Ratings Of Perceived Discomfort Research Articles

PERCEPTUAL AND HAEMODYNAMIC RESPONSES DURING MODERATE-SPEED WALKING ARE INCREASED BY BLOOD FLOW RESTRICTION IN OLDER ADULTS, BUT DO NOT EXCEED UNRESTRICTED FAST WALKING

INTRODUCTION & AIMS Moderate-speed blood flow restriction (BFR) walking is an efficient exercise modality for older adults who cannot tolerate vigorous activity. However, limited data exist to guide the prescription of this exercise. This study examined the impact of different walking speeds and BFR cuff pressures on perceptual and haemodynamic responses, and compared these to unrestricted fast walking. METHODS Fifteen older adults (67-77 years) performed 10 sessions of 10-minute treadmill walking. In the first session, participants walked “as quickly as possible” to calculate mean fast walk speed. The following nine randomised sessions included moderate-speed walking with 50, 60 or 70% fast walk speed and 0%, 40 or 60% arterial occlusion pressure (AOP). Ratings of perceived discomfort (RPD) and exertion (RPE) were obtained, and blood pressure was assessed to calculate mean arterial pressure (MAP) and pulse pressure (PP). Perceptual scores were examined with Friedman ANOVA and Wilcoxon signed ranks tests, while MAP and PP were examined using linear mixed models (participants as random effects and speed, AOP or condition as fixed effects). RESULTS Higher RPD was observed using 60% AOP, followed by 40%, and 0% (p<0.001). RPE was higher for the fast walk (5.1±0.8 AU) than all other sessions (1.1±0.4 to 2.9±1.4 AU; p<0.001). MAP and PP were increased with higher AOP and walking speeds (p≤0.043). However, MAP (87.2±8.8 to 102.7±15.6 mmHg) and PP (66.3±14.4 to 80.3±21.7 mmHg) from moderate-speed BFR sessions did not significantly exceed measurements during the fast walk trial (MAP=100.1±13.6 mmHg, PP=89.0±22.5 mmHg). CONCLUSION Walking with BFR at 40% and 60% AOP increased limb discomfort and haemodynamic demands. Importantly, these responses did not exceed unrestricted fast walking, which caused the highest RPE. This study suggests a dose-response relationship of BFR cuff pressure with limb discomfort and haemodynamics, though these responses were not exacerbated more than unrestricted fast walking.

Acute Effects of a Practical Blood Flow Restriction Device During Swimming Exercise

ABSTRACT Purpose: The present study aimed to analyze: 1) the reliability of the tissue saturation index (TSI) and ratings of perceived discomfort (RPD) responses wearing a neoprene practical cuff (PrC), comparing with the responses from traditional (TrC) pneumatic cuffs (study I); 2) the effects of PrC on metabolic (blood lactate concentration, BLC), perceptual (rate of perceived effort, RPE) and kinematic responses at sub-maximal swimming velocities (study II). Methods: Study I; 1) PrC test-retest at rest and during swimming ergometer exercise; 2) BFR at rest with TrC inflated to different percentages of the minimum arterial occlusion pressure (MAOP; 60, 80, 100, 120 and 140%). Test-retest reliability of TSI and RPD was assessed by the intraclass correlation coefficient (ICC) and comparisons among conditions were analyzed by one-way repeated-measures ANOVA. Study II; 1) 50, 200 and 400 m swimming performances; 2) sub-maximal incremental swimming protocol with and without PrC. Two-way repeated measures ANOVA was used to compare all variables during sub-maximal velocities. Results: TSI (ICC = 0.81; 95%CI 0.62–0.91) and RPD (ICC = 0.97; 95%CI 0.94–0.99) were reliable under restricted exercise using PrC. TSI during restricted exercise was lower (p <.001) compared to unrestricted exercise (6.8 ± 6.1% vs. 21.6 ± 8.2% of physiological normalization). PrC showed higher BLC only at or above 91% of critical velocity (p < .03), while stroke rate and RPE were higher (p < .005), and stroke length was lower (p < .03) during all swimming velocities.Conclusion: This easy-to-handle and affordable practical BFR device increased physiological stress at sub-maximal efforts which could be an additional training tool for swimmers.

