Diaphragm Fatigue after Submaximal Exercise with Chest Wall Restriction

Tomczak, Simone E.; Guenette, Jordan A.; Reid, W. Darlene; McKenzie, Donald C.; Sheel, A. William

doi:10.1249/mss.0b013e3181ef5e67

Cited by 33 publications

(53 citation statements)

References 33 publications

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“…Thoracic restriction modifies the normal breathing mechanics of the exercise hyperpnoea response and consequently heightens the work of breathing (22). Measurements of pulmonary function were similar between trials at baseline, post LC and post LCTT (P>0.05; See Table 2) and demonstrated excellent agreement with narrow confidence intervals and trial bias (See Tables 3 and 4).…”

Section: Respiratory Muscle and Pulmonary Functionmentioning

confidence: 76%

Preloaded Time Trial to Assess Load Carriage Performance

Faghy

Brown

2014

Journal of Strength and Conditioning Research

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Purpose:The relevance and importance of load carriage in recreational and occupational tasks has stimulated a large body of research. Exercise protocols have been criticised for a lack of relevance to occupational activities; accordingly the aim of this study was to assess the reliability of a preloaded time-trial protocol for load carriage assessment. Methods:After full familiarisation, eight healthy males performed two trials separated by one week. Each trial comprised 60min walking at 6.5km·h -1 and 0% gradient (LC), 15 min seated recovery followed by a 2.4km time-trial (LCTT). All trials were performed wearing a 25 kg backpack. Results:Performance time was 16.71 ± 1.82 min and 16.37 ± 1.78 min for LCTT one and two respectively; with a mean difference of -0.34 ± 0.89 min. Using log ratio limits of agreement the mean bias was 1.02 and random error component of the agreement ratio was 1.11. The intra-class correlation (ICC) was 0.85, coefficient of variation (CV) was 10.5% and Cohen's d was 0.35. The protocol demonstrated a very good level of reliability. Conclusions:We present a novel and reliable pre-loaded time-trial protocol that more closely reflects operational activities and can be used to quantify load carriage performance. This protocol provides greater ecologically validity with respect to physical demands of load carriage activities than those adopted previously and provides an excellent tool for the strength and conditioning practitioner to assess individual load carriage performance.

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Section: Respiratory Muscle and Pulmonary Functionmentioning

confidence: 76%

Preloaded Time Trial to Assess Load Carriage Performance

Faghy

Brown

2014

Journal of Strength and Conditioning Research

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“…The brainstem controls the rate and depth of breathing, with the respiratory muscles overcoming three forces (Roussos and Campbell 2011): the static elastic forces of the lung parenchyma and chest wall, the dynamic resistive forces generated by the movement of air through airways and the non-elastic deformation of tissues, and inertial forces. Increases within any one of these forces can impair ventilation through fatigue-inducing elevations of inspiratory muscle work (Milic-Emili and Zin 2011; Tomczak et al 2011;Brown and McConnell 2012). In the case of thoracic load carriage, increments in both the elastic (chest-wall restriction) and inertial (increased mass) contributions to the work of breathing will occur.…”

Section: Cardiopulmonary Effectsmentioning

confidence: 99%

“…These perturbations are most evident within the dynamic maximal ventilatory manoeuvres, and appear to be progressively exacerbated as the load is elevated (Muza et al 1989). Of those, reduced maximal voluntary ventilation has ramifications for the breathing reserve during near-maximal exercise, with chest-wall restriction independently increasing the work of breathing and inducing sensations of dyspnoea (Tomczak et al 2011). Such dynamic volume alterations are consistent with respiratory limitations commonly seen in restrictive pulmonary diseases (Pride and Macklem 2011), highlighting the relevance of those changes to occupational and employment standards research.…”

Section: Cardiopulmonary Effectsmentioning

confidence: 99%

Load carriage, human performance, and employment standards

Taylor

Peoples

Petersen

2016

Appl. Physiol. Nutr. Metab.

