Chin Moi Chow

Manual hyperinflation: a description of the technique

The aim of this study was to describe the technique of manual hyperinflation as applied by physiotherapists. Ten physiotherapists volunteered to manually hyperinflate a test lung. The protocol randomly altered resuscitation circuits (Laerdal and Macgill) and respiratory compliance conditions. Measurements of tidal volume, airway pressure, inspiratory flow rate and inflation rate were recorded during each test condition. The therapists applied a mean (SD) tidal volume of 1.4 (0.2) L with a mean (SD) airway pressure of 20.6 (6.6) cmH2O. The technique was significantly different between each test condition and between all therapists. Therapists were observed to hyperventilate the test lung and also apply positive end expiratory pressure with the Macgill circuit. A description of the technique on patients is required prior to evaluation of the technique in determining its effect on patients.

Roles of periaqueductal gray and nucleus tractus solitarius in cardiorespiratory function in the rat brainstem

Periaqueductal gray (PAG) and nucleus tractus solitarius (NTS) are important centres for regulation of cardiorespiratory function in cats. We aimed to study the effects of specific PAG stimulation on cardiorespiratory parameters in the rat. Microinjection of D, L-homocysteic acid (DLH) into dorsolateral PAG of anaesthetised rats, led to: marked increases in respiratory frequency (RF) and amplitude of diaphragmatic electromyogram, decreases in inspiratory and expiratory durations, and increased blood pressure and heart rate. Following injection of propranolol (150 pmol, 30 nl), a beta-adrenergic antagonist, into the commissural subnucleus of NTS, the DLH-induced increase in RF was markedly attenuated. Inspiratory neurones (late I cells) in NTS were excited upon stimulation of PAG and their increased activity was accompanied by increased RF. The changes in activity of the late I cells in response to stimulation of dorsolateral PAG provide physiological evidence of a link, possibly noradrenergic, between the two nuclei and involvement of the NTS in control of respiratory functions orchestrated by the PAG.

Training practices and ergogenic aids used by male bodybuilders.

Abstract Hackett, DA, Johnson, NA, and Chow, C-M. Training practices and ergogenic aids used by male bodybuilders. J Strength Cond Res 27(6): 1609–1617, 2013—Bodybuilding involves performing a series of poses on stage where the competitor is judged on aesthetic muscular appearance. The purpose of this study was to describe training practices and ergogenic aids used by competitive bodybuilders and to determine whether training practices comply with current recommendations for muscular hypertrophy. A web-based survey was completed by 127 competitive male bodybuilders. The results showed that during the off-season phase of training (OFF), the majority of respondents performed 3–6 sets per exercise (95.3%), 7–12 repetition maximum (RM) per set (77.0%), and 61- to 120-seconds recovery between sets and exercises (68.6%). However, training practices changed 6 weeks before competition (PRE), where there was an increased number of respondents who reported undertaking 3–4 sets per exercise at the expense of 5–6 sets per exercise (p < 0.001), an increase in the number reporting 10–15RM per set from 7–9RM per set (p < 0.001), and an increase in the number reporting 30–60 seconds vs. 61–180 seconds recovery between sets and exercises (p < 0.001). Anabolic steroid use was high among respondents competing in amateur competitions (56 of 73 respondents), whereas dietary supplementation was used by all respondents. The findings of this study demonstrate that competitive bodybuilders comply with current resistance exercise recommendations for muscular hypertrophy; however, these changed before competition during which there is a reduction resistance training volume and intensity. This alteration, in addition to an increase in aerobic exercise volume, is purportedly used to increase muscle definition. However, these practices may increase the risk of muscle mass loss in natural compared with amateur bodybuilders who reportedly use drugs known to preserve muscle mass.

Worksite intervention effects on sleep quality: a randomized controlled trial.

Employees with sleep disturbance are at increased risk of disease. Exercise is believed to be effective for improving sleep quality, but few studies have been conducted. This study investigated the effects of a 24-week worksite exercise/behavioral intervention on self-rated sleep quality, via the Pittsburgh Sleep Quality Index (PSQI), in 73 employees. Greater post-test improvements in the PSQI (-2.0 +/- 2.6 vs. -1.3 +/- 2.7 points, p = .006, and -16 +/- 61 vs. -1 +/- 76%, p = .02) were found in treatment versus controls, and in women versus men (by -2.7 points [-5.0 to -0.3 points, p = .03], and by -72% [-142 to -2%, p = .04]). Similar results were found in the shift worker subgroup. Changes in sleep scores were not significantly related to baseline characteristics, changes in psychological health or quality-of-life scores, or level of exercise compliance.

