Plantar flexor muscle stretching depresses the soleus late response but not tendon tap reflexes

We aimed to study intrinsic factors in 29 consecutive patients with well-documented unilateral stress fractures of the tibia. Anthropometry, range of motion, isokinetic plantar flexor muscle performance, and gait pattern were analyzed. The uninjured leg served as the control. A reference group of 30 uninjured subjects was compared regarding gait pattern. Anterior stress fractures of the tibia (N = 10) were localized in the push-off/ landing leg in 9/10 athletes, but were similarly distributed between legs in posteromedial injuries (N = 19). Ten (30%) of the stress fracture subjects had bilateral high foot arches, similar to those found in the reference group. There were no other systematic differences in anthropometry, range of motion, gait pattern, or isokinetic plantar flexor muscle peak torque and endurance between injured and uninjured legs. No other differences were found between anterior and posteromedial stress fractures. We conclude that anterior stress fractures of the tibia occur mainly in the push-off/landing leg in athletes. Within the limitations of our protocol, no registered intrinsic factor was found to be directly associated with the occurrence of a stress fracture of the tibia.

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Passive Ankle Stiffness in Subjects With Diabetes and Peripheral Neuropathy Versus an Age-Matched Comparison Group

Physical Therapy ◽

10.1093/ptj/80.4.352 ◽

2000 ◽

Vol 80 (4) ◽

pp. 352-362 ◽

Cited By ~ 60

Author(s):

Gretchen B Salsich ◽

Michael J Mueller ◽

Shirley A Sahrmann

Keyword(s):

Peripheral Neuropathy ◽

Range Of Motion ◽

Comparison Group ◽

Plantar Flexor ◽

Initial Angle ◽

Flexor Muscle ◽

Ankle Stiffness ◽

Torque Curve ◽

Muscle Excursion ◽

Matched Comparison

Abstract Background and Purpose. Patients with diabetes mellitus and peripheral neuropathy (DM and PN) often complain of joint stiffness. Although stiffness may contribute to some of the impairments and functional limitations found in these patients, it has not been quantified in this population. The purpose of this study was to quantify and compare passive ankle stiffness and dorsiflexion (DF) range of motion in subjects with DM and PN versus an age-matched comparison group. Subjects. Thirty-four subjects were tested (17 subjects with DM and PN and 17 subjects in an age-matched comparison group). There were 10 male subjects and 7 female subjects in each group. Methods. A Kin-Com dynamometer was used to measure passive plantar flexor torque as each subject's ankle was moved from plantar flexion into dorsiflexion at 60°/s. The following variables were compared using a Student t test: initial angle (angle of onset of plantar flexor torque), maximal dorsiflexion angle, plantar flexor muscle excursion (difference between initial angle and maximal dorsiflexion angle), slope of the first half of the plantar flexor torque curve (stiffness 1 measurement), and slope of the second half of the plantar flexor torque curve (stiffness 2 measurement). Results. The subjects with DM and PN group had smaller maximal dorsiflexion angles and less plantar flexor muscle excursion than the comparison group. There was no difference in initial angle, stiffness 1 measurement, or stiffness 2 measurement. Conclusion and Discussion. Although the subjects with DM and PN had less dorsiflexion range of motion than did the comparison group, there was no difference in stiffness between the groups. This finding suggests that people with DM and PN have “short” versus “stiff” plantar flexor muscles.

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Does clinically measured ankle plantar flexor muscle strength or weakness correlate with walking performance in healthy individuals?

Journal of Back and Musculoskeletal Rehabilitation ◽

10.3233/bmr-171082 ◽

2018 ◽

Vol 31 (6) ◽

pp. 1201-1209

Author(s):

N. Ekin Akalan ◽

Shavkat Kuchimov ◽

Adnan Apti ◽

Yener Temelli ◽

Merve Ören ◽

...

