Neuromuscular electrical stimulation during maximal voluntary contraction: a Delphi survey with expert consensus.

PURPOSE: The use of electrical stimulation to assess voluntary activation of muscle/s is a popular method employed in numerous exercise science and health research settings. This Delphi study aimed to collate expert opinion and provide recommendations for best practice when using electrical stimulation during maximal voluntary contractions. METHODS: A two-round Delphi study was undertaken with 30 experts who completed a 62-item questionnaire (Round 1) comprising of open- and closed-ended questions. Consensus was assumed if ≥ 70% of experts selected the same response; such questions were removed from the subsequent Round 2 questionnaire. Responses were also removed if they failed to meet a 15% threshold. Open-ended questions were analysed and converted into closed-ended questions for Round 2. It was assumed there was no clear consensus if a question failed to achieve a ≥ 70% response in Round 2. RESULTS: A total of 16 out of 62 (25.8%) items reached consensus. Experts agreed that electrical stimulation provides a valid assessment of voluntary activation in specific circumstances, such as during maximal contraction, and this stimulation can be applied at either the muscle or the nerve. Experts recommended using doublet stimuli, self-adhesive electrodes, a familiarisation session, real-time visual or verbal feedback during the contraction, a minimum current increase of + 20% to ensure supramaximal stimulation, and manually triggering stimuli. CONCLUSION: The results of this Delphi consensus study can help researchers make informed decisions when considering technical parameters when designing studies involving electrical stimulation for the assessment of voluntary activation.

Scheduling of eccentric lower limb injury prevention exercises during the soccer micro-cycle: Which day of the week?

Scheduling eccentric-based injury prevention programs (IPP) during the common 6-day micro-cycle in soccer is challenged by recovery and tapering phases. This study profiled muscle damage, neuromuscular performance, and perceptual responses to a lower limb eccentric-based IPP administered 1 (MD+1) vs 3 days (MD+3) postmatch. A total of 18 semi-professional players were monitored daily during 3 in-season 6-day micro-cycles, including weekly competitive fixtures. Capillary creatine kinase concentration (CK), posterior lower limb isometric peak force (PF), counter-movement jump (CMJ) performance, and muscle soreness were assessed 24 hours prior to match-day (baseline), and every 24 hours up to 120 hours postmatch. The IPP consisted of lunges, single stiff leg dead-lifts, single leg-squats, and Nordic hamstring exercises. Performing the IPP on MD+1 attenuated the decline in CK normally observed following match play (CON: 142%; MD+3: 166%; small differences). When IPP was delivered on MD+3, CK was higher vs CON and MD+1 trials on both MD+4 (MD+3: 260%; CON: 146%; MD+1: 151%; moderate differences) and MD+5 (MD+3: 209%; CON: 125%; MD+1: 127%; small differences). Soreness ratings were not exacerbated when the IPP was delivered on MD+1, but when prescribed on MD+3, hamstring soreness ratings remained higher on MD+4 and MD+5 (small differences). No between-trial differences were observed for PF and CMJ. Administering the IPP in the middle of the micro-cycle (MD+3) increased measures of muscle damage and soreness, which remained elevated on the day prior to the next match (MD+5). Accordingly, IPP should be scheduled early in the micro-cycle, to avoid compromising preparation for the following match.

Hamstring injury prevention in soccer: Before or after training?

We examined the effects of a 12-week program of Nordic hamstring exercises (NHE), administered before or after football training, upon eccentric hamstring strength, muscle activity, and architectural adaptations. Amateur soccer players were randomized into three groups. The control group (CON; n=11) undertook core stability exercises, whereas a periodized NHE program was delivered either before (NHEBEF ; n=10) or after (NHEAFT ; n=14) biweekly training sessions. Outcome measures included peak torque and concomitant normalized peak surface electromyography signals (sEMG) of the biceps femoris (BF) and medial hamstring (MH) muscles during knee flexor maximal eccentric contractions, performed at 30°·s-1 . Ultrasonography was used to determine BF muscle thickness, muscle fiber pennation angle, and fascicle length. Performing the NHE derived likely moderate peak torque increases in both NHEBEF (+11.9%; 90% confidence interval: 3.6%-20.9%) and NHEAFT (+11.6%; 2.6%-21.5%) vs CON. Maximum sEMG increases were moderately greater in the BF of both NHE training groups vs CON. There were likely moderate increases in BF muscle thickness (+0.17 cm; 0.05-0.29 cm) and likely small pennation angle increases (+1.03°; -0.08° to 2.14°) in NHEAFT vs CON and NHEBEF . BF fascicle length increases were likely greater in NHEBEF (+1.58 cm; 0.48-2.68 cm; small effect) vs CON and NHEAFT . A 12-week eccentric hamstring strengthening program increased strength and sEMG to a similar magnitude irrespective of its scheduling relative to the football training session. However, architectural adaptations to support the strength gains differed according to the timing of the injury prevention program.

