Eccentric Actions Research Articles

Micromechanical analysis of suction bucket-granular soil interaction under eccentric pulling action of mooring lines: Effect of horizontal pulling angle

Previous suction bucket-soil interaction simulations usually apply fixed loads on suction buckets as the action of mooring lines, ignoring the contact behaviors between mooring lines and suction buckets. This study investigates suction bucket-soil interaction under the above contact behaviors with the horizontal pulling angle effect. Granular soil was generated in the DEM part while the suction buckets were simulated with meshes in the FEM part. The pulling action of mooring lines was applied by a hanger that can slide and rotate at the contact point. The micro-to-macro results revealed that the shape difference in pulling force-displacement curves can be explained by the effect of decomposed pulling actions on soil behaviors. Besides, the horizontal pulling angle effect on discontinuity and occurrences of large soil deformation can be successfully modeled by the coupled DEM-FEM method. Meanwhile, the horizontal pulling angle effect associated with different interface frictions on the movement and deformation of suction buckets were discovered. Furthermore, conclusive failure patterns of suction bucket-soil interaction were identified after analyzing particle-scale soil behaviors. The study indicates that neglecting the horizontal pulling angle of the mooring lines could result in severely misestimating the uplift capacity of a suction bucket and the soil failure pattern.

Eccentric Contractions of the Diaphragm During Mechanical Ventilation.

Diaphragm dysfunction is a highly prevalent phenomenon in patients receiving mechanical ventilation, mainly due to ventilatory over-assistance and the development of diaphragm disuse atrophy. Promoting diaphragm activation whenever possible and facilitating an adequate interaction between the patient and the ventilator is encouraged at the bedside to avoid myotrauma and further lung injury. Eccentric contractions of the diaphragm are defined as muscle activation while muscle fibers are lengthening within the exhalation phase. There is recent evidence that suggests that eccentric activation of the diaphragm is very frequent and may occur during post-inspiratory activity or under different types of patient-ventilator asynchronies, which include ineffective efforts, premature cycling, and reverse triggering. The consequences of this eccentric contraction of the diaphragm may have opposite effects, depending on the level of breathing effort. For instance, during high or excessive effort, eccentric contractions can result in diaphragm dysfunction and injured muscle fibers. Conversely, when eccentric contractions of the diaphragm occur along with low breathing effort, a preserved diaphragm function, better oxygenation, and more aerated lung tissue are observed. Despite this controversial evidence, evaluating the level of breathing effort at the bedside seems crucial and is highly recommended to optimize ventilatory therapy. The impact of eccentric contractions of the diaphragm on the patient's outcome remains to be elucidated.

Effect of Aerobic Training on the Relationship Between Loading Rate and Quadriceps Muscle Activities in Men With Diabetic Neuropathy: A Clinical Trial

Background and Aims The increase in loading rate is associated with lower limb injuries such as tibial stress fracture. Quadriceps muscle activities absorb ground reaction force (GRF) shocks by eccentric activation. This study aims to evaluate the effect of aerobic training on the relationship between loading rate and quadriceps muscle activities in men with diabetic neuropathy (DN). Methods In this double-blinded, randomized, controlled clinical trial, participants were 40 men with DN who were selected by a convenience sampling method and randomly divided into two groups of training (n=20, age: 54.9±7.3, body mass index: 28.4±5.4) and control (n=20; age: 54.1±7.3, body mass index: 28.5±5.1). The GRF data was recorded using a force plate system during walking. The electrical activity of selected lower limb muscles was recorded using electromyography method. The training group performed aerobic training for 12 weeks (three sessions per week). Results The results showed an increase in the negative relationship between vertical loading rate and vastus lateralis activities after training (P=0.028). The activities of vastus medialis and rectus femoris muscles showed no significant relationship with loading rate after training (P>0.05). Conclusion Aerobic training can improve the relationship between vastus lateralis muscle activity and vertical loading rate in men with DN.

