Limitations and trainability of the respiratory system during exercise with thoracic loads

Thoracic loads (i.e., a heavy backpack) commonly used in occupational and recreational settings significantly challenge human physiological systems and increase the work of breathing, which may promote respiratory muscle fatigue and negatively impacts whole body performance during physical tasks. Accordingly this thesis: (Chapter number: II) designed a laboratory based protocol that closely reflects occupational demands and (III) assessed the effect that load carriage (LC) has upon physiological and respiratory muscle function. Consequently the thesis addressed (IV) acute, (V) chronic and (VI) functional inspiratory muscle loading strategies to assess the limitations and trainability of the respiratory muscles to load carriage performance. The novel laboratory protocol, performed wearing a 25 kg backpack load, combined submaximal load carriage (LC; 60 min treadmill march at 6.5 km·h-1) and self-paced time trial exercise (LCTT; 2.4 km) to better reflect the physiological demands of occupational performance (between trials mean difference -0.34 ± 0.89 min, coefficient of variation 10.5%). Following LC, maximal inspiratory muscle pressure (PImax) and maximal expiratory muscle pressure (P¬Emax) were reduced by 11% and 13% respectively (P<0.05), and further by 5% and 6%, respectively (P< 0.05), after LCTT. Acute inspiratory loading (2 × 30 forced inspiratory efforts 40% PImax) following an active warm-up (10 min lactate turnpoint) failed to improve LCTT despite a transient increase in PImax of ~7% (P<0.05). Chronic inspiratory loading (6 wk, 50% PImax, 30 breaths twice daily) increased PImax (31%, p<0.05) reduced HR and perceptual responses post-LC, and improved LCTT (8%, P< 0.05) with no change in a placebo control. Combining IMT with functional core muscle exercises improved PImax and LCTT by 7% and 4% respectively (P< 0.05), which was greater than traditional IMT alone. Acute, chronic and functional inspiratory muscle loading strategies did not protect against respiratory muscle or locomotor muscle fatigue during LC and LCTT

The acute and chronic implications of the COVID-19 virus on the cardiovascular system in adults: A systematic review

Despite coronavirus disease 2019 (COVID-19) primarily being identified as a respiratory illness, some patients who seemingly recovered from initial infection, developed chronic multi-system complications such as cardiovascular (CV), pulmonary and neurological issues leading to multiple organ injuries. However, to date, there is a dearth of understanding of the acute and chronic implications of a COVID-19 infection on the CV system in adults. A systematic review of the literature was conducted according to PRISMA guidelines and prospectively registered via Prospero (ID: CRD42022360444). The MEDLINE Ovid, Cochrane Library and PubMed databases were searched from inception to August 2022. The search strategy keywords and MeSH terms used included: 1) COVID; 2) coronavirus; 3) long COVID; 4) cardiovascular; and 5) cardiovascular disease. Reference lists of all relevant systematic reviews identified were searched for additional studies. A total of 11,332 records were retrieved from database searches, of which 310 records were duplicates. A further 9887 were eliminated following screening of titles and abstracts. After full-text screening of 1135 articles, 9 manuscripts were included for review. The evidence of CV implications post-COVID-19 infection is clear, and this must be addressed with appropriate management strategies that recognise the acute and chronic nature of cardiac injury in COVID-19 patients. Efficacious management strategies will be needed to address long standing issues and morbidity

Functional inspiratory muscle training (IMT) improves load carriage performance greater than traditional IMT techniques: 1652 Board #305 June 2, 9: 00 AM - 10: 30 AM.

The addition of external thoracic loads is common in occupational groups such as the military. The positioning upon the thorax poses a unique challenge to breathing mechanics and causes respiratory muscle fatigue (RMF) following exercise. IMT techniques provide a positive impact to exercise performance as well as attenuating RMF in both health and athletic populations. However in occupational groups, despite increased inspiratory muscle strength and performance, IMT has so far failed to attenuate RMF, potentially limiting the performance enhancement of IMT. It has been suggested that functional inspiratory muscle training (IMTF) may elicit performance adaptations above that of traditional IMT techniques as it targets the inspiratory muscles throughout the length-tension range adopted during exercise.N/

Impact of weekly swimming training distance on the ergogenicity of inspiratory muscle training in well trained youth swimmers.

