This pilot study examined whether an adapted gymnastics program, CAN-flip, could be a feasible ac... more This pilot study examined whether an adapted gymnastics program, CAN-flip, could be a feasible activity for children with cerebral palsy (CP) leading to improvements in muscle fitness, motor performance, and physical self-perception. Four girls and 1 boy (9.8 ± 1.3 yr) with CP participated in this multiple-baseline across-subjects design and were randomly assigned to start either the 6-wk gymnastics or the 6-wk control period. Muscle strength, neuromuscular activation, range of motion, gross motor performance, balance, and physical self-perception were assessed at baseline, after the first 6-wk period, and at the conclusion of the study. The gymnastics program comprised two 1-hr individualized classes per week. All participants were able to complete the gymnastics classes without injury and showed improvement in specific gymnastics skills. In addition, 3 of the 5 participants registered for regular gymnastics classes after the study, demonstrating the program's usability as a link to inclusive gymnastic classes.
Prolonged, supramaximal stimulation of the soleus muscle is painful to humans. A method is propos... more Prolonged, supramaximal stimulation of the soleus muscle is painful to humans. A method is proposed whereby percutaneous, supramaximal stimulation is possible using a cold cathode. Cooling the skin exposed to the stimulating current results in a sufficient anaesthesia of nociceptive cutaneous afferent nerves. This occurs without concomitant cooling of the muscle mass deep to the skin and subcutaneous tissue.
Щ btp Щ National Libran/ i" ' ïe oi Canada Bibliothèque nation.' du Canada Acquisi... more Щ btp Щ National Libran/ i" ' ïe oi Canada Bibliothèque nation.' du Canada Acquisitions and Direction dos acquisitions о I Bibliographic Services Branch dos so,vices biblioojaphiqu' 395 Wellington Siiiwt OlUv.vi О rito no K1A0N.1 30Tv lucU't'llin^lon OiUu.i (Oiil.iiKi) M Л ON-» NOTICE ...
Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent sign... more Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent signal origin is unknown. Microneurographic recordings from 83 single low-threshold a¡erents were made while participants performed triangular ramps either unloaded or with a viscous load. The neural discharges for each cycle were compared across load and velocity. Fifty-eight a¡erents did not respond. A¡erents with su⁄cient activity were classi¢ed as ambiguous^discharges correlated to velocity and load (n¼4), in¢nite viscosity^strong load and weak velocity signal (n¼6), no viscosity^strong velocity and weak load signal (n¼10) and those with neither (n¼5). No single class of a¡erent provides a coherent signal of viscosity.These data suggest that the central nervous system compares the population response of di¡erent inputs to discriminate viscosity.
To determine whether physiologic responses during treadmill walking in children with cerebral pal... more To determine whether physiologic responses during treadmill walking in children with cerebral palsy (CP) are affected by repeated walking bouts on different days, and whether effects are different at different speeds. Three girls and five boys (9.2-15.7 yr, 23.3-64.4 kg) with mild CP received 12-15 min of treadmill walking practice and had their fastest walking speed (FWS) determined during an introductory visit. During each of three subsequent visits (day 1, day 2, day 3), subjects walked for 3 min at 60, 75, and 90% FWS. Resting physiologic measures were taken on day 1. From day 1 to day 3, net ventilation ([OV0312]E), and net heart rate (HR) at 90% FWS decreased by 3.6 L.min-1 and 8 beats.min-1, respectively. There were no differences between day 1 and day 2 or day 1 and day 3 for any other physiologic variable at any speed. Day 3 was less than day 2 for net HR (60% FWS) and, independent of speed, net [OV0312]O2 (per kilogram of body mass and per stride) and net energy expenditur...
Critical Reviews in Physical and Rehabilitation Medicine, 2012
The objective of this study was to investigate the neuromuscular strategy used during a cyclical ... more The objective of this study was to investigate the neuromuscular strategy used during a cyclical reach and grasp test (CRGT) in patients with mechanical neck disorder. The CRGT is a paced and timed, repetitive reach and grasp task that was designed to monitor both kinematics and electromyography of the upper limb. Patients (n = 9) with moderate to severe neck pain were compared with healthy controls (n = 7). Activities from 10 muscles of the upper limb were acquired during performance of the CRGT and processed to render both temporal/spatial and amplitude indices. Cross-and Pearson correlations of selected muscle pairs were calculated. Comparisons were conducted using nonparametric statistics. All participants completed the CRGT but only patients self-reported pain after performance (visual analog scale rating of 3.9 ± 2.7 on the affected side). Modulation of activity was observed for posture (sitting vs. standing, P = 0.034) and side (affected/nondominant vs. unaffected) for controls (P = 0.005). The patient group did not demonstrate significant differences between these dependent variables. Neuromuscular strategies exhibited by patients during reaching did not alter significantly with variation in side and posture, as they did with controls, indicating the lack of a capacity to modulate muscle activity appropriate to the task. This is a significant consequence of the chronic pain experienced by patients with mechanical neck disorder and may underlie the upper limb disability reported in this patient population.
