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Background Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass (UWM) affects the muscular activity of the shoulder stabilizers. Aim of the study was to assess neuromuscular activity of dynamic shoulder stabilizers under four conditions of stable and UWM during three shoulder exercises. It was hypothesized that a combined condition of weight with UWM would elicit greater activation due to the increased stabilization demand. Methods Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 s.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different exercise conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root-mean-square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR: U.TA/L.TA; U.TA/SA) and contraction (CR: concentric/eccentric) ratios were analyzed (paired t-test; p <= 0.05; Bonferroni adjusted alpha = 0.008). Results PWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p > 0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles. Conclusion Higher weight generated greater muscle activation whereas an UWM raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an UWM increased the RMS%MVIC and SR ratio. This might improve training effects in shoulder prevention and rehabilitation programs.
Background Ankle sprain is the most common injury in basketball. Chronic ankle instability develops from an acute ankle sprain may cause negative effects on quality of life, ankle functionality or on increasing risk for recurrent ankle sprains and post-traumatic osteoarthritis. To facilitate a preventative strategy of chronic ankle instability (CAI) in the basketball population, gathering epidemiological data is essential. However, the epidemiological data of CAI in basketball is limited. Therefore, this study aims to investigate the prevalence of CAI in basketball athletes and to determine whether gender, competitive level, and basketball playing position influence this prevalence. Methods In a cross-sectional study, in total 391 Taiwanese basketball athletes from universities and sports clubs participated. Besides non-standardized questions about demographics and their history of ankle sprains, participants further filled out the standard Cumberland Ankle Instability Tool applied to determine the presence of ankle instability. Questionnaires from 255 collegiate and 133 semi-professional basketball athletes (male = 243, female = 145, 22.3 +/- 3.8 years, 23.3 +/- 2.2 kg/m(2)) were analyzed. Differences in prevalence between gender, competitive level and playing position were determined using the Chi-square test. Results In the surveyed cohort, 26% had unilateral CAI while 50% of them had bilateral CAI. Women had a higher prevalence than men in the whole surveyed cohort (X-2(1) = 0.515, p = 0.003). This gender disparity also showed from sub-analyses, that the collegiate female athletes had a higher prevalence than collegiate men athletes (X-2(1) = 0.203, p = 0.001). Prevalence showed no difference between competitive levels (p > 0.05) and among playing positions (p > 0.05). Conclusions CAI is highly prevalent in the basketball population. Gender affects the prevalence of CAI. Regardless of the competitive level and playing position the prevalence of CAI is similar. The characteristic of basketball contributes to the high prevalence. Prevention of CAI should be a focus in basketball. When applying the CAI prevention measures, gender should be taken into consideration.
Physical activity and exercise are effective approaches in prevention and therapy of multiple diseases. Although the specific characteristics of lengthening contractions have the potential to be beneficial in many clinical conditions, eccentric training is not commonly used in clinical populations with metabolic, orthopaedic, or neurologic conditions. The purpose of this pilot study is to investigate the feasibility, functional benefits, and systemic responses of an eccentric exercise program focused on the trunk and lower extremities in people with low back pain (LBP) and multiple sclerosis (MS). A six-week eccentric training program with three weekly sessions is performed by people with LBP and MS. The program consists of ten exercises addressing strength of the trunk and lower extremities. The study follows a four-group design (N = 12 per group) in two study centers (Israel and Germany): three groups perform the eccentric training program: A) control group (healthy, asymptomatic); B) people with LBP; C) people with MS; group D (people with MS) receives standard care physiotherapy. Baseline measurements are conducted before first training, post-measurement takes place after the last session both comprise blood sampling, self-reported questionnaires, mobility, balance, and strength testing. The feasibility of the eccentric training program will be evaluated using quantitative and qualitative measures related to the study process, compliance and adherence, safety, and overall program assessment. For preliminary assessment of potential intervention effects, surrogate parameters related to mobility, postural control, muscle strength and systemic effects are assessed. The presented study will add knowledge regarding safety, feasibility, and initial effects of eccentric training in people with orthopaedic and neurological conditions. The simple exercises, that are easily modifiable in complexity and intensity, are likely beneficial to other populations. Thus, multiple applications and implementation pathways for the herein presented training program are conceivable.
