Strength Training Effects on Muscular Regeneration after ACL Reconstruction

ABSTRACTPurposeProtracted quadriceps muscle atrophy is observed after anterior cruciate ligament reconstruction (ACL-R). The aim of this study was to assess if quadriceps strength training with eccentric overload (CON/ECC+) is more efficient to induce muscle regeneration after ACL-R than conventional concentric/eccentric (CON/ECC) strength training.MethodsBiopsies from the vastus lateralis muscle were obtained from 37 recreational athletes after 12 weeks of regular rehabilitation following ACL-R and again after 12 weeks with twice a week either conventional CON/ECC (n = 16) or CON/ECC+ (n = 21) one-legged supervised leg-press training. Immunohistochemical analyses were used to determine satellite cell number (SC, Pax7+), activated SCs (Pax7+/MyoD+), fibers expressing myosin heavy chain (MHC) I, II and neonatal, fiber cross sectional area (FCSA). Magnetic resonance imaging was performed to measure quadriceps cross sectional area (MCSA) and isokinetic testing for the measurement of quadriceps strength.ResultsCON/ECC+ induced a significantly (p = 0.002) greater increase in MCSA than CON/ECC. There also was a significant increase in the FCSAs of all fiber types and in quadriceps strength, however, without significant difference between training groups. Only CON/ECC+ training lead to a significant (p

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Effects of Acute Salbutamol Intake on Peripheral and Central Fatigue in Trained Men

ABSTRACTPurposeErgogenic effect in physically active subjects has been reported following acute salbutamol (SAL) intake. β2-agonists have potential stimulant effects within the central nervous system that could be involved in this ergogenic effect. We hypothesized that acute SAL intake would induce changes in cerebral responses during exercise, with significant improvement in cerebral oxygenation and voluntary activation (VA) contributing to an increase in muscle performance.MethodsFourteen trained male subjects (25 ± 5 years) performed repeated isometric knee extensions until task failure (TF) following 4 mg (oral) SAL, 800 μg (inhaled) SAL, or placebo intake. VA, corticospinal excitability and inhibition assessed by transcranial magnetic stimulation (TMS) and changes in hemoglobin concentrations assessed by near infrared spectroscopy were measured before and during the fatiguing task.ResultsSAL had no significant effect both at rest and during exercise on prefrontal cortex oxygenation (e.g. changes in oxyhemoglobin concentration at TF: 4 mg SAL 11.4 ± 11.1 versus 800 μg SAL 10.4 ± 10.6 versus placebo 10.8 ± 8.1 μmol; P = 0.314) and neuromuscular function (e.g. VATMS at TF: 90.2 ± 6.6 versus 92.6 ± 5.0 versus 90.1 ± 7.0%; P = 0.760). SAL had no effect on the number of contractions until TF (95 ± 51 versus 100 ± 52 versus 93 ± 47; P = 0.629).ConclusionThese results indicate that acute SAL intake had no effect on central and peripheral mechanisms of neuromuscular fatigue and did not improve quadriceps endurance. Purpose Ergogenic effect in physically active subjects has been reported following acute salbutamol (SAL) intake. β2-agonists have potential stimulant effects within the central nervous system that could be involved in this ergogenic effect. We hypothesized that acute SAL intake would induce changes in cerebral responses during exercise, with significant improvement in cerebral oxygenation and voluntary activation (VA) contributing to an increase in muscle performance. Methods Fourteen trained male subjects (25 ± 5 years) performed repeated isometric knee extensions until task failure (TF) following 4 mg (oral) SAL, 800 μg (inhaled) SAL, or placebo intake. VA, corticospinal excitability and inhibition assessed by transcranial magnetic stimulation (TMS) and changes in hemoglobin concentrations assessed by near infrared spectroscopy were measured before and during the fatiguing task. Results SAL had no significant effect both at rest and during exercise on prefrontal cortex oxygenation (e.g. changes in oxyhemoglobin concentration at TF: 4 mg SAL 11.4 ± 11.1 versus 800 μg SAL 10.4 ± 10.6 versus placebo 10.8 ± 8.1 μmol; P = 0.314) and neuromuscular function (e.g. VATMS at TF: 90.2 ± 6.6 versus 92.6 ± 5.0 versus 90.1 ± 7.0%; P = 0.760). SAL had no effect on the number of contractions until TF (95 ± 51 versus 100 ± 52 versus 93 ± 47; P = 0.629). Conclusion These results indicate that acute SAL intake had no effect on central and peripheral mechanisms of neuromuscular fatigue and did not improve quadriceps endurance. Accepted for Publication: 19 January 2018 Corresponding author: Dr. Samuel Verges, Laboratoire HP2 (U1042 INSERM), Univ. Grenoble Alpes, UM Sports Pathologies, Hôpital Sud, Avenue Kimberley, 38 434 Echirolles - France. E-mail: sverges@chu-grenoble.fr This work has been funded by the French Anti-Doping Agency. The authors declare that they have no conflict of interest. The authors declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine. © 2018 American College of Sports Medicine

