IJSPT
ORIGINAL RESEARCH
THE ACUTE EFFECTS OF CONCENTRIC VERSUS ECCENTRIC MUSCLE FATIGUE ON SHOULDER ACTIVE REPOSITIONING SENSE Guido Spargoli, PT, MSc1
ABSTRACT Purpose/Background: Shoulder proprioception is essential in the activities of daily living as well as in sports. Acute muscle fatigue is believed to cause a deterioration of proprioception, increasing the risk of injury. The purpose of this study was to evaluate if fatigue of the shoulder external rotators during eccentric versus concentric activity affects shoulder joint proprioception as determined by active reproduction of position. Study design: Quasi-experimental trial. Methods: Twenty-two healthy subjects with no recent history of shoulder pathology were randomly allocated to either a concentric or an eccentric exercise group for fatiguing the shoulder external rotators. Proprioception was assessed before and after the fatiguing protocol using an isokinetic dynamometer, by measuring active reproduction of position at 30° of shoulder external rotation, reported as absolute angular error. The fatiguing protocol consisted of sets of fifteen consecutive external rotator muscle contractions in either the concentric or eccentric action. The subjects were exercised until there was a 30% decline from the peak torque of the subjects’ maximal voluntary contraction over three consecutive muscle contractions. Results: A one-way analysis of variance test revealed no statistical difference in absolute angular error (p> 0.05) between concentric and eccentric groups. Moreover, no statistical difference (p> 0.05) was found in absolute angular error between pre- and post-fatigue in either group. Conclusions: Eccentric exercise does not seem to acutely affect shoulder proprioception to a larger extent than concentric exercise. Level of evidence: 2b Key words: Exercise, joint position sense, neuromuscular control
1
Centro Medico Genova, Genoa, Italy
CORRESPONDING AUTHOR Guido Spargoli, CP Servizi, Via di Santa Zita 1/10, 16129, Genoa, Italy Telephone: (39) 3294133778 Fax: (+39) 0108630446 E-mail: [email protected]
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 219
INTRODUCTION Shoulder proprioception has been acknowledged in physical therapy practice as a sensory component that needs to be addressed in rehabilitation of various disorders.1 Proprioception is defined as the specialized variation of sensory modality of touch, and encompasses the sensation of joint movement (kinesthesia) and joint position sense.2 It is commonly believed that joint proprioceptive feedback occurs due to the simultaneous activity of several different types of mechanoreceptors located in the skin, muscles, joints, capsular, and ligamentous structures.1,3 Such mechanoreceptors include: Ruffini receptors Golgi tendon receptors, Pancinian corpuscles, free nerve endings, and muscle spindles.1 Because mechanoreceptors located in muscles around a joint are believed to contribute to joint proprioception,2 it is possible that fatiguing the muscles surrounding a joint will affect the proprioception of that joint. Muscle fatigue is defined as impairment of physical performance that increases the perception of effort necessary to exert a specific force.4 The effects of muscle fatigue on joint proprioception are very important as proprioceptive afferent feedback has a key role in motor control, posture, and also in sport activities where optimal movement patterns are required.5-11 Impairment of joint proprioception may influence joint stability and has been associated with the occurrence of injuries that occur during sports and exercise.12-14 To date, while it seems clear that muscle fatigue affects joint proprioception, no study has investigated if there is an immediate difference on shoulder joint proprioception following muscle fatigue induced by either concentric or eccentric exercise of the shoulder rotators. Therefore, the purpose of this study was to evaluate if fatigue of the shoulder external rotators during eccentric versus concentric activity affects shoulder joint proprioception as determined by active reproduction of position. As eccentric exercise is reported to be more stressful and damaging than concentric exercise,15 the hypothesis for this investigation was that shoulder muscle fatigue induced by eccentric exercise would deteriorate shoulder joint proprioception to a larger extent than shoulder muscle fatigue induced by concentric exercise. The results of this study may help clinician
