Fatigue Protocol Research Articles

Comparison of shoulder external rotation fatigue protocols on kinetic determinants and fatigue index in overhead athletes: a cross over study

Abstract The purpose of present study is to compare prone lying and half kneeling external rotator fatigue protocols on the kinetic parameters of external rotators and fatigue index in collegiate overhead athletes. Twenty overhead collegiate male athletes were recruited in this randomised cross-over experimental study design with two different shoulder external rotator fatigue protocols. Subjects were performed with prone lying and half kneeling shoulder external rotation fatigue protocol with a washout period of at least 72 h. Outcome measures like peak force, peak velocity, peak power, average power, and total work were observed in concentric and eccentric contraction and fatigue index was assessed before and after fatigue protocols. Concentric peak force (P=0.001), peak velocity (P<0.001), peak power (P<0.001), average power (P<0.001) and total work (P=0.022) showed significant time difference whereas group difference and time× group interaction was found to be non-significant. Similarly, eccentric peak force (P=0.043), average power (P=0.001) and total work (P=0.032) showed only significant time difference. Prone-lying and half kneeling external rotation fatigue protocols reduces the peak force, peak velocity, peak power and total work in concentric contraction and peak force and total work in eccentric contraction in a similar fashion.

Real and perceived feet orientation under fatiguing and non-fatiguing conditions in an immersive virtual reality environment

Lower limbs position sense is a complex yet poorly understood mechanism, influenced by many factors. Hence, we investigated the position sense of lower limbs through feet orientation with the use of Immersive Virtual Reality (IVR). Participants had to indicate how they perceived the real orientation of their feet by orientating a virtual representation of the feet that was shown in an IVR scenario. We calculated the angle between the two virtual feet (α-VR) after a high-knee step-in-place task. Simultaneously, we recorded the real angle between the two feet (α-R) (T1). Hence, we assessed whether the acute fatigue impacted the position sense. The same procedure was repeated after inducing muscle fatigue (T2) and after 10 min from T2 (T3). Finally, we also recorded the time needed to confirm the perceived position before and after the acute fatigue protocol. Thirty healthy adults (27.5 ± 3.8: 57% women, 43% men) were immersed in an IVR scenario with a representation of two feet. We found a mean difference between α-VR and α-R of 20.89° [95% CI: 14.67°, 27.10°] in T1, 16.76° [9.57°, 23.94°] in T2, and 16.34° [10.00°, 22.68°] in T3. Participants spent 12.59, 17.50 and 17.95 s confirming the perceived position of their feet at T1, T2, T3, respectively. Participants indicated their feet as forwarding parallel though divergent, showing a mismatch in the perceived position of feet. Fatigue seemed not to have an impact on position sense but delayed the time to accomplish this task.

Landing Posture in Elite Female Athletes During a Drop Vertical Jump Before and After a High-Intensity Ergometer Fatigue Protocol: A Study of 20 Japanese Women’s Soccer League Players

Background: Even elite athletes, who usually show stable postural control, sometimes cannot control their posture after high-load training. This instability may contribute to anterior cruciate ligament injury. Purpose/Hypothesis: The purpose of this study was to evaluate the landing posture of elite female soccer players before and after a novel high-intensity fatigue-inducing exercise protocol. We hypothesized that the landing posture will change before versus after the fatigue protocol. Study Design: Descriptive laboratory study. Method: The study participants were 20 female elite soccer players. All athletes performed 3 drop vertical jumps (DVJs), pedaled an ergometer 8 times with full force for 10 seconds each (fatigue protocol), and then repeated the 3 DVJs. We measured and compared the athletes’ blood lactate levels before and after the fatigue protocol, as well as the hip flexion, knee flexion, and ankle dorsiflexion angles and final landing posture during the DJVs. Results: Blood lactate levels increased significantly pre- to postprotocol (from 2.7 ± 1.9 to 15.0 ± 3.6 mmol/L; P < .001), while there were decreases in hip flexion angle (from 35.0° ± 11.2° to 22.4° ± 8.8°; P < .001) and ankle dorsiflexion angle (from 26.4° ± 3.9° to 20.0° ± 3.7°; P < .001). The number of athletes who could not maintain a stable DVJ final landing posture increased from 10% before the fatigue protocol to 70% after. Conclusion: The elite female athletes in our study showed significant decreases in hip flexion and ankle dorsiflexion angles in the DVJ landing after a fatigue-inducing protocol. Most elite athletes were unable to maintain a stable posture on the DVJ landing after the fatigue protocol. Clinical Relevance: This study advances our understanding of how elite athletes land in a fatigued state.

