Effects of pulsed electromagnetic field therapy on symptoms associated with eccentric exercise-induced muscle damage

Unaccustomed exercise consisting of eccentric contractions induces muscle damage that is characterised by muscle weakness, soreness, swelling and increased muscle stiffness. These symptoms affect daily activities and athletic performance; therefore, interventions to attenuate the symptoms and enhance recovery from muscle damage are necessary. Pulsed electromagnetic field therapy (PEMFT) is anecdotally reported to increase muscle blood flow and oxygenation to enhance tissue healing. One previous study showed that PEMFT was effective for alleviating muscle soreness and losses in range of motion after exercise. However, studies investigating the effect of PEMFT on recovery of muscle strength following eccentric exercise are lacking. The purposes of this study were to investigate the effects of PEMFT treatment on muscle temperature, blood flow and oxygenation (Study 1), and on the symptoms associated with eccentric exerciseinduced muscle damage (Study 2). In Study 1, the effects of 30 min PEMFT on muscle temperature, blood flow and oxygenation were examined using nine healthy men (23.6 ± 3.7 years). A device called e-cell™was used for PEMFT in this study, which is the size and shape of a computer mouse weighing approximately 140 g, and sham treatment used a visually identical device without pulsed electromagnetic field production. PEMFT was applied over the bicep brachii of one arm for 30 min, and the other arm received sham treatment, while each subject was lying supine on a massage table. The device was marked A or B; thus, both the investigator and subjects were blinded as to which device was active e-cell™ or sham, and the use of dominant or non-dominant arm for device A or B was randomised and counterbalanced among subjects. Pre-treatment muscle temperature was measured by a thermistor needle (22 gauge, 70 mm) inserted to a depth of 20 mm at 10 mm laterally adjacent to a near infrared spectroscopy (NIRS) probe unit that was attached to the skin at the mid-belly of the biceps brachii, and the post-treatment measurement was taken at 5 mm proximal to the first site. The NIRS was used to measure tissue oxygenation index (TOI), a measure of muscle oxygenation, and total haemoglobin content (tHb), an indirect measure of blood flow, which were recorded throughout the treatment period. Changes in muscle temperature from before to immediately posttreatment were compared between e-cell™ and sham conditions using a paired t-test, and changes in TOI and tHb from baseline to 30 min of treatment (0, 10, 20 and 30 min) were compared between conditions by a two-way repeated measures analysis of variance (ANOVA). Muscle temperature significantly (p In Study 2, eight men and eight women (24.8 ± 6.2 years) performed two bouts of 60 maximal isokinetic (30°⋅s-1) eccentric contractions of the elbow flexors on each arm separated by 4 weeks. In each eccentric contraction, the elbow joint was forcibly extended from a flexed (90°) to a fully extended position (0°). At immediately after, and 1-4 days following the exercise, the exercised arm received 30 min of either e-cell™ or sham treatment described above. The arm dominance and the order of treatment conditions were randomised and counterbalanced among the subjects, and the study was conducted in a double-blinded manner. Dependant variables included maximal voluntary contraction (MVC) strength, range of motion (ROM), upper arm circumference (CIR), muscle soreness by a visual analogue scale, muscle tenderness measured by pressure pain threshold (PPT) and plasma CK activity. Changes in these variables for 7 days following the exercise were compared between e-cell™ and sham treatment conditions, men and women, and the first and second bouts of exercise by a two-way repeated measures ANOVA. The changes in the variables from pre- to post-treatment were also analysed by a two-way repeated measures ANOVA. All variables changed significantly (

Velocity-based training: Monitoring, implementation and effects on strength and power