better understand the physiology of proprioception of the shoulder joint. METHODS Subjects and experimental groups Between June and August 2012, twenty-two healthy people from the general student population at the University of Central Lancashire (UCLan), Preston, United Kingdom, responded to recruitment. Exclusion criteria for participation included a history of shoulder surgery, shoulder pain or any major event involving the shoulder complex (trauma or dislocation) within the previous two years, or any serious medical condition. All twenty-two subjects (14 males, 8 females, age 20-32 years; mean age 25.04) were included for the study and informed consent was obtained. Ethical approval was obtained from the UCLan Ethics Committee. All subjects had shoulder range of motion (ROM) within normal limits and no difficulty or discomfort in moving the shoulder in internal and external rotation in the ROM utilized for the testing protocol. Allocation to either concentric exercise group (CEG) or eccentric exercise group (EEG) was achieved by a computer generated table of random numbers. The CEG included 10 subjects (6 males, 4 females, mean age of 23.9 years, with a range from 20 and 32 years) while the EEG included 12 subjects (8 males, 4 females, mean age of 26 years, with a range from 23 and 28 years). TABLE 1 displays the characteristics of the two groups. Instrumentation and proprioception assessment Proprioception assessment was conducted using an isokinetic dynamometer (CSMI, Cybex Humac Norm, USA) at the UCLan Movement Analysis Laboratory. Proprioception was assessed as in a previous study by active reproduction of position (ARP).16 Each subject reported their arm dominance as the proprioception assessment and the fatigue protocol was performed on the dominant shoulder only. The shoulder was positioned at 30° of abduction, 0° of external rotation, in the plane of the scapula (30° anterior to the frontal plane), with the elbow flexed at 90°, in mid-pronation and was strapped to the arm device. For comfort reasons the height of
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 220
Table 1. SUBJECTS (22) ECCENTRIC GROUP (12)
CONCENTRIC GROUP (10)
26±1.95
23.9±4.09
8/4 11/1
6/4 9/1
Age (years ± Standard deviaon) Males/Females Right handed/Le handed
the dynamometer and the length of the arm device were personalized to each subject (Figure 1). This set-up allowed movement at the shoulder joint to be isolated to internal and external rotation along the shaft of the humerus. With the subjects blindfolded to prevent visual clues, subjects actively rotated their shoulder from 0° of external rotation to the reference angle of 30° external rotation and maintained in this position for 10 seconds, following which the subjects returned actively the shoulder to 0° of external rotation. Subjects were instructed to actively reposition the shoulder at the reference
Figure 1. Initial position for shoulder joint proprioception assessment.
position and notify the assessor when they thought they were at the reference position for three trials, each beginning from 0° of external rotation. The three absolute angular differences between the reference angle and the angle reproduced by the subjects were recorded and the average was calculated, which was called the absolute angular error (AAE), the dependent variable for this study. PROCEDURES Following the initial proprioception assessment, three maximal voluntary contractions (MVCs) of the shoulder external rotators consistent with the same contraction type of the fatiguing protocol were executed. For this task the subjects remained in the same position as in the shoulder proprioception assessment. The subjects in the CEG were instructed to move their shoulder into external rotation; from 40° of internal rotation to 80° of external rotation as intensely as they could. The subjects in the EEG were instead instructed to try to oppose a forced internal rotation induced by the dynamometer; from 80° of external rotation to 40° of internal rotation as intensely as they could. For both types of action, the speed of the dynamometer was set at 180°/second. To familiarize the subjects with the testing device, the type of contraction requested, and as a warm-up, before each MVC the subjects performed five lowintensity contractions consistent with their group allocation. To do so, the subjects were instructed to apply a force of approximately 20% of their maximal capability. There was one-minute rest between the three MVCs. As in a previous study, the cut point for shoulder muscle fatigue was considered the highest MVC’s peak torque minus 30%.17 According to the group allocation, shoulder external rotators were then fatigued using either concentric or eccentric muscle action. The subjects in the CEG performed external contractions from 40° of inter-
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 221
nal rotation to 80° of external rotation while the subjects in the EEG tried to oppose a forced internal rotation from 80° of external rotation to 40° of internal rotation. Subjects in both groups performed sets of fifteen repetitions with one-minute rest between sets. Both concentric and eccentric fatiguing protocols were stopped when the respective peak torques fell by 30% from the highest MCV’s peak torque over three consecutive contractions. As soon as the fatiguing protocols ceased, shoulder joint proprioception was re-assessed in the same manner as described earlier for the pretest. Proprioception re-assessment was completed immediately after completing the fatiguing protocol (within five minutes maximum). DATA ANALYSIS A one-way analysis of variance (ANOVA) with repeated measures was performed using the AAE data for each measure of proprioception at the level of statistical significance of p
ORIGINAL RESEARCH