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Abstract:The focus of this review is on the physiological considerations necessary for developing employment standards within occupations that have a heavy reliance on load carriage. Employees within military, fire fighting, law enforcement, and search and rescue occupations regularly work with heavy loads. For example, soldiers often carry loads >50 kg, whilst structural firefighters wear 20-25 kg of protective clothing and equipment, in addition to carrying external loads. It has long been known that heavy loads modify gait, mobility, metabolic rate, and efficiency, while concurrently elevating the risk of muscle fatigue and injury. In addition, load carriage often occurs within environmentally stressful conditions, with protective ensembles adding to the thermal burden of the workplace. Indeed, physiological strain relates not just to the mass and dimensions of carried objects, but to how those loads are positioned on and around the body. Yet heavy loads must be borne by men and women of varying body size, and with the expectation that operational capability will not be impinged. This presents a recruitment conundrum. How do employers identify capable and injury-resistant individuals while simultaneously avoiding discriminatory selection practices? In this communication, the relevant metabolic, cardiopulmonary, and thermoregulatory consequences of loaded work are reviewed, along with concomitant impediments to physical endurance and mobility. Also emphasised is the importance of including occupation-specific clothing, protective equipment, and loads during work-performance testing. Finally, recommendations are presented for how to address these issues when evaluating readiness for duty.Key words: backpacks, firefighter, load carriage, oxygen cost, military, employment standards, ventilation, work of breathing.Résumé : Cette analyse documentaire traite principalement des aspects physiologiques essentiels à l'élaboration de normes d'emploi pour des postes dont la fonction majeure est le transport de charges. Les employés dans l'armée, les pompiers, la police, les membres de recherche et sauvetage travaillent régulièrement avec de lourdes charges. Par exemple, les soldats transportent souvent des charges de >50 kg et les pompiers de bâtiments portent un vêtement de protection pesant de 20 à 25 kg et déplacent aussi des charges externes. On sait depuis longtemps que le port de charges lourdes modifie la démarche, la mobilité, le taux métabolique et le rendement tout en augmentant le risque de fatigue musculaire et de blessure. De plus, le déplacement des charges est effectué fréquemment dans des conditions environnementales stressantes et les vêtements de protection accroissent la charge thermique dans cet endroit. En outre, la contrainte physiologique ne dépend pas seulement de la masse et des dimensions des objets à déplacer, mais aussi de leur positionnement sur et autour du corps. Pourtant, il faut que ces charges soient déplacées par des hommes et des femmes de gabarit divers dont les capacités opérationnell...

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“…Load carriage presents a unique challenge to the respiratory system by combining chest wall restriction and loading, with recent evidence demonstrating impaired pulmonary function and breathing mechanics during exercise (Tomczak, Guenette, Reid, McKenzie, & Sheel, 2011).…”

Section: Introductionmentioning

confidence: 99%

Thoracic load carriage-induced respiratory muscle fatigue

Faghy

Brown

2014

Eur J Appl Physiol

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Purpose:We investigated the effect of carrying a 25 kg backpack upon exercise-induced respiratory muscle fatigue, pulmonary function and physiological and perceptual responses to exercise. Methods:Nineteen healthy males performed 60 min walking at 6.5 km·h -1 and 0% gradient with a 25 kg backpack (load carriage; LC). Following 15 min recovery participants then completed a 2.4 km time trial with the load (LCTT) and on a different day, repeated the trials without the load (CON and CONTT respectively). Respiratory muscle fatigue was determined by the transient change in maximal inspiratory (PImax) and expiratory (PEmax) pressure prior to and immediately following exercise. Results:PImax and PEmax were reduced from baseline by 11% and 13% (P<0.05), respectively, post-LC but remained Conclusions:This study provides novel evidence that constant speed walking and time trial exercise with 25 kg thoracic load carriage induces significant inspiratory and expiratory muscle fatigue and may have important performance implications in some recreational and occupational settings.

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Diaphragm Fatigue after Submaximal Exercise with Chest Wall Restriction

Abstract: We conclude that fatigue of the diaphragm occurs under restricted conditions and likely contributes to poor exercise tolerance in patients with restrictive disease.

Cited by 33 publications

References 33 publications

Preloaded Time Trial to Assess Load Carriage Performance

Preloaded Time Trial to Assess Load Carriage Performance

Load carriage, human performance, and employment standards

Thoracic load carriage-induced respiratory muscle fatigue

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