Minimization of metabolic cost of transport predicts changes in gait mechanics over a range of ankle-foot orthosis stiffnesses in individuals with bilateral plantar flexor weakness.

Neuromuscular disorders often lead to ankle plantar flexor muscle weakness, which impairs ankle push-off power and forward propulsion during gait. To improve walking speed and reduce metabolic cost of transport (mCoT), patients with plantar flexor weakness are provided dorsal-leaf spring ankle-foot orthoses (AFOs). It is widely believed that mCoT during gait depends on the AFO stiffness and an optimal AFO stiffness that minimizes mCoT exists. The biomechanics behind why and how an optimal stiffness exists and benefits individuals with plantar flexor weakness are not well understood. We hypothesized that the AFO would reduce the required support moment and, hence, metabolic cost contributions of the ankle plantar flexor and knee extensor muscles during stance, and reduce hip flexor metabolic cost to initiate swing. To test these hypotheses, we generated neuromusculoskeletal simulations to represent gait of an individual with bilateral plantar flexor weakness wearing an AFO with varying stiffness. Predictions were based on the objective of minimizing mCoT, loading rates at impact and head accelerations at each stiffness level, and the motor patterns were determined via dynamic optimization. The predictive gait simulation results were compared to experimental data from subjects with bilateral plantar flexor weakness walking with varying AFO stiffness. Our simulations demonstrated that reductions in mCoT with increasing stiffness were attributed to reductions in quadriceps metabolic cost during midstance. Increases in mCoT above optimum stiffness were attributed to the increasing metabolic cost of both hip flexor and hamstrings muscles. The insights gained from our predictive gait simulations could inform clinicians on the prescription of personalized AFOs. With further model individualization, simulations based on mCoT minimization may sufficiently predict adaptations to an AFO in individuals with plantar flexor weakness.

Fatigue-related gait adaptations in children with cerebral palsy.

AIM: To obtain insights into the effects of fatigue on the kinematics, kinetics, and energy cost of walking (ECoW) in children with cerebral palsy (CP). METHOD: In this prospective observational study, 12 children with CP (mean age 12 years 9 months, SD 2 years 7 months; four females, eight males) and 15 typically developing children (mean age 10 years 8 months, SD 2 years 4 months; seven females, eight males) followed a prolonged intensity-based walking protocol on an instrumented treadmill, combined with gas analysis measurements. The protocol consisted of consecutive stages, including a 6-minute walking exercise (6MW) at comfortable speed, 2 minutes of moderate-intensity walking (MIW) (with a heart rate > 70% of its predicted maximal), and 4 minutes walking after MIW. If necessary, the speed and slope were incremented to reach MIW. Outcomes were evaluated at the beginning and end of the 6MW and after MIW. RESULTS: With prolonged walking, Gait Profile Scores deteriorated slightly for both groups (p < 0.01). Knee flexion increased during early stance (p = 0.004) and ankle dorsiflexion increased during late stance (p = 0.034) in children with CP only. Negligible effects were found for kinetics. No demonstrable change in ECoW was found in either group (p = 0.195). INTERPRETATION: Kinematic deviations in children with CP are progressive with prolonged walking. The large variation in adaptations indicates that an individual approach is recommended to investigate the effects of physical fatigue on gait in clinical practice.

Efficacy of a physical activity programme combining individualized aerobic exercise and coaching to improve physical fitness in neuromuscular diseases (I'M FINE): study protocol of a randomized controlled trial.

