items in one hand instead of both hands during activities of daily living. Research Question The purpose of this study was to investigate low back and lower extremity frontal plane moments for loaded limb stance and unloaded limb stance when carrying symmetric and asymmetric loads during stair negotiation. Methods Participants were instructed to ascend and descend a three-step staircase at preferred pace using a right leg lead and a left leg lead for each load condition: no load, 20% body weight (BW) bilateral load, and 20% BW unilateral load. L5/S1 contralateral bending, hip abduction, external knee varus, and ankle inversion moments were calculated using inverse dynamics. Results Peak L5/S1 contralateral bending moments were significantly higher when carrying a 20% BW unilateral load as compared to a 20% BW bilateral load for both stair ascent and stair descent. In addition, peak L5/S1 contralateral bending moments were significantly higher during step one than for step two. Peak external knee varus and hip abduction moments were significantly higher in unloaded limb stance as compared to loaded limb stance when carrying a 20% BW unilateral load. Significance General load carriage recommendations include carrying less than 20% BW loads and splitting loads bilaterally when feasible. Assessment recommendations include analyzing the first stair step and analyzing both the loaded and unloaded limbs.This is a manuscript of an article published as Wang, Junsig, and Jason C. Gillette. "Carrying asymmetric loads during stair negotiation: Loaded limb stance vs. unloaded limb stance." Gait & Posture 64 (2018): 213-219. doi: 10.1016/j.gaitpost.2018.06.113. Posted with permission.</p

Postural Control Differences Between Patients with Posterior Tibial Tendon Dysfunction and Healthy People During Gait

Background: Patients with posterior tibial tendon dysfunction (PTTD) may exhibit postural instability during walking likely due to a loss of medial longitudinal arch, abnormal foot alignment, and pain. While many studies have investigated gait alterations in PTTD, there is no understanding of dynamic postural control mechanisms in this population during gait, which will help guide rehabilitation and gait training programs for patients with PTTD. The purpose of the study was to assess dynamic postural control mechanisms in patients with stage II PTTD as compared to age and gender matched healthy controls. Methods: Eleven patients with stage II PTTD (4 males and 7 females; age 59 ± 1 years; height 1.66 ± 0.12 m; mass 84.2 ± 16.0 kg) and ten gender and age matched controls were recruited in this study. Participants were asked to walk along a 10 m walkway. Ten Vicon cameras and four AMTI force platforms were used to collect kinematic and center of pressure (COP) data while participants performed gait. To test differences between PTTD vs. control groups, independent t-tests (set at α \u3c 0.05) were performed. Results: Patients with PTTD had significantly higher double stance ratio (+23%) and anterior-posterior (AP) time to contact (TTC) percentage (+16%) as compared to healthy control. However, PTTD had lower AP COP excursion (−19%), AP COP velocity (−30%), and medial-lateral (ML) COP velocity (−40%) as compared to healthy controls. Mean ML COP trace values for PTTD were significantly decreased (−23%) as compared to controls, indicating COP trace for PTTD tends to be closer to the medial boundary than controls during single-support phase of walking. Conclusion: PTTD patients showed more conservative and cautious postural strategies which may help maintain balance and reduce the need for postural adjustment during PTTD gait. They also showed more medially shifted COP patterns than healthy controls during single-support phase of walking. Dynamic postural control outcomes could be used to develop effective gait training programs aimed at alleviating a medial shift of COP (everted foot) for individuals with PTTD in order to improve their functionality and gait efficiency

Effect of Movement Speed on Lower and Upper Body Biomechanics During Sit-to-Stand-to-Sit Transfers: Self-Selected Speed vs. Fast Imposed Speed

Preferred and fast speed sit-to-stand and stand-to-sit (STS) tests are prevalent in literature, but biomechanical changes between the different speeds of STS have never been studied. Understanding differences between these STS techniques will better inform experimental design for research assessing functional ability in clinical populations. The purpose of this study was to investigate the effect of different speeds of STS transfers on lower body and trunk kinematics and kinetics in healthy adults. Nineteen healthy middle-aged and older adults participated in this study. Two different speeds of STS were tested: self-selected speed and fast speed (as quickly as possible). Ten Vicon cameras and two AMTI force platforms were used to collect three-dimensional kinematic and kinetic data. During sit-to-stand transfer, peak knee extension velocity and knee extension moment were significantly increased for the fast speed STS as compared to the preferred speed STS. During stand-to-sit transfer, peak knee extension moment and lower back moment were significantly increased while STS time was decreased for the fast speed STS as compared to the preferred speed STS. Our results indicate that the fast speed STS could be more challenging for participants compared to the preferred speed STS evidenced by greater knee and lower back joint movements. Therefore, fast STS tests should be reconsidered when testing middle-aged and older adults with chronic low back pain and knee joint problems

Kinematic and Kinetic Changes After Total Hip Arthroplasty During Sit-to-Stand Transfers: Systematic Review

Background: Total hip arthroplasty (THA) is a common and effective surgical procedure that allows patients with hip osteoarthritis to restore functional ability and relieve pain. Sit-to-stand transfers are common demanding tasks during activities of daily living and are performed more than 50 times per day. The purpose of this systematic review is to obtain a comprehensive understanding of biomechanical changes during sit-to-stand transfers after THA. Methods: Relevant articles were selected through MEDLINE, Scopus, Embase, and Web of Science. Articles were included if they met the following inclusion criteria: 1) participants underwent total hip arthroplasty without restriction on the arthroplasty design, 2) involved either kinematic or kinetic variables as the primary outcome measure, 3) evaluated sit-to-stand, and 4) were written in English. Results: A total of 11 articles were included in the current systematic review. The THA group exhibited altered movement patterns as compared to healthy controls. Improvement in loading asymmetry was found up to 1 year after THA, but other kinetic changes indicate intensified contralateral limb loading. Limb differences were apparent, but whether these differences persist over 10 months after THA is still unknown. Conclusion: Despite the inevitable changes in kinematics and kinetics in sit-to-stand transfers after THA, it appears to be important to resolve asymmetrical loading between the operative and nonoperative limbs to minimize risk for subsequent joint problems