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Marcus Börjesson, Carolina Lundqvist, Henrik Gustafsson and Paul Davis

example, an upset stomach, feelings of physical weakness, and muscle stiffness or tension (e.g.,  Grossbard, Smith, Smoll, & Cumming, 2009 ). Physiological indices of increased arousal include elevated heart rate, secretion of stress-hormones, muscle tension, and heightened blood-pressure ( Noteboom

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Cynthia J. Wright and Brent L. Arnold

Context:

Force sense (FS), the proprioceptive ability to detect muscle-force generation, has been shown to be impaired in individuals with functional ankle instability (FAI). Fatigue can also impair FS in healthy individuals, but it is unknown how fatigue affects FS in individuals with FAI.

Objective:

To assess the effect of fatigue on ankle-eversion force-sense error in individuals with and without FAI. Design: Case control with repeated measures.

Setting:

Sports medicine research laboratory.

Participants:

32 individuals with FAI and 32 individuals with no ankle sprains or instability in their lifetime. FAI subjects had a history of ≥1 lateral ankle sprain and giving-way ≥1 episode per month.

Interventions:

Three eversion FS trials were captured per load (10% and 30% of maximal voluntary isometric contraction) using a load cell before and after a concentric eversion fatigue protocol.

Main Outcome Measures:

Trial error was the difference between the target and reproduction forces. Constant error (CE), absolute error (AE), and variable error (VE) were calculated from 3 trial errors. A Group × Fatigue × Load repeated-measures ANOVA was performed for each error.

Results:

There were no significant 3-way interactions or 2-way interactions involving group (all P > .05). CE and AE had a significant 2-way interaction between load and fatigue (CE: F 1,62 = 8.704, P = .004; AE: F 1,62 = 4.024, P = .049), and VE had a significant main effect for fatigue (F 1,62 = 5.130, P = .027), all of which indicated increased FS error with fatigue at 10% load. However, at 30% load only VE increased with fatigue. The FAI group had greater error as measured by AE (F 1,62 = 4.571, P = .036) but not CE or VE (P > .05).

Conclusions:

Greater AE indicates that FAI individuals are less accurate in their force production. Fatigue impaired force sense in all subjects equally. These deficits provide evidence of impaired proprioception with fatigue and in individuals with FAI.

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Emily R. Hunt, Shelby E. Baez, Anne D. Olson, Timothy A. Butterfield and Esther Dupont-Versteegden

to decrease fear-avoidance beliefs to encourage long-term activity engagement after musculoskeletal injury in addition to addressing physiological barriers associated with pain and muscle tension. Therefore, the purpose of this paper is to describe how massage can be integrated into the Fear

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Paul W.M. Marshall, Ric Lovell and Jason C. Siegler

Purpose:

Passive muscle tension is increased after damaging eccentric exercise. Hamstring-strain injury is associated with damaging eccentric muscle actions, but no research has examined changes in hamstring passive muscle tension throughout a simulated sport activity. The authors measured hamstring passive tension throughout a 90-min simulated soccer match (SAFT90), including the warm-up period and every 15 min throughout the 90-min simulation.

Methods:

Passive hamstring tension of 15 amateur male soccer players was measured using the instrumented straight-leg-raise test. Absolute torque (Nm) and slope (Nm/°) of the recorded torque-angular position curve were used for data analysis, in addition to total leg range of motion (ROM). Players performed a 15-min prematch warm-up, then performed the SAFT90 including a 15-min halftime rest period.

Results:

Reductions in passive stiffness of 20–50° of passive hip flexion of 22.1−29.2% (P < .05) were observed after the warm-up period. During the SAFT90, passive tension increased in the latter 20% of the range of motion of 10.1−10.9% (P < .05) concomitant to a 4.5% increase in total hamstring ROM (P = .0009).

Conclusions:

The findings of this study imply that hamstring passive tension is reduced after an active warm-up that includes dynamic stretching but does not increase in a pattern suggestive of eccentric induced muscle damage during soccer-specific intermittent exercise. Hamstring ROM and passive tension increases are best explained by improved stretch tolerance.

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Gerald L. Gottlieb

The lambda version of the equilibrium-point (EP) hypothesis as developed by Feldman and colleagues has been widely used and cited with insufficient critical understanding. This article offers a small antidote to that lack. First, the hypothesis implicitly, unrealistically assumes identical transformations of lambda into muscle tension for antagonist muscles. Without that assumption, its definitions of command variables R, C, and lambda are incompatible and an EP is not defined exclusively by R nor is it unaffected by C. Second, the model assumes unrealistic and unphysiological parameters for the damping properties of the muscles and reflexes. Finally, the theory lacks rules for two of its three command variables. A theory of movement should offer insight into why we make movements the way we do and why we activate muscles in particular patterns. The EP hypothesis offers no unique ideas that are helpful in addressing either of these questions.

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Shinya Ogaya, Hisashi Naito, Akira Iwata, Yumi Higuchi, Satoshi Fuchioka and Masao Tanaka

Toe-out angle alternation is a potential tactic for decreasing the knee adduction moment during walking. Published reports have not examined the medial knee contact force during the toe-out gait, although it is a factor affecting knee articular cartilage damage. This study investigated the effects of increased toe-out angle on the medial knee contact force, using musculoskeletal simulation analysis. For normal and toe-out gaits in 18 healthy subjects, the muscle tension forces were simulated based on the joint moments and ground reaction forces with optimization process. The medial knee contact force during stance phase was determined using the sum of the muscle force and joint reaction force components. The first and second peaks of the medial knee contact force were compared between the gaits. The toe-out gait showed a significant decrease in the medial knee contact force at the second peak, compared with the normal gait. In contrast, the medial knee contact forces at the first peak were not significantly different between the gaits. These results suggest that the toe-out gait is beneficial for decreasing the second peak of the medial knee contact force.

