Fluctuations in plantar flexion force are reduced after prolonged tendon vibration.
(73/488)
The purpose of the study was to examine the effect of prolonged vibration on the force fluctuations during a force-matching task performed at low-force levels. Fourteen young healthy men performed a submaximal force-matching task of isometric plantar flexion before and after Achilles tendon vibration (n = 8, vibration subjects) or lying without vibration (n = 6, control subjects) for 30 min. The target forces were 2.5-10% of the previbration maximal voluntary contraction force. The standard deviation of force decreased by a mean of 29 +/- 20% across target forces after vibration, whereas it did not decrease significantly in control subjects (-5 +/- 12%). This change was significantly greater compared with control subjects (P < 0.01 for both). Power spectral density of the force was predominantly composed of signals of low-frequency bandwidth (+info)
Running exercises improve the strength of a partially ruptured Achilles tendon.
(74/488)
OBJECTIVES: To examine the effects of running and swimming exercises on the functional performance and mechanical strength of a recovering Achilles tendon. METHODS: 30 Sprague-Dawley rats had surgical transection of their right medial Achilles tendon. The rats were divided into running (n = 11), swimming (n = 10), and control (n = 9) groups. The running and swimming groups were given daily exercise training, starting from the fifth day after the injury; the control group did not exercise throughout the period of the experiment. An Achilles functional index (AFI) was recorded before the operation and on the third, 10th, and 30th days after the operation. On the 30th day, the rats were killed and their Achilles tendons harvested for biomechanical testing of load relaxation properties, stiffness, and ultimate tensile strength (UTS). The AFI data were analysed by two way analysis of variance; load relaxation, stiffness, and UTS data were analysed by multivariate analysis, with alpha at 0.05. RESULTS: The UTS of the running group was higher than in the control group (p = 0.015), while there was no significant difference between the swimming and control groups (p = 0.228). Differences in stiffness and load relaxation were non-significant (p = 0.823 and 0.633, respectively). The AFI results did not differ among the three groups (p = 0.242). CONCLUSIONS: Running exercises can improve the strength of partially ruptured Achilles tendons at 30 days after injury. (+info)
Tendon injury and repair after core biopsies in chronic Achilles tendinosis evaluated by serial magnetic resonance imaging.
(75/488)
OBJECTIVE: To evaluate the morphological response and healing process after transverse ultrasound guided core biopsies in chronic Achilles tendinosis using serial magnetic resonance imaging (MRI) over a period of one year. METHODS: The study included 10 patients. Six had five transverse core biopsies and were longitudinally evaluated by MRI before the biopsies and then after one week, three months, seven months, and one year. These patients started a three month eccentric training programme one to two weeks after the biopsy. Four "non-biopsied" and untreated patients were used for comparison. The clinical outcome was categorised according to the level of pain and performance. RESULTS: The MRI one week after the biopsies showed an increase in tendon volume (T1-WI) and mean signal intensity (PD-WI) of 29% and 30% (p = 0.04). During follow up, tendon volume and mean signal intensity gradually decreased. One year after the biopsy, the tendon volume had decreased by 20% and the intratendinous signal by 28% compared with the index MRI (p = 0.04). The untreated patients showed an increase in both tendon volume (39%, p = 0.06) and intratendinous signal (37%, p = 0.14) at the one year follow up. After one year, pain and performance had improved in the treated patients but not the untreated patients. CONCLUSION: Five transverse ultrasound guided core biopsies induced a lesion in the diseased Achilles tendon. Alterations during healing such as tendon size and intratendinous signal intensity could be evaluated by MRI. The tendon alterations had decreased one year after the core biopsies. (+info)
Mechanism of the vibration paradox: excitatory and inhibitory effects of tendon vibration on single soleus muscle motor units in man.
(76/488)
1. The parameters of presynaptic inhibition of the Ia spindle afferents from soleus muscle by vibration have been investigated. The inhibitory effects increase with the amplitude of vibration, but decrease when the vibration frequency is increased.2. The monosynaptic reflex threshold of twenty-one single soleus motor units activated in the H (Hoffmann) reflex by a single electrical stimulus to the posterior tibial nerve was estimated quantitatively and expressed in relation to the size of the simultaneously recorded H reflex.3. A parametric study of the effects of various Achilles tendon vibrations on the reflex threshold of the single soleus motor units indicated that their order of derecruitment is concordant with their rank order for activation in the phasic reflexes of the soleus. The last recruited motoneurones are the most susceptible to being silenced by steady vibration.4. Muscle vibration progressively recruits single motor units according to the motoneurone size principle through polysynaptic proprioceptive pathways. However the presynaptic inhibition of Ia spindle afferents simultaneously induced by the vibration works in reverse on the same rank order of motoneurones of the soleus spinal pool, thereby limiting the polysynaptic recruitment of units in the tonic vibration reflex while depressing the autogenic phasic proprioceptive reflexes. These mechanisms elucidate the so-called vibration paradox and extend the size principle of Henneman to presynaptic inhibitory effects. (+info)
Muscle mechanoreflex and metaboreflex responses after myocardial infarction in rats.
