Norman Morris

Comparison of thermoregulatory responses to exercise in dry heat among prepubertal boys young adults and older males

The purpose of this investigation was to compare the thermoregulatory responses during exercise in a hot climate among three age categories. Eight prepubertal (PP), eight young adult (Y) and eight elderly (O) male subjects cycled at an intensity of 50 ± 1% of their maximum oxygen uptake for 85 min (three 20 min bouts with three 7 min rest periods) in hot and dry conditions (41 ± 0.67°C, 21 ± 1% relative humidity). During the exercise‐in‐heat protocol, rectal temperature (Tre) skin temperatures (Tsk), heart rate (HR), , RER, sweat rate, and the number of heat activated sweat glands (HASG) were determined. Despite highest and lowest end‐exposure Tre in the Y and O groups, respectively, the rise in rectal temperature (accounting for differences in baseline Tre) was similar in all age groups. Changes in body heat storage (ΔS), both absolute and relative to body mass, were highest in the Y and O groups and lowest in the PP group. While end‐session as well as changes in mean skin temperature were similar in all three age groups, HR (absolute and percentage of maximum) was significantly lower for the O compared with the PP and Y groups. Total body as well as per body surface sweating rate was significantly lower for the PP group, while body mass‐related net metabolic heat production ((M−W) kg−1) and heat gained from the environment were highest in the PP and lowest in the O group. Since mass‐related evaporative cooling (Esk kg−1) and sweating efficiency (Esk/Msw kg−1) were highest in the PP and lowest in the O group, the mass‐dependent heat stored in the body (ΔS kg−1) was lowest in the PP (1.87 ± 0.03 W kg−1) and highest in Y and O groups (2.19 ± 0.08 and 1.97 ± 0.11 W kg−1, respectively). Furthermore, it was calculated that while the O group required only 4.1 ± 0.5 W of heat energy to raise their body core temperature by 1°C, and the Y group needed 6.9 ± 0.9 W (1°C)−1, the PP group required as much as 12.3 ± 0.7 W to heat up their body core temperature by 1°C. These results suggest that in conditions similar to those imposed during this study, age and age‐related characteristics affect the overall rate of heat gain as well as the mechanisms through which this heat is being dissipated. While prepubertal boys seem to be the most efficient thermoregulators, the elderly subjects appear to be the least efficient thermoregulators.

Can simulation replace part of clinical time? Two parallel randomised controlled trials

Medical Education 2012

The 6-minute walk test in outpatient cardiac rehabilitation: validity, reliability and responsiveness—a systematic review

BACKGROUND The 6-minute walk test (6MWT) is a common outcome measurement in cardiac rehabilitation. However, a search of the literature found no established guidelines for use of the 6MWT in cardiac rehabilitation. OBJECTIVES Systematic review of the validity, reliability and responsiveness of the 6MWT in cardiac rehabilitation. DATA SOURCES OvidMEDLINE, SPORTdiscus, EMBASE, CINAHL, Cochrane Reviews and Cochrane Clinical Trials between January 1948 and April 2011. ELIGIBILITY CRITERIA Studies using 6MWTs in subjects with coronary artery disease undergoing cardiac rehabilitation on an outpatient basis, published in English, were included. STUDY APPRAISAL AND METHODS: Quantitative and qualitative analyses were conducted, including quality assessment of methodology, meta-analysis and assessment against level of evidence criteria. RESULTS Fifteen articles met the inclusion criteria. One high-quality study was identified for reliability, six high-quality studies were identified for validity and 11 high-quality studies were identified for responsiveness. The meta-analysis found strong evidence that the 6MWT was responsive to change in clinical status following cardiac rehabilitation, with an estimated mean difference in 6-minute walk distance of 60.43m (95% confidence interval 54.57 to 66.30m; P<0.001). Qualitative analysis indicated moderate evidence for repeatability of the 6MWT in patients undergoing cardiac rehabilitation, for a 2% to 8% learning effect between repeated 6MWTs, for a relationship between peak heart rate during the 6MWT and during cycle exercise at the ventilatory threshold, and for moderate-to-high correlation between the 6-minute walk distance and maximum metabolic equivalents achieved on symptom-limited exercise tests. LIMITATIONS Few studies assessed similar aspects of validity for the 6MWT. CONCLUSION Strong evidence suggests that the 6MWT is responsive to clinical change following cardiac rehabilitation. Intra- and intertester reliability of the 6MWT and its validity in patients undergoing cardiac rehabilitation requires further research.

