The impact of thoracic load carriage up to 45 kg on the cardiopulmonary response to exercise

Abstract

Purpose

The purposes of this experiment were to, first, document the effect of 45-kg thoracic loading on peak exercise responses and, second, the effects of systematic increases in thoracic load on physiological responses to submaximal treadmill walking at a standardized speed and grade.

Methods

On separate days, 19 males (age 27 ± 5 years, height 180.0 ± 7.4 cm, mass 86.9 ± 15.1 kg) completed randomly ordered graded exercise tests to exhaustion in loaded (45 kg) and unloaded conditions. On a third day, each subject completed four randomly ordered, 10-min bouts of treadmill walking at 1.34 m s⁻¹ and 4 % grade in the following conditions: unloaded, and with backpacks weighted to 15, 30, and 45 kg.

Results

With 45-kg thoracic loading, absolute oxygen consumption ( \( \dot{V}{\text{O}}_{2} \) ), minute ventilation, power output, and test duration were significantly decreased at peak exercise. End-inspiratory lung volume and tidal volume were significantly reduced with no changes in end-expiratory lung volume, breathing frequency, and the respiratory exchange ratio. Peak end-tidal carbon dioxide and the ratio of alveolar ventilation to carbon dioxide production were similar between conditions. The reductions in peak physiological responses were greater than expected based on previous research with lighter loads. During submaximal treadmill exercise, \( \dot{V}{\text{O}}_{2} \) increased (P < 0.05) by 11.0 (unloaded to 15 kg), 14.5 (15–30 kg), and 18.0 % (30–45 kg) showing that the increase in exercise \( \dot{V}{\text{O}}_{2} \) was not proportional to load mass.

Conclusion

These results provide further insight into the specificity of physiological responses to different types of load carriage.

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Academy News – July PM&R Journal

As the primary medical society for the specialty of PM&R, your Academy is focused on moving the specialty and you forward. Academy membership supports initiatives to assist our members with:

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Spanish Translated Abstracts

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Ethical, Legal, and Medical Challenges When a Patient Refuses a Transfer From Rehabilitation to Acute Medical Services

I have asked Preya S. Tarsney, JD, to guest edit this Ethical/Legal column on a specific type of informed refusal in the rehabilitation context. Ms Tarsney started her legal career in litigation and health law, and then specialized in clinical medical ethics, completing a postdoctoral fellowship at the University of Chicago's MacLean Center for Clinical Medical Ethics. She is currently a Bioethicist in the Donnelley Ethics Program of the Rehabilitation Institute of Chicago, a Lecturer in physical medicine and rehabilitation (PM&R) at Northwestern University Feinberg School of Medicine, and a Faculty Lecturer at the University of Chicago.

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Driving Under the Influence of Opioids

A 45-year-old man presents to your clinic as a new patient. His medical history is negative; however, his surgical history reveals a history of an L4-S1 posterior decompression and fusion that was performed 5 years earlier. The fusion was performed for a well-established chronic left-sided L5 and S1 lumbar radiculopathy. The patient's low back pain and left lower extremity pain improved for 3 months and then returned to his presurgical level of 7/10. Postsurgical magnetic resonance imaging shows stable fusion structure without evidence of new disk herniations, with scar tissue surrounding the left-sided L5 and S1 nerve roots.

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Genomic location and expression analysis of expansin gene family reveals the evolutionary and functional significance in Triticum aestivum

Abstract

The plant-specific expansin proteins constitute an ancient and major gene family known to have roles in regulating diverse biological processes in plants. Although the functions of many expansin genes have been identified in wheat and other species, little is known about the evolution and genomic locations of the expansin genes in wheat (Triticum aestivum). In this study, a total of 87 expansin genes were identified in the wheat genome, including 52 EXPAs, 42 EXPBs and 4 EXLAs. The EXLB gene was not found in the wheat genome. Phylogenetic tree and comparative analysis revealed amplification of the EXPBs in rice, maize and wheat. The predicted wheat expansins were distributed across 14 of 21 chromosomes with different densities, 3 tightly co-located clusters and 15 paralogous pairs, indicating that tandem duplication and segmental duplication events also played roles in the evolution of expansins in wheat. In addition, the gene structures and conserved protein domains of wheat expansins suggest high levels of conservation within the phylogenetic subgroups. Analysis of a published microarray database showed that most wheat expansin genes exhibit different expression levels in different tissues and developmental stages. To our knowledge, this is the first report of a genome-wide analysis of the wheat expansin gene family, which should provide valuable information for further elucidating the classification and putative functions of the entire gene family.

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In memoriam: Professor Irena Hausmanowa-Petrusewicz (1917–2015)

Professor Irena Hausmanowa-Petrusewicz, one of the most distinguished Polish neurologists, a leader in the field of neuromuscular diseases and electromyography whose contribution was well recognized in international neurological society, passed away on July 7th, 2015.

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