Traditionally, resistance training has been prescribed using percent-based training (PBT) methods that use the loads relative to a maximal load lifted for one repetition (1RM). However, PBT does not take into account possible day-to-day fluctuations in performance that may occur from physical or psychological stressors. One approach to address this limitation is to monitor velocity changes during resistance training, based on research showing that declines in velocity are highly correlated with fatigue. Therefore, velocity-based training (VBT) methods are proposed to provide a more objective method to modify resistance training sessions based on individual differences in day-to-day performance and the rate of training adaptation. However, at the commencement of this dissertation in 2014, no previous research had examined VBT methods in comparison to PBT methods. Thus, this thesis aimed to verify the efficacy of different VBT methods using a resistance-trained population who could lift a minimum of 150% their own body mass for at least one repetition in the full-depth back squat. These parameters were chosen so that the findings of this research were applicable to strength-trained athletes who were likely to employ VBT methods in their resistance training programs. In the first of five research studies, two portable VBT devices were examined for their accuracy to assess peak velocity (PV) and mean velocity (MV) among other kinematic variables. On three separate days, ten strength-trained men performed three 1RM back squat trials that comprised loads of 20%, 40%, 60%, 80%, 90% and 100% of 1RM. Acceptable validity criteria was based on a Pearson moment correlation coefficient \u3e0.70, coefficient of variation (CV) ≤10% and Cohen d effect size (ES) r = 0.94 – 0.97, CV = 2.9 – 5.8%) and MV (r = 0.95 – 0.99, CV = 3.2 – 4.5%) across the relative load spectrum when compared to laboratory testing equipment. Thus, for the remainder of the VBT studies in this PhD thesis project, an LT was used to report the velocity data. In the second study, a novel velocity-based load monitoring method was investigated using 17 strength-trained men who performed three 1RM trials on separate days. Specifically, the reliability and validity of the load-velocity relationship to predict the back squat 1RM was calculated by entering MV at 100% 1RM into individualised linear regression equations which were derived from the load-velocity relationship of three (20%, 40%, 60% of 1RM), four (20%, 40%, 60%, 80% 1RM), or five (20%, 40%, 60%, 80%, 90% 1RM) incremental warm-up sets. The results showed that this predicted 1RM method was moderately reliable (ICC = 0.72 – 0.92, CV = 7.4 – 12.8%), and moderately valid (r = 0.78 – 0.93, CV = 5.7 – 12.2%). However, it could not be used as a VBT method to accurately modify training loads, since it significantly over-predicted the actual 1RM (SEE = 10.6 – 17.2 kg) due to the large variability of MV at 100% 1RM (ICC = 0.42, SEM = 0.05 m·s-1, CV = 22.5%). Therefore, this 1RM prediction method was no longer utilised as a method of adjusting training load for the remainder of the project. Despite its suggested importance, research had yet to investigate if velocity was stable between training sessions, so that individualised load-velocity profiles (LVP) could be created to track changes in velocity. Thus, the third study attempted to fill this research gap, where 18 strength-trained men performed three 1RM trials, which included warm-up loads pertaining to 20%, 40%, 60%, 80%, 90% and 100% 1RM, with the velocity of each repetition assessed by LT. It was found that PV, mean propulsive velocity (MPV) and MV were all reliable (ICC \u3e 0.70, CV ≤ 10%, ES \u3c 0.6) for the back squat performed at 20%, 40%, 60%, 80%, and 90% 1RM but not at 100% 1RM for MPV and MV. This meant that all three concentric velocity types could be used to develop LVPs. In addition, the smallest detectable difference was established across the relative load spectrum for PV (0.11 – 0.19 m·s-1), MPV (0.08 – 0.11 m·s-1) and MV (0.06 – 0.11 m·s-1), which then allows coaches to determine meaningful changes in velocity from their athletes between training sessions. Collectively, these results showed that LVPs could be utilised as a VBT method for monitoring sessional changes in velocity and modifying resistance-training loads according to individual differences in day-to-day performance. The fourth study compared the kinetic and kinematic data from three different VBT sessions and a PBT session in order to provide programmatic guidance to strength coaches who may choose to implement these novel methods to adjust resistance training load or volume. Fifteen strength-trained men performed four randomised resistance-training sessions 96 hours apart, which included a PBT session involving five sets of five repetitions at 80% 1RM, a LVP session (verified from Study 3) consisting of five sets of five repetitions with a load that could be adjusted to achieve a target velocity from an individualised LVP regression equation at 80% 1RM, a fixed sets 20% velocity loss threshold FSVL20 session that contained five sets at 80% of 1RM but sets were terminated once MV dropped below 20% of the maximal attainable MV from the first set or when five repetitions were completed, a variable sets 20% velocity loss threshold VSVL20 session that comprised 25 repetitions in total but participants performed as many repetitions in a set until the 20% velocity loss threshold was exceeded or 25 repetitions was completed. During the LVP and FSVL20 sessions, individuals performed repetitions with faster (p \u3c 0.05) sessional MV (ES = 0.81 – 1.05) and PV (ES = 0.98 – 1.12), avoided additional mechanical stress with less time under tension but maintained similar force and power outputs when compared to the PBT session. Therefore, the LVP and FSVL20 methods could be employed in a strength-oriented training phase to diminish fatigue-induced decreases in movement velocity that can occur in PBT. The VBT method employed in the fifth and final study was derived from the results of Study 4. Both the LVP and FSVL20 methods permitted faster repetition velocities throughout a training session compared to PBT, but it was decided that the FSVL20 method could decrease total training volume and reduce the training stimulus, which may be unwarranted. Therefore, in Study 5, the effects of the LVP-VBT approach (VBT) versus PBT on changes in strength, power and sports performance measures following six weeks of back squat training were examined. The study involved 24 strength-trained men who performed back squat training three times per week in a daily undulating format. The training protocols were matched for sets and repetitions but differed in the assigned training load. PBT group trained with relative loads varying from 59% – 85% 1RM, whereas the VBT group trained with loads that could be adjusted to achieve a target velocity from an individualised LVP that corresponded with 59% – 85% 1RM. Pre- and post-training assessments included 1RM, 30% of 1RM countermovement jump (CMJ), 20-m sprint, and 505 change of direction test (COD). Overall, the VBT group performed repetitions with faster velocities during training (p \u3c 0.05, MV = 0.76 m·s-1 vs. 0.66 m·s-1) that were perceived as less difficult (p \u3c 0.05, rating of perceived exertion = 5.1 vs. 6.0), and utilized marginally lower training loads (p \u3c 0.05, ~1.7%1RM) compared to PBT. Both VBT and PBT methods were effective for significantly enhancing 1RM (VBT: 11.3% vs. PBT: 12.5%), CMJ peak power (VBT: 7.4% vs. PBT: 6.0%), 20-m sprint (VBT: -1.9% vs. PBT: -0.9%), and COD (VBT: -5.4% vs. PBT: -3.6%). No significant differences were observed between groups for any testing assessment but likely favourable training effects were observed in 1RM for PBT group, whilst VBT group had likely favourable improvements in 5-m sprint time, and possibly favourable improvements in 10-m sprint time, and COD time. These findings suggest that both VBT and PBT methods are similarly effective; however, PBT may provide a slight 1RM strength advantage whilst VBT may be preferred by some individuals, since it permits faster training velocities, is perceived as less difficult, and is a more objective method for adjusting training load to account for individual differences in the rate of training adaptation. In conclusion, VBT (LVP approach) and PBT are similarly effective for promoting significant improvements in strength, power and sports performance tasks in strength-trained participants. However, even though the LVP-based VBT method did not provide significant increases in strength and power adaptations compared to PBT, it provided similar improvements while avoiding additional mechanical loading which may be important for the better management of training load, particularly with athletes who partake in numerous training modalities which can influence fatigue and recovery. That being said, if all repetitions are performed with maximal intended velocity but not to concentric muscular failure, a well-planned, periodised resistance training program with regular training frequency and progressive overload that accounts for bouts of recovery will provide adequate stimulus to significantly enhance strength, power and performance tasks like sprinting and changes in direction. Future training studies may look to examine the efficacy of VBT methods using multiple exercises (upper and lower body), and with different populations including women, adolescents, older adults, and potentially individuals during rehabilitation from injury so that training progress can be objectively monitored. Furthermore, future studies could look to incorporate multiple VBT methods into a training program such as the LVP method to modify resistance training load and the velocity loss thresholds method to control resistance training volume

