Recovery of the ability to maintain balance during standing is one of the primary and essential goals of rehabilitation programs for individuals with Spinal Cord Injury (SCI). Regaining functionality during standing by means of a neuroprosthesis would decrease secondary complications and increase independence, and would consequently improve the quality of life of these individuals. However, the development of a standing neuro- prosthesis requires techniques to generate reliable and predictable torque vectors in the lower limbs. We proposed and tested a method based on surface Functional Electrical Stimulation (FES) and the idea that three independent muscles can form a basis that would span the joint torque vector space. We tested the proposed stimulation technique on the quadriceps muscles that produce knee extension. The results of this study suggest that the quadriceps muscle basis vectors are insufficient to cover the knee joint vector space.

Recovery of the ability to maintain balance during standing is one of the primary and essential goals of rehabilitation programs for individuals with Spinal Cord Injury (SCI). Regaining functionality during standing by means of a neuroprosthesis would decrease secondary complications and increase independence, and would consequently improve the quality of life of these individuals. However, the development of a standing neuro- prosthesis requires techniques to generate reliable and predictable torque vectors in the lower limbs. We proposed and tested a method based on surface Functional Electrical Stimulation (FES) and the idea that three independent muscles can form a basis that would span the joint torque vector space. We tested the proposed stimulation technique on the quadriceps muscles that produce knee extension. The results of this study suggest that the quadriceps muscle basis vectors are insufficient to cover the knee joint vector space.

Dynamic standing balance is essential to perform functional activities and is included in the treatment of many lower extremity injuries. Physiotherapists utilize many methods to restore standing balance including stability exercises, functional retraining, and manual therapy. The purpose of this study was to investigate the effects of a rearfoot distraction manipulation on dynamic standing balance. Twenty healthy participants (age: 24.4 ± 2.8 years; height: 162.9 ± 37.7 cm; mass: 68.0 ± 4.8 kg; right leg dominant = 20) completed this study. Following familiarization, dynamic standing balance was assessed during: (1) an experimental condition immediately following a rearfoot distraction manipulation, and (2) a control condition. Dominant leg balance was quantified using the Y-balance test which measures lower extremity reach distances. Reach distances were normalized to leg length and measured in the anterior, posteromedial and posterolateral directions. Overall balance was calculated through the summing of all normalized directions. Paired t-tests and Wilcoxon rank tests were used to compare balance scores for parametric and non-parametric data as appropriate. Significance was set at 0.05 a priori. Effect size (ES) was calculated to determine the clinical impact of the manipulation. Increased reach distances (indicating improved balance) were noted following manipulation for overall balance (p = 0.03, ES = 0.26) and in the posteromedial direction (p = 0.01, ES = 0.42). Reach distances did not differ for the anterior (p = 0.11, ES = 0.16) or posterolateral (p = 0.11, ES = 0.25) components. Dynamic standing balance improved after a rearfoot distraction manipulation in healthy participants. It is hypothesized that manual therapy applied to the foot and ankle may be beneficial to augment other therapeutic modalities when working with patients to improve dynamic standing balance.

PURPOSE/BACKGROUND: Cryotherapy is commonly used in physical therapy with many known benefits; however several investigations have reported decreased functional performance following therapeutic application thereof. The purpose of this study was to determine the effect of cryotherapy applied to the ankle on static and dynamic standing balance. It was hypothesized that balance would be decreased after cryotherapy application. METHODS: Twenty individuals (aged 18 to 40 years) participated in this research project. Each participant was tested under two conditions: an experimental condition where subjects received ice water immersion of the foot and ankle for 15 minutes immediately before balance testing and a control condition completed at room temperature. A Biodex® Balance System was used to quantify balance using anterior/posterior (AP), medial/lateral (ML), and overall balance indices. Paired t-tests were used to compare the balance indices for the two conditions with alpha set at 0.05 a priori. Effect size was also calculated to account for the multiple comparisons made. RESULTS: The static balance indices did not display statistically significant differences between the post-cryotherapy and the control conditions with low effect sizes. Dynamic ML indices significantly increased following the cryotherapy application compared to the control exhibiting a moderate effect size indicating decreased balance following cryotherapy application. No differences were noted between experimental and control conditions for the dynamic AP or overall balance indices while a small effect size was noted for both. CONCLUSIONS: The results suggest that cryotherapy to the ankle has a negative effect on the ML component of dynamic balance following ice water immersion. CLINICAL RELEVANCE: Immediate return to play following cryotherapy application is cautioned given the decreased dynamic ML balance and potential for increased injury risk. LEVEL OF EVIDENCE: 3b Case-control study.