Physical activity and exercise are effective approaches in prevention and therapy of multiple diseases. Although the specific characteristics of lengthening contractions have the potential to be beneficial in many clinical conditions, eccentric training is not commonly used in clinical populations with metabolic, orthopaedic, or neurologic conditions. The purpose of this pilot study is to investigate the feasibility, functional benefits, and systemic responses of an eccentric exercise program focused on the trunk and lower extremities in people with low back pain (LBP) and multiple sclerosis (MS). A six-week eccentric training program with three weekly sessions is performed by people with LBP and MS. The program consists of ten exercises addressing strength of the trunk and lower extremities. The study follows a four-group design (N = 12 per group) in two study centers (Israel and Germany): three groups perform the eccentric training program: A) control group (healthy, asymptomatic); B) people with LBP; C) people with MS; group D (people with MS) receives standard care physiotherapy. Baseline measurements are conducted before first training, post-measurement takes place after the last session both comprise blood sampling, self-reported questionnaires, mobility, balance, and strength testing. The feasibility of the eccentric training program will be evaluated using quantitative and qualitative measures related to the study process, compliance and adherence, safety, and overall program assessment. For preliminary assessment of potential intervention effects, surrogate parameters related to mobility, postural control, muscle strength and systemic effects are assessed. The presented study will add knowledge regarding safety, feasibility, and initial effects of eccentric training in people with orthopaedic and neurological conditions. The simple exercises, that are easily modifiable in complexity and intensity, are likely beneficial to other populations. Thus, multiple applications and implementation pathways for the herein presented training program are conceivable.
Intervention in the form of core-specific stability exercises is evident to improve trunk stability. The purpose was to assess the effect of an additional 6 weeks sensorimotor or resistance training on maximum isokinetic trunk strength and response to sudden dynamic trunk loading (STL) in highly trained adolescent athletes. The study was conducted as a single-blind, 3-armed randomized controlled trial. Twenty-four adolescent athletes (14f/10 m, 16 +/- 1 yrs.;178 +/- 10 cm; 67 +/- 11 kg; training sessions/week 15 +/- 5; training h/week 22 +/- 8) were randomized into resistance training (RT; n = 7), sensorimotor training (SMT; n = 10), and control group (CG; n = 7). Athletes were instructed to perform standardized, center-based training for 6 weeks, two times per week, with a duration of 1 h each session. SMT consisted of four different core-specific sensorimotor exercises using instable surfaces. RT consisted of four trunk strength exercises using strength training machines, as well as an isokinetic dynamometer. All participants in the CG received an unspecific heart frequency controlled, ergometer-based endurance training (50 min at max. heart frequency of 130HF). For each athlete, each training session was documented in an individual training diary (e.g., level of SMT exercise; 1RM for strength exercise, pain). At baseline (M1) and after 6 weeks of intervention (M2), participants' maximum strength in trunk rotation (ROM:63 degrees) and flexion/extension (ROM:55 degrees) was tested on an isokinetic dynamometer (concentric/eccentric 30 degrees/s). STL was assessed in eccentric (30 degrees/s) mode with additional dynamometer-induced perturbation as a marker of core stability. Peak torque [Nm] was calculated as the main outcome. The primary outcome measurements (trunk rotation/extension peak torque: con, ecc, STL) were statistically analyzed by means of the two-factor repeated measures analysis of variance (alpha = 0.05). Out of 12 possible sessions, athletes participated between 8 and 9 sessions (SMT: 9 +/- 3; RT: 8 +/- 3; CG: 8 +/- 4). Regarding main outcomes of trunk performance, experimental groups showed no significant pre-post difference for maximum trunk strength testing as well as for perturbation compensation (p > 0.05). It is concluded, that future interventions should exceed 6 weeks duration with at least 2 sessions per week to induce enhanced trunk strength or compensatory response to sudden, high-intensity trunk loading in already highly trained adolescent athletes, regardless of training regime.
Background Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass (UWM) affects the muscular activity of the shoulder stabilizers. Aim of the study was to assess neuromuscular activity of dynamic shoulder stabilizers under four conditions of stable and UWM during three shoulder exercises. It was hypothesized that a combined condition of weight with UWM would elicit greater activation due to the increased stabilization demand. Methods Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 s.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different exercise conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root-mean-square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR: U.TA/L.TA; U.TA/SA) and contraction (CR: concentric/eccentric) ratios were analyzed (paired t-test; p <= 0.05; Bonferroni adjusted alpha = 0.008). Results PWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p > 0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles. Conclusion Higher weight generated greater muscle activation whereas an UWM raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an UWM increased the RMS%MVIC and SR ratio. This might improve training effects in shoulder prevention and rehabilitation programs.
