Dans les domaines de la réhabilitation, des sciences du sport et de l'ergonomie, l'évaluation des capacités de génération de force (CGF) peut aider à mieux comprendre les capacités motrices humaines. Le but de cette thèse a été d'évaluer les CGF du membre supérieur prédites au moyen de deux types de formalismes. Le premier provient du domaine de la robotique et a été utilisé pour déterminer l'ellipsoïde de force normalisé (EFN) et biomécanique (EFB), le polytope de force normalisé (PFN) et biomécanique (PFB). Pour une posture, ils sont calculés à partir d’un modèle polyarticulé du membre supérieur et de données sur les couples articulaires isométriques maximaux. Le second type fait appel à un modèle musculosquelettique afin de modéliser les CGF sous la forme d’un polytope de forces (PFMS). Tous ces modèles ont été comparés à un polytope de forces mesurées (PFM). Pour le construire, les forces maximales isométriques exercées par le membre supérieur au niveau de la main ont été évaluées dans vingt-six directions différentes. Enfin, le PFMS a été appliqué dans le cadre de la propulsion en fauteuil roulant afin de caractériser l'application des forces lors de cette tâche et un nouvel indice d’évaluation de la performance postural (IPP) a été proposé. / In fields like rehabilitation, sports sciences and ergonomics, the evaluation of the force feasible set (FFS) of the human limbs may help to better understand the human motor abilities. The aim of this thesis was to compare the upper-limb force capacity at the hand predicted by two different kinds of FFS formalism. The first one originating from the robotics field was used to compute the force ellipsoid (FE), scaled force ellipsoid (SFE), force polytope (FP) and scaled force polytope (SFP). For one posture, they are computed from the upper-limb model and hypotheses and data on maximum isometric joint torques. The second one permitted to compute the FFS modeled as a force polytope from a musculoskeletal model (MSFP). All the previously mentioned models were compared with a measured force polytope (MFP). To construct it, the maximum isometric forces exerted at the hand were assessed in twenty-six directions of the Cartesian space. Then, the MSFP was applied to the manual wheelchair propulsion in order to characterize the forces applied on the handrim during this task and a new evaluation index of postural performance (IPP) was also introduced.

The high demands of manual wheelchair propulsion put users at risk of additional pain and injury that can lead to further reductions in independence and quality of life. Seat position is an adjustable parameter that has been shown to influence propulsion biomechanics. As a result, a number of studies have attempted to optimize this position. However, due to complexities in quantifying upper extremity demand, seat position guidelines are often based on studies aimed at reducing indirect quantities (e.g., cadence, handrim forces, joint ranges of motion and muscle excitation levels) rather than more direct measures of demand (e.g., muscle stress and metabolic cost). Forward dynamics simulations provide an alternative approach to systematically investigate the influence of seat position on more direct measures of upper extremity demand. The objective of this study was to generate and analyze a set of forward dynamics simulations of wheelchair propulsion across the range of attainable seat positions to identify the optimal seat position that minimizes upper extremity demand (i.e., muscle stress, metabolic cost and muscle antagonism). The optimization results showed both metabolic cost and muscle stresses were near minimal values at superior/inferior positions corresponding to top dead center elbow angles between 110 and 120 degrees while at an anterior/posterior position with a hub-shoulder angle between 10 and 2.5 degrees. These minimal values coincided with a reduction in the level of antagonistic muscle activity, primarily at the glenohumeral joint. Seat positions that deviated from these minimal values increased the level of co-contraction required to maintain a stable, smooth propulsive stroke, and consequentially increased upper extremity demand. These results can provide guidelines for positioning the seat to help reduce upper extremity overuse injuries and pain, and thus improve the overall quality of life for wheelchair users. / text

