Assessment of Activity Pacing in Relation to Physical Activity and Health-Related Quality of Life in Adults with Multiple Sclerosis

Background: Activity pacing is a behavioral strategy for coping with fatigue, optimizing physical activity (PA) levels, and achieving a paced approach to lifestyle and sustainable self-regulated exercise practice to optimize health and well-being. Yet little is known about how activity pacing affects PA and health-related quality of life (HRQOL) while controlling for fatigue and demographic characteristics over time in adults with multiple sclerosis (MS). This study examined the natural use of activity pacing and how it is associated with PA and HRQOL over time in adults with MS. Methods: Sixty-eight adults with MS (mean ± SD age, 45.2 ± 10.9 years) completed questionnaires on their activity pacing, fatigue, PA, and HRQOL 14, 33, and 52 weeks after rehabilitation. Associations between the variables were examined using multilevel models. Results: No associations were found between activity pacing and PA (β = -0.01, P = .89) or between activity pacing and HRQOL (β = -0.15, P = .09). Conclusions: This study provides an initial understanding of how activity pacing relates to PA and HRQOL in people with MS over time and indicates that there is no clear strategy among adults with MS that is successful in improving PA and HRQOL in the short or long term. Persons with MS may benefit from goal-directed activity pacing interventions to improve longitudinal engagement in PA, and the present study provides a foundation for further intervention development

Test-retest reliability and concurrent validity of the Adapted Short QUestionnaire to ASsess Health-enhancing physical activity (Adapted-SQUASH) in adults with disabilities

The current study determined the test-retest reliability and concurrent validity of the Adapted Short QUestionnaire to ASsess Health-enhancing physical activity (Adapted-SQUASH) in adults with disabilities. Before filling in the Adapted-SQUASH twice with a recall period of 2 weeks, participants wore the Actiheart activity monitor up to 1 week. For the test-retest reliability (N = 68), Intraclass correlation coefficients (ICCs) were 0.67 (p <0.001) for the total activity score (min x intensity/week) and 0.76 (p <0.001) for the total minutes of activity (min/week). For the concurrent validity (N = 58), the Spearman correlation coefficient was 0.40 (p = 0.002) between the total activity score of the first administration of the Adapted-SQUASH and activity energy expenditure from the Actiheart (kcals kg min ). The ICC was 0.22 (p = 0.027) between the total minutes of activity assessed with the first administration of the Adapted-SQUASH and Actiheart. The Adapted-SQUASH is an acceptable measure to assess self-reported physical activity in large populations of adults with disabilities but is not applicable at the individual level due to wide limits of agreement. Self-reported physical activity assessed with the Adapted-SQUASH does not accurately represent physical activity assessed with the Actiheart in adults with disabilities, as indicated with a systematic bias between both instruments in the Bland-Altman analysis

Load on the upper extremity in manual wheelchair propulsion

To study joint contributions in manual wheelchair propulsion, we developed a three-dimensional model of the upper extremity. The model was applied to data collected in an experiment on a wheelchair ergometer in which mechanical advantage (MA) was manipulated. Five male able-bodied subjects performed two wheelchair exercise tests (external power output Pext = 0.25-0.50 W · kg-1) against increasing speeds (1.11-1.39-1.67 m.s-1), which simulated MA of 0.58-0.87. Results indicated a decrease in mechanical efficiency (ME) with increasing MA that could not be related to applied forces or joint torques. Increase in Pext was related to increases in joint torques. On the average, the highest torques were noted in shoulder flexion and adduction (35.6 and 24.6 N · m at MA = 0.58 and Pext= 0.50 W · kg-1). Peak elbow extension and flexion torques were -10.6 and 8.5 N · m. Based on the combination of torques and electromyographic (EMG) records of upper extremity muscles, anterior deltoid and pectoralis muscles are considered the prime movers in manual wheelchair propulsion. Coordinative aspects of manual wheelchair propulsion concerning the function of (biarticular) muscles in directing the propulsive forces and the redistribution of joint torques in a closed chain are discussed. We found no conclusive evidence for the role of elbow extensors in direction of propulsive forces

Physiological responses during hubcrank and handrim wheelchair propulsion:A pilot study

The purpose of this pilot study was to investigate the differences in physiological responses during manual wheelchair propulsion with a hubcrank driven and a handrim driven track wheelchair. Because of the low mechanical efficiency of a handrim driven wheelchair, it is appropriate to look for a more efficient propulsion mechanism. A newly designed hubcrank mechanism (Alpha Kinetics(} which is fixed onto the hub of each rear wheel of a sports (track) wheelchair was compared with a similar radius handrim mechanism, mounted to the same sports wheelchair. Seven male wheelchair sportsmen performed two submaximal wheelchair exercise tests on a motor driven treadmill, once with the hubcrank and once with the handrim propulsion mechanism. Each test consisted of 2 protocols. In the first protocol (I), the velocity increased every third minute, ranging from .83 m.s-1 up to 4.17 m.s-1. The inclination angle of the treadmill was kept constant at 1%. Subsequently, in the second protocol (II) the velocity of the belt of the treadmill was kept constant at 3.33 m.s-1 and the inclination angle increased to 2% and 3%, respectively. Only three subjects were able to complete both protocols. Statistical evaluation was therefore performed on a limited number of subjects for both protocols, while excluding also the final slope condition of 3% in protocol II. Concerning the speed-related protocol I (N = 5 subjects) only heart rate (HR) was significantly lower under the hubcrank condition, although there were clear trends for the other physiological parameters (oxygen uptake (V̇O2), energy cost (Ėn) and mechanical efficiency (ME)), with the exception of respiratory exchange ratio (RER) and power output (Po). In the slope-related protocol II only 4 subjects were able to perform at 2% slope and thus the inclination angle of 3% was omitted from further analysis. As a result of an increasing slope V̇O2, Ėn, and HR were significantly lower and ME was significantly higher under the hubcrank condition (P < .05). The hubcrank does seem to be more efficient both at increasing speed as well as slope. A major advantage of the hubcrank may be a more natural orientation of the hand and wrist and the use of both flexors and extensor muscles during a complete cyclic motion. Some subjects had problems negotiating the hubcrank propelled wheelchair on the treadmill. Further study must substantiate possible physiological and biomechanical advantages for this propulsion mechanism. Focus should be on experiments which: (1) exclude training effects on any one of the tested propulsion mechanisms (non-wheelchair users), (2) exclude the directional and steering problems of the wheelchair-user combination (a roller-based ergometer will prevent this problem), (3) study the role of different lower arm muscles, the characteristics of force generation and the kinametics of hand and wrist. However, the practical problems in terms of braking, steering, negotiating a door opening or other obstacles, and the possible advantages of different gear ratios must be considered with respect to the technical characteristics of the hubcrank design

