Validity of Cardiopulmonary Exercise Testing for Assessing Aerobic Capacity in Neuromuscular Diseases.

OBJECTIVES: To determine the content validity of cardiopulmonary exercise testing (CPET) for assessing peak oxygen uptake (VO2peak) in neuromuscular diseases (NMD). DESIGN: Baseline assessment of a randomized controlled trial. SETTING: Academic hospital. PARTICIPANTS: Eighty-six adults (age: 58.0±13.9 y) with Charcot-Marie-Tooth disease (n=35), postpolio syndrome (n=26), or other NMD (n=25). INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Workload, gas exchange variables, heart rate, and ratings of perceived exertion were measured during CPET on a cycle ergometer, supervised by an experienced trained assessor. Muscle strength of the knee extensors was assessed isometrically with a fixed dynamometer. Criteria for confirming maximal cardiorespiratory effort during CPET were established during 3 consensus meetings of an expert group. The percentage of participants meeting these criteria was assessed to quantify content validity. RESULTS: The following criteria were established for maximal cardiorespiratory effort: a plateau in oxygen uptake (VO2plateau) as the primary criterion, or 2 of 3 secondary criteria: (1) peak respiratory exchange ratio (RERpeak) ≥1.10 (2), peak heart rate ≥85% of predicted maximal heart rate; and (3) peak rating of perceived exertion (RPEpeak) ≥17 on the 6-20 Borg scale. These criteria were attained by 71 participants (83%). VO2plateau, RERpeak ≥1.10, peak heart rate ≥85%, and RPEpeak ≥17 were attained by 31%, 73%, 69%, and 72% of the participants, respectively. Peak workload, VO2peak, and knee extension muscle strength were significantly higher, and body mass index was lower (all P<.05), in participants with maximal cardiorespiratory effort than other participants. CONCLUSIONS: Most people with NMD achieved maximal cardiorespiratory effort during CPET. This study provides high quality evidence of sufficient content validity of VO2peak as a maximal aerobic capacity measure. Content validity may be lower in more severely affected people with lower physical fitness.

Physical strain of walking in people with neuromuscular diseases is high and relates to step activity in daily life.

OBJECTIVE: To determine the physical strain of walking and assess its relationship with daily steps and intensity of daily activity in people with neuromuscular diseases. DESIGN: Cross-sectional study. SUBJECTS/PATIENTS: Sixty-one adults with neuromuscular diseases. METHODS: Physical strain of walking, defined as oxygen consumption during comfortable walking relative to peak oxygen uptake. Daily step count and daily time spent in moderate and vigorous physical activity were assessed using accelerometry and heart rate measurements, respectively. Regression analyses assessed the relationships between log daily step count and log daily time spent in moderate and vigorous physical activity, and physical strain of walking. RESULTS: The mean (standard deviation) physical strain of walking was 73 (20)% Log daily step count and physical strain were negatively associated (ß = -0.47). No association was found with log daily time spent in moderate and vigorous physical activity. CONCLUSIONS: The highly increased physical strain of comfortable walking indicates that walking is very demanding for people with neuromuscular diseases and is associated with a reduction in daily step activity. The absence of a relationship between intensity of activities and physical strain indicates that, despite a reduction in daily step activity, strenuous daily activities may still be performed.

A Mobile Health App to Support Home-Based Aerobic Exercise in Neuromuscular Diseases: Usability Study.

BACKGROUND: Home-based aerobic exercise in people with neuromuscular diseases (NMDs) has benefits compared to exercise in the hospital or a rehabilitation center because traveling is often cumbersome due to mobility limitations, and societal costs are lower. Barriers to home-based aerobic exercise include reduced possibilities for monitoring and lack of motivation. To overcome these and other barriers, we developed a mobile health app: Keep on training with ReVi (hereafter referred to as ReVi). OBJECTIVE: We aimed to determine the usability of the ReVi app. METHODS: Patients followed a 4-month, polarized, home-based aerobic exercise program on a cycle or rowing ergometer, with 2 low-intensity sessions and 1 high-intensity session per week supported by the ReVi app. The app collected training data, including heart rate and ratings of perceived exertion, provided real-time feedback on reaching target intensity zones, and enabled monitoring via an online dashboard. Physiotherapists instructed patients on how to use the ReVi app and supervised them during their training program. Patients and physiotherapists separately evaluated usability with self-developed questionnaires, including 9 questions on a 5-point Likert scale, covering the usability elements efficiency, effectiveness, and satisfaction. RESULTS: Twenty-nine ambulatory adult patients (n=19 women; mean age 50.4, SD 14.2 years) with 11 different slowly progressive NMDs participated. Both patients and physiotherapists (n=10) reported that the app, in terms of its efficiency, was easy to use and had a rapid learning curve. Sixteen patients (55%) experienced 1 or more technical issue(s) during the course of the exercise program. In the context of effectiveness, 23 patients (81%) indicated that the app motivated them to complete the program and that it helped them to exercise within the target intensity zones. Most patients (n=19, 70%) and physiotherapists (n=6, 60%) were satisfied with the use of the app. The median attendance rate was 88% (IQR 63%-98%), with 76% (IQR 69%-82%) of time spent within the target intensity zones. Four adverse events were reported, 3 of which were resolved without discontinuation of the exercise program. CONCLUSIONS: The usability of the ReVi app was high, despite the technical issues that occurred. Further development of the app to resolve these issues is warranted before broader implementation into clinical practice.

