Recovery of medial gastrocnemius muscle grafts in rats: implications for the plantar flexor group

Medial gastrocnemius (MGN) muscles were grafted in 18 rats and evaluated at 60, 90, and 120 days after the operation. Our purpose was to investigate the degree of recovery of the vascularized MGN grafts and the entire plantar flexor muscle group. Compared with control values, muscle mass and maximum force of MGN grafts were decreased by 33 and 38% at 60 days, 22 and 32% at 90 days, and 13 and 15% at 120 days. At 60 and 90 days, the deficits in maximum force for the entire plantar flexor muscle group, including the graft, were 29 and 17%, respectively. No difference was observed at 120 days. At 60 days, the deficit in the total mass of the plantar flexor group was 14% compared with control values, but by 90 days no deficit was observed. The restoration of normal plantar flexor group structure and function indicates that the degree of recovery attained by MGN grafts, although not complete, was sufficient to ensure that the performance of the total muscle group was not compromised.

Download Full-text

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.

Download Full-text

Force Regulation of Ankle Extensor Muscle Activity in Freely Walking Cats

Journal of Neurophysiology ◽

10.1152/jn.90918.2008 ◽

2009 ◽

Vol 101 (1) ◽

pp. 360-371 ◽

Cited By ~ 31

Author(s):

J. M. Donelan ◽

D. A. McVea ◽

K. G. Pearson

Keyword(s):

Muscle Activity ◽

Force Feedback ◽

Muscle Length ◽

Medial Gastrocnemius ◽

Strongly Correlated ◽

Experimental Conditions ◽

Hind Foot ◽

Feedback Pathway ◽

Total Muscle ◽

Medial Gastrocnemius Muscle

To gain insight into the relative importance of force feedback to ongoing ankle extensor activity during walking in the conscious cat, we isolated the medial gastrocnemius muscle (MG) by denervating the other ankle extensors and measured the magnitude of its activity at different muscle lengths, velocities, and forces accomplished by having the animals walk up and down a sloped pegway. Mathematical models of proprioceptor dynamics predicted afferent activity and revealed that the changes in muscle activity under our experimental conditions were strongly correlated with Ib activity and not consistently associated with changes in Ia or group II activity. This allowed us to determine the gains within the force feedback pathway using a simple model of the neuromuscular system and the measured relationship between MG activity and force. Loop gain increased with muscle length due to the intrinsic force–length property of muscle. The gain of the pathway that converts muscle force to motoneuron depolarization was independent of length. To better test for a causal relationship between modulation of force feedback and changes in muscle activity, a second set of experiments was performed in which the MG muscle was perturbed during ground contact of the hind foot by dropping or lifting the peg underfoot. Collectively, these investigations support a causal role for force feedback and indicate that about 30% of the total muscle activity is due to force feedback during level walking. Force feedback's role increases during upslope walking and decreases during downslope walking, providing a simple mechanism for compensating for changes in terrain.

Download Full-text

Differences in Plantar Flexor Fascicle Length and Pennation Angle between Healthy and Poststroke Individuals and Implications for Poststroke Plantar Flexor Force Contributions

Stroke Research and Treatment ◽

10.1155/2014/919486 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 4

Author(s):

John W. Ramsay ◽

Thomas S. Buchanan ◽

Jill S. Higginson

Keyword(s):

Pennation Angle ◽

Medial Gastrocnemius ◽

Plantar Flexor ◽

Flexor Muscle ◽

Fascicle Length ◽

Cross Sectional ◽

Lateral Gastrocnemius ◽

Relative Contribution ◽

Muscle Fascicle ◽

The Individual

Poststroke plantar flexor muscle weakness has been attributed to muscle atrophy and impaired activation, which cannot collectively explain the limitations in force-generating capability of the entire muscle group. It is of interest whether changes in poststroke plantar flexor muscle fascicle length and pennation angle influence the individual force-generating capability and whether plantar flexor weakness is due to uniform changes in individual muscle force contributions. Fascicle lengths and pennation angles for the soleus, medial, and lateral gastrocnemius were measured using ultrasound and compared between ten hemiparetic poststroke subjects and ten healthy controls. Physiological cross-sectional areas and force contributions to poststroke plantar flexor torque were estimated for each muscle. No statistical differences were observed for any muscle fascicle lengths or for the lateral gastrocnemius and soleus pennation angles between paretic, nonparetic, and healthy limbs. There was a significant decrease (P<0.05) in the paretic medial gastrocnemius pennation angle compared to both nonparetic and healthy limbs. Physiological cross-sectional areas and force contributions were smaller on the paretic side. Additionally, bilateral muscle contributions to plantar flexor torque remained the same. While the architecture of each individual plantar flexor muscle is affected differently after stroke, the relative contribution of each muscle remains the same.