English

Overhead work is a main risk factor for upper limb work-related musculoskeletal disorders. In this paper, the research team evaluated the effectiveness of a passive exoskeleton(PE) with a mechanical arm linked to the exoskeleton body as an assistive device for overhead work. Ten male volunteers participated in the research by effectuating repetitive overhead lifting tasks using each of three payloads: (1kg, 3kg, and 6kg) and with/without passive exoskeleton (PE). The performance evaluation was then conducted by analyzing the electromyography (EMG) and ratings of perceived discomfort(RPD) of the shoulders and back muscles obtained from experiments.

Effect of fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration

Whole-body vibration and muscle fatigue have both been shown to delay the trunk muscle reflex response and increase trunk muscle activation, leading to an increased risk of low back injuries. However, the effects of whole-body vibration on previously fatigued trunk muscles have never been tested, despite studies showing that prolonged exposure to whole-body vibration can lead to muscle fatigue. The purpose of this research was to investigate the effects of muscle fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration. The results showed that a fatigued muscle state resulted in increased muscle latency, muscle activation and perceived discomfort, which all escalate the risk of low back injuries. Additionally, the ISO 2631-1 comfort ratings did not increase with fatigue, showing a disconnect between these comfort ratings and the perceived discomfort ratings in a fatigued muscle state. Practitioner summary: When exposed to whole-body vibration, fatigued back muscles result in delayed muscle contraction, higher overall muscle activation and increased perceived discomfort, all of which are known to increase low back injury risk. ISO 2631-1 comfort ratings are unable to increase with fatigue, showing a disconnect with perceived discomfort ratings. Abbreviations: EMG: electromyography; EO: external oblique; IO: internal oblique; LE: lumbar erector spinae; LEO: left externaloblique; LIO: left internal oblique; LLE: left lumbar erector spinae; LTE: left thoracic erector spinae; MVC: maximum voluntarycontraction; REO: right external oblique; RIO: right internal oblique; RLE: right lumbar erector spinae; RTE: right thoracicerector spinae; SEAT: Seat Effective Amplitude Transmissibility; TE: thoracic erector spinae; WBV: whole body vibration

A low caffeine dose improves maximal strength, but not relative muscular endurance in either heavier-or lighter-loads, or perceptions of effort or discomfort at task failure in females.

BackgroundThe body of literature considering caffeine as an ergogenic aid has primarily considered typically aerobic based exercise, male participants and moderate-to large-caffeine doses. With this in mind the aim of this project was to explore the effects of a low-caffeine dose upon maximal voluntary contraction (MVC) and muscular endurance (time to task failure, TTF) at heavier-and lighter-loads.MethodsNineteen physically active, habitual caffeine consuming females randomly performed four testing conditions; two with a low-dose of caffeine (100 mg equating to mean = 1.5 ± 0.18 mg·kg−1) and two placebo conditions, where they performed a maximal strength test (MVC) knee extension at 45° followed by a task of relative muscular endurance (sustained isometric contraction for TTF) using either heavier-(70% MVC) and lighter-(30% MVC) loads. Each participant performed each load condition following both caffeine and placebo consumption. Immediately following cessation of the muscular endurance test participants were asked to report their rating of perceived effort (RPE) and rating of perceived discomfort (RPD).ResultsAnalyses revealed a significant effect for caffeine upon MVC compared to placebo (p = 0.007). We also found a significantly greater TTF for the lighter-compared to the heavier-load condition (p < 0.0001); however, there was no significant effect comparing caffeine to placebo (p = 0.2368), but insufficient precision of estimates to infer equivalence in either lighter-(p = 0.750) or heavier-load (p = 0.262) conditions. There were no statistically significant effects for caffeine compared with placebo, or lighter-compared with heavier-loads, for RPE and RPD (all p > 0.05). RPE was statistically equivalent between caffeine and placebo for both lighter-(p = 0.007) and heavier-load (p = 0.002) conditions and RPD for heavier-(p = 0.006) but not lighter-load (p = 0.136).DiscussionThis is the first study to demonstrate a positive effect on strength from a low caffeine dose in female participants. However, it is unclear whether caffeine positively impacts upon relative muscular endurance in either heavier-or lighter-loads. Further, both RPE and RPD appear to be relatively similar during isometric tasks performed to task failure independently of caffeine supplementation or load. These findings may have implications for persons wishing to avoid side-effects or withdrawal symptoms associated with larger caffeine doses whilst still attaining the positive strength responses.