While human balance is known to be affected by altered sensory feedback, altered dynamics may also contribute to balance deficiencies in certain populations. The goal of this study was, therefore, to investigate the effects of altered dynamics, namely increased inertia and increased weight, on standing balance. Sixteen normal-weight male participants completed quiet standing in a custom-built backboard under four conditions: baseline, increased inertia only, increased weight only, and increased inertia and weight. Increased inertia did not affect body center of mass movement (COM) or center of pressure (COP) movement, suggesting that no additional ankle torque was necessary to control the increased inertial forces. Increased weight caused increased body COM movement (increased backboard angle range and angular speed) and greater acceleration of the COM (as evidenced by increased COP-COM), requiring an increased level of corrections needed to maintain upright posture (as evidenced by increased COP speed) and increased ankle torques (as evidenced by increased range of COP position). Increasing inertia and weight simultaneously had the same effects as increasing weight except that there was no increased COM movement when both inertia and weight were increased. This indicates that there may be a slight mediating effect of increasing inertia on the extreme changes in balance observed when only weight is increased. These results indicate that altered dynamics of the body have an effect on human standing balance, just as altered sensory function has an effect on balance. / Master of Science

No description available.

PURPOSE/BACKGROUND: Muscle fatigue is related to a decline in force output and proprioception. These can ultimately have an adverse effect on neuromuscular control and functional performance. Local muscle fatigue has been shown to have adverse consequences on dynamic standing balance; however, much less is known regarding the relationship between distant fatigue and dynamic standing. The purpose of this study was to investigate the effects of upper body fatigue on dynamic standing balance. It was hypothesized that distant fatigue in upper body musculature would show a significant decrease in dynamic standing balance as assessed by the Lower Quarter Y-Balance Test (YBT-LQ). METHODS: TWENTY HEALTHY INDIVIDUALS (AGE: 25.0 ± 3.42 years, height: 172.72 ± 13.11 cm, mass: 71.36 ± 13.50 kg) participated in this study. A kayak ergometer was used to implement a fatigue protocol for the upper body. The protocol consisted of a graded intensity session ranging from 50% to 90% of maximum effort lasting ten minutes in duration (2 minutes each at 50% 60%, 70%, 80%, and 90%). The anterior (ANT), posteromedial (PM), and posterolateral (PL) reach directions were normalized to leg length and measured on the YBT-LQ before and after the fatigue protocol for each participant. A fourth value termed overall balance was calculated as the sum of the furthest reach distance of the three directions. Blood lactate analysis taken before and immediately after the fatigue protocol was used to quantify fatigue. Multiple paired t-tests were performed for pre-fatigue and post-fatigue balance assessment. A Bonferroni correction was applied to set the significance value ≤0.0125 a priori. Effect size was calculated using the effect size index. RESULTS: Blood lactate values immediately following the fatigue protocol had an average concentration of 6.15 millimoles (pre: 2.3, post: 8.4). The ANT reach direction (ρ = 0.004) and the calculated overall balance (ρ = 0.011) significantly decreased post-fatigue in the dominant lower extremity. No significant differences were found for the PM (ρ = 0.017) or PL (ρ = 0.021) directions. The ANT reach direction (0.64) and overall balance (0.44) also showed a moderate effect size based on the effect size index. CONCLUSIONS: ANT and overall dynamic standing balance were negatively affected after completing the upper body fatigue protocol. The findings of this research demonstrate that upper body fatigue has adverse effects on dynamic standing balance, as measured by performance on the YBT-LQ. Significant and clinically relevant differences were noted in ANT and overall dynamic standing balance. CLINICAL RELEVANCE: Physical therapists should be aware of the adverse influence distant fatigue may exhibit on neuromuscular control in muscles not actively involved in the fatiguing exercise. The balance deficits noted may indicate an increased risk of injury with muscle fatigue in muscles not directly contributing to standing balance. LEVEL OF EVIDENCE: 3b, Case-control study.

