Herbert Groeller

Fish oil reduces heart rate and oxygen consumption during exercise

Dietary omega-3 polyunsaturated fatty acids (PUFAs) are readily incorporated into heart and skeletal muscle membranes where, in the heart, animal studies show they reduce O2 consumption. To test the hypothesis that omega-3 PUFAs alter O2 efficiency in humans, the effects of fish oil (FO) supplementation on O2 consumption during exercise were evaluated. Sixteen well-trained men (cyclists), randomly assigned to receive 8 × 1 g capsules per day of olive oil (control) or FO for 8 weeks in a double-blind, parallel design, completed the study (control: n = 7, age 27.1 ± 2.7 years; FO: n = 9, age 23.2 ± 1.2 years). Subjects used an electronically braked cycle ergometer to complete peak O2 consumption tests (VO2peak) and sustained submaximal exercise tests at 55% of peak workload (from the VO2peak test) before and after supplementation. Whole-body O2 consumption and indirect measurements of myocardial O2 consumption [heart rate and rate pressure product (RPP)] were assessed. FO supplementation increased omega-3 PUFA content of erythrocyte cell membranes. There were no differences in VO2peak (mL kg−1 min−1) (control: pre 66.8 ± 2.4, post 67.2 ± 2.3; FO: pre 68.3 ± 1.4, post 67.2 ± 1.2) or peak workload after supplementation. The FO supplementation lowered heart rate (including peak heart rate) during incremental workloads to exhaustion (P < 0.05). In addition, the FO supplementation lowered steady-state submaximal exercise heart rate, whole-body O2 consumption, and RPP (P < 0.01). Time to voluntary fatigue was not altered by FO supplementation. This study indicates that FOs may act within the healthy heart and skeletal muscle to reduce both whole-body and myocardial O2 demand during exercise, without a decrement in performance.

Parkinson's disease: An investigation of exercise capacity, respiratory function, and gait

OBJECTIVE To evaluate the exercise capacity of subjects with mild to moderate Parkinsons disease and determine whether abnormalities in respiratory function and gait affect exercise capacity. DESIGN Descriptive. Subjects were categorized according to exercise history, disease severity, and presence/absence of upper airway obstruction. SUBJECTS AND SETTING Sixteen volunteers with mild to moderate idiopathic Parkinsons disease attended a university research laboratory. MAIN OUTCOME MEASURES Subjects performed a maximum exercise test on a cycle ergometer, together with respiratory function tests and a walking test. Peak values for oxygen consumption and work rate were recorded for the maximum exercise test. Measures of respiratory function included spirometry, flow-volume loops, lung volumes, and mouth pressures. Velocity, stride length, and cadence were measured for preferred and fast speeds of walking. The values obtained on each of these tests were compared with published predicted age- and gender-matched normal values. RESULTS Peak oxygen consumptions and peak work loads achieved by subjects with Parkinsons disease were not significantly different from normal values, despite evidence of respiratory and gait abnormalities typical of Parkinsons disease. Exercise category was significantly correlated with percent predicted VO2peak (r = .64, p < .01), with sedentary subjects producing lower scores than exercising subjects. There was no significant correlation between disease severity and percent predicted VO2peak. CONCLUSION Despite their neurological deficit, individuals with mild to moderate Parkinsons disease have the potential to maintain normal exercise capacity with regular aerobic exercise.

Is repetition failure critical for the development of muscle hypertrophy and strength