Download Full-text

Knee extensor and plantar flexor muscle size and function following 90 days of bed rest with or without resistance exercise

European Journal of Applied Physiology ◽

10.1007/s00421-004-1172-8 ◽

2004 ◽

Vol 93 (3) ◽

pp. 294-305 ◽

Cited By ~ 177

Author(s):

Bj�rn A. Alkner ◽

Per A. Tesch

Keyword(s):

Resistance Exercise ◽

Knee Extensor ◽

Bed Rest ◽

Muscle Size ◽

Plantar Flexor ◽

Flexor Muscle ◽

And Function

Download Full-text

Effects of Ibuprofen on the Passive Properties of Musculotendinous Stiffness in the Plantar Flexor Muscle Group

Medicine & Science in Sports & Exercise ◽

10.1249/01.mss.0000487853.03579.7c ◽

2016 ◽

Vol 48 ◽

pp. 952

Author(s):

Jake A. Deckert ◽

Catherine A. Hambleton ◽

Trent J. Herda ◽

Eric M. Mosier ◽

Philip M. Gallagher

Keyword(s):

Muscle Group ◽

Plantar Flexor ◽

Flexor Muscle ◽

Musculotendinous Stiffness

Download Full-text

Can passive stretch inhibit motoneuron facilitation in the human plantar flexors?

Journal of Applied Physiology ◽

10.1152/japplphysiol.00809.2014 ◽

2014 ◽

Vol 117 (12) ◽

pp. 1486-1492 ◽

Cited By ~ 34

Author(s):

Gabriel S. Trajano ◽

Laurent B. Seitz ◽

Kazunori Nosaka ◽

Anthony J. Blazevich

Keyword(s):

Inhibitory Effect ◽

Triceps Surae ◽

Medial Gastrocnemius ◽

Plantar Flexor ◽

Plantar Flexors ◽

Stimulation Protocol ◽

Flexor Muscle ◽

Motor Unit Firing ◽

Torque Loss ◽

Passive Stretch

The purpose of the present study was to examine the possible inhibitory effect of passive plantar flexor muscle stretching on the motoneuron facilitatory system. Achilles tendon vibration (70 Hz) and triceps surae electrical stimulation (20 Hz) were imposed simultaneously in 11 subjects to elicit contraction through reflexive pathways in two experiments. In experiment 1, a vibration-stimulation protocol was implemented with the ankle joint plantar flexed (+10°), neutral (0°), and dorsiflexed (−10°). In experiment 2, the vibration-stimulation protocol was performed twice before (control), then immediately, 5, 10, and 15 min after a 5-min intermittent muscle stretch protocol. Plantar flexor torque and medial and lateral gastrocnemius and soleus (EMGSol) EMG amplitudes measured during and after (i.e., self-sustained motor unit firing) the vibration protocol were used as an indicator of this facilitatory pathway. In experiment 1, vibration torque, self-sustained torque and EMGSol were higher with the ankle at −10° compared with 0° and +10°, suggesting that this method is valid to assess motoneuronal facilitation. In experiment 2, torque during vibration was reduced by ∼60% immediately after stretch and remained depressed by ∼35% at 5 min after stretch ( P < 0.05). Self-sustained torque was also reduced by ∼65% immediately after stretch ( P < 0.05) but recovered by 5 min. Similarly, medial gastrocnemius EMG during vibration was reduced by ∼40% immediately after stretch ( P < 0.05), and EMGSol during the self-sustained torque period was reduced by 44% immediately after stretch ( P < 0.05). In conclusion, passive stretch negatively affected the motoneuronal amplification for at least 5 min, suggesting that motoneuron disfacilitation is a possible mechanism influencing the stretch-induced torque loss.

Download Full-text