(77/488)
BACKGROUND: During exercise, the sympathetic nervous system is activated and blood pressure and heart rate increase. In heart failure (HF), the muscle metaboreceptor contribution to sympathetic outflow is attenuated and the mechanoreceptor contribution is accentuated. Previous studies suggest that (1) capsaicin stimulates muscle metabosensitive vanilloid receptor subtype 1 (VR1), inducing a neurally mediated pressor response, and (2) activation of ATP-sensitive P2X receptors enhances the pressor response seen when muscle mechanoreceptors are engaged by muscle stretch. Thus, we hypothesized that the pressor response to VR1 stimulation would be smaller and the sensitizing effects of P2X stimulation greater in rats with HF due to chronic myocardial infarction (MI) than in controls. METHODS AND RESULTS: Eight to 14 weeks after coronary ligation, rats with infarcts >35% had an increased left ventricular end-diastolic pressure and a marked increase in heart weight. Capsaicin injected into the arterial supply of the hindlimb increased blood pressure by 39% (baseline, 93.9+/-9.5 mm Hg) in control animals but only by 8% (baseline, 94.8+/-10.1 mm Hg) in rats with large MIs (P<0.05). P2X receptor stimulation by alpha,beta-methylene ATP enhanced the pressor response to muscle stretch by 42% in control animals and by 72% in rats with large MIs (P<0.05). CONCLUSIONS: Compared with control animals, cardiovascular responses to VR1 stimulation are blunted and P2X-mediated responses are augmented in rats with HF owing to large MIs. (+info)
Augmented repair of acute Achilles tendon ruptures using gastrocnemius-soleus fascia.
(78/488)
Fifty-four consecutive acute Achilles tendon ruptures were treated with end-to-end suture augmented with gastrocnemius fascial flaps. Surgery was performed within 24 h. Mean patient age was 35 (23-57) years, and 46 were men. Mean follow-up time was 4.8 (2-8) years. At follow-up, the mean visual analogue scale for pain was 0.49, and the mean AOFAS ankle-hindfoot score was 95 (74-100) points. Fifty-three patients were able to stand on their tiptoes for 30 s and perform repeated toe raises, and 50 patients were able to perform single-limb hopping. Complications included rerupture in one case, deep infection in three cases, delayed wound healing in eight cases, and deep venous thrombosis in one case. Reconstruction of acute ruptures of the Achilles tendon augmented with gastrocnemius-soleus fascial flaps provided a good outcome but was associated with a high complication rate. (+info)
Repair of acute rupture of the Achilles tendon: a new technique using polyester tape without external splintage.
(79/488)
INTRODUCTION: A new method of treating acute rupture of the Achilles tendon using polyester tape is reported. This requires no postoperative splintage, allows earlier mobilisation and prompt return to work and sport. PATIENTS AND METHODS: Thirty patients were reviewed prospectively and at a mean of 3 years from surgery. RESULTS: The average time of return to work, full weight-bearing and to driving was 40 days, 45 days and 49 days, respectively. The average time for return to sport was 122 days. Three patients required further surgery, two for infected wounds and one for scar release. There was one sural nerve injury. Twenty-two patients regained a normal range of ankle and subtalar movement, with the mean power of plantar flexion 84% of the opposite side. Of the 22 patients who played sport, 14 were still performing at the same or a higher level. There were no re-ruptures over this period. CONCLUSIONS: The technique is straightforward and avoids splintage. It also conveys other short- and long-term advantages over more established methods. (+info)
Effect of Achilles tendon lengthening on ankle muscle performance in people with diabetes mellitus and a neuropathic plantar ulcer.
(80/488)
BACKGROUND AND PURPOSE: The effect of a tendo-Achilles lengthening (TAL) procedure on ankle muscle performance has not been clearly established. The purpose of this study was to compare the effects of TAL and total-contact casting (TCC) with TCC alone on ankle muscle performance in subjects with diabetes mellitus (DM) and a neuropathic plantar ulcer. SUBJECTS: Subjects were randomly assigned to either a TAL group (3 female and 12 male subjects) or a TCC group (4 female and 10 male subjects). METHODS: Muscle performance measurements were obtained using an isokinetic dynamometer. RESULTS: Concentric plantar-flexor peak torque decreased 31% after TAL but returned to the baseline level after 8 months. Dorsiflexor peak torque did not change in either group. Plantar-flexor passive torque at 0 degrees of dorsiflexion decreased after TAL but increased to 60% of the baseline level after 8 months. Maximal dorsiflexion angle increased 11 degrees after TAL and remained increased at 8 months. DISCUSSION AND CONCLUSION: The TAL resulted in an increase in ankle dorsiflexion range of motion and a temporary reduction in concentric plantar-flexor peak torque and passive torque at 0 degrees of dorsiflexion. If TAL is being considered for people with DM and a neuropathic forefoot ulcer, the initial compromise in plantar-flexor muscle performance should be addressed. (+info)