This investigation sought to determine the effect of resistance training to failure on functional, structural and neural elbow flexor muscle adaptation. Twenty‐eight males completed a 4‐week familiarization period and were then counterbalanced on the basis of responsiveness across; non‐failure rapid shortening (RS; rapid concentric, 2 s eccentric), non‐failure stretch‐shortening (SSC; rapid concentric, rapid eccentric), and failure control (C, 2 s concentric, 2 s eccentric), for a 12‐week unilateral elbow flexor resistance training regimen, 3 × week using 85% of one repetition maximum (1RM). 1RM, maximal voluntary contraction (MVC), muscle cross‐sectional area (CSA), and muscle activation (EMGRMS) of the agonist, antagonist, and stabilizer muscles were assessed before and after the 12‐week training period. The average number of repetitions per set was significantly lower in RS 4.2 [confidence interval (CI): 4.2, 4.3] and SSC 4.2 (CI: 4.2, 4.3) compared with C 6.1 (CI: 5.8, 6.4). A significant increase in 1RM (30.5%), MVC (13.3%), CSA (11.4%), and agonist EMGRMS (22.1%) was observed; however, no between‐group differences were detected. In contrast, antagonist EMGRMS increased significantly in SSC (40.5%) and C (23.3%), but decreased in RS (13.5%). Similar adaptations across the three resistance training regimen suggest repetition failure is not critical to elicit significant neural and structural changes to skeletal muscle.

Cardiovascular and thermal consequences of protective clothing: a comparison of clothed and unclothed states

We have undertaken a laboratory-based examination of the cardiovascular and thermal impact of wearing thermal (heat) protective clothing during fatiguing exercise in the heat. Seven males completed semi-recumbent, intermittent cycling (39.6°C, 45% relative humidity) wearing either protective clothing or shorts (control). Mean core and skin temperatures, cardiac frequency (f c), stroke volume (Q), cardiac output (), arterial pressure, forearm blood flow ( f), plasma volume change, and sweat rates were measured. In the clothed trials, subjects experienced significantly shorter times to fatigue (52.5 vs. 58.9 min), at lower peak work rates (204.3 vs. 277.4 W), and with higher core (37.9° vs. 37.5°C) and mean skin temperatures (37.3° vs. 36.9°C). There was a significant interaction between time and clothing on f c, such that, over time, the clothing effect became more powerful. Clothing had a significant main affect on , but not Q, indicating the higher was chronotropically driven. Despite a greater sweat loss when clothed (923.0 vs. 547.1 g.m−2·h − 1; P < 0.05), f and plasma volume change remained equivalent. Protective clothing reduced exercise tolerance, but did not affect overall cardiovascular function, at the point of volitional fatigue. It was concluded that, during moderately heavy, semi-recumbent exercise under hot, dry conditions, the strain on the unclothed body was already high, such that the additional stress imparted by the clothing ensemble represented a negligible, further impact upon cardiovascular stability.

Does intramuscular thermal feedback modulate eccrine sweating in exercising humans

Few investigators have considered the possibility that skeletal muscles might contain thermosensitive elements capable of modifying thermoeffector responses. In this experiment, the temporal relationships between dynamic changes in deep‐body and intramuscular temperatures and eccrine sweat secretion were explored during rhythmical and reproducible variations in heat production.

Age, human performance, and physical employment standards

The proportion of older workers has increased substantially in recent years, with over 25% of the Canadian labour force aged ≥55 years. Along with chronological age comes age-related declines in functional capacity associated with impairments to the cardiorespiratory and muscular systems. As a result, older workers are reported to exhibit reductions in work output and in the ability to perform and/or sustain the required effort when performing work tasks. However, research has presented some conflicting views on the consequences of aging in the workforce, as physically demanding occupations can be associated with improved or maintained physical function. Furthermore, the current methods for evaluating physical function in older workers often lack specificity and relevance to the actual work tasks, leading to an underestimation of physical capacity in the older worker. Nevertheless, industry often lacks the appropriate information and/or tools to accommodate the aging workforce, particularly in the context of physical employment standards. Ultimately, if appropriate workplace strategies and work performance standards are adopted to optimize the strengths and protect against the vulnerability of the aging workers, they can perform as effectively as their younger counterparts. Our aim in this review is to evaluate the impact of different individual (including physiological decline, chronic disease, lifestyle, and physical activity) and occupational (including shift work, sleep deprivation, and cold/heat exposure) factors on the physical decline of older workers, and therefore the risk of work-related injuries or illness.

Employment Standards for Australian Urban Firefighters: Part 4: Physical Aptitude Tests and Standards.