Keyword(s):

Muscle Strength ◽

Plantar Flexor ◽

Healthy Individuals ◽

Flexor Muscle ◽

Walking Performance

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Calf-raise senior: a new test for assessment of plantar flexor muscle strength in older adults: protocol, validity, and reliability

Clinical Interventions in Aging ◽

10.2147/cia.s115304 ◽

2016 ◽

Vol Volume 11 ◽

pp. 1661-1674 ◽

Cited By ~ 3

Author(s):

Helô André ◽

Filomena Carnide ◽

Edgar Borja ◽

Fátima Ramalho ◽

Rita Santos-Rocha ◽

...

Keyword(s):

Older Adults ◽

Muscle Strength ◽

Plantar Flexor ◽

Validity And Reliability ◽

Flexor Muscle

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Adaptations in human neuromuscular function following prolonged unweighting: I. Skeletal muscle contractile properties and applied ischemia efficacy

Journal of Applied Physiology ◽

10.1152/japplphysiol.01402.2005 ◽

2006 ◽

Vol 101 (1) ◽

pp. 256-263 ◽

Cited By ~ 75

Author(s):

Brian C. Clark ◽

Bo Fernhall ◽

Lori L. Ploutz-Snyder

Keyword(s):

Lower Limb ◽

Strength Loss ◽

Contractile Properties ◽

Plantar Flexor ◽

Postactivation Potentiation ◽

Flexor Muscle ◽

Muscle Properties ◽

Cross Sectional ◽

Lateral Gastrocnemius

Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor muscle properties following 4 wk of limb suspension (unilateral lower limb suspension), along with the effect of applied ischemia (Isc) on these properties. In the companion paper (Part II), we report our findings on the changes in neurological properties. Measurements of voluntary and evoked forces, the compound muscle fiber action potential (CMAP), and muscle cross-sectional area (CSA) were collected before and after 4 wk of unilateral lower limb suspension in adults ( n = 18; 19–28 yr). A subset of subjects ( n = 6) received applications of Isc 3 days/wk (3 sets; 5-min duration). In the subjects not receiving Isc, the loss in CSA and strength was as expected (∼9 and 14%). We observed a 30% slowing in the duration of the CMAP, a 10% decrease in evoked doublet force, a 12% increase in the twitch-to-doublet force ratio, and an altered postactivation potentiation response (11% increase in the postactivation potentiation-to-doublet ratio). We also detected a 10% slowing in the ability of the plantar flexor to develop force during the initial phase of an evoked contraction, along with a 6% reduction in in vivo specific doublet force. In the Isc subjects, no preservation was observed in strength or the evoked muscle properties. However, the Isc group did maintain CSA of the lateral gastrocnemius, as the control subjects’ lateral gastrocnemius atrophied 10.2%, whereas the subjects receiving Isc atrophied 4.7%. Additionally, Isc abolished the unweighting-induced slowing in the CMAP. These findings suggest that unweighting alters the contractile properties involved in the excitation-contraction coupling processes and that Isc impacts the sarcolemma.

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Series elasticity facilitates safe plantar flexor muscle–tendon shock absorption during perturbed human hopping

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2021.0201 ◽

2021 ◽

Vol 288 (1947) ◽

Author(s):

Taylor J. M. Dick ◽

Christofer J. Clemente ◽

Laksh K. Punith ◽

Gregory S. Sawicki

Keyword(s):