The purpose of this dissertation was to analyze shoulder joint kinematics and electromyographic activities of wheelchair propulsion between two stroke patterns. Twenty physical therapy students (14 females and 6 males, age 27.4 ± 5.9 years, body mass 64.41 ± 9.37 Kg and body height 169.32 ± 9.12 cm) participated. Eleven reflective markers were placed on thorax and right scapula, humerus, third metacarpophalangeal joint and wheelchair axle. Surface electrodes were placed on right pectoralis major, anterior and posterior deltoids, infraspinatus, middle trapezius, biceps brachialis long head and triceps brachialis. Participants propelled a standard wheelchair on a stationary roller system at 0.9 m/s and 1.8 m/s with semicircular (SC) and single loop (SL) stroke patterns for 20 seconds. Three-dimensional body movement and muscle activities were recorded at 100 and 1000 Hz, respectively. All data were compared for differences between two patterns and two speeds using 2-way repeated measures ANOVA (α < .05). Results showed longer drive phase and shorter recovery phase in SC when compared to SL, with no difference found on cycle time. Smaller release angles in SC caused longer angle ranges of hand contact on the pushrim while initial contact angles did not change. During drive phase, smaller scapular protraction range of motion (ROM) was found in SC. Shoulder abduction in drive phase was larger in terms of the maximal angle and ROM. In the recovery phase, minimal scapular tilting, protraction, and shoulder abduction and internal rotation were larger in SC when compared to SL pattern. Shoulder linear velocities and accelerations were higher in both phases for abduction/adduction and flexion/extension in SC. For SC pattern, pectorals major and middle trapezius showed lower activities during drive phase while posterior deltoid and triceps showed higher activities during both phases when compared to SL. Although posterior deltoid and triceps muscles work harder in SC pattern, longer drive phase and lower muscle activities in pectorals major and middle trapezius during the drive phase may make SC the better stroke pattern in wheelchair propulsion when compared to SL.

Wheelchair propulsion is an important part of daily living for many people with spinal cord injuries (SCI's). The aim of this project was to establish the validity of using a new approach for measuring wheelchair propulsion ability. The variation in methods observed by subject's hands in contacting and propelling their wheelchair, namely, using the push rims only; wedging the hands between push rims and tyre and grasping both push rims and tyres, highlighted that earlier studies using instrumented push rims (including the SMART ) for people with tetraplegia would not provide a true indication of propulsion ability for the participants in this study. As a result, a new inertia dynamometer was built and calibrated for measuring wheelchair propulsion ability. Kinetic and kinematic models were developed to calculate wheelchair propulsion parameters such as power output, wheelchair velocity and arm motion patterns. After testing 22 subjects with different SCI levels, the results indicated that arm function was a more important factor in wheelchair propulsion, in terms of power output, than trunk stability and strength. More importantly, people with C5/C6 tetraplegia had a significantly reduced capability in terms of wheelchair propulsion compared with other subjects with a lower lesion (T1-T8, T9-T12 and L1-S5). A further study for quantifying the contribution of triceps function on improving wheelchair propulsion for people with tetraplegia was performed by comparing kinetic and kinematics parameters in C5/C6 tetraplegia subjects. Depending on the control of elbow extension, the subjects were divided into groups with: no active elbow extension, deltoid to triceps transfer surgery (TROIDS) to provide elbow extension, and incomplete C5/C6 tetraplegia with retained active triceps function providing elbow extension. The results demonstrated that the restoration of triceps following TROIDS surgery not only allows active elbow extension, but also increased the amplitude and strength as well as the speed of arm movement. Finally, the results also point to TROIDS allowing a more pronounced and natural push phase and an improved arm movement pattern during both propulsion and recovery phase under normal and extreme conditions.

