Effect of selective and nonselective beta-blockade on skeletal muscle excitability and fatiguability

1994 ◽  
Vol 76 (6) ◽  
pp. 2461-2466 ◽  
Author(s):  
C. M. Cupido ◽  
A. L. Hicks ◽  
R. S. McKelvie ◽  
D. G. Sale ◽  
A. J. McComas
Keyword(s):  
Skeletal Muscle ◽  
Knee Extensors ◽  
Beta Blockade ◽  
Double Blind ◽  
M Wave ◽  
Fatigue Protocol ◽  
Placebo Trial ◽  
Double Blind Design ◽  
Voluntary Contractions ◽  
Muscle Excitability

The effects of beta-blockade on skeletal muscle excitability and fatiguability during exercise were examined. Ten healthy males (mean age 21.9 +/- 1.1 yr) performed a 4-min fatigue protocol consisting of intermittent isometric voluntary contractions of the knee extensors in one leg. Subjects performed the exercise after treatment with placebo, 100 mg metoprolol, or an equipotent dose of propranolol (60 mg, n = 1; 80 mg, n = 8; 100 mg, n = 1) twice a day for 76 h before testing according to a randomized double-blind design. The evoked twitch torque, maximal voluntary torque, and maximal M-wave amplitude were unaffected by the beta-blockade treatments before fatigue. During the placebo trial, there were significant reductions in the evoked and voluntary torques (77 +/- 15 and 55 +/- 11%, respectively) after the fatigue protocol; however, both the voluntary electromyogram and evoked M waves were well maintained throughout fatigue. The beta-blockade treatments had no significant effect on torque or electromyogram activity over the course of the exercise. Thus, despite evidence for an impairment of dynamic exercise performance with beta 1- and beta 1,2-blockade, there appears to be no effect of these agents on muscle excitability and fatiguability during isometric muscle activity.

Effects of Caffeine Ingestion on Exercise-induced Change during High-Intensity Intermittent Exercise

1995 ◽  
Vol 5 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Isaiah Trice ◽  
Emily M. Haymes
Keyword(s):  
Blood Glucose ◽  
Perceived Exertion ◽  
Intermittent Exercise ◽  
Time To Exhaustion ◽  
Double Blind ◽  
Serum Free Fatty Acid ◽  
Caffeine Ingestion ◽  
Serum Free ◽  
Placebo Trial ◽  
Double Blind Design

In this study a double-blind design was used to determine the effect of caffeine on time to exhaustion and on associated metabolic and circulatory measures. Eight male subjects ingested either caffeine (5 mg/kg body weight) or a placebo 1 hr prior to exercise at 85-90% of maximum workload. Subjects were encouraged to complete three 30-min intermittent cycling periods at 70 rpm with 5 min rest between each. The exercise was terminated when the subject failed to complete three 30-min periods or failed to maintain 70 rpm for at least 15 s consecutively. Serum free fatty acids, glycerol, blood glucose, lactate, perceived exertion, heart rate, andcost were measured. The time to exhaustion was significantly longer during the caffeine trial than during the placebo trial. Serum free fatty acid levels were significantly different between trials. The decline in blood glucose levels was significantly less during the caffeine trial than during the placebo trial. There were no significant differences between trials for the other measures. It was concluded that caffeine increases time to exhaustion when trained subjects cycled intermittently at high levels of intensity.

scholarly journals Contraction type influences the human ability to use the available torque capacity of skeletal muscle during explosive efforts

2012 ◽  
Vol 279 (1736) ◽  
pp. 2106-2115 ◽  
Author(s):  
Neale A. Tillin ◽  
Matthew T. G. Pain ◽  
Jonathan P. Folland
Keyword(s):  
Skeletal Muscle ◽  
Joint Angle ◽  
Knee Extensors ◽  
Concentric Contractions ◽  
Human Ability ◽  
Explosive Performance ◽  
Torque Capacity ◽  
Contraction Type ◽  
Voluntary Contractions ◽  
Maximum Voluntary Torque

