Thoracic Load Research Articles

Physiological Responses Of Thoracic Load Carriage During Walking In Men And Women

Physiological Responses Of Thoracic Load Carriage During Walking In Men And Women

Impact of Disabled Driver’s Mass Center Location on Biomechanical Parameters during Crash

Adapting a car for a disable person involves adding additional equipment to compensate for the driver’s disability. During this process, the change in the driver’s position and kinematics and their impact on safety levels during crash is not considered. There is also a lack of studies in the literature on this problem. This paper describes a methodology for conducting a study of the behavior of a disabled driver during a crash using the finite element method, based on an explicit time integration method. A validated car model and a commercial dummy model were used. The results show that the use of a handle on the steering wheel and a hand control unit causes dangerous lateral displacements relative to the seat. Amputation of the left leg or right arm causes significant shoulder rotations, amputation of the left leg causes increased thoracic loads. Amputation or additional equipment have no significant impact on head injuries.

Effects of heel height with backpack loading in young people.

There are many intrinsic and extrinsic factors that could affect posture. Two of them are backpack and heel height. The aim of this study is to investigate the immediate static effects on cervical and lumbosacral postural changes to determine the effects of heel and forefoot heights with backpack loading on both vertebral curves and posture. Craniovertebral (CVA), pelvic tilt (APT), and ankle joint motion angles were measured from sagittal photographs of 20 university students in a static posture while carrying backpacks. The same measurements were taken and recorded conventional shoes with heel and forefoot heights. Postural analysis software (PAS/SAPO) was used to conduct angle assessments of the photos. Postural angles of the vertebral column on the cervical and lumbosacral regions are changed immediately up to the posterior thoracic load with backpacks in young people. CVA was an average of 52° only shoes and no load condition, while the angle was reduced to 49° with loading. In contrast, an increasing angle with additional heel height and zero heel height in conventional shoes were reported. CVA increased with heights to 53° for the heel and 55° at the forefoot. The average APT angle was 14° only shoes and no load condition, and this angle increased to 18.9° with the 20% BW load. Accordingly for the no load and load conditions, the significant increase in the APT angle was 21° with the 20% BW load with heel height and 23° for the 20% BW load along with forefoot height. The heights provided negative effects on the vertebral posture and ankle angle. The results of the study indicate that it may not be advisable for young people to wear shoes with high heels and negative heel height by taking into account the risk factors in the body and ankle postural compensation while carrying a backpack.

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; O2: oxygen consumption; O2peak: peak oxygen consumption.

Ventilatory responses in males and females during graded exercise with and without thoracic load carriage.

To compare the effects of thoracic load carriage on the ventilatory and perceptual responses to graded exercise, 14 pairs of height-matched, physically active males and females completed randomly ordered modified Balke treadmill exercise tests with and without a correctly sized and fitted 20.4kg backpack and work clothing. Subjects walked at 1.56m.s- 1 while grade was increased by 2% every 2min until exhaustion. Ventilatory responses were measured with open circuit spirometry and perceptual responses were evaluated using the modified Borg scale. Inspiratory capacity maneuvers were performed to calculate operating lung volumes. Despite height matching, males had significantly greater lung volumes and peak oxygen uptake ([Formula: see text]O2peak). Peak [Formula: see text]O2 and ventilation ([Formula: see text]E) were lower (p < 0.05) for all subjects under load. Throughout exercise, the ventilatory equivalents for [Formula: see text]O2 and carbon dioxide production were significantly higher in females, independent of condition. At similar relative submaximal intensities (%[Formula: see text]O2peak), there was no difference in [Formula: see text]E between conditions in either group, however, all subjects adopted a rapid and shallow breathing pattern under load with decreased tidal volume secondary to lower end-inspiratory lung volume. The relative changes in breathing pattern and operating lung volume between unloaded and loaded conditions were similar between males and females. Females reported significantly higher dyspnea ratings for a given [Formula: see text]E compared to males; however, the relationship between dyspnea and [Formula: see text]E was unaffected by load carriage. The relative response patterns for ventilatory and perceptual responses to graded exercise with thoracic loading were similar in males and females.