Detection of Highly Pathogenic Avian Influenza Virus H5N1 Clade 2.3.4.4b in Great Skuas:A Species of Conservation Concern in Great Britain

The UK and Europe have seen successive outbreaks of highly pathogenic avian influenza across the 2020/21 and 2021/22 autumn/winter seasons. Understanding both the epidemiology and transmission of these viruses in different species is critical to aid mitigating measures where outbreaks cause extensive mortalities in both land- and waterfowl. Infection of different species can result in mild or asymptomatic outcomes, or acute infections that result in high morbidity and mortality levels. Definition of disease outcome in different species is of great importance to understanding the role different species play in the maintenance and transmission of these pathogens. Further, the infection of species that have conservation value is also important to recognise and characterise to understand the impact on what might be limited wild populations. Highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b has been detected in great skuas (Stercorarius skua) across different colonies on islands off the shore of Scotland, Great Britain during summer 2021. A large number of great skuas were observed as developing severe clinical disease and dying during the epizootic and mortalities were estimated to be high where monitored. Of eight skuas submitted for post-mortem examination, seven were confirmed as being infected with this virus using a range of diagnostic assays. Here we overview the outbreak event that occurred in this species, listed as species of conservation concern in Great Britain and outline the importance of this finding with respect to virus transmission and maintenance

Reliability and validity of the load-velocity relationship to predict the 1RM back squat