The impacts of Kinesio taping on muscular fatigue and proprioception following fatigue among adolescent basketball players

Aim: The present study attempted to investigate the impacts of Kinesio taping on proprioceptive responses of the knee joint before and after muscular fatigue. 
 Material and Method: Thirteen healthy basketball players were recruited for this study. A fatigue protocol was designed with a load of 70% of the maximum quadriceps muscle strength and applied to the dominant lower extremity, including repetitive knee flexion and extension in a sitting position between 0°-90°. Fatigue was assessed using the Borg scale. The protocol was administered to the same participants twice at a one-week interval. Proprioception in the knee joint was assessed using the angle reconstruction test. In the evaluation of proprioception, the target angle was set as 45° of knee flexion and was measured with a digital goniometer. In the second-week measurements, the same protocol was repeated immediately following Kinesio tape application to the quadriceps femoris muscle with the facilitation technique. 
 Results: The findings revealed no significant within-group differences between the proprioception measurements before and after fatigue (p > 0.05). It was also the case in the evaluation with Kinesio taping (p > 0.005). However, the number of movement repetitions significantly differed between the groups in the fatigue protocol (p < 0.05). 
 Conclusion: The proprioception values of pre- and post-fatigue did not significantly differ when Kinesio taping was applied. Overall, it was concluded that Kinesio taping was an effective factor in reducing fatigue and contributed to endurance by delaying the onset of fatigue.

Effects of an isokinetic fatigue protocol on knee flexion–extension performance and hamstrings-to-quadriceps ratio in women professional soccer players

Effects of an isokinetic fatigue protocol on knee flexion–extension performance and hamstrings-to-quadriceps ratio in women professional soccer players

Exercise-Induced Fatigue Impairs Change of Direction Performance and Serve Precision among Young Male Tennis Players.

This study investigates the effect of exercise-induced fatigue on change of direction performance and serve precision among young tennis players. A group of 21 players (age 12.90 ± 0.76 years), ranked among the top 50 players on the national tennis federation scale and the top 300 on the "Tennis Europe" scale, participated in the study. They underwent a standardized physiological load protocol using the "300-m running test" which consists of consecutive runs for 15 shares of 20 m (15 × 20). Its intensity was determined using the Borg Rating of Perceived Exertion (RPE) scale where subjects evaluated their level of experienced load on a scale from 0 to 10. Prior to and after the protocol, they performed a pre-planned change of direction T-test and serve precision test. Results showed significant increase of time in the T-test (from 11.75 ± 0.45 s to 12.99 ± 0.4 s, p = 0.00) and decrease in serve precision parameter from (6.00 ± 1.04 to 4.00 ± 1.26, p = 0.00) after the fatigue test protocol. The RPE increased from 5 to 9, after the fatigue protocol, indicating the desired fatigue effect. These findings indicate that exercise-induced fatigue impairs change of direction performance and serve precision among young tennis players.

Comparison of throwing kinematics and muscle activation of female elite handball players with and without pain – the effect of repeated maximal throws

ABSTRACT Shoulder pain is common in team handball; however, many continue playing. The purpose was to investigate whether a functional fatigue protocol (FFP) containing repeated sub and maximal standing throws affects throwing performance, upper body kinematics, muscle peak activation (MPA) and whether the effect was different between the players playing with or with no pain. Thirty female elite handball players performed five maximal standing throws before and after the FFP. Throwing velocity, throwing kinematics, and MPA were measured before and after the FFP. An increased ball velocity (p = .02) was found, but only the total throwing time increased significantly in pain group (p = .05). Fatigue also resulted in a larger maximal pelvis (p = .03) and trunk rotation (p = .03) in addition to an increased shoulder flexion at ball release in both groups (p = .03), but only the maximal external (p = .03) and internal shoulder rotation (p = .05) increased in the pain group. Furthermore, fatigue also affected MPA in the latissimus dorsi (p = .02) and infraspinatus (p = .01). It was concluded that fatigue influenced throwing performance, kinematics, MPA and timing, which may increase the risk of developing non-traumatic shoulder injuries in team handball. The information may help to understand how fatigue influences throwing kinematics and MPA in players playing with pain.