Continuous and intermittent exercise responses in individuals with chronic obstructive pulmonary disease

Background: While the acute physiological responses to continuous exercise have been well documented in individuals with chronic obstructive pulmonary disease (COPD), no previous study has examined the response to intermittent exercise in these patients. Methods: We examined the physiological responses of 10 individuals with moderate COPD (forced expiratory volume in 1 second 52 (15)% predicted) who performed both an intermittent (1 min exercise and rest intervals) and a continuous cycle ergometer test on separate days. Both intermittent and continuous exercise tests were performed at the same power output, calculated as 70% of the peak power attained during an incremental exercise test. Results: Intermittent exercise was associated with significantly lower values for oxygen uptake, carbon dioxide output, expired ventilation, heart rate, plasma lactate concentration, and ratings of breathlessness than continuous exercise. Subjects were able to complete a significantly greater total amount of work during intermittent exercise (71 (32) kJ) than during continuous exercise (31 (24) kJ). The degree of dynamic lung hyperinflation (change in end expiratory lung volume) was significantly lower during intermittent exercise (0.23 (0.07) l) than in continuous exercise (0.52 (0.13) l). Conclusions: The greater amount of work performed and lower measured physiological responses achieved with intermittent exercise may allow for greater peripheral training adaptations in individuals with more limited lung function. The results suggest that intermittent exercise may be superior to continuous exercise as a mode of training for patients with COPD.

The effects of multimodal exercise on cognitive and physical functioning and brain-derived neurotrophic factor in older women: a randomised controlled trial

OBJECTIVE to test the effect of a 16-week multimodal exercise program on neurocognitive and physical functioning and brain-derived neurotrophic factor (BDNF). DESIGN a single-blinded, parallel-group randomised controlled trial. SETTINGS university campus and community-based halls. SUBJECTS forty-nine women aged 65 to 75 years, with no cognitive impairment and not undertaking more than 1 h of formal exercise training per week. METHODS the intervention group attended a 60-min multimodal class twice each week which included cardiovascular, strength and motor fitness training. The primary outcome was neurocognitive functioning and secondary outcomes were physical functioning and plasma levels of BDNF. RESULTS twenty-five participants were randomised to the intervention group and 24 to the control group. One control participant withdrew before follow-up data collection. The intervention group performed significantly better than the control group at follow-up (when controlled for baseline) in the Trail Making test A and B, the California Older Adult Stroop test (Word, Interference and Total scores), Controlled Oral Word Association test and the Timed Up-and-Go test, Six-Minute Walk test, One-Legged Stance test and plasma BDNF. CONCLUSION this multimodal exercise program resulted in neurocognitive and physical performance improvements and increased levels of plasma BDNF, in older women, when compared with controls. This RCT provides evidence that a multimodal exercise intervention can achieve larger effect sizes than those generally resulting from single modality interventions. Increases in BDNF levels imply neurogenesis may be a component of the mechanism underpinning the cognitive improvements associated with multimodal exercise. TRIAL REGISTRATION Australian and New Zealand Clinical Trial Registration Number: ANZCTR12612000451808.