Resistance training improves fatigue and quality of life in previously sedentary breast cancer survivors: a randomised controlled trial.

The primary aim of this study was to evaluate the benefits of resistance training (RT) on quality of life (QOL) and fatigue in breast cancer survivors as an adjunct to usual care. We recruited 39 women who had survived breast cancer [mean age (y) 51.9 ± 8.8; time since diagnosis (m) 11.6 ± 13.2]. Primary outcomes were fatigue as assessed by the Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT) scale and QOL as assessed by the Functional Assessment of Cancer Therapy - General (FACT-G) scale. ANCOVA was used to assess the change in the primary outcomes while controlling for baseline values, with effect sizes (ES) displayed as partial Eta squared. The experimental group received supervised RT 3 days per week in a university clinic for 16 weeks. Perceptions of fatigue improved significantly in the RT group compared to controls [mean (SD) 6.7 (7.5) points vs. 1.5 (3.7) points], (P = 0.006, ES = 0.20) as did QOL [6.9 (8.5) points vs. 1.6 (4.4) points], (P = 0.015, ES = 0.16). We demonstrated both statistically and clinically important improvements in fatigue and QOL in response to RT in breast cancer survivors.

Test-retest reliability of dynamic plantar loading and foot geometry measures in diabetics with peripheral neuropathy.

Pedobarography is commonly employed in patients with diabetic peripheral neuropathy (DPN). However there is no evidence regarding test-retest reliability of this technique in this population, and therefore it was the purpose of the current study to address this clear gap. Dynamic plantar loading and foot geometry data were collected during barefoot gait with the EMED platform (Novel GmbH, Germany) from 10 patients with DPN over two sessions, separated by 28 days. Intra-class Correlation Coefficients (ICCs) and Coefficients of Variation (CoVs) were calculated to determine test-retest reliability. For dynamic plantar loading, reliability differed by outcome measure and foot region, with ICCs of >0.8 and CoVs of <15% observed in most cases. For dynamic foot geometry, ICCs of >0.88 and CoVs of <3% were observed for hallux angle, arch index and coefficient of spreading, while sub-arch angle was less reliable (ICC 0.76, CoV 23%). Overall, the current study observed high levels of test-retest reliability which were generally commensurate with that previously reported in healthy populations.

Strength and neuromuscular adaptation following one, four, and eight sets of high intensity resistance exercise in trained males.

The optimal volume of resistance exercise to prescribe for trained individuals is unclear. The purpose of this study was to randomly assign resistance trained individuals to 6-weeks of squat exercise, prescribed at 80% of a 1 repetition-maximum (1-RM), using either one, four, or eight sets of repetitions to failure performed twice per week. Participants then performed the same peaking program for 4-weeks. Squat 1-RM, quadriceps muscle activation, and contractile rate of force development (RFD) were measured before, during, and after the training program. 32 resistance-trained male participants completed the 10-week program. Squat 1-RM was significantly increased for all groups after 6 and 10-weeks of training (P < 0.05). The 8-set group was significantly stronger than the 1-set group after 3-weeks of training (7.9% difference, P < 0.05), and remained stronger after 6 and 10-weeks of training (P < 0.05). Peak muscle activation did not change during the study. Early (30, 50 ms) and peak RFD was significantly decreased for all groups after 6 and 10-weeks of training (P < 0.05). Peak isometric force output did not change for any group. The results of this study support resistance exercise prescription in excess of 4-sets (i.e. 8-sets) for faster and greater strength gains as compared to 1-set training. Common neuromuscular changes are attributed to high intensity squats (80% 1-RM) combined with a repetition to failure prescription. This prescription may not be useful for sports application owing to decreased early and peak RFD. Individual responsiveness to 1-set of training should be evaluated in the first 3-weeks of training.

A comparison of the effects of aspirin on bleeding time measured using the Simplate method and closure time measured using the PFA-100, in healthy volunteers.