Acute Effects of a Fatiguing Protocol on Peak Force and Rate of Force Development of the Hamstring Muscles in Soccer Players

Acute Effects of a Fatiguing Protocol on Peak Force and Rate of Force Development of the Hamstring Muscles in Soccer Players

INVESTIGATING THE EFFECTS OF FATIGUE PROTOCOL ON SPATIOTEMPORAL CHARACTERISTICS OF GAIT IN PATIENTS WITH CHRONIC NECK PAIN

Purpose: Chronic neck pain (CNP) may lead to problems, such as functional limitations, disability, and fatigue. Gait maintains postural orientation; It is important to investigate the effects of fatigue on walking in patients who subjectively define a certain level of fatigue, not for a certain period. This study aimed to investigate the effects of fatigue protocol on gait spatiotemporal characteristics in patients with CNP.
 Methods: Fifty-three patients with CNP, and twenty-six healthy controls were included. The groups were matched with Propensity Score Matching in terms of age and fatigue threshold as 26 individuals. Pain intensity and disability were evaluated with the Visual Analog Scale, and Neck Disability Index, respectively. Gait assessment was recorded with OptoGait (1.6.4.0, Microgate, Bolzano, Italy) for one minute while individuals walked at their preferred speed on the treadmill. Individuals keep walking on the treadmill and fatigue levels were asked for Modified Borg Scale. While fatigue reached 4 points, gait assessment was recorded for one minute. A two-way repeated-measures ANOVA was used for interaction time-by-group.
 Results: The median pain intensity was 7(4-9), and the disability was moderate in patients. Left step length, stride length, and cadence, showed significant, similar changes within the groups over time(p

Influence of unilateral and bilateral knee extension fatigue protocols on inter-limb asymmetries assessed through countermovement jumps

ABSTRACT This study explores the sensitivity of jump type (unilateral and bilateral) and output variable (mean force, propulsive impulse, and jump height) to detect the changes in inter-limb asymmetries induced by unilateral and bilateral fatigue protocols. Thirty-eight individuals performed two testing sessions that consisted of (I) nine “pre-fatigued” countermovement jumps (CMJs; three bilateral and six unilateral [three with each leg]), (II) fatigue protocol and (III) nine “post-fatigued” CMJs. The testing sessions only differed in the fatigue protocol (five sets to failure against the 15-repetition maximum load using either the unilateral or bilateral knee extension exercise). The magnitude of all CMJ-derived variables (mean force, impulse, and jump height) decreased following both unilateral (p ≤ 0.002) and bilateral fatigue protocols (p ≤ 0.018). However, only unilateral protocol accentuated inter-limb asymmetries, which was detected for all variables during the unilateral CMJ (from −4.33% to −2.04%; all p < 0.05) but not during the bilateral CMJ (from −0.64% to 0.54%; all p > 0.05). The changes in inter-limb asymmetries following the unilateral and bilateral fatigue protocols were not significantly correlated between the unilateral and bilateral CMJs (r s ≤ 0.172). The unilateral CMJ should be recommended for the testing purposes over the bilateral CMJ due to its greater sensitivity to detect the selective effects of fatigue.

A non-volitional skeletal muscle endurance test measures functional changes associated with impaired blood flow.

Introduction: An electrically stimulated intermittent fatigue test using mechanomyography was recently proposed as a possible tool for detecting clinically relevant changes in muscle function. This study was designed to determine whether the proposed test can detect additional fatigue when it should be present. Methods: Subjects (n = 10) underwent two trials each (occluded and normal blood flow) with a standardized fatigue protocol on the Ankle Dorsiflexors (AD) and Wrist Extensors (WE) using a clinical electrical stimulator. Results: Mean normalized twitch acceleration was strongly predictive of mean normalized torque (R 2 = 0.828). The WE experienced lower twitch magnitudes throughout the tourniquet trial (10.81 ± 1.25m/s2) compared to normal blood flow (18.05 ± 1.06m/s2). The AD twitches were overall reduced in the tourniquet trial (3.87 ± 0.48m/s2) compared with the control trial (8.57 ± 0.91m/s2). Conclusion: Occluding blood flow to a muscle should cause greater muscle fatigue. The ability to detect reduced contraction magnitudes during an electrically stimulated fatigue protocol resulting from low blood flow suggests the proposed test may be capable of detecting clinically relevant muscle deficits.