Steady State ◽

Neuromuscular Control ◽

Ground Contact ◽

Plantar Flexor ◽

Plantar Flexors ◽

Flexor Muscle ◽

Unpredictable Environments ◽

Co Activation ◽

Length Changes

In our everyday lives, we negotiate complex and unpredictable environments. Yet, much of our knowledge regarding locomotion has come from studies conducted under steady-state conditions. We have previously shown that humans rely on the ankle joint to absorb energy and recover from perturbations; however, the muscle–tendon unit (MTU) behaviour and motor control strategies that accompany these joint-level responses are not yet understood. In this study, we determined how neuromuscular control and plantar flexor MTU dynamics are modulated to maintain stability during unexpected vertical perturbations. Participants performed steady-state hopping and, at an unknown time, we elicited an unexpected perturbation via rapid removal of a platform. In addition to kinematics and kinetics, we measured gastrocnemius and soleus muscle activations using electromyography and in vivo fascicle dynamics using B-mode ultrasound. Here, we show that an unexpected drop in ground height introduces an automatic phase shift in the timing of plantar flexor muscle activity relative to MTU length changes. This altered timing initiates a cascade of responses including increased MTU and fascicle length changes and increased muscle forces which, when taken together, enables the plantar flexors to effectively dissipate energy. Our results also show another mechanism, whereby increased co-activation of the plantar- and dorsiflexors enables shortening of the plantar flexor fascicles prior to ground contact. This co-activation improves the capacity of the plantar flexors to rapidly absorb energy upon ground contact, and may also aid in the avoidance of potentially damaging muscle strains. Our study provides novel insight into how humans alter their neural control to modulate in vivo muscle–tendon interaction dynamics in response to unexpected perturbations. These data provide essential insight to help guide design of lower-limb assistive devices that can perform within varied and unpredictable environments.

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Increased Ankle Plantar Flexor Stiffness Is Associated With Reduced Mechanical Response to Stretch in Adults With CP

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.604071 ◽

2021 ◽

Vol 9 ◽

Author(s):

Jakob Lorentzen ◽

Rasmus Feld Frisk ◽

Jens Bo Nielsen ◽

Lee Barber

Keyword(s):

Ankle Joint ◽

Stretch Reflex ◽

Gastrocnemius Muscle ◽

Length Change ◽

Medial Gastrocnemius ◽

Reflex Response ◽

Plantar Flexor ◽

Flexor Muscle ◽

Muscle Fascicles ◽

Medial Gastrocnemius Muscle

Hyperexcitable stretch reflexes are often not present despite of other signs of spasticity in people with brain lesion. Here we looked for evidence that increased resistance to length change of the plantar flexor muscle-fascicles may contribute to a reduction in the stretch reflex response in adults with cerebral palsy (CP). A total of 17 neurologically intact (NI) adults (mean age 36.1; 12 female) and 13 ambulant adults with CP (7 unilateral; mean age 33.1; 5 female) participated in the study. Subjects were seated in a chair with the examined foot attached to a foot plate, which could be moved by a computer-controlled electromotor. An ultrasound probe was placed over the medial aspect of the leg to measure the length of medial gastrocnemius muscle fascicles. Slow (7 deg/s) and fast (200 deg/s) stretches with amplitude 6 deg of the plantar flexors were applied over an ankle range of 70 deg at 10 deg intervals between 60 and 130 deg plantarflexion. It was checked by EMG electrodes that the slow stretches were sufficiently slow not to elicit any activity and that the fast stretches were sufficiently quick to elicit a maximal stretch reflex in both groups. The torque elicited by the stretches was measured together with changes in the length of medial gastrocnemius muscle fascicles. Muscle fascicles increased significantly in length with increasing dorsiflexion position in both populations (p < 0.001), but the fascicles were shorter in the CP population at all positions. Slow stretches elicited significantly larger torque and significantly smaller length change of muscle fascicles as the ankle joint position was moved more towards dorsiflexion in CP than in NI (p < 0.001). Fast stretches elicited larger torque responses at ankle joint positions of 80–100 deg in the NI than in the CP group (p < 0.01). A significant negative correlation was observed between the torque response and muscle fascicle length change to slow stretch in CP (p < 0.05), but not in NI. These findings support that increased passive resistance of the ankle plantar flexor muscle-tendon unit and development of contractures may conceal stretch reflex response in adults with CP. We argue that this should be taken into account in the neurological examination of spasticity.

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