The Effect of Wearing Military Loads on Ventilatory Function and Soldier Performance
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The Effect of Wearing Military Loads on Ventilatory Function and Soldier Performance Nicola Carol Dawn Armstrong This thesis is submitted in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy of the University of Portsmouth. Date of submission: January 2020 Abstract This work aimed to provide an evidence-base to inform the evaluation of future soldier systems so that they minimise breathing restriction. The hypothesis that restrictions to ventilatory function observed with torso-borne load carriage would limit exercise and the performance of military tasks was tested. Four separate studies were conducted to quantify the effect of wearing body armour with backpack loads on infantry soldiers at rest and whilst marching. Load redistribution was also assessed as a potential intervention. The load configurations examined ranged from no load to 50 kg. Ventilatory function, maximum inspiratory / expiratory pressures (PImax and PEmax respectively, to estimate respiratory muscle fatigue (RMF)), shoulder pressure / force and cardiopulmonary parameters were measured pre / post and during the loaded marches. The marches were between 40 and 180 minutes in duration and included light to heavy exercise intensities. Military task performance was measured using cognitive performance tests and the time to complete a 2.4 km best effort test. Wearing military loads caused a restrictive ventilatory impairment of up to 20 % depending on the load carried. Soldiers developed a rapid / shallow breathing pattern whilst marching with load which led to RMF. PImax and PEmax were reduced post-exercise following short duration tasks in Assault Order loads (PImax: 8 %, PEmax: 17 %) and following long duration moderate intensity marches in body armour (PImax: 7 to 13 %, PEmax: 10 to 19 %). Expiratory flow limitation was evident in 72 % of participants tested during heavy exercise. Accuracy during working memory and response inhibition tasks reduced with load and time by up to 20 %. Load redistribution improved accuracy during cognitive tasks but did not affect physiological parameters. The study hypothesis was accepted. The restriction to breathing caused by military loads limited performance during heavy exercise. RMF was evident during long duration marching although this did not limit performance. Page i of xix Contents Page Abstract i Contents Page ii Declaration vi List of Tables vii List of Figures x List of Abbreviations xiii Acknowledgements xvi Dissemination xviii Chapter 1 Introduction 1 1.1 The Problem ...................................................................................... 2 1.2 Research Background ....................................................................... 5 1.3 Knowledge Gaps Identified During the Procurement Process ........... 5 1.4 Summary ......................................................................................... 13 1.5 Thesis Aim and Hypothesis ............................................................. 14 1.6 Summary of Individual Chapters ...................................................... 14 Chapter 2 General Methods 16 2.1 Introduction ...................................................................................... 17 2.2 Literature Review Procedure ........................................................... 17 2.3 Work Rate ........................................................................................ 18 2.4 Peak Inspiratory and Expiratory Mouth Pressures ........................... 25 Page ii of xix 2.5 Handgrip Strength ........................................................................... 27 2.6 Cognitive Function Tests ................................................................. 28 2.7 Pressure and Force ......................................................................... 36 2.8 Participant Characterisation............................................................. 38 2.9 Body Armour .................................................................................... 41 2.10 Statistics .......................................................................................... 44 2.11 Delimitations and Assumptions ........................................................ 45 Chapter 3 The Effect of Wearing Body Armour With Additional Load on Ventilatory Function Whilst Marching 47 3.1 Introduction ...................................................................................... 48 3.2 Literature Review ............................................................................. 58 3.3 Methods ........................................................................................... 65 3.4 Results............................................................................................. 73 3.5 Discussion ....................................................................................... 93 Appendix 1. Summary of Studies Involving Body Armour 102 Appendix 2. Peak Inspiratory (PImax) and Peak Expiratory (PEmax) Pressures Measured Pre and Post Load Carriage 103 Chapter 4 The Effect of Carrying Military Loads on Respiratory Muscle Fatigue, and Soldier Performance in Men 105 4.1 Introduction .................................................................................... 106 4.2 Aim, Objective and Hypotheses ..................................................... 113 4.3 Method .......................................................................................... 114 4.4 Results........................................................................................... 124 4.5 Discussion ..................................................................................... 154 Page iii of xix Appendix 3. Data Appendix 163 1-1 Physical Characteristics of Test “Completers” and “Non-Completers”. 163 Chapter 5 The Effect of Carrying Military Loads on Respiratory Muscle Fatigue, and Soldier Performance in Women 170 5.1 Introduction .................................................................................... 171 5.2 Method .......................................................................................... 178 5.3 Results........................................................................................... 181 5.4 Discussion ..................................................................................... 224 Appendix 4. Analysis of the Physical Characteristics of Test “Completers” and “Non-Completers”. 232 Appendix 5. Power Calculations Based on Data from Studies 2 and 3 234 Chapter 6 Can Load Redistribution be Used as a Strategy to Reduce the Negative Effects of Torso-Borne Load Carriage on Ventilatory Function? 236 6.1 Introduction .................................................................................... 237 6.2 Method .......................................................................................... 240 6.3 Results........................................................................................... 249 6.4 Discussion ..................................................................................... 265 6.5 Summary ....................................................................................... 272 Appendix 6. Participant Characteristics 273 Appendix 7. Correlation Between Participant Characteristics and 2-Back Accuracy 274 Appendix 8. Power Calculations Based on Data From Study 4 276 Chapter 7 General Discussion 278 Page iv of xix 7.1 Introduction .................................................................................... 279 7.2 Key Findings .................................................................................. 280 7.3 Practical Applications and Recommendations ............................... 289 7.4 Future Research ............................................................................ 291 7.5 Exploitation .................................................................................... 292 References 294 ANNEX 1. Letters from Ethics Committees Confirming Favourable Opinion 305 ANNEX 2. Form UP161: Research Ethics Review Checklist 313 Page v of xix Declaration Whilst registered as a candidate for the above degree, I have not been registered for any other research award. The results and conclusions embodied in this thesis are the work of the named candidate and have not been submitted to any other academic award. Signed ___________________________ Nicola Armstrong, PhD Candidate Date ___________________________ Word Count: 62842 © Crown copyright (2019), Dstl. This material is licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected] Note that the images used on the title and chapter pages were downloaded from the Defence Images Website; reuse of these images is also licensed under the terms of the Open Government Licence Page vi of xix List of Tables Table 1-1: Mean Patrol Loads Recorded During Operation HERRICK. .............. 4 Table 3-1: Load Configurations Used During Study 1. ...................................... 68 Table 3-2: Resting Spirometry Data in Each Load Configuration. ..................... 74 Table 3-3: Resting Spirometry Data: Percentage Change From NBA. ............. 75 Table 3-4: Resting Spirometry Data: Effect of Loosening the Body Armour. .... 76 Table 3-5: Cardio-Respiratory Data Measured During The Exercise Test. ....... 80 Table 3-6: Effect Sizes