Background Recent studies indicate the existence of a repeated bout effect on the contralateral untrained limb following eccentric and isometric contractions. Aims This review aims to summarize the evidence for magnitude, duration and differences of this effect following isometric and eccentric preconditioning exercises. Methods Medline, Cochrane, and Web of science were searched from January 1971 until September 2020. Randomized controlled trials, case-control studies and cross-sectional studies were identified by combining keywords and synonyms (e.g., "contralateral", "exercise", "preconditioning", "protective effect"). At least two of the following outcome parameters were mandatory for study inclusion: strength, muscle soreness, muscle swelling, limb circumference, inflammatory blood markers or protective index (relative change of aforementioned measures). Results After identifying 1979 articles, 13 studies were included. Most investigations examined elbow flexors and utilized eccentric isokinetic protocols to induce the contralateral repeated bout effect. The magnitude of protection was observed in four studies, smaller values of the contralateral when compared to the ipsilateral repeated bout effect were noted in three studies. The potential mechanism is thought to be of neural central nature since no differences in peripheral muscle activity were observed. Time course was examined in three investigations. One study showed a smaller protective effect following isometric preconditioning when compared to eccentric preconditioning exercises. Conclusions The contralateral repeated bout effect demonstrates a smaller magnitude and lasts shorter than the ipsilateral repeated bout effect. Future research should incorporate long-term controlled trials including larger populations to identify central mechanisms. This knowledge should be used in clinical practice to prepare immobilized limbs prospectively for an incremental load.
Repetitive overhead motions in combination with heavy loading were identified as risk factors for the development of shoulder pain. However, the underlying mechanism is not fully understood. Altered scapular kinematics as a result of muscle fatigue is suspected to be a contributor. PURPOSE: To determine scapular kinematics and scapular muscle activity at the beginning and end of constant shoulder flexion and extension loading in asymptomatic individuals. METHODS: Eleven asymptomatic adults (28±4yrs; 1.74±0.13m; 74±16kg) underwent maximum isokinetic loading of shoulder flexion (FLX) and extension (EXT) in the sagittal plane (ROM: 20- 180°; concentric mode; 180°/s) until individual peak torque was reduced by 50%. Simultaneously 3D scapular kinematics were assessed with a motion capture system and scapular muscle activity with a 3-lead sEMG of upper and lower trapezius (UT, LT) and serratus anterior (SA). Scapular position angles were calculated for every 20° increment between 20-120° humerothoracic positions. Muscle activity was quantified by amplitudes (RMS) of the total ROM. Descriptive analyses (mean±SD) of kinematics and muscle activity at begin (taskB) and end (taskE) of the loading task was followed by ANOVA and paired t-tests. RESULTS: At taskB activity ranged from 589±343mV to 605±250mV during FLX and from 105±41mV to 164±73mV during EXT across muscles. At taskE activity ranged from 594±304mV to 875±276mV during FLX and from 97±33mV to 147±57mV during EXT. Differences with increased muscle activity were seen for LT and UT during FLX (meandiff= 141±113mV for LT, p<0.01; 191±153mV for UT, p<0.01). Scapula position angles continuously increased in upward rotation, posterior tilt and external rotation during FLX and reversed during EXT both at taskB and taskE. At taskE scapula showed greater external rotation (meandiff= 3.6±3.7°, p<0.05) during FLX and decreased upward rotation (meandiff= 1.9±2.3°, p<0.05) and posterior tilt (meandiff= 1.0±2.1°, p<0.05) during EXT across humeral positions. CONCLUSIONS: Force reduction in consequence of fatiguing shoulder loading results in increased scapular muscle activity and minor alterations in scapula motion. Whether even small changes have a clinical impact by creating unfavorable subacromial conditions potentially initiating pain remains unclear.
PURPOSE: To determine the feasibility of upright compared to supine MRI measurements to determine characteristics of the lumbar spine in AA with spondylolisthesis.