THE ACUTE EFFECTS OF CONCENTRIC VERSUS ECCENTRIC MUSCLE FATIGUE ON SHOULDER ACTIVE REPOSITIONING SENSE Guido Spargoli, PT, MSc1
ABSTRACT Purpose/Background: Shoulder proprioception is essential in the activities of daily living as well as in sports. Acute muscle fatigue is believed to cause a deterioration of proprioception, increasing the risk of injury. The purpose of this study was to evaluate if fatigue of the shoulder external rotators during eccentric versus concentric activity affects shoulder joint proprioception as determined by active reproduction of position. Study design: Quasi-experimental trial. Methods: Twenty-two healthy subjects with no recent history of shoulder pathology were randomly allocated to either a concentric or an eccentric exercise group for fatiguing the shoulder external rotators. Proprioception was assessed before and after the fatiguing protocol using an isokinetic dynamometer, by measuring active reproduction of position at 30° of shoulder external rotation, reported as absolute angular error. The fatiguing protocol consisted of sets of fifteen consecutive external rotator muscle contractions in either the concentric or eccentric action. The subjects were exercised until there was a 30% decline from the peak torque of the subjects’ maximal voluntary contraction over three consecutive muscle contractions. Results: A one-way analysis of variance test revealed no statistical difference in absolute angular error (p> 0.05) between concentric and eccentric groups. Moreover, no statistical difference (p> 0.05) was found in absolute angular error between pre- and post-fatigue in either group. Conclusions: Eccentric exercise does not seem to acutely affect shoulder proprioception to a larger extent than concentric exercise. Level of evidence: 2b Key words: Exercise, joint position sense, neuromuscular control
1
Centro Medico Genova, Genoa, Italy
CORRESPONDING AUTHOR Guido Spargoli, CP Servizi, Via di Santa Zita 1/10, 16129, Genoa, Italy Telephone: (39) 3294133778 Fax: (+39) 0108630446 E-mail: [email protected]
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 219
INTRODUCTION Shoulder proprioception has been acknowledged in physical therapy practice as a sensory component that needs to be addressed in rehabilitation of various disorders.1 Proprioception is defined as the specialized variation of sensory modality of touch, and encompasses the sensation of joint movement (kinesthesia) and joint position sense.2 It is commonly believed that joint proprioceptive feedback occurs due to the simultaneous activity of several different types of mechanoreceptors located in the skin, muscles, joints, capsular, and ligamentous structures.1,3 Such mechanoreceptors include: Ruffini receptors Golgi tendon receptors, Pancinian corpuscles, free nerve endings, and muscle spindles.1 Because mechanoreceptors located in muscles around a joint are believed to contribute to joint proprioception,2 it is possible that fatiguing the muscles surrounding a joint will affect the proprioception of that joint. Muscle fatigue is defined as impairment of physical performance that increases the perception of effort necessary to exert a specific force.4 The effects of muscle fatigue on joint proprioception are very important as proprioceptive afferent feedback has a key role in motor control, posture, and also in sport activities where optimal movement patterns are required.5-11 Impairment of joint proprioception may influence joint stability and has been associated with the occurrence of injuries that occur during sports and exercise.12-14 To date, while it seems clear that muscle fatigue affects joint proprioception, no study has investigated if there is an immediate difference on shoulder joint proprioception following muscle fatigue induced by either concentric or eccentric exercise of the shoulder rotators. Therefore, the purpose of this study was to evaluate if fatigue of the shoulder external rotators during eccentric versus concentric activity affects shoulder joint proprioception as determined by active reproduction of position. As eccentric exercise is reported to be more stressful and damaging than concentric exercise,15 the hypothesis for this investigation was that shoulder muscle fatigue induced by eccentric exercise would deteriorate shoulder joint proprioception to a larger extent than shoulder muscle fatigue induced by concentric exercise. The results of this study may help clinician