BACKGROUND: In individuals with neuromuscular diseases (NMD), symptoms of muscle weakness, fatigue and pain may limit physical activity. Inactivity leads to reduced physical fitness, which further complicates daily life functioning. Due to inconclusive evidence regarding exercise in NMD, the optimal training approach and strategies to preserve an active lifestyle remain to be determined. The physical activity programme I'M FINE, consisting of individualized aerobic exercise to improve physical fitness and coaching to preserve an active lifestyle, was therefore developed. The primary objective of this study will be to evaluate the efficacy of the I'M FINE programme in terms of improved physical fitness in individuals with slowly progressive NMD, compared to usual care. METHODS: A multicentre, assessor-blinded, two armed, randomized controlled trial will be conducted in a sample of 90 individuals with slowly progressive NMD. Participants motivated to improve their reduced physical fitness will be randomized (ratio 1:1) to the I'M FINE intervention or usual care. The I'M FINE intervention consists of a six-month physical activity programme, including individualized home-based aerobic exercise to improve physical fitness (i.e. peak oxygen uptake), and motivational interviewing coaching (e.g. goal setting, self-management) to adopt and preserve an active lifestyle. Measurements will be performed at baseline, post-intervention, and at 12- and 18-months follow-up. The primary outcome is peak oxygen uptake (VO2 peak) directly post intervention. Main secondary outcomes are physical capacity, muscle strength, self-efficacy, daily activity, quality of life and markers of metabolic syndrome. The primary analysis compares change in VO2 peak post-intervention between the intervention and usual care group, with analysis of covariance. DISCUSSION: The I'M FINE study will provide evidence regarding the efficacy of a physical activity intervention on the physical fitness and active lifestyle over the short- and long-term in individuals with slowly progressive NMD. These outcomes could potentially improve the (inter)national guidelines for efficacy of aerobic exercise programmes and provide insight in achieving a more active lifestyle in NMD. TRIAL REGISTRATION: (5/11/2018): Netherlands Trial Register NTR7609 (retrospectively registered), https://www.trialregister.nl/trial/7344. However, the Ethics Review Committee of the Amsterdam Medical Center (AMC) approved the study protocol on 7/11/2017. No adjustments were made to the approved study protocol before the first participant enrolment and registration. Registration was done after the second participant enrolment and the information in the register corresponds one on one with the approved study protocol.

Aerobic exercise in adult neuromuscular rehabilitation: A survey of healthcare professionals.

OBJECTIVE: To evaluate the current application of aerobic exercise in adult neuromuscular rehabilitation. DESIGN: Cross-sectional survey. PARTICIPANTS: Dutch rehabilitation specialists and physical therapists in specialized centres for slowly progressive neuromuscular diseases and in primary care. METHODS: Participants received a self-designed, web-based, questionnaire, including 27 close-ended questions covering 4 categories: respondent profile, application of aerobic exercise, barri-ers to prescribing aerobic exercise, and need for support to improve the application of aerobic exercise. RESULTS: All respondents (n = 52) prescribed aerobic exercise and in a wide variety of neuromuscular diseases, mostly applying sessions of more than 20 min, 2 days per week, over a period of 9-16 weeks, using different exercise modes and methods to target intensity. The majo-rity (81%) agreed that aerobic exercise should be incorporated into neuromuscular rehabilitation. However, all respon-dents perceived barriers to the application of aerobic exercise in one or more domains, and 77% of the respondents indicated needing support to improve application of this type of training, mostly with respect to screening procedures (54%) and dosing of exercise programmes (48%). CONCLUSION: Aerobic exercise is widely applied, yet our results raise awareness of the necessity of more evidence based knowledge, in order to develop and implement guidelines in adult neuromuscular rehabilitation.

Correction: Aerobic Exercise Training in Post-Polio Syndrome: Process Evaluation of a Randomized Controlled Trial.

[This corrects the article DOI: 10.1371/journal.pone.0159280.].

Cognitive behavioural therapy for reducing fatigue in post-polio syndrome and in facioscapulohumeral dystrophy: A comparison.

BACKGROUND: Cognitive behavioural therapy does not reduce fatigue in post-polio syndrome, but is effective in facioscapulohumeral dystrophy. This difference in efficacy might be explained by a different role of cognitions in these conditions. OBJECTIVE: To compare fatigue-related cognitions between patients with post-polio syndrome and facio-scapulohumeral dystrophy. SUBJECTS: Patients with post-polio syndrome (n = 21) and facioscapulohumeral dystrophy (n = 24) allocated to a cognitive behavioural therapy intervention in 2 identical trials. METHODS: Assessed cognitions included: sense of control over fatigue; catastrophizing; acceptance; focusing on fatigue; and perceived social support. Group differences in cognitions (independent t-tests or Mann-Whitney U tests) and group differences in the association of cognitions with fatigue (linear regression models) were studied. RESULTS: No differences in cognitions were found between the 2 groups (p > 0.18). Furthermore, there were no cognition-by-group interaction effects, except for "perceived social support", for which a different association with fatigue was found between the 2 groups (p = 0.01). However, univariate models revealed no associations per group. CONCLUSION: Fatigue-related cognitions in severely fatigued patients with post-polio syndrome are not clearly different from that in facioscapulohumeral dystrophy. Thus, the lack of efficacy of cognitive behavioural therapy in post-polio syndrome cannot be attributed to unique cognitive characteristics of this population.