The Combined Effect of Taurine and Omega-3 Supplementation on Delayed Onset Muscle Soreness in High-Intensity Eccentric Exercise

Background: Eccentric exercise makes more tensions in active muscle fibers, resulting in muscle damage and delayed pain. Therefore, Delayed-Onset Muscle Soreness (DOMS) is a common result of severe eccentric contractions. This study aimed to clarify the combined effect of taurine and omega-3 supplementation on DOMS and muscle damage after high-intensity eccentric exercise in young untrained men.
 Methods: Forty-eight young untrained males were assigned to four groups (taurine+omega-3 [combined], taurine, omega-3, and one placebo group) and given 1,500 mg taurine and 1,500 mg omega-3 or 1,500 mg taurine or 1,500 mg omega-3 or placebo twice a day respectively. Each group received its supplements for twenty-eight days. DOMS and muscle damage in the lower body developed using a leg press with a weight equivalent to 70% of 1RM (One-Repetition Maximum). Lactate dehydrogenase (LDH), Creatine kinase (CK) and perceived muscle soreness measures were repeated before, immediately, 24, 48, and 72 hr after eccentric activity. p<0.05 was considered to be statistically significant.
 Results: In the combined group, there was no increase in CK and LDH in immediate time and 72 hr after the exercise, respectively, compared to the period before the workout. At 24 and 48 hr after the training, there was a significant decrease in muscle pain perception in all groups compared to placebo (p<0.05).
 Coclusion: A combination of 1500 mg taurine and 1500 mg omega-3, two times a day, for four weeks can reduce the levels of CK and LDH enzymes as some indicators of muscle damage. It also attenuates exercise-induced DOMS and muscle damage.

Astaxanthin Supplementation Reduces Subjective Markers of Muscle Soreness following Eccentric Exercise in Resistance-Trained Men

Strenuous exercise involving eccentric muscle actions induces skeletal muscle damage resulting in delayed onset muscle soreness (DOMS). Antioxidant supplementation, such as astaxanthin (AX), may alleviate muscle injury following intense exercise. The purpose of this study was to investigate the effect of a four-week course of AX supplementation at 12 mg/day−1 on subjective markers of DOMS, recovery, and performance after a bout of muscle damaging eccentric exercise. Nineteen resistance-trained men (mean ± SD: age, 22.6 ± 2.2 y) completed a between-group design with a four-week supplementation period of 12 mg/day−1 of either AX or a placebo. Subjects completed four trials, with trials One and Three designed to induce muscle damage, consisting of a one repetition maximum test (1RM) for leg-press, followed by five sets of ten repetitions at 65% of 1RM. Trials Two and Four were performance trials, conducted 48 h later and consisting of repetitions to failure at 65%, 70%, and 75% of 1RM. Subjective markers of DOMS and recovery were collected at multiple timepoints post-trial for trials One and Three. Although performance was not affected (p > 0.05), AX supplementation significantly decreased subjective markers of DOMS (p = 0.01) compared to the placebo. The results demonstrated that AX may enhance recovery by reducing DOMS without detriment to performance in resistance-trained men.

Low Stiffness Dance Flooring Increases Peak Ankle Plantar Flexor Muscle Activation During a Ballet Jump.

Research in court sports shows that factors which aid in extrinsic shock absorption, that is, flooring and footwear, can help reduce lower extremity injuries. However, since students and performers of ballet or most styles of contemporary dance cannot depend upon footwear, the only extrinsic factor to help them with shock absorption is flooring. We investigated whether doing sauté on a low stiffness dance floor produced a difference in EMG output of the vastus lateralis, gastrocnemius, of soleus compared to a high stiffness floor. Average and average peak amplitude EMG output from 18 dance students or active dancers performing 8 repetitions of sauté on a low stiffness floor (Harlequin® Woodspring) was compared to a maple hardwood floor on concreted subflooring. The data showed a significant increase in average peak EMG muscle amplitude during jumping on the low stiffness floor compared to a high stiffness floor for the soleus muscle (P = .033) and a trend for increase average peak output for the medial gastrocnemius (P = .088). The difference in average peak amplitude of EMG output is explained through the difference in force absorption between floors. With the high stiffness floor, more force of the landing was returned to the dancers' legs, but the low stiffness floor absorbed some of the force of landing the jump, and therefore muscles needed to contribute more to maintain the same jump height. The force absorption characteristic of the low stiffness floor may decrease injury rates in dance through causing an adjustment in muscle velocity. Rapid eccentric muscle activity carries the greatest possibility of musculotendinous injury and is experienced in lower body muscles controlling all joints during impact absorption, which includes landing of jumps in dance. If a surface can decelerate the landing of a high velocity dance movement, it also decreases the musculotendinous demand for high velocity tension generation.