Des anomalies dans la morphologie pelvienne, la posture du tronc et le contrôle de l’équilibre de jeunes filles atteintes de scoliose idiopathique de l’adolescence (SIA) ont souvent été l’objet d’études. Rares sont celles ayant distingué ces troubles en fonction de la sévérité de la déformation vertébrale. De plus, aucune n’a évalué à l’intérieur d’une même étude l’orientation et la distorsion pelvienne, l’asymétrie posturale et l’instabilité en position debout de sujets SIA. Une telle étude permettrait de comprendre le développement de la maladie et de mettre en évidence des facteurs de risque aidant au pronostic. L’objectif général de cette thèse est d’identifier des facteurs biomécaniques associés à la croissance osseuse, la posture et l’équilibre distinguant une SIA modérée d’une sévère. Les positions 3D de 14 repères prises sur 46 filles ayant une SIA droite (modérée et sévère) et 28 sujets témoins ont été captées pour quantifier la morphologie pelvienne et la posture. Un maintien en position debout de 64 s sur une plate-forme de force a aussi été enregistré afin d’évaluer leur équilibre. Les paramètres retenus sont les angles d’orientation pelvienne et du tronc; les distances entre la crête iliaque et S1 mesurant la distorsion pelvienne; la moyenne, l’amplitude et la vitesse du centre de pression (COP) en médiolatéral (ML) et antéropostérieur ainsi que la moyenne et l’amplitude du moment libre. Les différences entre les trois groupes (témoin, SIA modérée et SIA sévère) sont testées par des ANOVA et les relations entre l’angle de Cobb et les paramètres pelviens, posturaux ou d’équilibre, par des coefficients de corrélations. De plus, des régressions multiples exprimant l’angle de Cobb sont effectuées avec les paramètres pelviens, posturaux et d’équilibre afin de déterminer la classe de paramètres prédisant le mieux l’angle de Cobb. Aucune ANOVA n’est significative pour l’orientation pelvienne, bien que des différences de géométrie pelvienne soient notées entre les deux groupes de sujets SIA. Les SIA modérées ont un pelvis gauche moins profond que les SIA sévères et les sujets témoins, tandis que les SIA sévères ont un pelvis droit plus large d’environ 1,5 cm que celui des SIA modérées. Un coefficient de corrélation de -0,54 associe une rotation pelvienne droite à l’augmentation de la largeur de la crête iliaque. Au niveau postural, les SIA sévères démontrent des inclinaisons latérales et antérieures du tronc ainsi qu’une rotation axiale du haut du corps plus marquées que les SIA modérées. Les corrélations entre les paramètres posturaux, l’angle de Cobb et la morphologie pelvienne indiquent que l’attitude posturale est associée à la distorsion pelvienne dans tous les plans anatomiques, tandis qu’elle ne l’est que dans les plans sagittal et horizontal à l’angle de Cobb. Les différences retrouvées entre les deux groupes SIA concernant les troubles d’équilibre résultent en une augmentation de l’amplitude et de la vitesse du COPML. Une régression multiple de 0,896 est observée par l’emploi des paramètres pelviens, posturaux et d’équilibre, bien que ceux se rapportant à la distorsion pelvienne soient les mieux corrélés à l’angle de Cobb. Cette thèse permet de distinguer la morphologie pelvienne de sujets SIA sévères des modérées, soulignant la détection d’une anomalie de croissance avant que l’angle de Cobb ne soit élevé. Bien que les indices de croissance pelvienne soient davantage corrélés à ce dernier, c’est en considérant globalement la morphologie pelvienne, la posture et l’équilibre qu’une détermination précise de la sévérité d’une scoliose est réalisée. La mise en évidence de tels facteurs de prédiction de la SIA peut faciliter le pronostic d’une courbure. / The effect of adolescent idiopathic scoliosis (AIS) on pelvis morphology, body posture and standing balance in young girls has been studied many times. However, only few studies have distinguished the effect associated with moderate AIS from a severe one. Moreover, no one ever assessed within one investigation pelvis orientation and distortions, postural asymmetry and standing imbalance in AIS subjects. This would help understanding the evolution of the disease and to shed light on risk factors that would facilitate the prognostic. The aim of this thesis is to identify biomechanical factors related to bone growth, posture and balance which can distinguish a moderate AIS from a severe one. The 3D coordinates position of 14 body landmarks taken on 46 young girls with right AIS (moderate and severe) curvature and 28 control subjects is captured to quantify pelvis morphology and body posture. An upright standing is recorded during 64 s on a force plate to assess standing balance. From these data, the following parameters are calculated: orientation angle in all 3 planes for pelvis and trunk; distances between S1 and iliac crest to evaluate pelvis distortion; mean position, range and velocity of the center of pressure (COP) in mediolateral (ML) and anteroposterior axis and mean and range of the free moment. Differences between groups (control, AIS moderate and AIS severe) are tested by ANOVA and relationship between Cobb angle and pelvis, postural and balance parameters are calculated by correlation coefficients. Multiple regressions expressing Cobb angle by pelvis, postural and balance parameters are also carried out to determine which class of parameters is able to predict more effectively the Cobb angle’s curvature. No significant ANOVA is found for pelvis orientation, even though differences in pelvis geometry are noticed between the two groups of AIS subjects. Moderate AIS have a left pelvis with a depth less than severe AIS, whereas AIS severe have a larger right pelvis of 1,5 cm than moderate AIS. A correlation coefficient of -0,54 relates a right pelvis rotation to an increase in iliac crest’s width. About postural asymmetries, severe AIS shows lateral and anterior trunk bending and an axial rotation in the upper level of the trunk that are more pronounced compared to moderate AIS. Correlations between postural parameters, Cobb angle and pelvis morphology indicate a relationship between posture and pelvis distortion in all three planes, but only in the sagittal and horizontal plane between posture and Cobb angle. Differences in standing balance between the two groups of AIS show an increase in COPML range and velocity. A multiple regression of 0,896 is found for the Cobb angle using pelvis, postural and balance parameters. Parameters related to pelvis distortion correlate the most with Cobb angle (0,70). This thesis was able to differentiate severe AIS pelvis morphology from those of the moderate one. Pelvis morphology allows detecting a growth abnormality before the Cobb angle becomes high. Even if pelvis growth is more correlated to the Cobb angle, considering globally pelvis morphology, posture and standing balance will allow determining precisely the severity of AIS. Shedding light on such factors during the evolution of the disease helps an AIS curvature prognosis.