METHODS: Ten AA (n=10; m/f: 4/6; 14.5±1.7y; 163±7cm; 52±8kg) from various sports, diagnosed with spondylolisthesis grade I-II Meyerding confirmed by x-ray in standing lateral view, were included. Open low-field MRI images (0.25 Tesla) in upright (82°) and supine (0°) position were evaluated by two observers. Medical imaging software was used to measure the anterior translation (AT, mm), lumbosacral joint angle (LSJA, °) and lordosis angle (LA, °). Reliability was analyzed by the intra-rater correlation coefficient (ICC) and standard error of measurements (SEM).
RESULTS: Due to motion artifacts during upright position, measures of three participants had to be excluded. Between observers, AT ranged from 4.2±2.7mm to 5.5±1.9mm (ICC=0.94, SEM=0.6mm) in upright and from 4.9±2.4mm to 5.9±3.0mm (ICC=0.89, SEM=0.9mm) in supine position. LSJA varied from 5.1±2.2° to 7.3±1.5° (ICC=0.54, SEM=1.5°) in upright and from 9.8±2.5° to 10±2.4° (ICC=0.73, SEM=1.1°) in supine position. LA differed from 58.8±14.6° to 61.9±6° (ICC=0.94, SEM=1.19°) in upright and from 51.9±11.7° to 52.6±11.1° (ICC=0.98, SEM=1.59°) in supine position.
CONCLUSIONS: Determination of AT and LA showed good to excellent reliability in both, upright and supine position. In contrast, reliability of LSJA had only moderate to good correlation
between observers and should therefore be interpreted with caution. However, motion artifacts should be taken into consideration during upright imaging procedures.
Schomoller, A, Schugardt, M, Kotsch, P, and Mayer, F. The effect of body composition on cycling power during an incremental test in young athletes. J Strength Cond Res 35(11): 3225-3231, 2021-As body composition (BC) is a modifiable factor influencing sports performance, it is of interest for athletes and coaches to optimize BC to fulfill the specific physical demands of one sport discipline. The purpose of this study is to test the impact of body fat (BF) and fat-free mass (FFM) on aerobic performance in young athletes. Body composition parameters were evaluated among gender and age groups of young athletes undergoing their mandatory health examination. The maximal power (in Watts per kilogram body mass) of a stepwise incremental ergometer test was compared between 6 BC types: high BF, high FFM, high BF and high FFM, normal BC values, low BF, and low FFM. With increasing age (11-13 vs. 14-16 years) BF decreased and FFM increased in both genders. Both BC parameters, as well as body mass, correlated moderately with performance output (r = 0.36-0.6). Subjects with high BF or high FFM or both had significantly lower ergometer test results compared with those with low BF and FFM in all age and gender groups (p < 0.05). The finding that high levels of BF and FFM are detrimental for cycle power output is important to consider in disciplines that demand high levels of aerobic and anaerobic performance.
Cardiac remodeling in child and adolescent athletes in association with sport discipline and sex
(2020)
Continuous high training loads are associated with structural cardiac adaptations and development of an athletic heart in adult athletes, especially in sport disciplines with high dynamic training components. In child and adolescent athletes these effects are increasingly reported. However, study populations are still very small.
Objective: To assess the reliability of measurements of paraspinal muscle transverse relaxation times (T2 times) between two observers and within one observer on different time points. <br /> Methods: 14 participants (9f/5m, 33 +/- 5 years, 176 +/- 10 cm, 73 +/- 12 kg) underwent 2 consecutive MRI scans (M1,M2) on the same day, followed by 1 MRI scan 13-14 days later (M3) in a mobile 1.5 Tesla MRI. T2 times were calculated in T-2 weighted turbo spin- echo-sequences at the spinal level of the third lumbar vertebrae (11 slices, 2 mm slice thickness, 1 mm interslice gap, echo times: 20, 40, 60, 80, 100 ms) for M. erector spinae (ES) and M. multifidius (MF). The following reliability parameter were calculated for the agreement of T2 times between two different investigators (OBS1 & OBS2) on the same MRI (inter rater reliability, IR) and by one investigator between different MRI of the same participant (intersession variability, IS): Test-Retest Variability (TRV, Differences/Mean*100); Coefficient of Variation (CV, Standard deviation/Mean*100); Bland-Altman Analysis (systematic bias = Mean of the Differences; Upper/Lower Limits of Agreement = Bias+/-1.96*SD); Intraclass Correlation Coefficient 3.1 (ICC) with absolute agreement, as well as its 95% confidence interval. <br /> Results: Mean TRV for IR was 2.6% for ES and 4.2% for MF. Mean TRV for IS was 3.5% (ES) and 5.1% (MF). Mean CV for IR was 1.9 (ES) and 3.0 (MF). Mean CV for IS was 2.5% (ES) and 3.6% (MF). A systematic bias of 1.3 ms (ES) and 2.1 ms (MF) were detected for IR and a systematic bias of 0.4 ms (ES) and 0.07 ms (MF) for IS. ICC for IR was 0.94 (ES) and 0.87 (MF). ICC for IS was 0.88 (ES) and 0.82 (MF). <br /> Conclusion: Reliable assessment of paraspinal muscle T2 time justifies its use for scientific purposes. The applied technique could be recommended to use for future studies that aim to assess changes of T2 times, e.g. after an intense bout of eccentric exercises.