Associations among work-related stress, cortisol, inflammation, and metabolic syndrome.

This cross-sectional study examined the relationship between work-related stress, cortisol, and C-reactive protein (CRP) in predicting metabolic syndrome (MtS). Self-reported work stress measured by the effort reward imbalance ratio (ERI), anthropometric data, CRP, and saliva cortisol were collected from 204 healthy Jordanian male workers. ERI and cortisol were significantly associated with the presence of MtS (OR = 4.74, 95% CI: 2.13-10.55; OR = 3.03, 95% CI: 2.08-4.40; OR = 11.50, 95% CI: 2.16-59.14, respectively). The odds of MtS in men with high ERI and high cortisol were significantly higher than that of men with low ERI and low cortisol (OR = 11.50, 95% CI: 2.16-59.14). CRP was significantly associated with MtS (OR = 2.51, 95% CI: 1.50-4.20). The odds of MtS were significantly higher in centrally obese men with both high ERI and CRP level. Thus, high ERI along with high cortisol or high CRP increases the risk for MtS, especially among centrally obese men.

An Arabic version of the perceived stress scale: translation and validation study.

BACKGROUND The Perceived Stress Scale has been designed to measure the degree to which situations in a persons life are perceived as stressful. OBJECTIVE The paper describes the development of an Arabic version of the Perceived Stress Scale. DESIGN A translation process with cross-cultural considerations was employed to produce an Arabic version of the Perceived Stress Scale. SETTINGS Participants were asked to complete the Arabic version Perceived Stress Scale twice in their homes. PARTICIPANTS The Jordanian study population for the Arabic version Perceived Stress Scale validation consisted of 126 volunteers (74 male, 52 female). Ninety participants completed the scale twice (55 male, 35 female), of whom 58 were high schools teachers and 32 technical workers. Arabic was the first language of all participants and all gave informed consent. RESULTS The Arabic version Perceived Stress Scale reliability and validity were evaluated. Prior to an exploratory factor analysis, the suitability of data for factor analysis was assessed with acceptable results. The exploratory factor analysis showed two factors with eigenvalues greater than 1.0 (45.0% of variance). The Cronbachs alpha coefficients were 0.74 (Factor 1), 0.77 (Factor 2) and 0.80 for the Arabic version Perceived Stress Scale overall. The test-retest reliability had an intra-correlation coefficient of 0.90. CONCLUSIONS The Arabic version Perceived Stress Scale showed an adequate reliability and validity. Therefore, the Arabic Perceived Stress Scale is considered a suitable instrument to assess perceived stress in Arabic people.

Effect of temperature and duration of hyperthermia on HSP72 induction in rat tissues.

The aim of the present study was to determine whether heat shock protein 72 (HSP72) is induced in a heated rat model at rectal temperatures below 42 °C.Rats were divided into a control group and six groups (n=6) heated to different rectal temperatures: 39 °C for 1 h (39), 40.0 °C for either 15 min (40S) or 1 h (40L), 41.0 °C for either 15 min (41S) or 1 h (41L) and 42.0 °C for 15 min (42). Tissues were sampled 4 h after heating.Following 1 h at 40.0 °C, HSP72 was significantly elevated in heart (p < 0.005), but not in gut or liver tissue. In all three tissues, HSP72 was significantly elevated under the conditions 41L and 42 compared to control tissue (p < 0.005). Marked differences were found in the amount of HSP72 induced in different tissues in response to the same heat stress. Duration of heating was important in modulating HSP72 induction, with a significantly greater induction of HSP72 following 1 h compared to 15 min at 41 °C in all three tissues (p < 0.02). A correlation was found between thermal load and HSP72 content in liver, heart (both p < 0.01) and gut (p < 0.001) for the rats heated to 41 and 42 °C. These data show that HSP72 is induced at temperatures below 42 °C, with striking differences between tissues. (Mol Cell Biochem 267: 187–194, 2004)

Identification of different types of respiratory neurones in the dorsal brainstem nucleus tractus solitarius of the rat