Does Acute Fatigue Affect Lumbar Proprioception and Balance?

Purpose: To investigate the acute effects of trunk extensor, abdominal, and calf muscle fatigue on lumbar proprioception and balance. Method: Seventy healthy individuals, aged between 18-25, without pain in the low back and lower extremities, with right dominant lower extremities, were included in the study. Dynamic balance with the Y-balance Test, lumbar proprioception sense with the application of the IOS software, and fatigue level with the 6-20 Borg Scale were evaluated before and immediately after the back extensor, abdominal, and calf muscle fatigue protocols were applied to the individuals at 72-hour intervals. Results: After all fatigue protocols, proprioception sense at 30˚ lumbar flexion was found to change significantly (pConclusionsThis study determined that acute fatigue negatively affects proprioceptive sense and dynamic postural control in the anterior direction. Understanding how the trunk extensor, abdominal, and ankle plantar flexor muscles respond to a fatigue-inducing exercise, especially concerning postural control and trunk proprioception, is important for understanding and preventing injury risk.

Effect of Fatigue on the Core Muscle Endurance in Female Athletes With and Without Non-specific Chronic Low Back Pain

Purpose: Non-specific chronic low back pain (LBP) is the most common type of chronic LBP and a common debilitating condition, especially in athletes, that can also affect performance. The core muscles are necessary to create a stable level of support for sports performance and appropriate movements of all organs, and its deficiency is related to complications, such as LBP. This research aims to investigate the effect of a fatigue protocol on core muscle endurance in athletes with and without non-specific chronic LBP. Methods: A controlled laboratory study was conducted; 42 female athletes with and without non-specific chronic LBP were selected through convenience sampling method and divided into two groups with non-specific chronic LBP and without non-specific chronic LBP. McGill’s core endurance test was used to measure core muscle endurance. The measurements were done before and after the implementation of the functional core fatigue protocol (FCFP). SPSS software, version 22 and dependent t-tests and analysis of covariance (ANCOVA) were used to evaluate mean differences obtained in the two groups. The significance level was considered 95%, and the α level was ≤0.05. Results: The analysis of covariance (ANCOVA) showed a significant difference between the two groups with and without non-specific chronic LBP after performing the functional core fatigue protocol (FCFP) in McGill’s test scores in isometric flexion exercise (P=0.001), isometric extensor exercise (P=0.001), right side bridge (P=0.001) and left side bridge (P=0.001). In the post-test measurement, the endurance of the core muscles decreased in the LBP group. Conclusion: The findings revealed that fatigue can affect the core stability and reduce the core muscles endurance of female athletes with non-specific chronic LBP. Therefore, core muscle weakness can be recognized as a risk factor for chronic LBP, and in order to prevent this damage, it is recommended to strengthen this area in rehabilitation programs.

Acute effects of fatigue on internal and external load variables determining cyclists’ power profile

ABSTRACT The aim of the present study was to determine whether fatigue affects internal and external load variables determining power profile in cyclists. Ten cyclists performed outdoor power profile tests (lasting 1-, 5 and 20-min) on two consecutive days, subject either to a fatigued condition or not. Fatigue was induced by undertaking an effort (10-min at 95% of average power output obtained in a 20-min effort followed by 1-min maximum effort) until the power output decreased by 20% compared to the 1-min power output. Fatigued condition decreased power output (p < 0.05, 1-min: 9.0 ± 3.8%; 5-min: 5.9 ± 2.5%; 20-min: 4.1 ± 1.9%) and cadence in all test durations, without differences in torque. Lactate decreased in longer efforts when a fatigue protocol had previously been conducted (e.g., 20-min: 8.6 ± 3.0 vs. 10.9 ± 2.7, p < 0.05). Regression models (r2 ≥ 0.95, p < 0.001) indicated that a lower variation in load variables of 20-min in fatigued condition compared with the non-fatigued state resulted in a lower decrease in critical power after the fatigue protocol. The results suggest that fatigued condition on power was more evident in shorter efforts and seemed to rely more on a decrease in cadence than on torque.