Thorax and pelvis kinematics during the downswing of male and female skilled golfers

Thorax and pelvis motion during the golf swing have most frequently been described for male golfers at discrete points during the swing, such as top of backswing (TBS) and ball contact (BC). Less is known about the continual motion and coordination of the thorax and pelvis throughout the downswing for either male or female golfers. The purpose of this study was to present detailed 3D kinematic profiles of thorax and pelvis motion during the downswing, and to determine if differences in kinematics exist between male and female skilled golfers. Thorax and pelvis data were collected from 19 male (26+/-7 years) and 19 female (25+/-7 years) skilled golfers (handicap < or =4) using an optical motion analysis system. 3D segment position, orientation and angular velocity were calculated, along with phase plane trajectories and thorax-pelvis separation angles. At BC males had greater pelvis posterior tilt, greater pelvis and thorax lateral tilt to the right, and less pelvis and thorax axial rotation to the left compared to females. Males achieved greater peak thorax and pelvis angular velocity, and angular velocity at BC, in the anterior-posterior and lateral tilt directions. Phase plane trajectories revealed that males and females had similar thorax lateral tilt and anterior-posterior tilt angular velocity-displacement relationships at TBS, yet by BC males had greater tilt angles and velocities compared to females. Collectively, the results suggest that male and female skilled golfers have different kinematics for thorax and pelvis motion, predominantly for lateral and anterior-posterior tilt. What might be considered optimal swing characteristics for male golfers should not be generalized to female golfers.

Rate and amplitude of adaptation to intermittent and continuous exercise in older men

PURPOSE This study determined the amplitude and rate of adaptation to 10 wk of continuous (CEx) and intermittent exercise (IEx) in a group of older men when the training intensity and total amount of work completed by each exercise group were the same. METHODS Ten healthy men were assigned to either a CEx (63 +/- 1 yr) or IEx (65 +/- 1 yr) group while a further five subjects (65 +/- 1 yr) acted as nonexercising controls (CON). The three groups (CEx, IEx, and CON) were matched for age, peak oxygen uptake (VO2peak), and cardiac output (Qpeak) before commencing training. The CEx group trained for 30 min at an intensity corresponding to 70-75% VO2peak, and the IEx group trained for a total exercise time of 30 min using intermittent exercise (60-s exercise, 60-s rest) at the same absolute intensity as the CEx group (CEx 112 +/- 5W; IEx 112 +/- 5W). The exercise groups trained three times per week and completed a similar amount of work during each training session (CEx, 199 +/- 9 kJ; IEx 195 +/- 9 kJ, P = 0.67). RESULTS The CEx and IEx groups had similar and significant amplitude increases in peak VO2, ventilation (VEpeak), power, Q, and SV after training. Peak VO2, Qpeak, SVpeak, and peak arteriovenous O2 difference for the CON group were unchanged. The change in VO2peak, peak ventilation, and peak power for CEx and IEx groups were best described by a linear model. Moreover, the CEx and IEx groups had the same rate of change in VO2peak (CEx: 0.02 +/- 0.00 L x min(-1) x wk(-1), IEx: 0.02 +/- 0.00 L x min(-1) x wk(-1), P = 0.32), VEpeak (CEx: 2.0 +/- 0.2 L x min(-1) x wk(-1), IEx: 1.2 +/- 0.5 L x min(-1) x wk(-1), P = 0.10), and peak power (CEx: 2.6 +/- 0.4 W x wk(-1), IEx: 2.6 +/- 0.4 W x wk(-1), P = 0.92). CONCLUSION These results suggest that the amplitude and rate of change of select adaptations in men aged 60-70 yr are independent of the mode of training (i.e., continuous or intermittent exercise) when the absolute training intensity and the total amount of work completed were similar.