Geochemistry and Petrology of the Bellecombe Lava Sequence, Enclos Fouqué Caldera, Piton de la Fournaise Volcano (Réunion, France)

Piton de la Fournaise is an active shield volcano located in the eastern area of the Réunion Island (Indian Ocean) whose activity is characterized by effusive and explosive episodes with the emission of scarcely differentiated magmas with mostly tholeiitic affinity. The presently active edifice has grown within the Enclos Fouqué caldera, a polylobate plain bounded on its western side by the 80–200 m high Bellecombe vertical cliffs. This escarpment exposes a vertical sequence of 12 lava flows cut by a dike with an age > 5.5 kyrs. In this work, the Bellecombe products were investigated by X-ray fluorescence, Inductively Coupled Plasma Mass Spectroscopy, a Scanning Electron Microscope and X-ray computed microtomography in order to characterize the evolution over time of the magmatic system feeding the eruptive activity prior to the Enclos Fouqué caldera collapse. The results indicate that lava flows share a geochemical affinity with the two main series documented at Piton de la Fournaise, namely, Steady State Basalts (SSB) at the bottom and top of the sequence and Abnormal basalt Group (AbG) with different degrees of differentiation in the central part. The emission of these two different products in both a restricted area and timespan testifies to the dynamic activity of the plumbing system, capable of shifting rapidly from central to eccentric activity in the recent past.

Electromyographic and mechanomyographic responses of the biceps brachii during concentric and eccentric muscle actions to failure at high and low relative loads.

This study examined neuromuscular responses of the biceps brachii (BB) for concentric and eccentric muscle actions during bilateral, dynamic constant external resistance (DCER), reciprocal forearm flexions and extensions to failure at high (80% 1 repetition maximum [1RM]) and low (30% 1RM) relative loads. Nine women completed 1RM testing and repetitions to failure (RTF) at 30 and 80% 1RM. Electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) signals were measured from the BB. Analyses included repeated measures ANOVAs (p < 0.05) and post-hoc pairwise comparisons with Bonferroni corrected alpha of p < 0.008 and p < 0.01 for between and within factor pairwise comparisons, respectively. EMG AMP and MPF were significantly greater for concentric than eccentric muscle actions, regardless of load or time. However, time course of change analysis revealed parallel increases in EMG AMP for concentric and eccentric muscle actions during the RTF trials at 30% 1RM, but no change at 80% 1RM. There were significant increases in MMG AMP during concentric muscle actions, but decreases or no change during eccentric muscle actions. EMG and MMG MPF decreased over time, regardless of muscle action type and loading condition. The greater EMG AMP and MPF values during concentric compared to eccentric muscle actions may reflect the difference in the efficiency characteristic of these muscle actions. The neuromuscular responses suggested that fatigue may be mediated by recruitment of additional motor units with lower firing rates during concentric muscle actions, and changes in motor unit synchronization during eccentric muscle actions.

The acute and repeated bout effects of multi-joint eccentric exercise on physical function and balance in older adults.

Eccentric muscle actions generate high levels of force at a low metabolic cost, making them a suitable training modality to combat age-related neuromuscular decline. The temporary muscle soreness associated with high intensity eccentric contractions may explain their limited use in clinical exercise prescription, however any discomfort is often alleviated after the initial bout (repeated bout effect). Therefore, the aims of the present study were to examine the acute and repeated bout effects of eccentric contractions on neuromuscular factors associated with the risk of falling in older adults. Balance, functional ability [timed up-and-go and sit-to-stand], and lower-limb maximal and explosive strength were measured in 13 participants (67.6 ± 4.9 year) pre- and post-eccentric exercise (0, 24, 48, and 72hr) in Bout 1 and 14days later in Bout 2. The eccentric exercise intervention was performed on an isokinetic unilateral stepper ergometer at 50% of maximal eccentric strength at 18 step‧min-1 per limb for 7min (126 steps per limb). Two-way repeated measures ANOVAs were conducted to identify any significant effects (P ≤ 0.05). Eccentric strength significantly decreased (-13%) in Bout 1 at 24hr post-exercise; no significant reduction was observed at any other time-point after Bout 1. No significant reductions occurred in static balance or functional ability at any time-point in either bout. Submaximal multi-joint eccentric exercise results in minimal disruption to neuromuscular function associated with falls in older adults after the initial bout.