Effect of pulse waveforms on movement amplitudes and perceived discomfort in electric muscle stimulation in unresolved facial nerve palsy

Studies on the effects of the pulse waveform used in electrical muscle stimulation on the activations and perceived discomfort of the waveform have been mainly executed on limb muscles with variable results, however, knowledge of these effects on facial muscles is currently lacking. We studied two waveforms, square wave and sinusoidal wavelet, for the activation of the frontalis muscle in 9 individuals with unresolved facial nerve palsy. Both waveforms produced a movement that was greater in amplitude compared with the maximal voluntary movement of the affected side in 8 participants and at least as great as the healthy side’s maximal voluntary movement in 4 participants. Both waveforms were equally successful in producing movements, and there was no significant difference in perceived discomfort ratings between the two waveforms. These findings will be useful for the future development of neuroprosthetic applications for reanimating facial muscles using electrical stimulation. Trial registration: ClinicalTrials.gov NCT03496025, registration date March 19, 2018.

Resistance Training Performed to Failure or Not to Failure Results in Similar Total Volume, but With Different Fatigue and Discomfort Levels.

Santos, WDNd, Vieira, CA, Bottaro, M, Nunes, VA, Ramirez-Campillo, R, Steele, J, Fisher, JP, and Gentil, P. Resistance training performed to failure or not to failure results in similar total volume, but with different fatigue and discomfort levels. J Strength Cond Res 35(5): 1372-1379, 2021-The purpose of this study was to compare the acute response to 4 sets of high velocity parallel squats performed to momentary failure (MF) or not to momentary failure (NF). Twelve women (24.93 ± 5.04 years) performed MF and NF protocols, in a randomized order with 2-3 interday rest. The protocol involved 4 sets of parallel squats executed at high velocity at 10RM load, with 2 minutes of rest interval between sets. During the NF protocol, the sets were interrupted when the subject lost more than 20% of mean propulsive velocity. The analysis involved the number of repetitions performed per set, total number of repetitions, movement velocity loss, power output loss, rating of perceived exertion (RPE), rating of perceived discomfort (RPD), and session rating of perceived exertion (sRPE). Compared with NF, MF resulted in a higher number of repetitions in the first set (11.58 ± 1.83 vs. 7.58 ± 1.72, p < 0.05), but a lower in the last set (3.58 ± 1.08 vs. 5.41 ± 1.08, p < 0.05). Total number of repetitions was similar between the protocols (MF 26.25 ± 3.47 vs. NF 24.5 ± 3.65, p > 0.05). In both protocols, there were significant decreases in maximum and mean movement velocity loss and power output loss, but higher decreases were observed in MF than NF (p < 0.05). Values for RPE, sRPE, and RPD were higher during MF than NF (p < 0.05). Controlling the movement velocity in NF protocol enabled performance of a similar total volume of repetitions with lower movement velocity and power output losses, RPE, sRPE, and RPD than during an MF protocol.