The influence of contraction type on the human ability to use the torque capacity of skeletal muscle during explosive efforts has not been documented. Fourteen male participants completed explosive voluntary contractions of the knee extensors in four separate conditions: concentric (CON) and eccentric (ECC); and isometric at two knee angles (101°, ISO101 and 155°, ISO155). In each condition, torque was measured at 25 ms intervals up to 150 ms from torque onset, and then normalized to the maximum voluntary torque (MVT) specific to that joint angle and angular velocity. Explosive voluntary torque after 50 ms in each condition was also expressed as a percentage of torque generated after 50 ms during a supramaximal 300 Hz electrically evoked octet in the same condition. Explosive voluntary torque normalized to MVT was more than 60 per cent larger in CON than any other condition after the initial 25 ms. The percentage of evoked torque expressed after 50 ms of the explosive voluntary contractions was also greatest in CON (ANOVA; p < 0.001), suggesting higher concentric volitional activation. This was confirmed by greater agonist electromyography normalized to M max (recorded during the explosive voluntary contractions) in CON. These results provide novel evidence that the ability to use the muscle's torque capacity explosively is influenced by contraction type, with concentric contractions being more conducive to explosive performance due to a more effective neural strategy.

Thermoregulation during prolonged exercise in heat: alterations with beta-adrenergic blockade

1987 ◽  
Vol 63 (3) ◽  
pp. 930-936 ◽  
Author(s):  
B. J. Freund ◽  
M. J. Joyner ◽  
S. M. Jilka ◽  
J. Kalis ◽  
J. M. Nittolo ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Beta Blockers ◽  
Cycle Ergometer ◽  
Beta Blockade ◽  
Adrenergic Blockade ◽  
Sweat Loss ◽  
Double Blind ◽  
Beta Adrenergic ◽  
Cardiovascular Drift ◽  
Placebo Trial

Thermoregulation and cardiovascular drift were studied under conditions of prolonged exercise in a warm environment (dry bulb temperature 31.7 +/- 0.3 degrees C, rh 44.7 +/- 4.7%) during beta-adrenergic blockade. Fourteen subjects performed 90-min rides on a cycle ergometer at a work rate equivalent to 40% of their control maximal O2 uptake under each of three treatments provided in a randomized double-blind manner: atenolol (100 mg/day), propranolol (160 mg/day), and a placebo. Exercise during the propranolol trial resulted in significantly higher forearm vascular resistance values and significantly lower forearm blood flows (FBF) compared with the placebo trial. However, the significantly lower FBF during propranolol did not significantly alter the rectal temperature (Tre) response to prolonged exercise. In addition, both beta-blockers produced lower FBF for any given Tre, suggesting that beta-adrenergic blockade affects FBF through nonthermal factors. The slight differences in Tre, despite the large differences in FBF between the various treatments, are apparently the result of an enhanced sweat loss and a lower mean skin temperature during exercise with beta-blockade. The uncoupling of FBF and sweat loss provides evidence of independent regulation. The reduction in FBF at any given Tre was concomitant to lower blood pressure values during beta-blockade and suggests that baroreflexes provide significant input to the control of skin blood flow when both pressure and temperature maintenance are simultaneously challenged.

Skeletal Muscle Function in Young Patients With Cystic Fibrosis

2016 ◽  
Vol 28 (3) ◽  
pp. 364-373 ◽  
Author(s):  
Lothar Stein ◽  
Constanze Pacht ◽  
Sibylle Junge ◽  
Tobias S. Kaeding ◽  
Momme Kück ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cystic Fibrosis ◽  
Muscle Function ◽  
Vastus Lateralis ◽  
Young Patients ◽  
Forced Expiratory Volume ◽  
Knee Extensors ◽  
Emg Activity ◽  
Skeletal Muscle Function ◽  
M Wave