Simulation can contribute a part of cardiorespiratory physiotherapy clinical education: Two randomized trials

Introduction Simulated learning environments (SLEs) are used worldwide in health professional education, including physiotherapy, to train certain attributes and skills. To date, no randomized controlled trial (RCT) has evaluated whether education in SLEs can partly replace time in the clinical environment for physiotherapy cardiorespiratory practice. Methods Two independent single-blind multi-institutional RCTs were conducted in parallel using a noninferiority design. Participants were volunteer physiotherapy students (RCT 1, n = 176; RCT 2, n = 173) entering acute care cardiorespiratory physiotherapy clinical placements. Two SLE models were investigated as follows: RCT 1, 1 week in SLE before 3 weeks of clinical immersion; RCT 2, 2 weeks of interspersed SLE/clinical immersion (equivalent to 1 SLE week) within the 4-week clinical placement. Students in each RCT were stratified on academic grade and randomly allocated to an SLE plus clinical immersion or clinical immersion control group. The primary outcome was competency to practice measured in 2 clinical examinations using the Assessment of Physiotherapy Practice. Secondary outcomes were student perception of experience and clinical educator and patient rating of student performance. Results There were no significant differences in student competency between the SLE and control groups in either RCT, although students in the interspersed group (RCT 2) achieved a higher score in 5 of 7 Assessment of Physiotherapy Practice standards (all P < 0.05). Students rated the SLE experience positively. Clinical educators and patients reported comparability between groups. Conclusions An SLE can replace clinical time in cardiorespiratory physiotherapy practice. Part education in the SLE satisfied clinical competency requirements, and all stakeholders were satisfied.

The resistive and elastic work of breathing during exercise in patients with chronic Heart Failure

Patients with heart failure (HF) display numerous derangements in ventilatory function, which together serve to increase the work of breathing (Wb) during exercise. However, the extent to which the resistive and elastic properties of the respiratory system contribute to the higher Wb in these patients is unknown. We quantified the resistive and elastic Wb in patients with stable HF (n=9; New York Heart Association functional class I–II) and healthy control subjects (n=9) at standardised levels of minute ventilation (V′E) during graded exercise. Dynamic lung compliance was systematically lower for a given level of V′E in HF patients than controls (p<0.05). HF patients displayed slightly higher levels of inspiratory elastic Wb with greater amounts of ventilatory constraint and resistive Wb than control subjects during exercise (p<0.05). Our data indicates that the higher Wb in HF patients is primarily due to a greater resistive, rather than elastic, load to breathing. The greater resistive Wb in these patients probably reflects an increased hysteresivity of the airways and lung tissues. The marginally higher inspiratory elastic Wb observed in HF patients appears related to a combined decrease in the compliances of the lungs and chest wall. The clinical and physiological implications of our findings are discussed.

Verbal numerical scales are as reliable and sensitive as visual analog scales for rating dyspnea in young and older subjects

This study compared the use of a simple verbal 0-10 numerical rating scale (verbal NRS) and a visual analog scale (VAS) for the rating of dyspnea during exercise in a group of young and older subjects. Twelve younger (32+/-9 yr) and 12 older (71+/-7 yr) subjects used either the verbal NRS or the VAS in a randomised fashion to rate dyspnea during 60 s of uphill treadmill walking (range 5.6-8.8 km h(-1)) performed at either a low (17% grade) or high workload (26% grade) and then during recovery. Rating scales were evaluated twice on separate days (day 1 and day 2) at each workload. While the verbal NRS scores proved to be reliable throughout exercise and recovery, VAS scores were significantly (p<0.05) lower on day 2 during the low workload test (younger group) and the high workload test (older group). Verbal NRS ratings were consistently greater than VAS ratings at both workloads (p<0.001) for both young and older groups. The intra-class correlation coefficients for rating peak dyspnea using either the VAS or verbal NRS were consistently lower for the older subjects (range: r=0.54-0.67) than the younger subjects (range: r=0.70-0.86). Overall, subjects preferred the verbal NRS to the VAS. These results suggest that the verbal NRS compares favourably with the VAS for rating dyspnea during exercise without mask or mouthpiece. However, when rating peak dyspnea both scales appear less reliable when used by the older compared to young subjects.