Ergonomic evaluation of a new truck seat design: a field study

A postural evaluation of commercial licensed truck drivers was conducted to determine the ergonomic benefits of a truck seat prototype in comparison with an industry standard seat. Twenty commercially licensed truck drivers were recruited to perform a 90-min driving task. Postures were assessed using accelerometers and a backrest and seat pan pressure mapping system. Subjective discomfort measurements were monitored using two questionnaires: ratings of perceived discomfort (RPD) and the automotive seating discomfort questionnaire (ASDQ). Participants reported significantly higher discomfort scores when sitting in the industry standard seat. Participants sat with more lumbar lordosis and assumed a more extended thoracic posture when seated in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan also helped reduce the average sitting pressure on both the seat pan and the backrest. The prototype provided several postural benefits for commercially certified truck drivers, as it did for a young and healthy population.

Biomechanical investigation of prolonged driving in an ergonomically designed truck seat prototype

A postural evaluation during a prolonged driving task was conducted to determine the ergonomic validity of a new freely adjustable truck seat prototype. Twenty participants were recruited to perform two 2-h simulated driving sessions. Postures were assessed using motion capture, accelerometers and pressure pads. Subjective discomfort was also monitored in 15-min increments using ratings of perceived discomfort (RPD) and the Automotive Seating Discomfort Questionnaire. Participants had a more neutral spine posture during the first hour of the drive and reported lower RPDs while sitting in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan helped reduce the average sitting pressure. The industry-standard truck seat may lead to the development of poor whole body posture, and the proposed ergonomic redesign of a new truck seat helped improve sitting posture and reduce perceived discomfort.Practitioner Summary: A new freely adjustable truck seat prototype was compared to an Industry standard seat to assess hypothesised improvements to sitting posture and discomfort for long haul driving. It was found that the adjustable panels in the prototype helped promote spine posture, reduce sitting pressure and improved discomfort ratings.

Study of skin conductance and perceived discomfort of the hand/finger system under controlled atmospheric conditions

ABSTRACTThe purpose of this study was to investigate the effect of factors such as temperature, relative humidity and physical exertion on the skin perspiration/moisture levels and subjective perceived discomfort ratings. The skin perspiration/moisture was measured using skin conductance meter. Nine male participants performed three hours of experimental trials that routinely required the physical exertion of lateral pinching. The skin conductance increased significantly with the increase in the temperature, relative humidity and presence of physical exertion. For the trials with physical exertion, the skin conductance was higher than similar trials with no physical exertion. A significant interaction effect of temperature and exertion on perceived discomfort was also observed. The results of this study seem to indicate that factors such as insulation, water permeability and cooing ability of the occupational gloves should be given priority in addition to the safety.

The effects of a simple intervention on exposures to low back pain risk factors during traditional posterior load carriage

Traditional posterior load carriage (PLC), typically performed without the use of an assistive device, is associated with a high prevalence of low back pain (LBP). However, there are few studies that have evaluated potential interventions to reduce exposures to LBP risk factors. This work examined the effects of a simple, potentially low-cost intervention using an assistive device (i.e., carrying aid) on exposures to factors related to LBP risk during PLC. Torso kinematics and kinetics, slip risk, and ratings of perceived discomfort (RPD) were obtained during simulated PLC on a walkway. Consistent with earlier results, increasing load mass substantially increased torso flexion and lumbosacral flexion moment, as well as RPDs in all anatomical regions evaluated. Using the carrying aid with a higher load placement resulted in substantially lower mean lumbosacral moments when carrying the heaviest load. In contrast, using the carrying aid with a lower load placement resulted in substantially higher torso flexion angles, higher mean lumbosacral moments when carrying heavier loads, and higher peak lumbosacral moments across all load masses. With use of the carrying aid, both higher and lower load placement resulted in significantly lower RPDs in the elbows and hands compared to the control condition. In summary, use of a carrying aid with higher load placement may be beneficial in reducing the risk of LBP during PLC. Future studies are needed, though, to improve the device design and to enhance external validity.