Functional tests in women with patellofemoral pain: Which tests make a difference in physical therapy evaluation

BackgroundPatellofemoral pain (PFP) is characterized by anterior knee, which intensifies during functional activities that require the eccentric action of the quadriceps muscle, specially. In ths way, quantitatively measurable functional tests that simulate these activities should be included in the physical therapy evaluation. ObjectiveTo identify which functional tests are most indicated for the evaluation of women with PFD. MethodThis study evaluated 100 young women (50 with PFP), during the execution of the following functional performance tests: Triple hop, Vertical Jump, Single leg squat, Step Down, YBalance tests, Lunge test and running. Dynamic valgus was also assessed in the tests. The isometric muscle strength of the following muscle groups: hip abductors, extensors and lateral rotators, knee extensors, evertors, and plantar flexors were evaluated. Functional Perception were evaluated by Anterior Knee Pain Scale and Activities of Daily Living Scale. ResultsPFP group showed lower performance during the Y-Balance, triple hop, vertical jump tests and running. Was observed an increase in dynamic valgus during Triple Hop, Vertical Jump tests and running in PFP group, besides a poorer perception of function. For all lower limb muscle groups, the PFP group showed a reduction in peak isometric force. ConclusionThe YBalance, triple hop, vertical jump tests, and running should be included in the physical therapy evaluation, in addition to aspects of lower limb muscle strength.

AP-452681-4 UNUSUAL INITIATION OF ORTHODROMIC ATRIOVENTRICULAR REENTRANT TACHYCARDIA WITH A JUNCTIONAL BEAT

Spontaneous initiation of orthodromic atrioventricular reentrant tachycardia (AVRT) is commonly noted with premature ventricular beat (PVC). In the lab it can be initiated with programmed atrial or ventricular stimulation. We report the initiation of AVRT (with left lateral accessory pathway) with a junctional beat. Case report A 69-year-old male with history of Parkinson’s, HTN, who has had palpitations for few years. Event monitor showed narrow and wide complex tachycardia and he was scheduled for electrophysiology (EP) study and catheter ablation. He presented in sinus rhythm. EP study revealed normal AH and HV intervals with no evidence of preexcitation. Narrow complex supraventricular tachycardia (SVT) initiated spontaneously as noted in the Figure. SVT (short RP) was also initiated with ventricular and atrial extra stimuli without critical AH dependence. There was eccentric atrial activation during SVT with the earliest atrial activation on distal CS. Ventricular overdrive pacing (VOD) during SVT lead to VAV response ruling out atrial tachycardia. There was LBBB during SVT that increased the VA time from 94 ms to 170 ms. The tachycardia terminated with single fused PVC with VA block. Based on these findings a diagnosis of AVRT was made and the concealed left lateral accessory pathway was ablated at 1’o clock on mitral annulus via transseptal catheterization. This case illustrates spontaneous initiation of AVRT using a left lateral accessory pathway with a junctional beat that conducted retrogradely through the accessory pathway. This is a novel finding that has not been demonstrated prior to this. Hence a junctional beat can spontaneously initiate AVRT similar to a PVC. Similarly JPC can initiate AVNRT especially during ablation at the slow pathway region and should not be presumed to be junctional tachycardia.

Pedal cadence does not affect muscle damage to eccentric cycling performed at similar mechanical work.