Progression or impediment of fundamental motor skills performance (FMSP) in children depends on internal and environmental factors. Shoes as an environmental constraint are believed to affect these movements as children showed to perform qualitatively better with sports shoes than flip-flop sandals. However, locomotor performance assessments based on biomechanical variables are limited. Therefore, the objective of this experiment was to assess the biomechanical effects of wearing shoes while performing fundamental motor skills in children. Barefoot and shod conditions were tested in healthy children between the age of 4 and 7 years. They were asked to perform basic and advanced motor skills including double-leg stance, horizontal jumps, walking as well as counter-movement jumps, single-leg stance and sprinting. Postural control and ground reaction data were measured with two embedded force plates. A 3D motion capture system was used to analyse the spatiotemporal parameters of walking and sprinting. Findings showed that the parameters of single- and double-leg stance, horizontal and counter-movement jump did not differ between barefoot and shod conditions. Most of the spatiotemporal variables including cadence, stride length, stride time, and contact time of walking and sprinting were statistically different between the barefoot and shod conditions. Consequently, tested shoes did not change performance and biomechanics of postural control and jumping tasks; however, the spatiotemporal gait parameters indicate changes in walking and sprinting characteristics with shoes in children.
Acute ankle sprain leads in 40% of all cases to chronic ankle instability (CAI). CAI is related to a variety of motor adaptations at the lower extremities. Previous investigations identified increased muscle activities while landing in CAI compared to healthy control participants. However, it remains unclear whether muscular alterations at the knee muscles are limited to the involved (unstable) ankle or are also present at the uninvolved leg. The latter might potentially indicate a risk of ankle sprain or future injury on the uninvolved leg. Purpose: To assess if there is a difference of knee muscle activities between the involved and uninvolved leg in participants with CAI during perturbed walking. Method: 10 participants (6 females; 4 males; 26±4 years; 169±9 cm; 65±7 kg) with unilateral CAI walked on a split-belt treadmill (1m/s) for 5 minutes of baseline walking and 6 minutes of perturbed walking (left and right side, each 10 perturbations). Electromyography (EMG) measurements were performed at biceps femoris (BF) and rectus femoris (RF). EMG amplitude (RMS; normalized to MVIC) were analyzed for 200ms pre-heel contact (Pre200), 100ms post heel contact (Post100) and 200ms after perturbation (Pert200). Data was analyzed by paired t-test/Wilcoxon test based on presence or absence of normal distribution (Bonferroni adjusted α level p≤ 0.0125). Results: No statistical difference was found between involved and uninvolved leg for RF (Pre200: 4±2% and 11± 22%, respectively, p= 0.878; Post100: 10± 5 and 18±31%, p=0.959; Pert200: 6±3% and 13±24%, p=0.721) as well as for BF (Pre200: 12±7% and 11±6, p=0.576; Post100: 10±7% and 9±7%, p=0.732; Pert200: 7±4 and 7±7%, p=0.386). Discussion: No side differences in muscle activity could be revealed for assessed feedforward and feedback responses (perturbed and unperturbed) in unilateral CAI. Reduced inter-individual variability of muscular activities at the involved leg might indicate a rather stereotypical response pattern. It remains to be investigated, whether muscular control at the knee is not affected by CAI, or whether both sides adapted in a similar style to the chronic condition at the ankle.