Interaction Between Ambient Temperature, Hypoxia, and Load Carriage on Respiratory Muscle Fatigue.

BACKGROUND: While respiratory muscle fatigue is present following load carriage activity at sea level, the effect of environmental conditions on respiratory strength while undertaking load carriage is unknown.METHODS: The effect of thoracic load carriage during walks (5.5 km) in four environments [(thermo-neutral sea level (SL), -10°C (C), 4300 m (H) and 4300 m at -10°C (HC)] was evaluated on respiratory muscle fatigue. Ten subjects completed eight self-paced randomized treadmill walks comprising a variety of gradients, unloaded and loaded (18.2 kg), across the four environments. Respiratory muscle strength was measured via maximal inspiratory pressure (PImax) and expiratory pressure (PEmax) assessments.RESULTS: Submaximal walking in HC elicited respiratory muscle fatigue when compared to SL. Inspiratory muscle fatigue was independent of load. The relative change in PImax from baseline was significantly greater in HC compared to SL (9.6% vs. 1.3%). PEmax showed a significant reduction during HC (-22.3 cmH₂O, -14.4%) when compared to the other three environments.CONCLUSION: These results highlight the need to focus on respiratory muscle strength in preparation for exercise in cold hypoxic conditions.Hinde K, Low C, Lloyd R, Cooke C. Interaction between ambient temperature, hypoxia, and load carriage on respiratory muscle fatigue. Aerosp Med Hum Perform. 2018; 89(11):952-960.

Inspiratory muscle training improves exercise capacity with thoracic load carriage.

Thoracic load carriage (LC) exercise impairs exercise performance compared to unloaded exercise, partially due to impaired respiratory mechanics. We investigated the effects of LC on exercise and diaphragmatic fatigue in a constant‐load exercise task; and whether inspiratory muscle training (IMT) improved exercise capacity and diaphragmatic fatigue with LC. Twelve recreationally active males completed three separate running trials to exhaustion (T lim) at a fixed speed eliciting 70% of their V˙O2max. The first two trials were completed either unloaded (UL) or while carrying a 10 kg backpack (LC). Subjects then completed 6 weeks of either true IMT or placebo‐IMT. Posttraining, subjects completed an additional LC trial identical to the pretraining LC trial. Exercise metabolic and ventilatory measures were recorded. Diaphragm fatigue was assessed as the difference between preexercise and postexercise twitch diaphragmatic pressure (P di, tw), assessed by bilateral stimulation of the phrenic nerve with esophageal balloon‐tipped catheters measuring intrathoracic pressures. T lim was significantly shorter (P < 0.001) with LC compared with UL by 42.9 (29.1)% (1626.5 (866.7) sec and 2311.6 (1246.5) sec, respectively). The change in P di, tw from pre‐ to postexercise was significantly greater (P = 0.001) in LC (−13.9 (5.3)%) compared with UL (3.8 (6.5)%). Six weeks of IMT significantly improved T lim compared to pretraining (P = 0.029, %Δ +29.3 (15.7)% IMT, −8.8 (27.2)% Placebo), but did not alter the magnitude of diaphragmatic fatigue following a run to exhaustion (P > 0.05). Minute ventilation and breathing mechanics were unchanged post‐IMT (P > 0.05). Six weeks of flow‐resistive IMT improved exercise capacity, but did not mitigate diaphragmatic fatigue following submaximal, constant‐load running to volitional exhaustion with LC.

Respiratory Effects of Thoracic Load Carriage Exercise and Inspiratory Muscle Training as a Strategy to Optimize Respiratory Muscle Performance with Load Carriage.

Many occupational and recreational settings require the use of protective and/or load-bearing apparatuses worn over the thoracic cavity, known as thoracic load carriage (LC). Compared to normal, unloaded exercise, thoracic LC exercise places an additional demand on the respiratory and limb locomotor systems by altering ventilatory mechanics as well as circulatory responses to exercise, thus accelerating the development of fatigue in the diaphragm and accessory respiratory muscles compared to unloaded exercise. This may be a consequence of the unique demands of thoracic LC, which places an additional mass load on the thoracic cavity and can restrict chest wall expansion. Therefore it is important to find effective strategies to ameliorate the detrimental effects of thoracic LC. Inspiratory muscle training is an intervention that aims to increase the strength and endurance of the diaphragm and accessory inspiratory muscle and may therefore be a useful strategy to optimize performance with thoracic LC.