Study Objectives: Nocturnal awakenings may constitute a unique risk for falls among older adults. We describe differences in gait and balance between presleep and midsleep testing, and whether changes in the lighting environment during the midsleep testing further affect gait and balance. Methods: Twenty-one healthy, late middle-aged and older (64.7 ± 8.0 y) adults participated in this repeated-measures design consisting of four overnight laboratory stays. Each night, participants completed baseline visual acuity, gait, and balance testing. After a 2-h sleep opportunity, they were awakened for 13 min into one of four lighting conditions: very dim white light (< 0.5 lux); dim white light (∼28.0 lux); dim orange light (∼28.0 lux); and white room-level light (∼200 lux). During this awakening, participants completed the same sequence of testing as at baseline. Results: Low-contrast visual acuity significantly decreased with decreasing illuminance conditions (F(3,45) = 98.26, p < 0.001). Our a priori hypothesis was confirmed in that variation in stride velocity and center of pressure path length were significantly worse during the mid-sleep awakening compared to presleep baseline. Lighting conditions during the awakening, however, did not influence these parameters. In exploratory analyses, we found that over one-third of the tested gait and balance parameters were significantly worse at the midsleep awakening as compared to baseline (p < 0.05), and nearly one-quarter had medium to large effect sizes (Cohen d ≥ 0.5; r ≥ 0.3). Conclusions: Balance and gait are impaired during midsleep awakenings among healthy, late middle-aged and older adults. This impairment is not ameliorated by exposure to room lighting, when compared to dim lights.