Aerobic Exercise Training in Post-Polio Syndrome: Process Evaluation of a Randomized Controlled Trial.

OBJECTIVE: To explore reasons for the lack of efficacy of a high intensity aerobic exercise program in post-polio syndrome (PPS) on cardiorespiratory fitness by evaluating adherence to the training program and effects on muscle function. DESIGN: A process evaluation using data from an RCT. PATIENTS: Forty-four severely fatigued individuals with PPS were randomized to exercise therapy (n = 22) or usual care (n = 22). METHODS: Participants in the exercise group were instructed to exercise 3 times weekly for 4 months on a bicycle ergometer (60-70% heart rate reserve). RESULTS: The attendance rate was high (median 89%). None of the participants trained within the target heart rate range during >75% of the designated time. Instead, participants exercised at lower intensities, though still around the anaerobic threshold (AT) most of the time. Muscle function did not improve in the exercise group. CONCLUSION: Our results suggest that severely fatigued individuals with PPS cannot adhere to a high intensity aerobic exercise program on a cycle ergometer. Despite exercise intensities around the AT, lower extremity muscle function nor cardiorespiratory fitness improved. Improving the aerobic capacity in PPS is difficult through exercise primarily focusing on the lower extremities, and may require a more individualized approach, including the use of other large muscle groups instead. TRIAL REGISTRATION: Netherlands National Trial Register NTR1371.

No Reduction of Severe Fatigue in Patients With Postpolio Syndrome by Exercise Therapy or Cognitive Behavioral Therapy: Results of an RCT.

BACKGROUND: People with postpolio syndrome (PPS) commonly experience severe fatigue that persists over time and negatively affects functioning and health-related quality of life (HRQoL). OBJECTIVES: To study the efficacy of exercise therapy (ET) and cognitive behavioral therapy (CBT) on reducing fatigue and improving activities and HRQoL in patients with PPS. METHODS: We conducted a multicenter, single-blinded, randomized controlled trial. Over 4 months, severely fatigued patients with PPS received ET, CBT, or usual care (UC). The primary end point (fatigue) was assessed using the subscale fatigue severity of the Checklist Individual Strength (CIS20-F). Secondary end points included activities and HRQoL, which were assessed with the Sickness Impact Profile and the 36-Item Short-Form, respectively. End points were measured at baseline and at 4, 7, and 10 months. RESULTS: A total of 68 patients were randomized. No differences were observed between the intervention groups and UC group for fatigue (mean differences in CIS20-F score = 1.47, 95%CI = -2.84 to 5.79, for ET versus UC; and 1.87, 95%CI = -2.24 to 5.98, for CBT versus UC), activities, or HRQoL. CONCLUSIONS: Our results demonstrate that neither ET nor CBT were superior to UC in reducing fatigue in severely fatigued PPS patients. Further research should investigate explanations for the lack of efficacy of these 2 currently advised approaches in clinical practice, which may provide clues to improving treatment aimed at reducing fatigue in PPS.

Reliability of contractile properties of the knee extensor muscles in individuals with post-polio syndrome.