Ergonomic evaluation of a wearable assistive device for overhead work

Overhead work is an important risk factor for upper extremity (UE) musculoskeletal disorders. We examined the potential of a mechanical arm and an exoskeletal vest as a wearable assistive device (WADE) for overhead work. Twelve participants completed 10 minutes of simulated, intermittent overhead work, using each of three payloads (1.1, 3.4 and 8.1 kg) and with/without the WADE. Ratings of perceived discomfort (RPDs) and electromyography (EMG) were obtained for the upper arms, shoulders and low back. Using the WADE, UE RPDs decreased by ∼50% with the heavier payloads, whereas smaller (∼25%) and non-significant increases in low-back RPDs were found and were relatively independent of payload. Changes in RPDs with WADE use were consistent with physical demands indicated by EMG, though EMG-based differences in fatigue were less apparent. Participants generally preferred using the WADE, particularly with heavier payloads. These results supported the potential utility of a WADE as an intervention for overhead work.

Effects of elevated oxygen and carbon dioxide partial pressures on respiratory function and cognitive performance.

Hyperoxia during diving has been suggested to exacerbate hypercapnic narcosis and promote unconsciousness. We tested this hypothesis in male volunteers (12 at rest, 10 at 75 W cycle ergometer exercise) breathing each of four gases in a hyperbaric chamber. Inspired Po2 (PiO2 ) was 0.21 and 1.3 atmospheres (atm) without or with an individual subject's maximum tolerable inspired CO2 (PiO2 = 0.055-0.085 atm). Measurements included end-tidal CO2 partial pressure (PetCO2 ), rating of perceived discomfort (RPD), expired minute ventilation (V̇e), and cognitive function assessed by auditory n-back test. The most prominent finding was, irrespective of PetCO2 , that minute ventilation was 8-9 l/min greater for rest or exercise with a PiO2 of 1.3 atm compared with 0.21 atm (P < 0.0001). For hyperoxic gases, PetCO2 was consistently less than for normoxic gases (P < 0.01). For hyperoxic hypercapnic gases, n-back scores were higher than for normoxic gases (P < 0.01), and RPD was lower for exercise but not rest (P < 0.02). Subjects completed 66 hyperoxic hypercapnic trials without incident, but five stopped prematurely because of serious symptoms (tunnel vision, vision loss, dizziness, panic, exhaustion, or near syncope) during 69 normoxic hypercapnic trials (P = 0.0582). Serious symptoms during hypercapnic trials occurred only during normoxia. We conclude serious symptoms with hyperoxic hypercapnia were absent because of decreased PetCO2 consequent to increased ventilation.

Should we be more on the ball? The efficacy of accommodation training on lumbar spine posture, muscle activity, and perceived discomfort during stability ball sitting.

The aim of this study was to evaluate the efficacy of a 9-day accommodation protocol on reducing perceived discomfort while sitting on a stability ball (SB); trunk muscle activity levels and lumbar spinal postures were also considered. Previous studies have compared SB sitting with office chair sitting with few observed differences in muscle activity or posture; however, greater discomfort during SB sitting has been reported. These findings may indicate an accommodation period is necessary to acclimate to SB sitting. For this study, 6 males and 6 females completed two separate, 2-hr sitting sessions on an SB. Half the participants completed a 9-day accommodation period between the visits, whereas the other half did not use an SB during the time. On both occasions, self-reported perceived discomfort ratings were collected along with erector spinae and abdominal muscle activity and lumbar spinal postures. Discomfort ratings were reduced in female participants following the accommodation; no effects on muscle activation or lumbar spine postures were observed. Accommodation training may reduce perceived low-back discomfort in females.Trunk muscle activity and lumbar spine postures during seated office work on an SB did not differ between groups; however, greater sample power was required to conclusively address these variables. Regarding whether to use an SB in place of a standard office chair, this study indicates that females electing to use an SB can decrease discomfort by following an accommodation protocol; no evidence was found to indicate that SB chair use will improve trunk strength or posture, even following an accommodation period.