Des anomalies dans la morphologie pelvienne, la posture du tronc et le contrôle de l’équilibre de jeunes filles atteintes de scoliose idiopathique de l’adolescence (SIA) ont souvent été l’objet d’études. Rares sont celles ayant distingué ces troubles en fonction de la sévérité de la déformation vertébrale. De plus, aucune n’a évalué à l’intérieur d’une même étude l’orientation et la distorsion pelvienne, l’asymétrie posturale et l’instabilité en position debout de sujets SIA. Une telle étude permettrait de comprendre le développement de la maladie et de mettre en évidence des facteurs de risque aidant au pronostic. L’objectif général de cette thèse est d’identifier des facteurs biomécaniques associés à la croissance osseuse, la posture et l’équilibre distinguant une SIA modérée d’une sévère. Les positions 3D de 14 repères prises sur 46 filles ayant une SIA droite (modérée et sévère) et 28 sujets témoins ont été captées pour quantifier la morphologie pelvienne et la posture. Un maintien en position debout de 64 s sur une plate-forme de force a aussi été enregistré afin d’évaluer leur équilibre. Les paramètres retenus sont les angles d’orientation pelvienne et du tronc; les distances entre la crête iliaque et S1 mesurant la distorsion pelvienne; la moyenne, l’amplitude et la vitesse du centre de pression (COP) en médiolatéral (ML) et antéropostérieur ainsi que la moyenne et l’amplitude du moment libre. Les différences entre les trois groupes (témoin, SIA modérée et SIA sévère) sont testées par des ANOVA et les relations entre l’angle de Cobb et les paramètres pelviens, posturaux ou d’équilibre, par des coefficients de corrélations. De plus, des régressions multiples exprimant l’angle de Cobb sont effectuées avec les paramètres pelviens, posturaux et d’équilibre afin de déterminer la classe de paramètres prédisant le mieux l’angle de Cobb. Aucune ANOVA n’est significative pour l’orientation pelvienne, bien que des différences de géométrie pelvienne soient notées entre les deux groupes de sujets SIA. Les SIA modérées ont un pelvis gauche moins profond que les SIA sévères et les sujets témoins, tandis que les SIA sévères ont un pelvis droit plus large d’environ 1,5 cm que celui des SIA modérées. Un coefficient de corrélation de -0,54 associe une rotation pelvienne droite à l’augmentation de la largeur de la crête iliaque. Au niveau postural, les SIA sévères démontrent des inclinaisons latérales et antérieures du tronc ainsi qu’une rotation axiale du haut du corps plus marquées que les SIA modérées. Les corrélations entre les paramètres posturaux, l’angle de Cobb et la morphologie pelvienne indiquent que l’attitude posturale est associée à la distorsion pelvienne dans tous les plans anatomiques, tandis qu’elle ne l’est que dans les plans sagittal et horizontal à l’angle de Cobb. Les différences retrouvées entre les deux groupes SIA concernant les troubles d’équilibre résultent en une augmentation de l’amplitude et de la vitesse du COPML. Une régression multiple de 0,896 est observée par l’emploi des paramètres pelviens, posturaux et d’équilibre, bien que ceux se rapportant à la distorsion pelvienne soient les mieux corrélés à l’angle de Cobb. Cette thèse permet de distinguer la morphologie pelvienne de sujets SIA sévères des modérées, soulignant la détection d’une anomalie de croissance avant que l’angle de Cobb ne soit élevé. Bien que les indices de croissance pelvienne soient davantage corrélés à ce dernier, c’est en considérant globalement la morphologie pelvienne, la posture et l’équilibre qu’une détermination précise de la sévérité d’une scoliose est réalisée. La mise en évidence de tels facteurs de prédiction de la SIA peut faciliter le pronostic d’une courbure. / The effect of adolescent idiopathic scoliosis (AIS) on pelvis morphology, body posture and standing balance in young girls has been studied many times. However, only few studies have distinguished the effect associated with moderate AIS from a severe one. Moreover, no one ever assessed within one investigation pelvis orientation and distortions, postural asymmetry and standing imbalance in AIS subjects. This would help understanding the evolution of the disease and to shed light on risk factors that would facilitate the prognostic. The aim of this thesis is to identify biomechanical factors related to bone growth, posture and balance which can distinguish a moderate AIS from a severe one. The 3D coordinates position of 14 body landmarks taken on 46 young girls with right AIS (moderate and severe) curvature and 28 control subjects is captured to quantify pelvis morphology and body posture. An upright standing is recorded during 64 s on a force plate to assess standing balance. From these data, the following parameters are calculated: orientation angle in all 3 planes for pelvis and trunk; distances between S1 and iliac crest to evaluate pelvis distortion; mean position, range and velocity of the center of pressure (COP) in mediolateral (ML) and anteroposterior axis and mean and range of the free moment. Differences between groups (control, AIS moderate and AIS severe) are tested by ANOVA and relationship between Cobb angle and pelvis, postural and balance parameters are calculated by correlation coefficients. Multiple regressions expressing Cobb angle by pelvis, postural and balance parameters are also carried out to determine which class of parameters is able to predict more effectively the Cobb angle’s curvature. No significant ANOVA is found for pelvis orientation, even though differences in pelvis geometry are noticed between the two groups of AIS subjects. Moderate AIS have a left pelvis with a depth less than severe AIS, whereas AIS severe have a larger right pelvis of 1,5 cm than moderate AIS. A correlation coefficient of -0,54 relates a right pelvis rotation to an increase in iliac crest’s width. About postural asymmetries, severe AIS shows lateral and anterior trunk bending and an axial rotation in the upper level of the trunk that are more pronounced compared to moderate AIS. Correlations between postural parameters, Cobb angle and pelvis morphology indicate a relationship between posture and pelvis distortion in all three planes, but only in the sagittal and horizontal plane between posture and Cobb angle. Differences in standing balance between the two groups of AIS show an increase in COPML range and velocity. A multiple regression of 0,896 is found for the Cobb angle using pelvis, postural and balance parameters. Parameters related to pelvis distortion correlate the most with Cobb angle (0,70). This thesis was able to differentiate severe AIS pelvis morphology from those of the moderate one. Pelvis morphology allows detecting a growth abnormality before the Cobb angle becomes high. Even if pelvis growth is more correlated to the Cobb angle, considering globally pelvis morphology, posture and standing balance will allow determining precisely the severity of AIS. Shedding light on such factors during the evolution of the disease helps an AIS curvature prognosis.