Purpose: This study aimed to investigate muscle damage when performing equal mechanical work of fast and slow pedaling speed by eccentric muscle actions (ECCs) cycling. Methods: Nineteen young men [mean ± standard deviation (SD) age: 21.0 ± 2.2years; height: 172.7 ± 5.9cm; and body mass: 70.2 ± 10.5kg] performed maximal effort of ECCs cycling exercise with fast speed (Fast) and slow speed trials (Slow). First, subjects performed the Fast for 5min by one leg. Second, Slow performed until the total mechanical work was equal to that generated during Fast other one leg. Changes in maximal voluntary isometric contraction (MVC) torque of knee extension, isokinetic pedaling peak torque (IPT), range of motion (ROM), muscle soreness, thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, and 1 and 4days after exercise. Results: Exercise time was observed in the Slow (1422.0 ± 330.0s) longer than Fast (300.0 ± 0.0s). However, a significant difference was not observed in total work (Fast:214.8 ± 42.4J/kg, Slow: 214.3 ± 42.2J/kg). A significant interaction effect was not observed in peak values of MVC torque (Fast:1.7 ± 0.4 Nm/kg, Slow: 1.8 ± 0.5Nm/kg), IPT, muscle soreness (Fast:4.3 ± 1.6cm, Slow: 4.7 ± 2.9cm). In addition, ROM, circumference, muscle thickness, muscle echo intensity, and muscle stiffness also showed no significant interaction. Conclusion: The magnitude of muscle damage is similar for ECCs cycling with equal work regardless of velocity.

Repeated measurements of Adaptive Force: Maximal holding capacity differs from other maximal strength parameters and preliminary characteristics for non-professional strength vs. endurance athletes.

The Adaptive Force (AF) reflects the neuromuscular capacity to adapt to external loads during holding muscle actions and is similar to motions in real life and sports. The maximal isometric AF (AFisomax) was considered to be the most relevant parameter and was assumed to have major importance regarding injury mechanisms and the development of musculoskeletal pain. The aim of this study was to investigate the behavior of different torque parameters over the course of 30 repeated maximal AF trials. In addition, maximal holding vs. maximal pushing isometric muscle actions were compared. A side consideration was the behavior of torques in the course of repeated AF actions when comparing strength and endurance athletes. The elbow flexors of n = 12 males (six strength/six endurance athletes, non-professionals) were measured 30 times (120s rest) using a pneumatic device. Maximal voluntary isometric contraction (MVIC) was measured pre and post. MVIC, AFisomax, and AFmax (maximal torque of one AF measurement) were evaluated regarding different considerations and statistical tests. AFmax and AFisomax declined in the course of 30 trials [slope regression (mean ± standard deviation): AFmax = -0.323 ± 0.263; AFisomax = -0.45 ± 0.45]. The decline from start to end amounted to -12.8% ± 8.3% (p < 0.001) for AFmax and -25.41% ± 26.40% (p < 0.001) for AFisomax. AF parameters declined more in strength vs. endurance athletes. Thereby, strength athletes showed a rather stable decline for AFmax and a plateau formation for AFisomax after 15 trials. In contrast, endurance athletes reduced their AFmax, especially after the first five trials, and remained on a rather similar level for AFisomax. The maximum of AFisomax of all 30 trials amounted 67.67% ± 13.60% of MVIC (p < 0.001, n = 12), supporting the hypothesis of two types of isometric muscle action (holding vs. pushing). The findings provided the first data on the behavior of torque parameters after repeated isometric-eccentric actions and revealed further insights into neuromuscular control strategies. Additionally, they highlight the importance of investigating AF parameters in athletes based on the different behaviors compared to MVIC. This is assumed to be especially relevant regarding injury mechanisms.

The Efficacy of a Multimodal Recovery Strategy Implemented After a High-Intensity Rugby League Training Session.

Aben, HGJ, Hills, SP, Higgins, D, Cooke, CB, Davis, D, Jones, B, and Russell, M. The efficacy of a multimodal recovery strategy implemented after a high-intensity rugby league training session. J Strength Cond Res 37(8): 1634-1642, 2023-The efficacy of a multimodal recovery strategy implemented within 4 hours of rugby league (RL) training was investigated using repeated-measures, randomized, crossover methods in 10 professional academy RL players (age: 17 ± 1 years). Following standardized training (5,383 m covered, 350-m high-speed running, 28 repeated high-intensity efforts, 24 collisions), players completed a multimodal recovery (REC) strategy (i.e., ∼640 kcal meal + ∼1,285 kcal snacks or drinks, cold-water immersion, sleep hygiene recommendations) or control (i.e., ∼640 kcal meal: CONT) practices. Isometric mid-thigh pulls (IMTP), countermovement jumps (CMJ), and wellness questionnaires were completed before (-3 hours) and after (+24, +48 hours) training. The recovery strategy influenced IMTP peak force ( p = 0.026), but between-trial differences were undetectable. No other between-trial effects (all p > 0.05) were seen for IMTP, CMJ, or wellness variables. Training-induced reductions in CMJ peak power (-4 ± 6% vs baseline: 4,878 ± 642 W) at +24 hours ( p = 0.016) dissipated by +48 hours. Fatigue and lower-body soreness reduced by 16 ± 19% ( p = 0.01) and 32 ± 44% ( p = 0.024) at +48 hours versus +24 hours, respectively. Relative to CONT (i.e., posttraining nutrition), the effects of a single bout of recovery practices appeared limited when implemented after RL-specific training. Therefore, when training included limited collisions, balanced postexercise meals appeared equally effective relative to a multimodal recovery strategy. Transient changes in performance and wellness variables after training may have implications for practitioners. Consecutive training sessions, including a high frequency and intensity of eccentric muscle actions, should be carefully planned, especially near match-play.