better understand the physiology of proprioception of the shoulder joint. METHODS Subjects and experimental groups Between June and August 2012, twenty-two healthy people from the general student population at the University of Central Lancashire (UCLan), Preston, United Kingdom, responded to recruitment. Exclusion criteria for participation included a history of shoulder surgery, shoulder pain or any major event involving the shoulder complex (trauma or dislocation) within the previous two years, or any serious medical condition. All twenty-two subjects (14 males, 8 females, age 20-32 years; mean age 25.04) were included for the study and informed consent was obtained. Ethical approval was obtained from the UCLan Ethics Committee. All subjects had shoulder range of motion (ROM) within normal limits and no difficulty or discomfort in moving the shoulder in internal and external rotation in the ROM utilized for the testing protocol. Allocation to either concentric exercise group (CEG) or eccentric exercise group (EEG) was achieved by a computer generated table of random numbers. The CEG included 10 subjects (6 males, 4 females, mean age of 23.9 years, with a range from 20 and 32 years) while the EEG included 12 subjects (8 males, 4 females, mean age of 26 years, with a range from 23 and 28 years). TABLE 1 displays the characteristics of the two groups. Instrumentation and proprioception assessment Proprioception assessment was conducted using an isokinetic dynamometer (CSMI, Cybex Humac Norm, USA) at the UCLan Movement Analysis Laboratory. Proprioception was assessed as in a previous study by active reproduction of position (ARP).16 Each subject reported their arm dominance as the proprioception assessment and the fatigue protocol was performed on the dominant shoulder only. The shoulder was positioned at 30° of abduction, 0° of external rotation, in the plane of the scapula (30° anterior to the frontal plane), with the elbow flexed at 90°, in mid-pronation and was strapped to the arm device. For comfort reasons the height of
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 220
Table 1. SUBJECTS (22) ECCENTRIC GROUP (12)
CONCENTRIC GROUP (10)
26±1.95
23.9±4.09
8/4 11/1
6/4 9/1
Age (years ± Standard deviaon) Males/Females Right handed/Le handed
the dynamometer and the length of the arm device were personalized to each subject (Figure 1). This set-up allowed movement at the shoulder joint to be isolated to internal and external rotation along the shaft of the humerus. With the subjects blindfolded to prevent visual clues, subjects actively rotated their shoulder from 0° of external rotation to the reference angle of 30° external rotation and maintained in this position for 10 seconds, following which the subjects returned actively the shoulder to 0° of external rotation. Subjects were instructed to actively reposition the shoulder at the reference
Figure 1. Initial position for shoulder joint proprioception assessment.
position and notify the assessor when they thought they were at the reference position for three trials, each beginning from 0° of external rotation. The three absolute angular differences between the reference angle and the angle reproduced by the subjects were recorded and the average was calculated, which was called the absolute angular error (AAE), the dependent variable for this study. PROCEDURES Following the initial proprioception assessment, three maximal voluntary contractions (MVCs) of the shoulder external rotators consistent with the same contraction type of the fatiguing protocol were executed. For this task the subjects remained in the same position as in the shoulder proprioception assessment. The subjects in the CEG were instructed to move their shoulder into external rotation; from 40° of internal rotation to 80° of external rotation as intensely as they could. The subjects in the EEG were instead instructed to try to oppose a forced internal rotation induced by the dynamometer; from 80° of external rotation to 40° of internal rotation as intensely as they could. For both types of action, the speed of the dynamometer was set at 180°/second. To familiarize the subjects with the testing device, the type of contraction requested, and as a warm-up, before each MVC the subjects performed five lowintensity contractions consistent with their group allocation. To do so, the subjects were instructed to apply a force of approximately 20% of their maximal capability. There was one-minute rest between the three MVCs. As in a previous study, the cut point for shoulder muscle fatigue was considered the highest MVC’s peak torque minus 30%.17 According to the group allocation, shoulder external rotators were then fatigued using either concentric or eccentric muscle action. The subjects in the CEG performed external contractions from 40° of inter-
The International Journal of Sports Physical Therapy | Volume 12, Number 2 | April 2017 | Page 221
nal rotation to 80° of external rotation while the subjects in the EEG tried to oppose a forced internal rotation from 80° of external rotation to 40° of internal rotation. Subjects in both groups performed sets of fifteen repetitions with one-minute rest between sets. Both concentric and eccentric fatiguing protocols were stopped when the respective peak torques fell by 30% from the highest MCV’s peak torque over three consecutive contractions. As soon as the fatiguing protocols ceased, shoulder joint proprioception was re-assessed in the same manner as described earlier for the pretest. Proprioception re-assessment was completed immediately after completing the fatiguing protocol (within five minutes maximum). DATA ANALYSIS A one-way analysis of variance (ANOVA) with repeated measures was performed using the AAE data for each measure of proprioception at the level of statistical significance of p