The study was conducted to estimate the extent to which pressure pain sensitivity (PPS) and patie... more The study was conducted to estimate the extent to which pressure pain sensitivity (PPS) and patient factors predict pain-related disability in patients with neck pain (NP), and to determine if PPS differs by gender. Forty-four participants with a moderate level of chronic NP were recruited for this cross sectional study. All participants were asked to complete self-reported assessments of pain, disability and comorbidity and then underwent PPS testing at 4-selected body locations. Pearson`s r w was computed to explore relationships between the PPS measures and the self-reported assessments. Regression models were built to identify predictors of pain and disability. An independent sample t-test was done to identify gender-related differences in PPS, pain-disability and comorbidity. In this study, greater PPS (threshold and tolerance) was significantly correlated to lower pain-disability (r = -.30 to -.53, p≤0.05). Age was not correlated with pain or disability but comorbidity was (r= 0.42-.43, p≤0.01). PPS at the 4-selected body locations was able to explain neck disability (R 2 =25-28%). Comorbidity was the strongest predictor of neck disability (R 2 =30%) and pain (R 2 =25%). Significant mean differences for gender were found in PPS, disability and comorbidity, but not in pain intensity or rating. This study suggests that PPS may play a role in outcome measures of pain and disability but between-subject comparisons should consider gender and comorbidity issues.
Critical Reviews in Physical and Rehabilitation Medicine, 2012
Executive function (EF) is a control mechanism of human cognition that provides the capability to... more Executive function (EF) is a control mechanism of human cognition that provides the capability to select actions in relation to internal goals organized by the prefrontal cortex (PFC). The PFC is essential for the temporal integration of sensory information in the sequencing of optimum motor behavior to achieve an internal goal. The temporal integration of sensory information also explains why the PFC has an additional role in the central modulation of pain. Pain modulation and motor function are altered in chronic pain, and this alteration can contribute to the reduced physical activity. EF is the driver of conscious control of thought and action that is critical to rehabilitation in chronic pain. However, EF is impaired in chronic pain. Rehabilitation practitioners typically use activity modification, exercise, and movement to enhance function in patients with chronic pain; exercise has beneficial effects on EF. However, impairments in EF can be barriers to adherence to exercise, activity, and lifestyle modifications required to optimize rehabilitation. Greater awareness of EF can enhance rehabilitation. This narrative review explores current theories of EF structure and function, how impairment of EF can be assessed in a clinical context, and its implications for rehabilitation in chronic pain.
Motor unit number estimation (MUNE) is a methodology eminently suited to the study of motoneuron ... more Motor unit number estimation (MUNE) is a methodology eminently suited to the study of motoneuron disorders. An account of the findings from our laboratory in ALS is given elsewhere in the Proceedings (Turnbull et al., this volume), and now, for contrast, we present our observations in two ...
MUNE (motor unit number estimation) provides the only means of determining the number of motor un... more MUNE (motor unit number estimation) provides the only means of determining the number of motor units, and hence the number of functioning motoneurons, during life. For this reason it has the potential to provide valuable information concerning the natural history of ...