Physiological responses during hubcrank and handrim wheelchair propulsion: A pilot study

The purpose of this pilot study was to investigate the differences in physiological responses during manual wheelchair propulsion with a hubcrank driven and a handrim driven track wheelchair. Because of the low mechanical efficiency of a handrim driven wheelchair, it is appropriate to look for a more efficient propulsion mechanism. A newly designed hubcrank mechanism (Alpha Kinetics(} which is fixed onto the hub of each rear wheel of a sports (track) wheelchair was compared with a similar radius handrim mechanism, mounted to the same sports wheelchair. Seven male wheelchair sportsmen performed two submaximal wheelchair exercise tests on a motor driven treadmill, once with the hubcrank and once with the handrim propulsion mechanism. Each test consisted of 2 protocols. In the first protocol (I), the velocity increased every third minute, ranging from .83 m.s-1 up to 4.17 m.s-1. The inclination angle of the treadmill was kept constant at 1%. Subsequently, in the second protocol (II) the velocity of the belt of the treadmill was kept constant at 3.33 m.s-1 and the inclination angle increased to 2% and 3%, respectively. Only three subjects were able to complete both protocols. Statistical evaluation was therefore performed on a limited number of subjects for both protocols, while excluding also the final slope condition of 3% in protocol II. Concerning the speed-related protocol I (N = 5 subjects) only heart rate (HR) was significantly lower under the hubcrank condition, although there were clear trends for the other physiological parameters (oxygen uptake (V̇O2), energy cost (Ėn) and mechanical efficiency (ME)), with the exception of respiratory exchange ratio (RER) and power output (Po). In the slope-related protocol II only 4 subjects were able to perform at 2% slope and thus the inclination angle of 3% was omitted from further analysis. As a result of an increasing slope V̇O2, Ėn, and HR were significantly lower and ME was significantly higher under the hubcrank condition (P < .05). The hubcrank does seem to be more efficient both at increasing speed as well as slope. A major advantage of the hubcrank may be a more natural orientation of the hand and wrist and the use of both flexors and extensor muscles during a complete cyclic motion. Some subjects had problems negotiating the hubcrank propelled wheelchair on the treadmill. Further study must substantiate possible physiological and biomechanical advantages for this propulsion mechanism. Focus should be on experiments which: (1) exclude training effects on any one of the tested propulsion mechanisms (non-wheelchair users), (2) exclude the directional and steering problems of the wheelchair-user combination (a roller-based ergometer will prevent this problem), (3) study the role of different lower arm muscles, the characteristics of force generation and the kinametics of hand and wrist. However, the practical problems in terms of braking, steering, negotiating a door opening or other obstacles, and the possible advantages of different gear ratios must be considered with respect to the technical characteristics of the hubcrank design

Geometry parameters for musculoskeletal modelling of the shoulder system

A dynamical finite-element model of the shoulder mechanism consisting of thorax, clavicula, scapula and humerus is outlined. The parameters needed for the model are obtained in a cadaver experiment consisting of both shoulders of seven cadavers. In this paper, in particular, the derivation of geometry parameters from the measurement data is described. The results for one cadaver are presented as a typical example. Morphological structures are modelled as geometrical forms. Parameters describing this form are estimated from 3-D position coordinates of a large number of datapoints on the morphological structure, using a least-squares criterion. Muscle and ligament attachments are represented as a plane or as a (curved) line. Muscle paths are determined by a geometrical form of the bony contour around which the muscle is wrapped. Muscle architecture is determined by the distribution of muscle bundles over the attachment area, mapping the distribution of the origin to the insertion. Joint rotation centers are derived from articular surfaces. Hence, muscle moment arms can be calculated. The result of this study is a set of parameters for each cadaver, describing very precisely the geometry of the shoulder mechanism. This set allows positioning of muscle force vectors a posteriori, and recalculation of position coordinates and moment arms for any position of the shoulder

Inertia and muscle contraction parameters for musculoskeletal modelling of the shoulder mechanism

To develop a musculoskeletal model of the shoulder mechanism, both shoulders of seven cadavers were measured to obtain a complete set of parameters. Using anthropometric measurements, the mass and rotational inertia of segments were estimated, followed by three-dimensional measurements of all morphological structures relevant for modelling, i.e. muscle origins and insertions, muscle bundle directions, ligament attachments and articular surfaces; all in relation to selected bony landmarks. Subsequently, muscle contraction parameters as muscle mass and physiological cross-sectional area were measured. The method of data collection and the results for inertia and muscle contraction parameters as prerequisites for modelling are described