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Kyle Matsel, Claire Davies and Tim Uhl

Clinical Scenario: Shoulder pain is a very common symptom encountered in outpatient physical therapy practice. In addition to therapeutic exercise and manual therapy interventions, trigger point dry needling (TDN) has emerged as a possible treatment option for reducing shoulder pain and improving function. Dry needling consists of inserting a thin stainless-steel filament into a myofascial trigger point with the intention of eliciting a local twitch response of the muscle. It is theorized that this twitch response results in reduced muscle tension and can aid in reduced pain and disability. To this point, multiple studies have found TDN to be effective at reducing pain and improving function in the short-term, but the long-term outcomes remain unknown. Clinical Question: Does the addition of TDN to an exercise program result in better long-term pain intensity and disability reduction in patients with shoulder pain? Summary of Findings: Improvement in long-term pain and function can be expected regardless of the addition of TDN to an evidence-based exercise program for patients with shoulder pain. Clinical Bottom Line: Either TDN or an evidence-based therapeutic exercise program elicits improved long-term pain and disability reduction in patients with shoulder pain, which suggests that clinicians can confidently use either approach with their patients. Strength of Recommendation: Strong evidence (level 2 evidence with PEDro scores >8/10) suggesting that TDN does not outperform therapeutic exercise regarding long-term pain reduction.

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James M. Robbins and Paul Joseph

The types and frequency of sensations experienced by runners when required to miss a run or series of runs was studied. Most of 345 runners of various weekly mileage levels reported some kind of distress; irritability, restlessness, frustration, guilt, and depression were reported most often. Sleeping problems, digestive difficulties, and muscle tension and soreness were reported less frequently. Three causes of exercise withdrawal were proposed: (a) a misinterpretation of the return of dysphoria that had been temporarily masked by the effects of running; (b) an inability to cope with stress in periods when the coping mechanism of running is temporarily unavailable; and (c) the loss of regular, predictable reinforcement of feelings of self-fulfillment gained through success or achievement in previously unimagined and unattainable ways. Results, based on cross-sectional data, were consistent with these hypotheses but do not rule out alternative explanations. The reciprocal nature of number of miles run in an average week and exercise deprivation sensations was also studied. Results indicated that runners tended to run longer in order to avoid the negative sensations that would come from not running, but that an escalation in mileage did not necessarily result in more frequent experiences of distress when not able to run.

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Matthew T.G. Pain and John H. Challis

The aims of this study were to quantify intrasegmental motion using an array of 28 surface-mounted markers to examine frequency and amplitude measurements of the intrasegmental motion to calculate forces and energy transfer; and to show that the underlying muscles are a major contributor to the skin marker motion. One participant performed 27 trials under three conditions in which his forearm was struck against a solid object fixed to a force plate while the locations of the markers were recorded at 240 Hz. For impacts with equal peak forces, the muscle tension significantly affected the amount of intrasegmental motion. Tensing the arm reduced the intrasegmental motion by 50%. The quadrilateral sectors defined by the markers changed in area by 11% with approximately equal motion in the vertical and horizontal direction. The maximum linear marker motion was 1.7 cm. The intrasegmental motion had distinct frequency components around 14 and 20 Hz. Soft tissue deformation could account for 70% of the energy lost from the forearm during these impacts. The study has demonstrated the important role that intrasegment soft tissue motion can have on the kinetics of an impact.

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Lewis J. Macgregor, Massimiliano Ditroilo, Iain J. Smith, Malcolm M. Fairweather and Angus M. Hunter

Context:

Assessments of skeletal-muscle functional capacity often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated as a means to assess muscle contractile function after fatigue; however, observations have not been contextualized by concurrent physiological measures.

Objective:

To measure peripheral-fatigue-induced alterations in mechanical and contractile properties of the plantar-flexor muscles through noninvasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) to validate TMG as a gauge of peripheral fatigue.

Design:

Pre- and posttest intervention with control.

Setting:

University laboratory.

Participants:

21 healthy male volunteers.

Interventions:

Subjects’ plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5-min rest period (control) or a 5-min electrical-stimulation intervention (fatigue).

Main Outcome Measures:

Temporal (contraction velocity) and spatial (radial displacement) contractile parameters of the gastrocnemius medialis were recorded through TMG. MVC was measured as an indicator of muscle fatigue, and PMT was measured to assess muscle stiffness.

Results:

Radial displacement demonstrated a fatigue-associated reduction (3.3 ± 1.2 vs 4.0 ± 1.4 mm, P = .031), while contraction velocity remained unaltered. In addition, MVC significantly declined by 122.6 ± 104 N (P < .001) after stimulation (fatigue). PMT was significantly increased after fatigue (139.8 ± 54.3 vs 111.3 ± 44.6 N, P = .007).

Conclusions:

TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement accompanied by elevated PMT. TMG could be useful in establishing skeletalmuscle fatigue status without exacerbating the functional decrement of the muscle.