Following a spinal cord injury (SCI), participation in regular exercise can enhance physical capacity and performance in activities of daily living. With this in mind, the use of subjective ratings of perceived exertion (RPE) may provide an easy-to-administer alternative to traditional methods of regulating exercise intensity (e.g. heart rate and power output (PO)). A physically active lifestyle is also associated with a reduced risk of cardiovascular disease, in part because exercise exerts anti-inflammatory effects. Examining the plasma response of inflammation-mediating chemical messengers, known as cytokines, to traditional and novel exercise modalities may help maximise the anti-inflammatory potential of regular exercise. Participants with a cervical level SCI successfully self-regulated a 20 min bout of moderate intensity wheelchair propulsion (Chapter three). No differences in physiological or PO responses were observed during the imposed-intensity and self-regulated wheelchair propulsion in the trained population group. In a non-SCI group of novice wheelchair-users, a differentiated RPE specific to the exercising muscle mass (RPEP) was the dominant perceptual signal during submaximal wheelchair propulsion (Chapter four). The novice group successfully self-regulated a 12 min bout of moderate intensity wheelchair propulsion, comprising of a discontinuous 3 x 4 min protocol, using differentiated RPEP. In contrast, a more accurate self-regulation of light intensity wheelchair propulsion was observed when employing traditional overall RPE compared to RPEP. Following strenuous wheelchair propulsion, plasma concentrations of the inflammation-mediating cytokine interleukin-6 (IL-6) were significantly elevated in non-SCI and thoracic level SCI participants (Chapter five). Impaired sympathetic nervous system (SNS) function was associated with a reduced IL-6 response in participants with a cervical level SCI. The plasma IL-6 response to 30 min moderate intensity (60% VO2peak) arm-crank ergometry (ACE) was associated with an elevation in the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1ra) independent of SNS activation (Chapter six). Light intensity ACE resulted in a small, significant plasma IL-6 response but no IL-1ra response. The addition of functional electrical stimulation-evoked lower-limb cycling to concurrent hand cycling, termed hybrid exercise, resulted in a greater plasma IL-6 response compared to moderate intensity hand cycling alone in participants with a thoracic level SCI (Chapter seven).

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The increased participation in elite wheelchair sport has provided the need to investigate the physiological requirements of wheelchair sporting competition and daily wheelchair propulsion. However, from a nutritional perspective, guidelines that have been established from the able-bodied population tend to be used by the practitioners working in disability sport and it is not known whether this information is directly transferable to the wheelchair athlete. Wheelchair sport is complex and athletes differ with respect to their sports classification based on factors relating to disability and functional capacity. Therefore, if nutritional guidance is required to optimise performance then information regarding energy expenditure (EE) in the wheelchair sports population becomes important for specific feedback. The aim of this thesis was to investigate EE in wheelchair athletes. The results from Chapter 3 found resting energy expenditure (REE) in tetraplegic athletes to be lower than that calculated using predictive equations derived from an ablebodied cohort. However, paraplegic athletes showed comparable values to those which were predicted, suggesting these equations may be of use in paraplegic athletes. Chapter 4 extended this work and found similarities in the REE of the two aforementioned cohorts. This could have been due to the similarities that were found in their total-body fat free mass (FFM). The results from Chapter 5 showed EE reduced after both a short 36 minute exposure of wheelchair propulsion and after 3 weeks of wheelchair propulsion practice in novice wheelchair users. Temporal parameters improved after the practice period, suggesting there is an association between EE and propulsion technique. Chapter 6 extended these findings with results confirming that experienced wheelchair users expended significantly less energy during wheelchair propulsion than novice individuals who had up to 3 weeks practice. It is clear that EE of daily wheelchair ambulation should not be a generic value and different levels of experience must be considered so that the nutritional needs can be tailored accordingly. Chapters 7 and 8 examined the physiological demands of elite competitive wheelchair basketball players in relation to the International Wheelchair Basketball Federation (IWBF) classification categories and identified differences in the physiological demands and physiological fitness of wheelchair basketball and tennis players. These results found that IWBF Class 3 - 4.5 (high point) players expended more energy per hour during competition than those with a lower classification (IWBF Class 1 - 2.5). However, when actual playing time was considered the low classification group showed a similar EE to the higher classification group. Furthermore, wheelchair basketball players had a higher EE per hour than wheelchair tennis players during elite competition. However, the wheelchair tennis players spent a significantly longer duration on court resulting in similar EE during a typical competition within each sport. This suggests nutritional advice should be tailored both to the duration of competitive play (where EE may be similar between sports (basketball vs. tennis)); and to training (where athletes with a higher functional capacity may have higher EE). This thesis revealed several important physiological considerations to appreciate when investigating the EE of wheelchair sportsmen and women. Findings would suggest that type of disability, wheelchair propulsion experience and sport classification are all important considerations for the accurate assessment of EE in this cohort of athletes.