1. The effects of repeated excitation on the compound action potential, or M wave, of mammalian m... more 1. The effects of repeated excitation on the compound action potential, or M wave, of mammalian muscle fibres have been investigated in the human biceps brachii. 2. During continuous indirect stimulation at 10 and 20 Hz the mean voltage-time area of the M wave doubled within the first minute, while the mean peak-to-peak amplitude increased by approximately half. The enlargement of the M wave was sustained during stimulation at 10 Hz but not at 20 Hz. Stimulation at 3 Hz caused a small increase which was significant for M wave amplitude only. 3. When the 20 Hz stimulation was performed under ischaemic conditions, the M wave first enlarged and then gradually declined. After 20 Hz stimulation was discontinued, the M wave increased in size; in the ischaemic experiments the release of the cuff produced a further, rapid augmentation. In both the ischaemic and non-ischaemic experiments, the amplitudes and areas of the M waves during the recovery period became significantly larger than the resting values (range, 15-60% at the endplate zone). 4. The mean muscle fibre impulse conduction velocity decreased to less than half the resting value during 20 Hz stimulation, with or without ischaemia, and then increased above the resting value during recovery. 5. On the basis of previous experiments in animals, the augmentation of the M wave was attributed to enhanced electrogenic Na-K+ pumping, and the biceps brachii appeared to be an excellent preparation for studying the time course of this enhancement.
Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent sign... more Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent signal origin is unknown. Microneurographic recordings from 83 single low-threshold a¡erents were made while participants performed triangular ramps either unloaded or with a viscous load. The neural discharges for each cycle were compared across load and velocity. Fifty-eight a¡erents did not respond. A¡erents with su⁄cient activity were classi¢ed as ambiguous^discharges correlated to velocity and load (n¼4), in¢nite viscosity^strong load and weak velocity signal (n¼6), no viscosity^strong velocity and weak load signal (n¼10) and those with neither (n¼5). No single class of a¡erent provides a coherent signal of viscosity.These data suggest that the central nervous system compares the population response of di¡erent inputs to discriminate viscosity.
The possible causes of the transient enlargement of muscle compound action potentials during repe... more The possible causes of the transient enlargement of muscle compound action potentials during repetitive stimulation ("pseudofacilitation") are considered. The phenomenon cannot be due to mechanical artefact, while hypersynchronization of the muscle fiber action potentials, the usual explanation, can only make a minor contribution. A more convincing explanation, for which there is now experimental evidence, is that the muscle fibers undergo hyperpolarization, due to the intramuscular release of norepinephrine and consequent stimulation of the electrogenic Na+,K+-pump. Defective phosphorylation of the Na+,K+pump is a possible cause of the transient weakness and myotonia in myotonic dystrophy. 0 1994 John Wiley & Sons, Inc.
... Short Report. Muscle shortening, response latency, and conduction velocity. Timothy Brown BA,... more ... Short Report. Muscle shortening, response latency, and conduction velocity. Timothy Brown BA,; Victoria Galea PhD,; Alan J. McComas MB. Article first published online: 7 DEC 1998. DOI: 10.1002/(SICI)1097-4598(199611)19:11<1493::AID-MUS17>3.0.CO;2-U. ...
Motor unit number estimation (MUNE) was applied to the biceps brachii muscles of 13 young patient... more Motor unit number estimation (MUNE) was applied to the biceps brachii muscles of 13 young patients (age 5--24 years) with spinal muscular atrophy (SMA) and the results compared with those of healthy control subjects matched for age and gender. In the SMA patients, all motor unit (MU) estimates fell below the control range, and there was good correspondence between the values for the two arms in the same subject. No correlation could be found between the MUNEs and the severity of the weakness. This unexpected result was attributed to the presence of small and normal-sized MUs in the muscles of patients, in addition to MUs that appeared to be considerably enlarged. The threefold mean increase in MU potential size was insufficient to compensate for the MU loss. In addition, the study confirmed that there are, on average, approximately 130 MUs in the healthy biceps brachii muscle.
A fully automated system is described for estimating the numbers and relative sizes of functionin... more A fully automated system is described for estimating the numbers and relative sizes of functioning motor units in proximal and distal muscles of the arm and leg. In this system, a computer controls the motor nerve stimulation, and analyzes the potentials evoked from the muscles; a subprogram searches for instances of "alternation." In 33 healthy volunteers, aged 21 to 56 years, the median-innervated thenar muscles of one hand were tested 2 to 3 times; the mean motor unit estimate was 228 2 93 SD. For similar numbers of biceps brachii, extensor digitorum brevis, and vastus medialis muscles, the respective mean values were 113 rf: 40,131 k 45, and 229 k 108 units. The reproducibility of the method was such that the overall coefficient of variation, for the normalized results from the 121 muscles studied, was 22%. The reliability of the automated method was doubled if 3 estimates, rather than one, were performed on each muscle. Comparisons of the results obtained by automated and "manual" methods indicated that the computer-derived values tended to be lower by approximately 33%.