OBJECTIVE: To assess the reliability of contractile properties of the knee extensor muscles in 23 individuals with post-polio syndrome (PPS) and 18 age-matched healthy individuals. METHODS: Contractile properties of the knee extensors were assessed from repeated electrically evoked contractions on 2 separate days, with the use of a fixed dynamometer. Reliability was determined for fatigue resistance, rate of torque development (MRTD), and early and late relaxation time (RT50 and RT25), using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM, expressed as % of the mean). RESULTS: In both groups, reliability for fatigue resistance was good, with high ICCs (>0.90) and small SEM values (PPS: 7.1%, healthy individuals: 7.0%). Reliability for contractile speed indices varied, with the best values found for RT50 (ICCs>0.82, SEM values <2.8%). We found no systematic differences between test and retest occasions, except for RT50 in healthy subjects (p = 0.016). CONCLUSIONS: In PPS and healthy individuals, the reliability of fatigue resistance, as obtained from electrically evoked contractions is high. The reliability of contractile speed is only moderate, except for RT50 in PPS, demonstrating high reliability. SIGNIFICANCE: This was the first study to examine the reliability of electrically evoked contractile properties in individuals with PPS. Our results demonstrate its potential to study mechanisms underlying muscle fatigue in PPS and to evaluate changes in contractile properties over time in response to interventions or from natural course.

Measuring fatigue in polio survivors: content comparison and reliability of the Fatigue Severity Scale and the Checklist Individual Strength.

OBJECTIVES: To compare the content of the Fatigue Severity Scale and the subscale "subjective experience of fatigue" of the Checklist Individual Strength, and (ii) to assess the reliability of both questionnaires in polio survivors. DESIGN: Repeated-measures at a 3-week interval. SUBJECTS: Consecutive series of 61 polio survivors. METHODS: Concepts contained in the questionnaire items were linked to the International Classification of Functioning, Disability and Health (ICF), using standardized linking rules. Reliability analyses included tests of internal consistency, test-retest reliability and measurement error. RESULTS: Questionnaires differed in the extent to which they measured other than fatigue-related aspects of functioning (represented ICF components: "Body functions": 50% and 80%, "Activities and Participation": 30% and 0%, for the Fatigue Severity Scale and Checklist Individual Strength, respectively). Internal consistency and test-retest reliability were considered acceptable, while measurement error was large (Cronbach's α: 0.90 and 0.93, intraclass correlation coefficient: 0.80 and 0.85, smallest detectable change: 28.7% and 29.4% for the Fatigue Severity Scale and Checklist Individual Strength, respectively). CONCLUSION: Considering the acceptable clinimetric properties, we conclude that both the Fatigue Severity Scale and the Checklist Individual Strength can be applied in research on post-poliomyelitis syndrome when measuring fatigue. However, because the 2 questionnaires differ in content they cannot be used interchangeably.

Reliability of isometric lower-extremity muscle strength measurements in children with cerebral palsy: implications for measurement design.

BACKGROUND: Children with cerebral palsy (CP) typically show muscle weakness of the lower extremities, which can be measured with the use of handheld dynamometry (HHD). OBJECTIVE: The purposes of this study were: (1) to determine test-retest reliability and measurement error of isometric lower-extremity strength measurements in children with CP with the use of HHD and (2) to assess implications for measurement design. DESIGN: A test-retest design was used. METHODS: Fourteen children with hemiplegic (n=6) or diplegic (n=8) spastic CP (Gross Motor Function Classification System levels I-III), ages 7 to 13 years, were assessed for isometric strength on 2 separate days (occasions) with the use of HHD, with 3 trials per muscle group. The intraclass correlation coefficient, standard error of measurement, and smallest detectable difference (SDD) were calculated for different measurement designs. RESULTS: Intraclass correlation coefficient values of single measurements for all muscle groups ranged from .70 to .90, and the SDD was large (>30%). Regarding measurement error, the largest source of variability was found for occasion. A 2-occasion mean decreased the SDD by 9% to 14%. For trials, a greater improvement in SDD was found when 2 trials were averaged instead of 3. A measurement design of 2 trials-2 occasions was superior to the often-used approach of 3 trials-1 occasion. LIMITATIONS: The small sample size was the major study limitation. CONCLUSIONS: Handheld dynamometry is reliable and can be used to detect changes in isometric muscle strength in children with CP when using the mean of at least 2 trials. To further improve reliability, taking the average of 2 occasions on separate days is recommended, depending on group size and muscle group.