Changes in motor unit activity in the biceps brachii muscle under different intensities of isometric loading

In patients with cancer, loss of muscle mass is observed in many cases and tumour types. This can lead to a drastic deterioration in the patient's quality of life, with the inability to support themselves. Nowadays, in addition to primary treatment of the tumour, physical training of patients has become a priority in order to maintain their quality of life. One key to this is resistance training to prevent sudden muscle loss, which the patient can do alongside primary treatment, and isometric training may be one option. Our aim was to measure the activation frequency characteristics of the biceps brachii muscle in our subjects during a fatigue protocol while creating a constant controlled isometric tension in the muscle. 19 healthy university students participated in our study. After determining the dominant side, the subjects' single repetition maximum was assessed using the GymAware RS tool and then 65% and 85% of this was calculated. We placed electrodes on the biceps brachii muscle and had them hold the weight at 65% and 85% until full fatigue. Immediately afterwards, subjects performed an isometric maximal contraction (Imax). The measured electromyography recordings were divided into 3 equal parts, then the first, middle and last 3 s (W1, W2, W3) were analyzed. Our results show that, consistent with fatigue, at both 1RM 65% and 1RM 85% load, the activity of the low-frequency motor units increases, while the activation of the high-frequency motor units decreases. The present study is consistent with our previous study. Our test protocol is not suitable for prolonged activation of high-frequency motor units because the activity of high-frequency motor units decreases over time. Orv Hetil. 2023; 164(10): 376-382.

Lower-limb resistance training reduces exertional dyspnea and intrinsic neuromuscular fatigability in individuals with chronic obstructive pulmonary disease.

Skeletal muscle atrophy, dysfunction, and fatigue are important complications of chronic obstructive pulmonary disease (COPD). Greater reliance on glycolytic metabolism and increased type III/IV muscle afferent activity increase ventilatory drive, promote ventilatory constraint, amplify exertional dyspnea, and limit exercise tolerance. To investigate whether muscular adaptation with resistance training (RT) could improve exertional dyspnea, exercise tolerance, and intrinsic neuromuscular fatigability in individuals with COPD (n = 14, FEV1 = 62 ± 21% predicted), we performed a proof-of-concept single-arm efficacy study utilizing 4 wk of individualized lower-limb RT (3 times/wk). At baseline, dyspnea (Borg scale), ventilatory parameters, lung volumes (inspiratory capacity maneuvers), and exercise time were measured during a constant-load test (CLT) at 75% maximal workload to symptom limitation. On a separate day, fatigability was assessed using 3 min of intermittent stimulation of the quadriceps (initial output of ∼25% maximal voluntary force). Following RT, the CLT and fatigue protocols were repeated. Compared with baseline, isotime dyspnea was reduced (5.9 ± 2.4 vs. 4.5 ± 2.4 Borg units, P = 0.02) and exercise time increased (437 ± 405 s vs. 606 ± 447 s, P < 0.01) following RT. Isotime tidal volume increased (P = 0.01), whereas end-expiratory lung volumes (P = 0.02) and heart rate (P = 0.03) decreased. Quadriceps force, relative to initial force, was higher at the end of the stimulation protocol posttraining (53.2 ± 9.1 vs. 46.8 ± 11.9%, P = 0.04). This study provides evidence that 4 wk of RT attenuates exertional dyspnea and improves exercise tolerance in individuals with COPD, which in part, is likely due to delayed ventilatory constraint and reduced intrinsic fatigability. A pulmonary rehabilitation program beginning with individualized lower-limb RT may help mitigate dyspnea before performing aerobic training in individuals with COPD.NEW & NOTEWORTHY This study presents the novel finding that 4-wk resistance training (RT) focused specifically on the lower limbs can reduce exertional dyspnea during constant-load cycling, improve exercise tolerance, and reduce intrinsic fatigability of the quadriceps in individuals with COPD.

Assessment of muscle fatigue in multiple sclerosis patients in electromyographic examinations.