Most manual wheelchair users will experience upper extremity injury and pain during their lifetime, which can be partly attributed to the high load requirements, repetitive motions and extreme joint postures required during wheelchair propulsion. Recent efforts have attempted to determine how different propulsion techniques influence upper extremity demand using broad measures of demand (e.g., metabolic cost). However studies using more specific measures (e.g., muscle stress), have greater potential to determine how altering propulsion technique influences demand. The goal of this research was to use a musculoskeletal model with forward dynamics simulations of wheelchair propulsion to determine how altering propulsion technique influences muscle demand. Three studies were performed to achieve this goal. In the first study, a wheelchair propulsion simulation was used with a segment power analysis to identify muscle functional roles. The analysis showed that muscles contributed to either the push (i.e. delivering handrim power) or recovery (i.e. repositioning the hand) subtasks, with the transition period between the subtasks requiring high muscle co-contraction. The high co-contraction suggests that future studies focused on altering transition period biomechanics may have the greatest potential to reduce upper extremity demand. The second study investigated how changing the fraction effective force (i.e. the ratio of the tangential to total handrim force, FEF) influenced muscle demand. Simulations maximizing and minimizing FEF both had higher muscle work and stress relative to the nominal simulation. Therefore, the optimal FEF value appears to balance increasing FEF with minimizing upper extremity demand and care should be taken when using FEF to reduce demand. In the third study, simulations of biofeedback trials were used to determine the influence of cadence, push angle and peak handrim force on muscle demand. Although minimizing peak force had the lowest total muscle stress, individual stresses of many muscles were >20% and the simulation had the highest cadence, suggesting that this variable may not reduce demand. Instead minimizing cadence may be most effective, which had the lowest total muscle work and slowest cadence. These results have important implications for designing effective rehabilitation strategies that can reduce upper extremity injury and pain among manual wheelchair users. / text

Spinal Cord Injuries (SCIs) are debilitating injuries where damage to the spinal cord causes a loss of mobility and feeling in muscles innervated below the injury point. Tetraplegia refers to an SCI in the cervical region of the spinal cord that impacts on the functionality of all four limbs. ‘Complete’ tetraplegia results in complete paralysis of the legs, partial or complete paralysis of the arms and trunk, and in the most severe cases, the neck. The independence of people living with tetraplegia is heavily dependent on assistive and mobility devices. Understanding the strength characteristics of people with tetraplegia is crucially important for the suitable and effective design of mobility and rehabilitative devices such as wheelchairs. A study using a stationary dynamometer and video capture measured kinetic and kinematic characteristics of wheelchair propulsion for 15 subjects with C5-C7 tetraplegia. This study differentiated between subjects with different injuries, at two different test resistances, and was more comprehensive than other reported studies on MWC propulsion. Some of the subjects in the study with C5-C6 injuries had no elbow extension capability, while others had undergone a deltoids-to-triceps tendon transfer procedure called TROIDS, which restores some elbow extension capability. No differences were found in any of the push phase metrics between those who had undergone the TROIDs procedure, and those who had not, suggesting that TROIDs provides no significant benefit for mobility. As expected, subjects with C7 tetraplegia recorded velocity and power outputs significantly higher than those for subjects with C5-C6 tetraplegia. To better understand the strength characteristics over the full range of motion in the sagittal plane, and thus potentially modify the design of mobility devices to better suit these characteristics, a novel method for gathering strength data in multiple directions and positions was developed. This method had advantages over other commonly used methods. In particular, it was inclusive of complex muscle and joint interactions that would otherwise be very difficult to build into a model. Sagittal horizontal push strength was measured using this method for 8 able bodied and 4 tetraplegic subjects. There were clear trends in the data from the able-bodied subjects, and a fourth order polynomial (R-squared = 0.8) was fitted to the data for modelling purposes. Data for the tetraplegic subjects varied significantly from the able-bodied data, but inter-individual variation was such that no model would provide a satisfactory fit to the data indicating a very high degree of patient-specific behaviour. One multi-directional data set, consisting 1584 measurements in the sagittal plane, was gathered for an able-bodied subject. The main trends in this measured data were successfully captured by a model consisting of twelve fourth-order polynomials. Building on these measurements, and employing a human model in the constraint modelling environment, SWORDS, this thesis develops a conceptual design tool for comparing the effectiveness of different hand force paths. Initial simulations using hypothetical hand paths indicated that the proposed method for predicting the direction of the applied force needs to be verified, and likely refined, for hand paths that differ significantly from the traditional wheelchair push-rim path. This proposed procedure has the potential to be a powerful tool for optimising and modifying the design of wheelchairs or human powered devices to utilise previously untapped abilities for any given population.