This pilot study examined whether an adapted gymnastics program, CAN-flip, could be a feasible ac... more This pilot study examined whether an adapted gymnastics program, CAN-flip, could be a feasible activity for children with cerebral palsy (CP) leading to improvements in muscle fitness, motor performance, and physical self-perception. Four girls and 1 boy (9.8 ± 1.3 yr) with CP participated in this multiple-baseline across-subjects design and were randomly assigned to start either the 6-wk gymnastics or the 6-wk control period. Muscle strength, neuromuscular activation, range of motion, gross motor performance, balance, and physical self-perception were assessed at baseline, after the first 6-wk period, and at the conclusion of the study. The gymnastics program comprised two 1-hr individualized classes per week. All participants were able to complete the gymnastics classes without injury and showed improvement in specific gymnastics skills. In addition, 3 of the 5 participants registered for regular gymnastics classes after the study, demonstrating the program&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s usability as a link to inclusive gymnastic classes.
Prolonged, supramaximal stimulation of the soleus muscle is painful to humans. A method is propos... more Prolonged, supramaximal stimulation of the soleus muscle is painful to humans. A method is proposed whereby percutaneous, supramaximal stimulation is possible using a cold cathode. Cooling the skin exposed to the stimulating current results in a sufficient anaesthesia of nociceptive cutaneous afferent nerves. This occurs without concomitant cooling of the muscle mass deep to the skin and subcutaneous tissue.
Щ btp Щ National Libran/ i" ' ïe oi Canada Bibliothèque nation.' du Canada Acquisi... more Щ btp Щ National Libran/ i" ' ïe oi Canada Bibliothèque nation.' du Canada Acquisitions and Direction dos acquisitions о I Bibliographic Services Branch dos so,vices biblioojaphiqu' 395 Wellington Siiiwt OlUv.vi О rito no K1A0N.1 30Tv lucU't'llin^lon OiUu.i (Oiil.iiKi) M Л ON-» NOTICE ...
Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent sign... more Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent signal origin is unknown. Microneurographic recordings from 83 single low-threshold a¡erents were made while participants performed triangular ramps either unloaded or with a viscous load. The neural discharges for each cycle were compared across load and velocity. Fifty-eight a¡erents did not respond. A¡erents with su⁄cient activity were classi¢ed as ambiguous^discharges correlated to velocity and load (n¼4), in¢nite viscosity^strong load and weak velocity signal (n¼6), no viscosity^strong velocity and weak load signal (n¼10) and those with neither (n¼5). No single class of a¡erent provides a coherent signal of viscosity.These data suggest that the central nervous system compares the population response of di¡erent inputs to discriminate viscosity.
To determine whether physiologic responses during treadmill walking in children with cerebral pal... more To determine whether physiologic responses during treadmill walking in children with cerebral palsy (CP) are affected by repeated walking bouts on different days, and whether effects are different at different speeds. Three girls and five boys (9.2-15.7 yr, 23.3-64.4 kg) with mild CP received 12-15 min of treadmill walking practice and had their fastest walking speed (FWS) determined during an introductory visit. During each of three subsequent visits (day 1, day 2, day 3), subjects walked for 3 min at 60, 75, and 90% FWS. Resting physiologic measures were taken on day 1. From day 1 to day 3, net ventilation ([OV0312]E), and net heart rate (HR) at 90% FWS decreased by 3.6 L.min-1 and 8 beats.min-1, respectively. There were no differences between day 1 and day 2 or day 1 and day 3 for any other physiologic variable at any speed. Day 3 was less than day 2 for net HR (60% FWS) and, independent of speed, net [OV0312]O2 (per kilogram of body mass and per stride) and net energy expenditur...
Critical Reviews in Physical and Rehabilitation Medicine, 2012
The objective of this study was to investigate the neuromuscular strategy used during a cyclical ... more The objective of this study was to investigate the neuromuscular strategy used during a cyclical reach and grasp test (CRGT) in patients with mechanical neck disorder. The CRGT is a paced and timed, repetitive reach and grasp task that was designed to monitor both kinematics and electromyography of the upper limb. Patients (n = 9) with moderate to severe neck pain were compared with healthy controls (n = 7). Activities from 10 muscles of the upper limb were acquired during performance of the CRGT and processed to render both temporal/spatial and amplitude indices. Cross-and Pearson correlations of selected muscle pairs were calculated. Comparisons were conducted using nonparametric statistics. All participants completed the CRGT but only patients self-reported pain after performance (visual analog scale rating of 3.9 ± 2.7 on the affected side). Modulation of activity was observed for posture (sitting vs. standing, P = 0.034) and side (affected/nondominant vs. unaffected) for controls (P = 0.005). The patient group did not demonstrate significant differences between these dependent variables. Neuromuscular strategies exhibited by patients during reaching did not alter significantly with variation in side and posture, as they did with controls, indicating the lack of a capacity to modulate muscle activity appropriate to the task. This is a significant consequence of the chronic pain experienced by patients with mechanical neck disorder and may underlie the upper limb disability reported in this patient population.