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Ablation of the carotid bodies in disease: meeting its adverse effects

Abstract

Its now 26 years since the publication of a seminal study that showed that carotid body (CB) chemoreceptors are involved in the progression of chronic intermittent hypoxia-induced hypertension.

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Phrenic motor neuron adenosine 2A receptors elicit phrenic motor facilitation

Abstract

Cervical spinal adenosine 2A (A2A) receptor activation elicits a prolonged increase in phrenic nerve activity, an effect known as phrenic motor facilitation (pMF). The specific cervical spinal cells expressing the relevant A2A receptors for pMF are unknown. This is an important question since the physiological outcome of A2A receptor activation is highly cell-type specific. Thus, we tested the hypothesis that the relevant A2A receptors for pMF are expressed in phrenic motor neurons per se versus non-phrenic neurons of the cervical spinal cord. A2A receptor immunostaining significantly colocalizes with NeuN-positive neurons (89 ± 2%). Intrapleural siRNA injections were used to selectively knock down A2A receptors in cholera toxin B-subunit-labelled phrenic motor neurons. A2A receptor knock down was verified by a ∼45% decrease in A2A receptor immunoreactivity within phrenic motor neurons versus non-targeting siRNAs (siNT; P < 0.05). There was no evidence for knock-down in cervical non-phrenic motor neurons. In anaesthetized, paralyzed and ventilated rats, pMF induced by cervical (C3-4) intrathecal injections of the A2A receptor agonist CGS21680 was greatly attenuated in siA2A (21%) versus siNT treated rats (147%; P < 0.01). There were no significant effects of siA2A on phrenic burst frequency. Collectively, our results support the hypothesis that phrenic motor neurons express the A2A receptors relevant to A2A receptor-induced pMF.

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Immediate and delayed loading of fixed dental prostheses supported by single or two splinted implants. A histomorphometric study in dogs

Abstract

Objective

To evaluate presumptive differences in osseointegration at implants supporting crowns that are physiologically loaded either immediately or 3 months after installation.

Material and methods

All premolars and first molars were extracted bilaterally in six dogs. After 3 months of healing, three implants were installed in the premolar region and two in the molar region in one side of the mandible. Likewise, after another 3 months, five implants were installed in the contralateral side, and impressions were taken bilaterally. Within 48 hours, two single crowns were screwed bilaterally onto two implants in the premolar region, and two splinted crowns reproducing the shape of the first molar were screwed bilaterally onto the implants in the molar region. The mesial implants were used as no-loaded controls. Sacrifices were performed after 3 months and histological analyses were performed.

Results

At the premolar sites, mineralized bone-to-implant contact (MBIC%) was 78.0±4.0% and 70.9±7.9% at the delayed and immediately loaded sites, respectively. This difference was statistically significant. At the control implants, MBIC% was 61.4±14.7% and 63.1±13.1% at the delayed and the immediately loaded sites, respectively. At the molar sites, MBIC% was 79.2 ±10.9% and 61.1±10.3% at the delayed and immediately loaded sites, respectively.

Conclusions

Applying a delayed loading to fixed dental prostheses supported by single- or two-splinted implants yielded higher proportions of bone-to-implant contact (osseointegration) compared to immediately loaded implants. Moreover, both types of loading protocols yielded a higher rate of osseointegration compared to unloaded implant sites after 3 months following implant installation.

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