Objective: Firefighter physical aptitude tests were administered to unskilled subjects and operational firefighters to evaluate the impact that testing bias associated with gender, age, activity-specific skills, or task familiarity may have upon establishing performance thresholds. Methods: These tests were administered in sequence, simulating hazmat incidents, ventilation fan carriage (stairs), motor-vehicle rescues, bushfire incidents, fire attacks, and a firefighter rescue. Participants included two unskilled samples (N = 14 and 22) and 143 firefighters. Results: Firefighter performance was not significantly different from the unskilled subjects. Participants from both genders passed the test, with scores unrelated to performance skill or age; however, familiarization significantly improved performance when the test was repeated. Conclusion: These outcomes confirmed this test to be gender-, age-, and skill-neutral. Familiarization effects could be removed through performing a single, pre-selection trial of the test battery.

Employment Standards for Australian Urban Firefighters: Part 1: The Essential, Physically Demanding Tasks.

Objective: This communication is the first of four describing the development of defensible firefighter-selection tests. The purpose was to identify a subset of essential, physically demanding tasks performed by contemporary urban firefighters. Methods: From existing procedural documentation and job analyses, 11 fire-station visits and interviews with 106 firefighters, and one focus-group meeting, 31 physically demanding tasks were identified and incorporated into a workforce survey. Using this tool, firefighters rated the importance, perceived difficulty, typical task durations, and annual performance frequency of each task. Results: Data from 989 respondents were analyzed, enabling a consolidation of these tasks into a subset of essential activities. Conclusions: These processes yielded a content-valid list of 15 essential, physically demanding tasks covering the full width of duties performed by urban firefighters from Australias largest fire and rescue organization.

Employment Standards for Australian Urban Firefighters: Part 3: The Transition From Criterion Task to Test.

Objective: In this third communication, the processes for converting criterion occupational tasks into bona fide pre-employment selection tests are presented using urban firefighters as the worked example. Methods: A total of 14 individuals participated in potential screening tests that targeted three loaded movement categories: single-sided load carriage (4 tests), dragging loads (2 tests), and overhead pushing and holding objects (5 tests). Results: Seven tests emerged, one performed as an isolated pass/fail barrier test (ladder raise) and six incorporated into a sequential, timed circuit simulating hazmat incidents, ventilation fan carriage (stairs), motor-vehicle rescues, bushfire incidents, fire attacks, and a firefighter rescue. Conclusion: Because three tests provided predicted performance speeds to replicate the oxygen cost of firefighters performing the corresponding occupational simulations, notional performance thresholds could be projected and recommended for the final phase of this research.

The effect of a familiarisation period on subsequent strength gain

Abstract Untrained subjects can display diverse strength gain following an identical period of resistance exercise. In this investigation, 28 untrained males completed 16-weeks of resistance exercise, comprising 4-weeks familiarisation, and 12-weeks of heavy-load (80–85%) activity. High and low responders were identified by the Δ1RM (Δ one repetition maximum) observed following familiarisation (25.1 ± 1.4%, 9.5 ± 1.4%, P < 0.0001) and differences in electromyographic root mean square amplitude (ΔEMGRMS 29.5 ± 8.3%, 2.4 ± 6.0%, P = 0.0140), and habitual and occupational activity patterns were observed between these respective groups. The strength gain (P < 0.0001) observed within high (29.6 ± 1.7%) and low (31.4 ± 2.7%) responding groups was similar during the heavy-load phase, yet ΔEMGRMS increased (P = 0.0048) only in low responders (31.5 ± 9.3%). Retrospectively, differences (P < 0.0001) in baseline 1RM strength of high- (19.7 ± 0.9 kg) and low-responding (15.6 ± 0.7 kg) groups were identified, and a strong negative correlation with Δ1RM after 16-weeks (r 2 = −0.85) was observed. As such, baseline 1RM strength provided a strong predicative measure of strength adaptation. The ΔEMGRMS suggests strength variability within high and low responders may be attributed to neural adaptation. However, differences in habitual endurance and occupational physical activity suggests one should consider screening not only recent resistance training, but also other modes of physical activity during participant recruitment.