Analysis of individual and occupational risk factors on task performance and biomechanical demands for a simulated drilling task

The purpose of this study was to evaluate age- and gender-dependent effects of shoulder fatigue on task performance and muscular responses of a drilling task commonly observed within the construction industry. Twelve younger (18–35 years) and ten older (45–60 years) participants, balanced by gender, were recruited from the local community. Task performance (task completion times and errors made), muscle activity of the anterior deltoid (static, mean, and peak amplitude probability density function), coactivity indices of the upper and lower arm, and perceived discomfort ratings were obtained for a series of drilling tasks at three levels of task difficulty, before and after manifestation of shoulder fatigue. To induce fatigue, participants performed a sustained sub-maximal fatigue task at 40% of their maximum voluntary shoulder exertion. Fatigue decreased task completion times, irrespective of age and gender. Higher errors were observed in the fatigued condition, especially for younger participants. Females showed higher shoulder muscle activity compared to men. Additionally, fatigue resulted in lower shoulder APDF measures compared to the no-fatigue condition. Muscle recruitment patterns differed within the fatigue condition, with higher coactivity indices in the upper and lower arm muscles compensating for decreases in shoulder muscle activity. Task difficulty was not found to affect any dependent measures. Participants reported higher discomfort in the fatigued state; this effect was more prominent in females. Overall, this study demonstrated, through objective and subjective measures, that task performance and biomechanical demands are affected by fatigue, and that this effect varies with individual factors such as gender and age. Relevance to industry This paper explored the influence of task demands (fatigue and task difficulty) and individual factors (gender and age) of a drilling task on the development of musculoskeletal injuries of construction workers. The results may contribute towards an understanding of the interplay of certain occupational task demands and worker characteristics on common construction tasks.

The Potential for Actigraphy to Be Used as an Indicator of Sitting Discomfort

A novel technique that uses actigraphy, the study of activity involving the use of body-mounted accelerometers, to detect the discomfort-related movements of a sitting individual has been proposed as a potential indicator of sitting discomfort, and the purpose of this study was to test its validity. Objective measurement of sitting discomfort has always been challenging for researchers. Electromyographic measurements, pressure mapping, and a wide range of other techniques have all been investigated with limited success. The activity monitor's ability to detect and measure seated movement was assessed, and 12 participants were tested on four different chairs (100-min sessions for each). The activity monitor was able to detect participants' sitting movements (Pearson coefficients > 0.9). The chairs were shown to have significantly different subjective discomfort ratings, all of which increased over time. The movements detected by the activity monitor also increased significantly with time, and the amount measured was greater in the chairs rated as most uncomfortable. Regression analysis indicated that the actigraphy data were able to account for 29.6% of the variation in perceived discomfort ratings. Actigraphy can reliably detect sitting movements and may be of use in measuring sitting discomfort. Potential applications of this technique exist for seating research in the automotive industry, health care, and office and leisure chairs.

Muscle fatigue during intermittent isokinetic shoulder abduction: Age effects and utility of electromyographic measures

Most existing evidence regarding the effects of age on muscular fatigue has focused on prolonged isometric contractions, repeated maximum dynamic contractions and individuals beyond traditional retirement age (>65 years). In the present study, age-related differences in muscle fatigue during submaximal dynamic efforts were examined. There were 24 younger (18–25 years) and 24 older (55–65 years) participants, all of whom were healthy and active, with equal numbers of each gender within each age group. Participants performed repetitive, intermittent shoulder abductions until exhaustion, at peak moments of 30% and 40% of individual maximum voluntary isokinetic contraction (MVIC) and with cycle durations of 20 and 40 s. Fatigue development was determined based on changes in MVIC, electromyographic (EMG) signals and ratings of perceived discomfort (RPD). Following the exhaustive exercises, strength recovery was monitored using a series of MVICs over a 15-min period. Results indicated the existence of an age-related fatigue resistance, with the older group demonstrating significantly slower rates of MVIC decline and RPD increase and smaller modifications in EMG-based fatigue measures. These age effects were generally more pronounced at the higher effort level. Main effects of effort level and cycle duration were also significant, while gender effects appeared to be marginal. Rates of strength recovery were not significantly influenced by age. In addition, the utility of standard EMG-based fatigue measures was assessed. Findings indicated that time-dependent changes in static and dynamic EMG-based measures were roughly comparable in terms of sensitivity and variability, supporting the use of standard EMG analyses for fatigue monitoring during intermittent dynamic contractions.