AIMS: The aim of this study was to compare the effects of aspirin on platelet function as measured by the 'classical' template bleeding time with a new ex vivo method measuring closure times using the PFA-100 machine. Platelet aggregation in response to arachidonic acid was also measured ex vivo. METHODS: The trial was a randomized, double-blind, placebo-controlled crossover design, with each volunteer taking 750 mg aspirin (BP) or placebo, three times a day for 5 days, with an 18 day wash-out period between treatments. Bleeding times and closure times were measured before the first dose on the first day and 0.5 h after the last dose on the fifth day of each treatment period. They were also measured 2 weeks after the last day of the trial. RESULTS: Baseline bleeding times (pre-placebo) were 415 s using the Simplate, whilst baseline closure times were 115 s using the PFA-100. Aspirin treatment caused an increase of both the template bleeding time (61%) and the closure time of the PFA-100 (79%) when compared with the effects of placebo. The platelet aggregatory response to arachidonic acid was completely inhibited following aspirin treatment and was unaffected following placebo. Two weeks after the end of the trial, all values had returned to pre-treatment levels. The template bleeding time was unaltered in 1 of the 12 volunteers during aspirin treatment and was significantly prolonged in 3 of the 12 volunteers during placebo treatment. The PFA-100 closure time was unaltered in 1 of the 12 volunteers during aspirin treatment and was prolonged in 1 subject during placebo treatment. CONCLUSIONS: The change in closure time using the PFA-100 is as sensitive and reproducible to the effects of aspirin on platelet function as is the template bleeding time test. However, the PFA-100 produced less variable effects with fewer false positive results.

Extreme Value Theory Applications to Space Radiation Damage Assessment in Satellite Microelectronics.

Calculations of the first and second moments of displacement damage energy distributions from clastic collisions and from nuclear reactions, at proton energies ranging from 10 MeV to 300 MeV, are incorporated into a model describing the probability of damage as a function of the proton fluence and the size of the sensitive micro-volume in Si. Comparisons between the predicted and measured leakage currents in Si imaging arrays illustrate how the Poisson distribution of higher energy nuclear reaction recoils affects the pixel-to-pixel variance in the damage across the array for proton exposures equivalent to mission duration of a few years within the earth's trapped proton belts. Extreme value statistics (EVS) quantify the largest expected damage extremes following a given proton fluence, and an analysis derived from the first-principle damage calculations shows excellent agreement with the measured extremes. EVS is also used to demonstrate the presence of high dark current pixels, or "spikes," which occur from different mechanisms. Different sources of spikes were seen in two different imager designs.

ICI D7288, a novel sinoatrial node modulator.

We evaluated the cardiovascular effects of the sinoatrial (SA) node modulating agent, ICI D7288, in guinea pig isolated atria and SA node, anaesthetised and exercising dogs, and conscious rats. ICI D7288 (0.1-100 microM) caused a reduction in spontaneous beating rate in guinea pig isolated right atria without affecting the contractile force of paced left atria. The effect was associated with a reduction in the rate of diastolic depolarisation recorded intracellularly from pacemaker cells in the SA node. In anaesthetised dogs, ICI D7288 (0.02-1 mg/kg intravenously, i.v.) caused a dose-related reduction in heart rate (HR) without directly affecting left ventricular (LV) contractility. Exercise tachycardia in dogs was reduced by the compound (0.1-1 mg/kg i.v. and 0.3-10 mg/kg orally, p.o.). The increase in cardiac output (CO) during exercise was well maintained unless the tachycardia was reduced by > 30%, when it was attenuated. Administration of ICI D7288 p.o. (3-100 mg/kg) to conscious rats reduced HR by < or = 40%, but had no effects on blood pressure (BP). We suggest that ICI D7288, through its selective effects on the SA node, may be of use in treatment of ischaemic heart disease to reduce increased HR without impairing cardiac function.

Attenuation of chemically induced defence response by 5-HT1 receptor agonists administered into the periaqueductal gray.

The ability of 5-HT1 receptor agonists to modulate a chemically induced defence response has been studied in Lister hooded rats. Microinjections of the excitatory amino acid D,L-homocysteic acid (DLH) in both rostral and caudal dorsal periaqueductal gray matter (PAG) caused explosive motor behaviour characteristic of defence. This behaviour was quantified in terms of response duration, arena revolutions and number of defensive jumps. Direct administration into the PAG of either 5-carboxamidotryptamine (5-CT) or 8-hydroxy-2-(di-n-propylamino) tetralin (8-OHDPAT) produced behaviours (decreased exploratory rearing, dose related onset of flat body posture) indicative of 5-HT1A receptor activation. Pretreatment with either 5-CT or 8-OHDPAT directly in the PAG caused a significant attenuation, and in some cases a complete abolition, of the DLH evoked response. These agonists share high affinity in vitro for the 5-HT1A receptor. Thus the results suggest that in vivo activation of 5-HT1A receptors mediates an antiaversive response with respect to defensive behaviour elicited by specific chemical stimulation of the dorsal PAG.