Purpose:Defects in the gene encoding the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) cause CF. Absence of the CFTR may result in skeletal muscle dysfunction. Here, we tested skeletal muscle function in male adolescent patients with CF.Methods:Ten CF and 10 control participants (age: 16.8 ± 0.6 years) performed 7 repetitive sets of maximum voluntary contractions (MVCs) and underwent an isometric fatigue test of the knee extensors. Electromyography (EMG) activity was recorded from the m. vastus lateralis (VL) and m. vastus medialis (VM).Results:In CF, the MVC torque was lower and correlated with the predicted forced expiratory volume in one second (r = .73, p = .012, n = 10). The M-wave in the VL was shorter in CF than in controls (18.6 ± 0.5 vs. 20.3 ± 0.5 ms, p < .028). In the VM, both the M-wave (4.96 ± 0.61 vs. 7.97 ± 0.60 mV, p = .001) and the EMG (0.29 ± 0.04 vs. 0.47 ± 0.04 mV, p = .004) amplitudes were smaller in CF.Conclusion:The differences in the VL and VM EMG signals between the groups indicate that the lower MVC torque in CF did not result from the direct impact of a CFTR defect on the sarcolemmal excitability; the differences more likely resulted from the less developed musculature in the patients with CF.

scholarly journals Cerebellar rTMS in PSP: a Double-Blind Sham-Controlled Study Using Mobile Health Technology

2021 ◽  
Author(s):  
Andrea Pilotto ◽  
Maria Cristina Rizzetti ◽  
Alberto Lombardi ◽  
Clint Hansen ◽  
Michele Biggi ◽  
...  
Keyword(s):  
Digital Technology ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Health Technology ◽  
Controlled Study ◽  
Double Blind ◽  
Non Invasive ◽  
Lower Back ◽  
Before And After ◽  
Double Blind Design ◽  
Theta Burst

AbstractThere are no effective treatments in progressive supranuclear palsy (PSP). The aim of this study was to test the efficacy of theta burst repetitive transcranial magnetic stimulation (rTMS) on postural instability in PSP. Twenty PSP patients underwent a session of sham or real cerebellar rTMS in a crossover design. Before and after stimulation, static balance was evaluated with instrumented (lower back accelerometer, Rehagait®, Hasomed, Germany) 30-s trials in semitandem and tandem positions. In tandem and semitandem tasks, active stimulation was associated with increase in time without falls (both p=0.04). In the same tasks, device-extracted parameters revealed significant improvement in area (p=0.007), velocity (p=0.005), acceleration and jerkiness of sway (p=0.008) in real versus sham stimulation. Cerebellar rTMS showed a significant effect on stability in PSP patients, when assessed with mobile digital technology, in a double-blind design. These results should motivate larger and longer trials using non-invasive brain stimulation for PSP patients.

scholarly journals The Composition and Diversity of the Gut Microbiota in Children Is Modifiable by the Household Dogs: Impact of a Canine-Specific Probiotic

2021 ◽  
Vol 9 (3) ◽  
pp. 557
Author(s):  
Carlos Gómez-Gallego ◽  
Mira Forsgren ◽  
Marta Selma-Royo ◽  
Merja Nermes ◽  
Maria Carmen Collado ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Home Environment ◽  
Double Blind ◽  
Before And After ◽  
Probiotic Intervention ◽  
Probiotic Product ◽  
Acid Producing Bacteria ◽  
Double Blind Design ◽  
To Receive ◽  
Gut Microbiota Composition

The development of the infant gut microbiota is initiated during pregnancy and continued through early life and childhood, guided by the immediate environment of the child. Our aim was to characterize the shared microbiota between dogs and children as well as to determine whether introduction to dogs of a dog-specific probiotic combination modifies the transfer process. We studied 31 children from allergic families with pet dog(s) and 18 control families without a dog. Altogether 37 dogs were randomized for a 4-week period in a double-blind design to receive canine-derived probiotic product containing a mixture of L. fermentum, L. plantarum, and L. rhamnosus, or placebo. Fecal samples from children and dogs were taken before and after the treatment. Distinctive gut microbiota composition was observed in children with dogs compared to those without a dog, characterized by higher abundance of Bacteroides and short-chain fatty acid producing bacteria such as Ruminococcus and Lachnospiraceae. Probiotic intervention in dogs had an impact on the composition of the gut microbiota in both dogs and children, characterized by a reduction in Bacteroides. We provide evidence for a direct effect of home environment and household pets on children microbiota and document that modification of dog microbiota by specific probiotics is reflected in children’s microbiota.

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