Chronic ankle instability (CAI) is not only an ankle issue, but also affects sensorimotor system. People with CAI show altered muscle activation in proximal joints such as hip and knee. However, evidence is limited as controversial results have been presented regarding changes in activation of hip muscles in CAI population. PURPOSE: To investigate the effect of CAI on activity of hip muscles during normal walking and walking with perturbations. METHODS: 8 subjects with CAI (23 ± 2 years, 171 ± 7 cm and 65 ± 4 kg) and 8 controls (CON) matched by age, height, weight and dominant leg (25 ± 3 years, 172 ± 7 cm and 65 ± 6 kg) walked shoed on a split-belt treadmill (1 m/s). Subjects performed 5 minutes of baseline walking and 6 minutes walking with 10 perturbations (at 200 ms after heel contact with 42 m/s2 deceleration impulse) on each side. Electromyography signals from gluteus medius (Gmed) and gluteus maximus (Gmax) were recorded while walking. Muscle amplitudes (Root Mean Square normalized to maximum voluntary isometric contraction) were calculated at 200 ms before heel contact (Pre200), 100 ms after heel contact (Post100) during normal walking and 200 ms after perturbations (Pert200). Differences between groups were examined using Mann Whitney U test and Bonferroni correction to account for multiple testing (adjust α level p≤ 0.0125). RESULT: In Gmed, CAI group showed lower muscle amplitude than CON group after heel contact (Post100: 18±7 % and 47±21 %, p< .01) and after walking perturbations ( 31±13 % and 62±26 %, p< .01), but not before heel contact (Pre200: 5±2 % and 11±10 %, p= 0.195). In Gmax, no difference was found between CAI and CON groups in all three time points (Pre200: 12±5 % and 17±12 %, p= 0.574; Post100: 41±21 % and 41±13 %, p= 1.00; Pert200: 79±46 % and 62±35 %, p= 0.505). CONCLUSION: People with CAI activated Gmed less than healthy control in feedback mechanism (after heel contact and walking with perturbations), but not in feedforward mechanism (before heel contact). Less activation on Gmed may affect the balance in frontal plane and increase the risk of recurrent ankle sprain, giving way or feeling ankle instability in patients with CAI during walking. Future studies should investigate the effect of Gmed strengthening or neuromuscular training on CAI rehabilitation.
BACKGROUND: The Achilles tendon (AT) requires optimal material and mechanical properties to function properly. Calculation of these properties depends on accurate measurement of input parameters (i.e. tendon elongation). However, the measurement of AT elongation with ultrasound during maximum voluntary isometric contraction (MVIC) is overestimated by ankle joint rotation (AJR). Methods to correct the influence of this rotation on AT elongation exist, yet their reproducibility in clinical settings is unknown. OBJECTIVE: To evaluate the test-retest reproducibility of AT elongation during MVIC after AJR correction. METHODS: Ten participants attended test and retest measurements where they performed plantar-flexion MVIC on a dynamometer. Simultaneously, ultrasound recorded AT elongation as the displacement of the medial gastrocnemius-myotendinous junction, while an electrogoniometer measured AJR. The ankle was then passively rotated to the AJR achieved during MVIC and AT elongation again determined. Elongation was corrected by subtracting this passive AT elongation from the total AT elongation during MVIC. Reproducibility was evaluated using ICC (2.1), test-retest variability (TRV, %), Bland-Altman analyses (Bias +/- LoA [1.96*SD]) and standard error of the measurement (SEM). RESULTS: Corrected AT elongation reproducibility exhibited an ICC = 0.79, SEM = 0.2 cm and TRV = 20 +/- 19%. Bias +/- LoA were determined to be 0.0 +/- 0.8 cm. CONCLUSIONS: Using this ultrasound and electrogoniometer-based method, corrected AT elongation can be assessed reproducibly.