The study was conducted to estimate the extent to which pressure pain sensitivity (PPS) and patie... more The study was conducted to estimate the extent to which pressure pain sensitivity (PPS) and patient factors predict pain-related disability in patients with neck pain (NP), and to determine if PPS differs by gender. Forty-four participants with a moderate level of chronic NP were recruited for this cross sectional study. All participants were asked to complete self-reported assessments of pain, disability and comorbidity and then underwent PPS testing at 4-selected body locations. Pearson`s r w was computed to explore relationships between the PPS measures and the self-reported assessments. Regression models were built to identify predictors of pain and disability. An independent sample t-test was done to identify gender-related differences in PPS, pain-disability and comorbidity. In this study, greater PPS (threshold and tolerance) was significantly correlated to lower pain-disability (r = -.30 to -.53, p≤0.05). Age was not correlated with pain or disability but comorbidity was (r= 0.42-.43, p≤0.01). PPS at the 4-selected body locations was able to explain neck disability (R 2 =25-28%). Comorbidity was the strongest predictor of neck disability (R 2 =30%) and pain (R 2 =25%). Significant mean differences for gender were found in PPS, disability and comorbidity, but not in pain intensity or rating. This study suggests that PPS may play a role in outcome measures of pain and disability but between-subject comparisons should consider gender and comorbidity issues.
Critical Reviews in Physical and Rehabilitation Medicine, 2012
Executive function (EF) is a control mechanism of human cognition that provides the capability to... more Executive function (EF) is a control mechanism of human cognition that provides the capability to select actions in relation to internal goals organized by the prefrontal cortex (PFC). The PFC is essential for the temporal integration of sensory information in the sequencing of optimum motor behavior to achieve an internal goal. The temporal integration of sensory information also explains why the PFC has an additional role in the central modulation of pain. Pain modulation and motor function are altered in chronic pain, and this alteration can contribute to the reduced physical activity. EF is the driver of conscious control of thought and action that is critical to rehabilitation in chronic pain. However, EF is impaired in chronic pain. Rehabilitation practitioners typically use activity modification, exercise, and movement to enhance function in patients with chronic pain; exercise has beneficial effects on EF. However, impairments in EF can be barriers to adherence to exercise, activity, and lifestyle modifications required to optimize rehabilitation. Greater awareness of EF can enhance rehabilitation. This narrative review explores current theories of EF structure and function, how impairment of EF can be assessed in a clinical context, and its implications for rehabilitation in chronic pain.
Motor unit number estimation (MUNE) is a methodology eminently suited to the study of motoneuron ... more Motor unit number estimation (MUNE) is a methodology eminently suited to the study of motoneuron disorders. An account of the findings from our laboratory in ALS is given elsewhere in the Proceedings (Turnbull et al., this volume), and now, for contrast, we present our observations in two ...
MUNE (motor unit number estimation) provides the only means of determining the number of motor un... more MUNE (motor unit number estimation) provides the only means of determining the number of motor units, and hence the number of functioning motoneurons, during life. For this reason it has the potential to provide valuable information concerning the natural history of ...
1. The effects of repeated excitation on the compound action potential, or M wave, of mammalian m... more 1. The effects of repeated excitation on the compound action potential, or M wave, of mammalian muscle fibres have been investigated in the human biceps brachii. 2. During continuous indirect stimulation at 10 and 20 Hz the mean voltage-time area of the M wave doubled within the first minute, while the mean peak-to-peak amplitude increased by approximately half. The enlargement of the M wave was sustained during stimulation at 10 Hz but not at 20 Hz. Stimulation at 3 Hz caused a small increase which was significant for M wave amplitude only. 3. When the 20 Hz stimulation was performed under ischaemic conditions, the M wave first enlarged and then gradually declined. After 20 Hz stimulation was discontinued, the M wave increased in size; in the ischaemic experiments the release of the cuff produced a further, rapid augmentation. In both the ischaemic and non-ischaemic experiments, the amplitudes and areas of the M waves during the recovery period became significantly larger than the resting values (range, 15-60% at the endplate zone). 4. The mean muscle fibre impulse conduction velocity decreased to less than half the resting value during 20 Hz stimulation, with or without ischaemia, and then increased above the resting value during recovery. 5. On the basis of previous experiments in animals, the augmentation of the M wave was attributed to enhanced electrogenic Na-K+ pumping, and the biceps brachii appeared to be an excellent preparation for studying the time course of this enhancement.
Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent sign... more Humans can discriminate changes in load viscosity during voluntary contractions. The a¡erent signal origin is unknown. Microneurographic recordings from 83 single low-threshold a¡erents were made while participants performed triangular ramps either unloaded or with a viscous load. The neural discharges for each cycle were compared across load and velocity. Fifty-eight a¡erents did not respond. A¡erents with su⁄cient activity were classi¢ed as ambiguous^discharges correlated to velocity and load (n¼4), in¢nite viscosity^strong load and weak velocity signal (n¼6), no viscosity^strong velocity and weak load signal (n¼10) and those with neither (n¼5). No single class of a¡erent provides a coherent signal of viscosity.These data suggest that the central nervous system compares the population response of di¡erent inputs to discriminate viscosity.
The possible causes of the transient enlargement of muscle compound action potentials during repe... more The possible causes of the transient enlargement of muscle compound action potentials during repetitive stimulation ("pseudofacilitation") are considered. The phenomenon cannot be due to mechanical artefact, while hypersynchronization of the muscle fiber action potentials, the usual explanation, can only make a minor contribution. A more convincing explanation, for which there is now experimental evidence, is that the muscle fibers undergo hyperpolarization, due to the intramuscular release of norepinephrine and consequent stimulation of the electrogenic Na+,K+-pump. Defective phosphorylation of the Na+,K+pump is a possible cause of the transient weakness and myotonia in myotonic dystrophy. 0 1994 John Wiley & Sons, Inc.
... Short Report. Muscle shortening, response latency, and conduction velocity. Timothy Brown BA,... more ... Short Report. Muscle shortening, response latency, and conduction velocity. Timothy Brown BA,; Victoria Galea PhD,; Alan J. McComas MB. Article first published online: 7 DEC 1998. DOI: 10.1002/(SICI)1097-4598(199611)19:11<1493::AID-MUS17>3.0.CO;2-U. ...
Motor unit number estimation (MUNE) was applied to the biceps brachii muscles of 13 young patient... more Motor unit number estimation (MUNE) was applied to the biceps brachii muscles of 13 young patients (age 5--24 years) with spinal muscular atrophy (SMA) and the results compared with those of healthy control subjects matched for age and gender. In the SMA patients, all motor unit (MU) estimates fell below the control range, and there was good correspondence between the values for the two arms in the same subject. No correlation could be found between the MUNEs and the severity of the weakness. This unexpected result was attributed to the presence of small and normal-sized MUs in the muscles of patients, in addition to MUs that appeared to be considerably enlarged. The threefold mean increase in MU potential size was insufficient to compensate for the MU loss. In addition, the study confirmed that there are, on average, approximately 130 MUs in the healthy biceps brachii muscle.
A fully automated system is described for estimating the numbers and relative sizes of functionin... more A fully automated system is described for estimating the numbers and relative sizes of functioning motor units in proximal and distal muscles of the arm and leg. In this system, a computer controls the motor nerve stimulation, and analyzes the potentials evoked from the muscles; a subprogram searches for instances of "alternation." In 33 healthy volunteers, aged 21 to 56 years, the median-innervated thenar muscles of one hand were tested 2 to 3 times; the mean motor unit estimate was 228 2 93 SD. For similar numbers of biceps brachii, extensor digitorum brevis, and vastus medialis muscles, the respective mean values were 113 rf: 40,131 k 45, and 229 k 108 units. The reproducibility of the method was such that the overall coefficient of variation, for the normalized results from the 121 muscles studied, was 22%. The reliability of the automated method was doubled if 3 estimates, rather than one, were performed on each muscle. Comparisons of the results obtained by automated and "manual" methods indicated that the computer-derived values tended to be lower by approximately 33%.
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