Metabolic load during morning care and active bed exercises in critically ill patients: An explorative study.

BACKGROUND: To avoid overexertion in critically ill patients, information on the physical demand, i.e., metabolic load, of daily care and active exercises is warranted. OBJECTIVE: The objective of this study was toassess the metabolic load during morning care activities and active bed exercises in mechanically ventilated critically ill patients. METHODS: This study incorporated an explorative observational study executed in a university hospital intensive care unit. Oxygen consumption (VO2) was measured in mechanically ventilated (≥48 h) critically ill patients during rest, routine morning care, and active bed exercises. We aimed to describe and compare VO2 in terms of absolute VO2 (mL) defined as the VO2 attributable to the activity and relative VO2 in mL per kilogram bodyweight, per minute (mL/kg/min). Additional outcomes achieved during the activity were perceived exertion, respiratory variables, and the highest VO2 values. Changes in VO2 and activity duration were tested using paired tests. RESULTS: Twenty-one patients were included with a mean (standard deviation) age of 59 y (12). Median (interquartile range [IQR]) durations of morning care and active bed exercises were 26 min (21-29) and 7 min (5-12), respectively. Absolute VO2 of morning care was significantly higher than that of active bed exercises (p = 0,009). Median (IQR) relative VO2 was 2.9 (2.6-3.8) mL/kg/min during rest; 3.1 (2.8-3.7) mL/kg/min during morning care; and 3.2 (2.7-4) mL/kg/min during active bed exercises. The highest VO2 value was 4.9 (4.2-5.7) mL/kg/min during morning care and 3.7 (3.2-5.3) mL/kg/min during active bed exercises. Median (IQR) perceived exertion on the 6-20 Borg scale was 12 (10.3-14.5) during morning care (n = 8) and 13.5 (11-15) during active bed exercises (n = 6). CONCLUSION: Absolute VO2 in mechanically ventilated patients may be higher during morning care than during active bed exercises due to the longer duration of the activity. Intensive care unit clinicians should be aware that daily-care activities may cause intervals of high metabolic load and high ratings of perceived exertion.

Relationship Between Heart Rate and Perceived Exertion in Neuromuscular Diseases: How do Laboratory-Based Exercise Testing Results Translate to Home-Based Aerobic Training Sessions?

OBJECTIVE: To examine the heart rate-perceived exertion relationship between maximal exercise testing and home-based aerobic training in neuromuscular diseases. DESIGN: Multicentre randomized controlled trial, intervention group data. PARTICIPANTS: Individuals with Charcot-Marie-Tooth disease (n = 17), post-polio syndrome (n = 7) or other neuromuscular diseases (n = 6). METHODS: Participants followed a 4-month, homebased aerobic training programme guided by heart rate. Heart rate and ratings of perceived exertion (6-20 Borg Scale) were assessed for each minute during a maximal exercise test, and at the end of each exercise interval and recovery period during training. Heart rate and corresponding ratings of perceived exertion values of individual participants during training were visualized using plots, together with the exercise testing linear regression line between heart rate and ratings of perceived exertion. RESULTS: High correlation coefficients (i.e. > 0.70) were found between heart rate and ratings of perceived exertion, in all participants during testing (n = 30), and in 57% of the participants during training. Based on the plots the following distribution was found; participants reporting lower (n = 12), similar (n = 10), or higher (n = 8) ratings of perceived exertion values for corresponding heart rates during training compared with testing. CONCLUSION: Most participants had a different perception of effort for corresponding heart rates during training in comparison with exercise testing. Healthcare professionals should be aware that this may imply under- and over-training.

Efficacy of aerobic exercise on aerobic capacity in slowly progressive neuromuscular diseases: A systematic review and meta-analysis.