Although surface electromyography (sEMG) is the method used to assess muscle fatigue in patients with multiple sclerosis (PwMS), no pattern of signal change has been established. The differences shown in the parameters of other neurophysiological tests between PwMS and control groups (CG) suggest the differentiation of the sEMG signal. The purpose of the study was to verify potential differences in the fatigue sEMG signal in PwMS compared to CG. Cross-sectional study. Chair and Department of Functional Diagnostics and Physical Medicine. A randomised group of patients diagnosed with MS (30, 20-41 years). A random sample of young, healthy adults (median 28, 20-39 years). Measurement of sEMG was performed from extensor carpi radialis (ECR) and FCR (flexor carpi radialis) during 60-80% of maximum voluntary contraction (MVC) of extension and then flexion for 60sec, accordance with the fatigue protocol in Research XP Master Edition software (v. 1.08.27). Root mean square amplitude (A<inf>RMS</inf>) were lower for muscle in the PwMS compared to the CG (ECR P=0.0001, FCU P<0.0001). In the CG, the A<inf>RMS</inf> value increases during fatigue contraction (ECR P=0.0003, FCU P<0.0001), while in the PwMS) the A<inf>RMS</inf> value decreases (ECR: P<0.0001, FCU P<0.0001. The PwMS show an opposite pattern of preservation of the absolute value of A<inf>RMS</inf> during prolonged contraction to fatigue, compared with healthy subjects. The results are important for clinical trials using sEMG to assess fatigue in PwMS. Knowledge of the differences in the time domain changes in sEMG signal between healthy subjects and PwMS is crucial for correctly interpreting the results.

무릎 신전근 피로 수준이 외발 드롭 착지 시 무릎 관절 안정성에 미치는 영향

This study was to investigate the effect of experimentally induced knee extensor muscle fatigue on biomechanical variables related to knee stability during landing after a drop jump. Methods: A total of 14 young men participated voluntarily. As for the fatigue induction method, isokinetic equipment (Biodex System 4, Biodex Medical Systems, Inc. USA) was used, Kinematic data of the lower limbs were collected using a 3D Motion Analysis Eagle system (EVART 4.6, Santa Rosa, CA, USA) connected to 12 cameras at a sampling rate of 200 Hz, and ground reaction forces were obtained using an AMTI OR6-5 force platform (Watertown, MA, USA) was used to collect at a sampling rate of 1200 Hz. Results: The maximum knee flexion angle during one-leg drop landing was significantly increased after fatigue induction than before fatigue induction, but there was no significant difference among the fatigue induction conditions in knee valgus and varus, lateral rotation and medial rotation during one-leg drop landing. The shear stress in the tibia showed a tendency to increase according to the level of fatigue, but no significant difference was found. On the other hand, in the sagittal plane, the maximum knee joint moment was significantly decreased after fatigue induction, and the maximum ground reaction force was also found to be significantly decreased in the condition after fatigue induction compared to the condition before fatigue induction. Conclusion: Fatigue of the knee joint extensors following the fatigue protocol did not lead to significant changes in biomechanical variables related to knee stability. However, there was a significant decrease in maximum knee joint moment and maximum ground reaction force, and a significant increase in maximum knee joint angle during one-leg drop landing after fatigue induction. Therefore, the results of the study demonstrated that local fatigue (knee extensor fatigue exercise) according to the fatigue protocol did not affect biomechanical variables related to knee stability, but did affect biomechanical variables related to task performance.

Is human bone matrix a sufficient augmentation method revising loosened pedicle screws in osteoporotic bone? – A biomechanical evaluation of primary stability

IntroductionDespite good screw anchorage and safe screw trajectory, screw loosening occurs in several cases, especially in osteoporotic individuals. The aim of this biomechanical analysis was to evaluate the primary stability of revision screw placement in individuals with reduced bone quality. Therefore, revision via enlarged diameter screws was compared to the use of human bone matrix as augmentation to improve the bone stock and screw coverage. Methods11 lumbar vertebral bodies from cadaveric specimens with a mean age of 85.7 years (± 12.0 years) at death were used. 6.5 mm diameter pedicle screws were inserted in both pedicles and hereafter loosened using a fatigue protocol. Screws were revised inserting a larger diameter screw (8.5 mm) in one pedicle and a same diameter screw with human bone matrix augmentation in the other pedicle. The previous loosening protocol was then reapplied, comparing maximum load and cycles to failure between both revision techniques. Insertional torque was continuously measured during insertion of both revision screws. FindingsThe number of cycles and the maximum load until failure were significantly greater in enlarged diameter screws than in augmented screws. The enlarged screws' insertional torque was also significantly higher than of the augmented screws. InterpretationHuman bone matrix augmentation does not reach the same ad-hoc fixation strength as enlarging the screw's diameter by 2 mm and is therefore biomechanically inferior. Regarding the immediate stability, a thicker screw should therefore be prioritised.