The aim of this study was to examine the impact of weekly swimming training distance upon the ergogenicity of inspiratory muscle training (IMT). Thirty-three youth swimmers were recruited and separated into a LOW and HIGH group based on weekly training distance ( 41 km.wk-1, respectively). The LOW and HIGH groups were further subdivided into control and IMT groups for a 6-week IMT intervention giving a total of four groups: LOWcon, LOWIMT, HIGHcon, HIGHIMT. Before and after the intervention period, swimmers completed maximal effort 100 m and 200 m front crawl swims, with maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively) assessed before and after each swim. IMT increased PImax (but not PEmax) by 36% in LOWIMT and HIGHIMT groups (P < 0.05) but 100 m and 200 m swims were faster only in the LOWIMT group (3% and 7% respectively, P < 0.05). Performance benefits only occurred in those training up to 31 km.wk-1 and indicate that the ergogenicity of IMT is affected by weekly training distance. Consequently, training distances are important considerations, among others, when deciding whether or not to supplement swimming training with IMT.N/

Effects of load mass carried in a backpack upon respiratory muscle fatigue.

The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20 kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60 min walking at 6.5 km h−1 wearing a backpack of either 0 (LC0), 10 (LC10), 15 (LC15) or 20 kg (LC20). Inspiratory (PImax) and expiratory (PEmax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60 s of each trial. Results: Group mean PImax and PEmax were unchanged following 60-min load carriage in all conditions (p > .05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p  .05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20 kg in a backpack for up to 60 min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.N/

Functional training of the inspiratory muscles improves load carriage performance

Inspiratory Muscle Training (IMT) whilst adopting body positions that mimic exercise (functional IMT; IMTF) improves running performance above traditional IMT methods in unloaded exercise. We investigated the effect of IMTF during load carriage tasks. Seventeen males completed 60 min walking at 6.5 km·h-1 followed by a 2.4 km load carriage time-trial (LCTT) whilst wearing a 25 kg backpack. Trials were completed at baseline; post 4 weeks IMT (consisting of 30 breaths twice daily at 50% of maximum inspiratory pressure) and again following either 4 weeks IMTF (comprising four inspiratory loaded core exercises) or maintenance IMT (IMTCON). Baseline LCTT was 15.93 ± 2.30 min and was reduced to 14.73 ± 2.40 min (mean reduction 1.19 ± 0.83 min, p < 0.01) after IMT. Following phase two, LCTT increased in IMTF only (13.59 ± 2.33 min, p < 0.05) and was unchanged in post-IMTCON. Performance was increased following IMTF, providing an additional ergogenic effect beyond IMT alone. Practitioner Summary: We confirmed the ergogenic benefit of Inspiratory Muscle Training (IMT) upon load carriage performance. Furthermore, we demonstrate that functional IMT methods provide a greater performance benefit during exercise with thoracic loads. Abbreviations: [Lac-]B: blood lactate; FEV1: forced expiratory volume in one second; FEV1/FVC: forced expiratory volume in one second/forced vital capacity ratio; FVC: forced vital capacity; HR: heart rate; IMT: inspiratory muscle training; IMTCON: inspiratory muscle training maintenance; IMTF: functional inspiratory muscle training; LC: load carriage; LCTT: load carriage time trial; Pdi: transdiaphragmatic pressure; PEF: peak expiratory flow; PEmax: maximum expiratory mouth pressure; PImax: maximum inspiratory mouth pressure; RPE: rating of perceived exertion; RPEbreating: rating of perceived exertion for the breathing; RPEleg: rating of perceived exertion for the legs; SEPT: sport-specific endurance plank test; V̇ O2: oxygen consumption; V̇ O2peak: peak oxygen consumption.N/