BACKGROUND: Aerobic exercise aims to improve aerobic capacity. OBJECTIVE: To summarize the evidence on the efficacy of aerobic exercise on aerobic capacity in slowly progressive neuromuscular diseases (NMDs). METHODS: We searched the electronic databases MEDLINE, EMBASE, SPORTDiscus and Web of Science Conference Proceedings Index for articles published up to June 17, 2021, selecting randomized controlled trials that included adults with slowly progressive NMDs and compared aerobic exercise to no aerobic exercise. The primary outcome was peak oxygen uptake (VO2peak) directly post-intervention. Secondary outcomes included other peak test parameters, submaximal test parameters, long-term outcomes ≥8 weeks post-intervention, adherence and adverse events. Meta-analyses were performed for the primary outcome and for secondary outcomes when reported in more than 2 studies. Risk of bias was assessed with the Cochrane Risk of Bias tool and quality of evidence according to GRADE. RESULTS: Nine studies were included (195 participants with 8 different NMDs). Eight studies were rated at high risk of bias and 1 study was rated at some concerns. Duration of exercise programs ranged from 6 to 26 weeks, with 3 weekly training sessions of 20 to 40 min, based on maximal capacity. Meta-analyses revealed short-term moderate beneficial effects of aerobic exercise on VO2peak (standardized mean difference [SMD] 0.55, 95% CI 0.23; 0.86) and peak workload (SMD 0.61, 95% CI 0.24; 0.99). Long-term effects were not assessed. Most training sessions (83-97%) were completed, but time spent in target intensity zones was not reported. Included studies lacked detailed adverse event reporting. CONCLUSIONS: There is low-quality evidence that aerobic exercise is safe and leads to moderate improvement of aerobic capacity directly post-intervention in slowly progressive NMDs, but the long-term efficacy remains unclear. Detailed information about the time spent in target intensity zones and adverse events is lacking. PROSPERO: CRD42020200083.

Measurement Properties of Aerobic Capacity Measures in Neuromuscular Diseases: A Systematic Review.

OBJECTIVE: To systematically evaluate the measurement properties of aerobic capacity measures in neuromuscular diseases. DATA SOURCES: MEDLINE, EMBASE, SportDiscus and Web of Science Conference Proceedings Citation Index - Science were systematically searched from inception until 30 June 2021. STUDY SELECTION AND DATA EXTRACTION: Screening, data extraction, risk of bias assessment and quality assessment were performed by 2 independent researchers. Studies were included if they evaluated measurement properties of aerobic capacity measures in adults with neuromuscular diseases. Risk of bias was assessed using the COnsensus based Standards for the selection of health status Measurement INstruments (COSMIN) checklist. Results were pooled and the quality of the evidence was determined using a modified Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. DATA SYNTHESIS: Nine studies including 187 participants were included in this review. Low quality of evidence was found for sufficient content validity of peak oxygen consumption through maximal exercise testing. Criterion validity of 4 out of 7 different measures to predict peak oxygen consumption was sufficient; however, quality of evidence was low or very low for all measures. No studies were found evaluating reliability or responsiveness. CONCLUSION: There was a lack of high-quality studies with sufficiently large sample sizes that evaluated the measurement properties of aerobic capacity measures in neuromuscular diseases.

Steps to recovery: Body weight-supported treadmill training for critically ill patients: A randomized controlled trial.

PURPOSE: Early mobilization of critically ill patients improves functional recovery, but is often hampered by tubes, drains, monitoring devices and muscular weakness. A mobile treadmill with bodyweight support facilitates early mobilization and may shorten recovery time to independent ambulation as compared to usual care physiotherapy alone. MATERIALS AND METHODS: Single center RCT, comparing daily bodyweight supported treadmill training (BWSTT) with usual care physiotherapy, in patients who had been or were mechanically ventilated (≥48 h) with ≥MRC grade 2 quadriceps muscle strength. BWSTT consisted of daily treadmill training in addition to usual care physiotherapy (PT). Primary outcome was time to independent ambulation measured in days, using the Functional Ambulation Categories (FAC-score: 3). Secondary outcomes included hospital length of stay and serious adverse events. RESULTS: The median (IQR) time to independent ambulation was 6 (3 to 9) days in the BWSTT group (n = 19) compared to 11 (7 to 23) days in the usual care group (n = 21, p = 0.063). Hospital length of stay was significantly different in favour of the BWSTT group (p = 0.037). No serious adverse events occurred. INTERPRETATION: BWSTT seems a promising intervention to enhance recovery of ambulation and shorten hospital length of stay of ICU patients, justifying a sufficiently powered multicenter RCT. TRIAL REGISTRATION NUMBER: Dutch Trial Register ID: NTR6943.

Individualized Aerobic Exercise in Neuromuscular Diseases: A Pilot Study on the Feasibility and Preliminary Effectiveness to Improve Physical Fitness.