Is the figure-8 fatigue protocol a suitable tool to investigate shoulder muscle fatigue in wheelchair users with spinal cord injury?

Introduction&#x0D; Shoulder pain is common in persons with spinal cord injury (SCI) and has been associated with wheelchair use. Previous studies identified fatigue related compensation strategies that could impact the development of shoulder injury and pain (Bossuyt et al., 2020). The aim of this study was to determine the presence of performance and perceived fatigability during a figure-8 fatigue protocol (F8F; Collinger et al., 2010) and thereby validate the protocols suitability to assess fatigue in wheelchair users with SCI.&#x0D; Methods&#x0D; Wheelchair users with paraplegia (N = 43, age = 50.2 ±10.1 years, body weight = 72.1 ±13.3 kg, time since injury = 27.1 ±11.6 years) completed a F8F introduced by Collinger et al. (2010). The F8F consists of 3 bouts of 4 minutes maximum voluntary propulsion including turns and full stops with 90 seconds of rest between the bouts thereby simulating wheelchair propulsion during daily life. The surface EMG signal of the biceps brachii, pectoralis major (pars sternalis), deltoideus pars acromialis, lower and upper trapezius of the non-dominant shoulder was recorded. To analyse performance fatigability, root mean square (RMS) (expected to increase with fatigue) of the five muscles was calculated with a short-time Fourier transformation. RMS means were normalised to the starting RMS values. In addition, heart rate (HR) was measured using a heart rate monitor. To analyse perceived fatigability, rate of perceived exertion (RPE) was captured with a 20-point Borg scale. A one-way repeated measure ANOVA was used to analyse changes in the dependent variables RMS, HR and RPE over time (α = 0.05). Correlation coefficients (Spearman- or Pearson-Test) between changes in HR, RPE and RMS of muscles with significant effects for time, were calculated.&#x0D; Results and Discussion&#x0D; RPE as well as HR and RMS of pectoralis major and upper trapezius showed the expected increases at the end of the demanding parts of the protocol. The changes in RMS demonstrate a shift in the power of the EMG signal indicating fatigue. The presence of fatigue in only a subset of the muscles may lead to muscular imbalances and over time induce injury and/or pain. Weak to moderate correlations were found between changes in HR and RPE as well as between changes in RMS of pectoralis major and RMS of upper trapezius. The correlation of changes in HR and RPE further demonstrates the association of more global measures of performance and perceived fatigability. Nevertheless, these global measures of fatiguability did not correlate with the changes in RMS, a local measure of performance fatiguability. The lack of association between global and local parameters demonstrates the importance of recording local parameters like RMS and suggests the integration of local RPE-scores for future research. Exercise programs targeting the trapezius and pectoralis major may have a role in preventing fatigue during wheelchair propulsion.&#x0D; Conclusions&#x0D; The detected changes in markers of performance and perceived fatigability support F8F as an adequate choice to evaluate the effect of wheelchair propulsion induced fatigue in wheelchair users with paraplegia. Furthermore, these findings support the value of investigating biomechanical changes during fatiguing wheelchair propulsion that resembles daily life activities, when the neuromuscular system is prone to adaptations, as it may give us further insights into the development of shoulder injury and pain.&#x0D; References&#x0D; Bossuyt, F. M., Arnet, U., Cools, A., Rigot, S., de Vries, W., Eriks-Hoogland, I., Boninger, M. L., &amp; Group, S. S. (2020). Compensation strategies in response to fatiguing propulsion in wheelchair users: Implications for shoulder injury risk. American Journal of Physical Medicine &amp; Rehabilitation, 99(2), 91-98. https://doi.org/10.1097/PHM.0000000000001267&#x0D; Collinger, J. L., Impink, B. G., Ozawa, H., &amp; Boninger, M. L. (2010). Effect of an intense wheelchair propulsion task on quantitative ultrasound of shoulder tendons. PM&amp;R, 2(10), 920-925. https://doi.org/10.1016/j.pmrj.2010.06.007