Muscle Activation during the Squat Performed in Different Ranges of Motion by Women

Purpose: To analyze the muscle activation of the rectus femoris (RF), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) in concentric and eccentric actions in the squat at 90° and 140° range of motion. Methods: Thirty-five women (32.9 ± 7.4 years; 64.5 ± 11.5 kg; 1.63 ± 0.1 m; BMI: 24.2 ± 2.9 kg/m2; %fat: 24.9 ± 6.5%) experienced exercise for at least eight weeks. Electrodes were positioned in standardized locations. The signals were acquired by an A/D SAS1000 V8 converter and the electromyographic activity normalized in the percentage of the highest produced value (%RMS). The data were analyzed using repeated measures two-way ANOVA, with effect size (η2) and differences calculated in percentage points (∆ p.p.). Results: The RF (p = 0.001; ∆ = 5.1 p.p.) and BF activation (p = 0.020; ∆ = 4.0 p.p.) was higher at 90° in the eccentric action. The RF showed an interaction between the range of motion and %RMS, with a large effect size (F = 37.9; p = 0.001; η2 = 0.485). The VL activation was higher at 140° (p = 0.005; ∆ = 3.9 p.p.) in the concentric action and higher at 90° (p = 0.006; ∆ = 3.7 p.p.) in the eccentric action, with a large effect size significant interaction (F = 21.3; p = 0.001; η2 = 0.485). The GM activation was higher at 90° in the concentric (p = 0.020; ∆ = 5.4 p.p.) and eccentric action (p = 0.022; ∆ = 41 p.p.). Conclusions: The biarticular muscles were influenced by the squat range only in the eccentric action of the movement, while the monoarticular muscles were influenced by the squat in both concentric and eccentric muscle action.

Dynamic analysis of grinding electric spindle bearing-rotor system under eccentric action

To study the influence of eccentricity on the dynamic characteristics of grinding electric spindle, firstly, the nonlinear oil film force (NOFF) expression of sliding bearing is established based on the boundary condition of adhesion pressure. Then, the expression of the unbalanced magnetic pull (UMP) under the eccentricity of the air gap is derived. Finally, the bearing-rotor dynamics equation of the grinding electric spindle considering the NOFF and UMP is established, and the dimensionless processing is carried out. The nonlinear dynamics study of the bearing-rotor system under the influence of geometric eccentricity and mass eccentricity is carried out through the shaft center trajectory and the shaft center vibration spectrum. The research results can provide reference for the optimal design of grinding electric spindle.

Passive force enhancement is not abolished by shortening of single rabbit psoas fibres

Passive force enhancement is defined as the increase in steady-state passive force following deactivation of an actively stretched muscle compared to the corresponding passive force following passive stretching of the muscle. Passive force enhancement has been associated with contributing to the residual force enhancement property, providing stability to sarcomeres, and preventing sarcomeres from over-stretching during eccentric muscle action. Despite its functional importance, the molecular mechanisms underlying passive force enhancement remain unknown. Specifically, it remains unknown how passive force enhancement develops and how it is abolished. Incidental observations on cat soleus muscles led to the speculation that passive force enhancement is abolished when the actively stretched muscle is deactivated and then passively shortened to its pre-stretched length. Here, we tested this hypothesis using skinned fibres from rabbit psoas and rejected it. Rather, we found that passive force enhancement increased following shortening of the fibres to their pre-stretched length (2.4 µm), and furthermore, that the passive force enhancement increased by 70–106% when the shortening and subsequent stretch to the original length (3.6 µm) increased in duration (200 ms, 6 s, and 14 s). These results indicate that passive force enhancement increases during a shortening–stretch cycle, and that this increase is time-dependent. We propose that this increase in passive force enhancement is caused by titin; specifically, with a refolding of titin’s immunoglobulin domains that were unfolded during the active fibre stretching that produced the residual and passive force enhancement. Molecular level experiments are required to test this proposal.