OBJECTIVE: Clear guidelines to prescribe aerobic exercise in neuromuscular diseases (NMD) are lacking, which hampers effective application in neuromuscular rehabilitation. This pilot study evaluated the feasibility and preliminary effectiveness of an individualized aerobic exercise program according to a recently developed training guide (B-FIT) to improve physical fitness in individuals with NMD. METHODS: Thirty-one individuals who were ambulatory and had 15 different slowly progressive NMD participated in a 4-month, polarized, home-based, aerobic exercise program. The program included 2 low-intensity sessions and 1 high-intensity session per week. Feasibility outcomes were the following: completion rate, proportion of followed sessions, adverse events, and participant and therapist satisfaction based on a self-designed questionnaire. Submaximal incremental exercise tests were used to assess the effects on physical fitness. RESULTS: Twenty-six participants (84%) completed the B-FIT program, and the proportion of followed sessions was >75%. Three adverse events were reported and resolved. Regarding satisfaction, participants (based on n = 9) reported feeling fitter, but training was considered insufficiently challenging. Physical therapists (n = 5) reported that B-FIT provides a clear, well-grounded guidance. They perceived the time investment for initiating the program and the carry-over to primary care as the main barriers. The mean (SD) submaximal heart rate (based on n = 20) reduced significantly by -6.5 beats per minute (95% CI = -11.8 to -1.2), from 121.7 (16.5) at baseline to 115.2 (14.3) after intervention. Submaximal ratings of perceived exertion, anaerobic threshold, and peak workload also improved significantly (P < .05). CONCLUSION: The outcomes of this pilot study suggest that individualized aerobic exercise according to B-FIT is feasible and has potential to improve physical fitness in a wide variety of slowly progressive NMD. However, some barriers must be addressed before investigating the efficacy in a randomized controlled trial. IMPACT: The outcomes of this study demonstrate the feasibility of individualized aerobic exercise according to the B-FIT training guide and the potential to improve physical fitness in NMD. Physical therapists indicated that the use of B-FIT provides a clear, well-grounded guidance. The training guide can support health care professionals in the application of aerobic exercise in adult neuromuscular rehabilitation. LAY SUMMARY: Individualized exercise according to the B-FIT training guide is feasible in a wide variety of slowly progressive NMD and might help improve physical fitness.

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.].

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.

Determining the anaerobic threshold in postpolio syndrome: comparison with current guidelines for training intensity prescription.

OBJECTIVES: To determine whether the anaerobic threshold (AT) can be identified in individuals with postpolio syndrome (PPS) using submaximal incremental exercise testing, and to compare current guidelines for intensity prescription in PPS with the AT. DESIGN: Cohort study. SETTING: Research laboratory. PARTICIPANTS: Individuals with PPS (N=82). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Power output, gas exchange variables, heart rate, and rating of perceived exertion (RPE) were measured in an incremental submaximal cycle ergometry test. Two independent observers identified the AT. Comparison of current guidelines for training intensity prescription in PPS (40%-60% heart rate reserve [HRR] or RPE of 12) with the AT was based on correlations between recommended heart rate and the heart rate at the AT. In addition, we determined the proportion of individuals that would have been recommended to train at an intensity corresponding to their AT. RESULTS: The AT was identified in 63 (77%) of the participants. Pearson correlation coefficients between the recommended heart rate and the heart rate at the AT were lower in cases of 40% HRR (r=.56) and 60% HRR (r=.50) than in cases of prescription based on the RPE (r=.86). Based on the RPE, 55% of the individuals would have been recommended to train at an intensity corresponding to their AT. This proportion was higher compared with 40% HRR (41%) or 60% HRR (18%) as criterion. CONCLUSIONS: The AT can be identified in most individuals with PPS offering an individualized target for aerobic training. If the AT cannot be identified (eg, because gas analysis equipment is not available), intensity prescription can best be based on the RPE.

Fatigue resistance of the knee extensor muscles is not reduced in post-polio syndrome.

The present study investigated whether intrinsic fatigability of the muscle fibers is reduced in patients with post-polio syndrome (PPS). This may contribute to the muscle fatigue complaints reported by patients with PPS. For this purpose, we assessed contractile properties and fatigue resistance of the knee extensor muscles using repeated isometric electrically evoked contractions in 38 patients with PPS and 19 age-matched healthy subjects. To determine whether any difference in fatigue resistance between both groups could be attributed to differences in aerobic capacity of the muscle fibers, 9 patients with PPS and 11 healthy subjects performed the same protocol under arterial occlusion. Results showed that fatigue resistance of patients with PPS was comparable to that in controls, both in the situation with intact circulation and with occluded blood flow. Together, our findings suggest that there are no differences in contractile properties and aerobic muscle capacity that may account for the increased muscle fatigue perceived in PPS.