In-vitro activity of enoxacin against aminoglycoside-resistant gram-negative bacilli and other clinical isolates.

The in-vitro activity of enoxacin was tested against 500 clinical isolates of Gram-negative bacilli that were resistant to one or more of gentamicin, tobramycin and amikacin, and against 1060 recent consecutive clinical isolates of Gram-negative bacilli and Gram-positive cocci. Enoxacin was active against staphylococci (MICs less than or equal to 4 mg/l) but less active against Streptococcus faecalis (MICs mostly 8 mg/l). It was active against Pseudomonas aeruginosa (MICs 0.5-4 mg/l) and very active against Enterobacteriaceae. In the series of consecutive isolates 97% of Enterobacteriaceae had MICs less than or equal to 1 mg/l. The aminoglycoside-resistant series of Enterobacteriaceae included more strains with higher MICs (13% were 2-4 mg/l and 10% were greater than or equal to 8 mg/l); the majority of the isolates with MICs greater than or equal to 8 mg/l); the majority of the isolates with MICs greater than or equal to 8 mg/l were Serratia marcescens and Providencia spp. Among the non-fermenting species the least sensitive were Acinetobacter calcoaceticus and Ps. maltophilia. Enoxacin-resistant strains of Enterobacteriaceae were resistant to nalidixic acid, but nalidixic acid-resistant strains ranged from fully sensitive to highly resistant to enoxacin.

A model of reflex tracheal constriction in the dog.

1 A tracheal pouch with its nerve and blood supply intact has been prepared in situ in dogs. 2 Mechanical stimulation of the upper airways in dogs anaesthetized with chloralose induced a consistent increase in pouch pressure which was abolished by bilateral vagal section. 3 The response of the pouch following mechanical stimulation of the airways was abolished by intravenous pentobarbitone, atropine, administered systemically or when present in the pouch, and tetracaine, applied to the stimulus area or when present in the pouch. 4 Salbutamol had no inhibitory effects on the response regardless of its route of administration. 5 These results suggest that the increase in pouch pressure following mechanical stimulation of the upper airways is mediated by a vagal reflex arc. 6 The technique may distinguish between drugs the site of action of which is at the afferent or efferent end of this reflex arc.

A model of irritant-induced bronchoconstriction in the spontaneously breathing guinea-pig.

1 Inhalation of an aqueous aerosol of citric acid caused bronchoconstriction in anaesthetized guinea-pigs which was abolished by bilateral vagal section. 2 Conscious guinea-pigs developed slow, laboured breathing within 90 s of exposure to citric acid aerosol. The onset of this pattern of breathing was delayed by prior aerosol administration of atropine, ipratropium bromide, isoprenaline and tetracaine. 3 The data suggest that exposure of guinea-pigs to citric acid may be a useful model of reflex bronchoconstriction.

The mechansim of tachyphylaxis to ICI 74,917 and disodium cromoglycate.

Pre-incubation in vitro of sensitised peritoneal mast cells for 10 min with either ICI 74,917 (10-5 M) abolished the ability of either drug to inhibit histamine release when subsequently presented to the cells at the same time as antigen. In the case of disodium cromoglycate, tachyphylaxis was abolished by washing the cells after pre-incubation with the drug. The failure to abolish tachyphylaxis to ICI 74,917 was due to the high pre-incubation concentration employed, as at lower concentrations (10-8 M) tachyphylaxis to ICI 74917 was readily abolished by washing. Tachyphylaxis to these anti-allergic agents may be related to a physical blocking of drug receptor sites on or in mast cells.

Inhibition of immediate hypersensitivity reactions in the rat by ICI 74,917 and disodium cromoglycate.

ICI 74,917, a potent inhibitor of IgE-mediated passive cutaneous anaphylaxis (PCA) in the rat, exhibited tachyphylaxis in that pre-dosing sensitised rats with a high dose of compound reduced the inhibitory effect on rat PCA of a second dose given at challenge. This phenomenon was most apparent when the pre-dose-challenge dose interval was 15--60 min. Similar findings were obtained using antigen-induced histamine release in vitro from rat peritoneal cells. In these respects, ICI 74,917 was similar to disodium cromoglycate (DSCG) although DSCG appeared less effective in inducing tachyphylaxis than ICI 74,917. There was no evidence in vivo or in vitro that a high dose of either DSCG or ICI 74,917 enhanced the activity of a second low dose of either drug given at challenge.