This study investigated the reliability and validity of the load–velocity relationship to predict the free-weight back squat one repetition maximum (1RM). Seventeen strength-trained males performed three 1RM assessments on 3 separate days. All repetitions were performed to full depth with maximal concentric effort. Predicted 1RMs were calculated by entering the mean concentric velocity of the 1RM (V1RM) into an individualized linear regression equation, which was derived from the load–velocity relationship of 3 (20, 40, 60% of 1RM), 4 (20, 40, 60, 80% of 1RM), or 5 (20, 40, 60, 80, 90% of 1RM) incremental warm-up sets. The actual 1RM (140.3 ± 27.2 kg) was very stable between 3 trials (ICC = 0.99; SEM = 2.9 kg; CV = 2.1%; ES = 0.11). Predicted 1RM from 5 warm-up sets up to and including 90% of 1RM was the most reliable (ICC = 0.92; SEM = 8.6 kg; CV = 5.7%; ES = −0.02) and valid (r = 0.93; SEE = 10.6 kg; CV = 7.4%; ES = 0.71) of the predicted 1RM methods. However, all predicted 1RMs were significantly different (p ≤ 0.05; ES = 0.71–1.04) from the actual 1RM. Individual variation for the actual 1RM was small between trials ranging from −5.6 to 4.8% compared with the most accurate predictive method up to 90% of 1RM, which was more variable (−5.5 to 27.8%). Importantly, the V1RM (0.24 ± 0.06 m·s−1) was unreliable between trials (ICC = 0.42; SEM = 0.05 m·s−1; CV = 22.5%; ES = 0.14). The load–velocity relationship for the full depth free-weight back squat showed moderate reliability and validity but could not accurately predict 1RM, which was stable between trials. Thus, the load–velocity relationship 1RM prediction method used in this study cannot accurately modify sessional training loads because of large V1RM variability

Validity of various methods for determining velocity, force, and power in the back squat

Purpose: To examine the validity of 2 kinematic systems for assessing mean velocity (MV), peak velocity (PV), mean force (MF), peak force (PF), mean power (MP), and peak power (PP) during the full-depth free-weight back squat performed with maximal concentric effort. Methods: Ten strength-trained men (26.1 ± 3.0 y, 1.81 ± 0.07 m, 82.0 ± 10.6 kg) performed three 1-repetition-maximum (1RM) trials on 3 separate days, encompassing lifts performed at 6 relative intensities including 20%, 40%, 60%, 80%, 90%, and 100% of 1RM. Each repetition was simultaneously recorded by a PUSH band and commercial linear position transducer (LPT) (GymAware [GYM]) and compared with measurements collected by a laboratory-based testing device consisting of 4 LPTs and a force plate. Results: Trials 2 and 3 were used for validity analyses. Combining all 120 repetitions indicated that the GYM was highly valid for assessing all criterion variables while the PUSH was only highly valid for estimations of PF (r = .94, CV = 5.4%, ES = 0.28, SEE = 135.5 N). At each relative intensity, the GYM was highly valid for assessing all criterion variables except for PP at 20% (ES = 0.81) and 40% (ES = 0.67) of 1RM. Moreover, the PUSH was only able to accurately estimate PF across all relative intensities (r = .92–.98, CV = 4.0–8.3%, ES = 0.04–0.26, SEE = 79.8–213.1 N). Conclusions: PUSH accuracy for determining MV, PV, MF, MP, and PP across all 6 relative intensities was questionable for the back squat, yet the GYM was highly valid at assessing all criterion variables, with some caution given to estimations of MP and PP performed at lighter loads

A comparison study between official records and self-reports of childhood adversity

Article first published online: 13 NOV 2012The aim of this paper was to assess the degree and nature of any mismatch between officially recognised child maltreatment and adolescent self-report of adverse child experiences. Participants included 136 adolescents (72 males, 64 females, Mage = 17 years, age range 14–23 years) who had been confirmed as victims of maltreatment prior to age 13 by Child Protective Services. Participants' self-reports were obtained in adolescence, at least four years after identification. Physical neglect was the most prevalent experience found in the records (87%, n = 118). When this experience was assessed through self-report, only 36 per cent (n = 49) of participants reported physical neglect. Sexual abuse was self-reported by 17 per cent (n = 23) of the sample, compared with eight per cent (n = 11) in the records. Only 17 per cent (n = 23), a small number of self-reports, were consistent with official records. Kappa values show that agreement is low (under 0.40) for seven of the ten categories. Our findings suggest substantial unreliability in the reporting of child abuse and neglect, including household adverse experiences. They also suggest the failure of professionals to discover several adverse experiences during childhood, even after identification by authorities.Fundação para a Ciência e a Tecnologia (FCT) SFRH/BD/45414/200