Eccentric (ECC) exercises might cause muscle damage, characterized by delayed-onset muscle soreness, elevated creatine kinase (CK) levels and local muscle oedema, shown by elevated T2 times in magnet resonance imaging (MRI) scans. Previous research suggests a high inter-individual difference regarding these systemic and local responses to eccentric workload. PURPOSE: To analyze ECC exercise-induced muscle damage in lumbar paraspinal muscles assessed via MRI. METHODS: Ten participants (3f/7m; 33±6y; 174±8cm; 71±12kg) were included in the study. Quantitative paraspinal muscle constitution of M. erector spinae and M. multifidius were assessed in supine position before and 72h after an intense eccentric trunk exercise bout in a mobile 1.5 tesla MRI device. MRI scans were recorded on spinal level L3 (T2-weighted TSE echo sequences, 11 slices, 2mm slice thickness, 3mm gap, echo times: 20, 40, 60, 80, 100ms, TR time: 2500ms). Muscle T2 times were calculated for manually traced regions of interest of the respective muscles with an imaging software. The exercise protocol was performed in an isokinetic device and consisted of 120sec alternating ECC trunk flexion-extension with maximal effort. Venous blood samples were taken before and 72h after the ECC exercise. Descriptive statistics (mean±SD) and t-testing for pre-post ECC exercises were performed. RESULTS: T2 times increased from pre- to post-ECC MRI measurements from 55±3ms to 79±28ms in M. erector spinae and from 62±5ms to 78±24ms in M. multifidius (p<0.001). CK increased from 126±97 U/L to 1447±20579 U/L. High SDs of T2 time and CK in post-ECC measures could be due to inter-individual reactions to ECC exercises. 3 participants showed high local and systemic reactions (HR) with T2 time increases of 120±24% (M. erector spinae) and 73±50% (M. multifidius). In comparison, the remaining 7 participants showed increases of 11±12% (M. erector spinae) and 7±9% (M. multifidius) in T2 time. Mean CK increased 9.5-fold in the 3 HR subjects compared with the remaining 7 subjects. CONCLUSIONS: The 120sec maximal ECC trunk flexion-extension protocol induced high amounts of muscle damage in 3 participants. Moderate to low responses were found in the remaining 7 subjects, assuming that inter-individual predictors play a role regarding physiological responses to ECC workload.
Eccentric exercises (ECC) induce reversible muscle damage, delayed-onset muscle soreness and an inflammatory reaction that is often followed by a systemic anti-inflammatory response. Thus, ECC might be beneficial for treatment of metabolic disorders which are frequently accompanied by a low-grade systemic inflammation. However, extent and time course of a systemic immune response after repeated ECC bouts are poorly characterized.
PURPOSE: To analyze the (anti-)inflammatory response after repeated ECC loading of the trunk.
METHODS: Ten healthy participants (33 ± 6 y; 173 ± 14 cm; 74 ± 16 kg) performed three isokinetic strength measurements of the trunk (concentric (CON), ECC1, ECC2, each 2 wks apart; flexion/extension, velocity 60°/s, 120s MVC). Pre- and 4, 24, 48, 72, 168h post-exercise, muscle soreness (numeric rating scale, NRS) was assessed and blood samples were taken and analyzed [Creatine kinase (CK), C-reactive protein (CRP), Interleukin-6 (IL-6), IL-10, Tumor necrosis factor-α (TNF-α)]. Statistics were done by Friedman‘s test with Dunn‘s post hoc test (α=.05).
RESULTS: Mean peak torque was higher during ECC1 (319 ± 142 Nm) than during CON (268 ± 108 Nm; p<.05) and not different between ECC1 and ECC2 (297 ± 126 Nm; p>.05). Markers of muscle damage (peaks post-ECC1: NRS 48h, 4.4±2.9; CK 72h, 14407 ± 19991 U/l) were higher after ECC1 than after CON and ECC2 (p<.05). The responses over 72h (stated as Area under the Curve, AUC) were abolished after ECC2 compared to ECC1 (p<.05) indicating the presence of the repeated bout effect. CRP levels were not changed. IL-6 levels increased 2-fold post-ECC1 (pre: 0.5 ± 0.4 vs. 72h: 1.0 ± 0.8 pg/ml). The IL-6 response was enhanced after ECC1 (AUC 61 ± 37 pg/ml*72h) compared to CON (AUC 33 ± 31 pg/ml*72h; p<.05). After ECC2, the IL-6 response (AUC 43 ± 25 pg/ml*72h) remained lower than post-ECC1, but the difference was not statistically significant. Serum levels of TNF-α and of the anti-inflammatory cytokine IL-10 were below detection limits. Overall, markers of muscle damage and immune response showed high inter-individual variability.
CONCLUSION: Despite maximal ECC loading of a large muscle group, no anti-inflammatory and just weak inflammatory responses were detected in healthy adults. Whether ECC elicits a different reaction in inflammatory clinical conditions is unclear.