Low-dye taping may enhance physical performance and muscle activation in basketball players with overpronated feet.

Low-dye taping (LTD) is widely used by athletes and medical practitioners but the research regarding its impacts on athletic performance is lacking. This study investigated the effects of using low-dye taping on plyometric performance and muscle activities in recreational basketball players with overpronated feet. Twelve collegiate males with at least three years basketball training experience and navicular drop (ND) value ≥10 mm performed the navicular drop, drop jump and countermovement jump tests. Surface electromyography of selected lower limb muscles were observed during bilateral free squat. All tests in non-taped (NT) and taped (TAP) conditions were counterbalanced using repeated crossover study design. Paired t-test with an alpha level of 0.05 and non-clinical magnitude-based decision (MBD) with standardized effects were used to analyze data. Contact time and reactive strength index (RSI) in the TAP condition were significantly shorter (p = 0.041) and higher (p<0.01) than the NT condition respectively. No significant difference in CMJ performance between NT and TAP was observed. MBD demonstrated clear effects on both ND (standardized effect: -1.54±0.24), flight time (standardized effect: 0.24±0.30), contact time (standardized effect: -0.27±0.21), RSI (standardized effect: 0.69±0.35) and eccentric activities of inferior gluteus maximus (standardized effect: 0.23±0.35), gluteus medius (standardized effect: 0.26±0.29) and tibialis anterior (standardized effect: 0.22±0.06). LDT is effective in correcting overpronated feet by increasing ND height. Meanwhile, it provides a small increase in RSI and gluteal muscle activity during the eccentric (down) phase of the bilateral squat, and without affecting CMJ performance. Conditioning coaches or therapists may use LDT to enhance gluteal activation for reducing injury occurrence and reactive strength performance in drop jump tasks.

Muscle function and functional performance after pulmonary rehabilitation in patients with chronic obstructive pulmonary disease: a prospective observational study

This study aimed to measure changes in different properties of skeletal muscles and evaluate their contribution and relationship to changes in functional performance after pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD). COPD outpatients attending 5 weeks of conventional PR were recruited. Functional performance [5-repetitions sit-to-stand (5STS), and 4-m gait speed (4mGS)], and muscle function (maximal isometric strength, power, force control, and relative concentric and eccentric activation during 5STS) were assessed after PR and 3 months of follow-up. Twenty patients (71 years; 52% of predicted FEV1) completed the study. 4mGS and relative concentric activation during 5STS decreased respectively by 7.7% and 26% between the beginning of PR and follow-up. Quadriceps strength, power, and force control improved by 10.4%, 27.3%, and 15.2%, respectively, from the beginning of PR to follow-up the relative eccentric activation during 5STS explained 31% of the variance in 4mGS changes. In conclusion, functional performance appeared to decline after conventional PR, whereas several properties of skeletal muscles were maintained at follow-up in COPD outpatients. Of note, eccentric contractions might play a role in the improvement of functional performance. Therefore, future studies with interventional design should include eccentric training in PR programs during clinical COPD practice.

Erratum: Fast-Speed Compared With Slow-Speed Eccentric Muscle Actions Are Detrimental to Jump Performance in Elite Soccer Players In-Season.

TO OUR READERS: An error appeared in the ahead-of-print version of the following article: Segers N, Waldron M, Howe LP, et al. Fast-speed compared with slow-speed eccentric muscle actions are detrimental to jump performance in elite soccer players in-season [published online June 23, 2022]. Int J Sports Physiol Perform. https://doi.org/10.1123/ijspp.2021-0542. The words “fast” and “slow” were inadvertently transposed, leading to a misinterpretation of the study’s findings. The title should have been “Slow-Speed Compared With Fast-Speed Eccentric Muscle Actions Are Detrimental to Jump Performance in Elite Soccer Players In-Season.” The article was corrected July 27, 2022. The authors apologize for the error.