In Nembutal anaesthetised, spontaneously breathing rats, stereotaxic mapping of the nucleus tractus solitarius (NTS) for respiratory neuronal activity was undertaken. Eight different types of respiratory cells were found between 0.25 and 1.5 mm lateral to midline, extending 0.5 mm caudal to 1.5 mm rostral to obex, and 0.4-1.5 mm below the dorsal surface. A study of the respiratory motor (diaphragm EMG) and neuronal responses to excitatory amino acid (EAA) stimulation of the NTS areas was undertaken. Electrical stimulation of the vagus nerve was employed to study the NTS cellular responses to activation of pulmonary afferents. The effects of chemical activation of the midbrain periaqueductal grey (PAG) on NTS respiratory neuronal activity were investigated. EAA microinjections into the ventrolateral NTS rostral to the obex resulted in an increase in respiratory motor frequency along with increases to inspiratory cell discharge, whilst microinjections into the medial NTS caudal to the obex caused respiratory depression. EAA stimulation of calamus scriptorius produced apnea. NTS inspiratory neurones were inhibited following stimulation of ipsilateral vagus nerve, suggesting their involvement in the Hering-Breuer reflex pathway. PAG stimulation caused excitation of the NTS inspiratory cells indicating the presence of an excitatory respiratory pathway between the two nuclei. Following beta-adrenergic antagonist pre-treatment of ventrolateral NTS, EAA microinjections into PAG did not evoke a cardiorespiratory effect. Based on the various findings the role of NTS in organising respiration in the rat is discussed.

The validity of Actiwatch2 and SenseWear armband compared against polysomnography at different ambient temperature conditions.

There were no validation studies on portable sleep devices under different ambient temperature, thus this study evaluated the validity of wrist Actiwatch2 (AW2) or SenseWear armband (SWA) against polysomnography (PSG) in different ambient temperatures. Nine healthy young participants (6 males, aged 23.3±4.1 y) underwent nine nights of study at ambient temperature of 17 °C, 22 °C and 29 °C in random order, after an adaptation night. They wore the AW2 and SWA while being monitored for PSG simultaneously. A linear mixed model indicated that AW2 is valid for sleep onset latency (SOL), total sleep time (TST) and sleep efficiency (SE) but significantly overestimated wake after sleep onset (WASO) at 17 °C and 22 °C. SWA is valid for WASO, TST and SE at these temperatures, but severely underestimates SOL. However, at 29 °C, SWA significantly overestimated WASO and underestimated TST and SE. Bland–Altman plots showed small biases with acceptable limits of agreement (LoA) for AW2 whereas, small biases and relatively wider LoA for most sleep variables were observed in SWA. The kappa statistic showed a moderate sleep–wake epoch agreement, with a high sensitivity but poor specificity; wake detection remains suboptimal. AW2 showed small biases for most of sleep variables at all temperature conditions, except for WASO. SWA is reliable for measures of TST, WASO and SE at 17–22 °C but not at 29 °C, and SOL approximates that of PSG only at 29 °C, thus caution is needed when monitoring sleep at different temperatures, especially in home sleep studies, in which temperature conditions are more variable.

A novel scale to assess resistance-exercise effort

Abstract In this study, we examined the validity of a novel subjective scale for assessing resistance-exercise effort. Seventeen male bodybuilders performed five sets of 10 repetitions at 70% of one-repetition maximum, for the bench press and squat. At the completion of each set, participants quantified their effort via the rating of perceived exertion (RPE) and novel estimated-repetitions-to-failure scales, and continued repetitions to volitional exhaustion to determine actual-repetitions-to-failure. There were high correlations between estimated- and actual-repetitions-to-failure across sets for the bench press and squat (r ≥ 0.93; P < 0.05). During sets 3, 4, and 5, estimated-repetitions-to-failure predicted the number of repetitions to failure for the bench press and squat, as indicated by smaller effect sizes for differences (ES = 0.37–0.0). The estimated-repetitions-to-failure scale was reliable as indicated by high intraclass correlation coefficients (≥0.92) and narrow 95% limits of agreement (≤0.63 repetitions) for both the bench press and squat. Despite high correlations between RPE and actual-repetitions-to-failure (P < 0.05), RPE at volitional fatigue was less than maximal for both exercises. Our results suggest that the estimated-repetitions-to-failure scale is valid for predicting onset of muscular failure, and can be used for the assessment and prescription of resistance exercise.