Fatigue during prolonged intermittent overhead work: reliability of measures and effects of working height

Shoulder pain is prevalent among industrial workers and existing evidence supports that overhead work is an important specific risk factor. Existing guidelines are limited, with overhead work typically recommended to be avoided, and research on overhead work has been mixed in terms of the effects of increasing arm reach. A laboratory-based simulation of overhead work was conducted, at three working heights, in order to facilitate improved guidelines and to identify potential non-linear effects of overhead work height. Several indicators of shoulder fatigue served as outcome measures and a preliminary study was performed to assess the reliability of several of these measures. Fatigue measures based on electromyography (EMG) generally had low reliability, whereas excellent reliability was exhibited for ratings of perceived discomfort (RPD). Consistent with this, no effects of overhead work height were found on EMG-based measures, yet clear non-linear effects were found on RPD and task performance. The source of the effects of work height appeared to be related to a combination of muscle activation levels and demands on precision/control at the highest location. These results support the utility of subjective measures for relatively low-level intermittent exertions and demonstrate increasingly detrimental fatigue and performance effects at extremes in reach during overhead work.

The Effects of Differing Overhead Heights on Shoulder Fatigue during a Repetitive Intermittent Task

The purpose of this study was to determine the effect of different overhead work heights on shoulder fatigue. Ten participants (6 males, 4 females) with manual work experience were recruited to perform a dynamic intermittent overhead task simulating automotive assembly work. Participants performed a keyboard tapping task using a hand tool at three different heights, relatively to individual anthropometry, for up to one hour. Throughout the trials, electromyography (EMG) was recorded from three shoulder muscles (anterior deltoid, middle deltoid, and trapezius), and subjective ratings of perceived discomfort (RPD) were obtained. Key striking accuracy was used as a measure of task performance. Though results were not always statistically significant, the EMG, RPD, and performance measures all indicated that higher working heights generally lead to more rapid onset of fatigue.

CAN RELAXATION LOWER METABOREFLEX-MEDIATED BLOOD PRESSURE ELEVATIONS?

Self-induced relaxation (SIR) has been effectively used to lower resting blood pressure. PURPOSE: To determine if this centrally-mediated mechanism could reduce blood pressure elevations generated during post-exercise circulatory occlusion (peripheral metabolic stimulus). METHODS: Data for heart rate and (HR) mean blood pressure (MBP) were collected using a Finpres device; ratings for perceived level of relaxation (RR) and perceived discomfort ratings from cuff occlusion (DR) were obtained using a 1–10 rating scale. The 16 volunteers (10 female; 6 male) all trained with relaxation techniques and demonstrated an ability to decrease MBP at rest by at least 5 mmHg within two minutes of SIR. They were tested under four conditions, performed in random order on the same day, which involved: i). hand-grip exercise followed by post-exercise cuff occlusion (PECO); ii). hand-grip followed by PECO with SIR; iii). rest with cuff occulsion; and iv.) rest and cuff occlusion with SIR. Differences in dependent variables were compared during cuff occlusion across conditions using an ANOVA; a Tukey post-hoc analysis was used to identify and significant pairwise differences. RESULTS: The HR was significantly lower during both relaxation conditions as compared with control (−7 ± 4 bpm vs. −2 ± 3 bpm; p < 0.05). The MBP was significantly reduced during SIR at rest (−6 ± 3.7 mmHg; p < 0.05), but not during PECO (−2 ± 3.1 mmHg; p > 0.05). The RR was higher during relaxation (6.8 ± 1.3 units) vs. control (3.5 ± 1.2 units), but were not different between both SIR conditions. Also, the DR were higher during PECO (p < 0.05). CONCLUSION: These findings suggest that while the central effects of self-induced relaxation can affect cardiovascular regulation and lower HR and MBP at rest, these central factors cannot lower reflex increases in blood pressure originating from a peripheral metabolic stimulus.