The wheelchair tennis evidence base has developed considerably in recent years. For those with a spinal cord injury (SCI), or severe physical impairment, tennis participation represents an opportunity for skill and motor development, and potential for disease risk reduction (Abel et al., 2008). However, as a complex series of technical, tactical and physical elements are implicated, participation for novice, developmental or low-skill players can be challenging. Hence, extension of the evidence base to consider the responses of such groups during play is of considerable value. Initial experimental studies in this thesis investigated the validity, reliability and applicability of instrumentation for the assessment of wheelchair tennis court-movement. Comparisons were made between a global positioning system (GPS) and the data logger (DL) device (Study 1). GPS underestimated criterion distance in tennis-specific drills and reported lower match-play values than the DL. In contrast, DL placed on the outside wheel offered an accurate representation of distance. However, underestimations for DL were revealed at speeds > 2.50 m·s-1 during treadmill testing. Consequently, Study 2 extended this work with consideration of DL applicability for wheelchair tennis match-play. Examination of speed profiles revealed that time spent below the threshold for accuracy was trivial, confirming DL applicability for court-movement assessment. Further between-group comparisons for rank [highly-ranked (HIGH), low-ranked (LOW)], sex (male, female) and format (singles, doubles) revealed that LOW were stationary for longer than HIGH and spent more time at low propulsion speeds. Time in higher speed zones was greatest for HIGH and doubles players. Between-group differences (rank) were further scrutinised in Study 3 with attention paid to describing the physiological response of competitive match-play aligned to court-movement. Set outcome (result) was also examined. Independent of result, HIGH covered greater overall, forwards, reverse and forwards-to-reverse distances than LOW. Interestingly, HIGH winners covered greater distances than HIGH losers and had a higher mean average and minimum heart rate (HR) than LOW winners. In contrast, LOW losers had a higher mean average and mean minimum HR than LOW winners. Collectively, these outcomes suggest an enhanced ability for HIGH to respond to ball movement and the physiological and skill challenges of match-play. While this thesis confirmed that the activity duration and playing intensity is sufficient to confer health-related effects (Study 3), differences identified for rank suggested that strategies to 4 enable performance improvements in LOW were merited. The International Tennis Federation (ITF) has suggested that all starter players should be able to serve, rally and score from their first lesson (ITF, 2007). The reality however, is that chair propulsion whilst holding a racket is complex, and therefore, tennis play is challenging for novice and developmental players. Hence, the remainder of experimental work focused on interventions to enable increased court-movement and development of wheelchair tennis-specific court-mobility for LOW. The ITF have endorsed the use of a low-compression ball (LCB) for novices. An LCB bounces lower and moves more slowly through the air than a standard-compression ball (SCB). Novel findings from Study 4 revealed that greater total and forwards distances, greater average speeds and less time stationary result from use of the LCB. Increased movement activity occurred without associated increases in physiological cost, but was considered advantageous, with players adopting stronger positions for shot-play. Further examination of the linkage between movement and physiological variables were explored in the final experimental investigation (Study 5). A short period of organised practice enabled higher overall and forwards distances, and peak and average speeds to be achieved during match-play, without associated increases in physiological cost. Changes were desirable and represented enhanced court-mobility and mechanical efficiency (ME). Wheelchair tennis players were also more self-confident in tennis-specific chair-mobility, post-practice. The racket was a constraint, with lower distances and speeds, and a lower peak physiological response, achieved during tennis practice completed with a racket. This thesis advocates the use of an LCB and a short period of pre-match court-mobility practice for the novice wheelchair tennis player. Collectively, these interventions are likely to prompt greater court-movement enabling better court-positioning, develop confidence in court-mobility and shot-play, develop competence in racket handling whilst pushing, and enhancing ME. These characteristics are likely to enable participation with the likely inference being that greater competence, skill and self-confidence promotes greater enjoyment and therefore enhances longer-term compliance. This is of considerable practical significance given that tennis typically attracts new players to the game, but is less successful at retaining them (ITF, 2007).