The effects of increasing thoracic load carriage, using a backpack and body armour ensemble, on ambulatory lung volumes

Introduction: Thoracic load carriage reduces pulmonary function as a consequence of increased inertial and elastic forces. When heavy loads are carried during periods of increased metabolic demand, those forces can have adverse consequences on operational lung volumes. In this investigation, the impact of a backpack and body-armour ensemble on the ventilatory pump was explored during a steady-state marching simulation.

The effects of increasing thoracic load carriage, using a backpack and body-armour ensemble, on peak aerobic power and exercise tolerance

The effects of increasing thoracic load carriage, using a backpack and body-armour ensemble, on peak aerobic power and exercise tolerance

Flow-resistive Inspiratory Muscle Training Improves Running Time To Exhaustion With Thoracic Load Carriage

Exercise while carrying an external load upon the thoracic cavity imposes extra stress on the cardiopulmonary and limb locomotor systems. This in turn, negatively impacts exercise tolerance and performance, as well as pulmonary and respiratory muscle function. Thoracic load carriage exercise (LC) has been shown to induce global respiratory muscle fatigue as assessed by volitional mouth pressures, with a concomitant impairment in running time-trial performance. Inspiratory muscle training (IMT) has been shown to improve performance in a running time-trial with thoracic LC. However, in many occupational and recreational activities that require thoracic LC, the capacity to sustain prolonged exercise may be of equal or greater importance than performance in a time-trial. PURPOSE: To determine the efficacy of 6 weeks of flow-resistive IMT on running time to exhaustion with thoracic LC; and to determine whether 6 weeks of flow-resistive IMT moderates diaphragmatic fatigue that may occur following a thoracic LC running time to exhaustion test. METHODS: Twelve recreationally active males completed two runs to exhaustion (Tlim) at a fixed speed eliciting 70 % of V˙O2max while carrying a 10 kg backpack. Visits were completed at baseline and after 6 weeks of either IMT or placebo-IMT. Exercise metabolic and ventilatory measures were recorded and diaphragm strength was measured using bilateral phrenic nerve stimulation in conjunction with esophageal balloon-tipped catheters to measure intrathoracic pressures. Twitch transdiaphragmatic pressure amplitude was recorded pre-exercise and immediately post-exercise in both trials. Maximal volitional mouth pressures (PImax) were recorded at baseline and post-IMT. RESULTS: 6 weeks of IMT significantly improved Tlim (p = 0.029, %Δ +29.3 ± 6.4 % IMT, -8.8 ± 11.1 %), but did not alter the change in diaphragm strength following a run to exhaustion (p > 0.05). The %Δ in PImax from pre- to post-training was significantly correlated with the %Δ in Tlim from pre- to post-training (p = 0.031, r = 0.622). No changes were observed in minute ventilation or breathing mechanics (all p > 0.05). CONCLUSIONS: IMT improves exercise tolerance with thoracic LC, but does not attenuate the severity of diaphragmatic fatigue following a running time to exhaustion test.

Whole-body active warm-up and inspiratory muscle warm-up do not improve running performance when carrying thoracic loads.

Whole-body active warm-ups (AWU) and inspiratory muscle warm-up (IMW) prior to exercise improves performance on some endurance exercise tasks. This study investigated the effects of AWU with and without IMW upon 2.4-km running time-trial performance while carrying a 25-kg backpack, a common task and backpack load in physically demanding occupations. Participants (n = 9) performed five 2.4-km running time-trials with a 25-kg thoracic load preceded in random order by (i) IMW comprising 2 × 30 inspiratory efforts against a pressure-threshold load of 40% maximal inspiratory pressure (PImax), (ii) 10-min unloaded running (AWU) at lactate turnpoint (10.33 ± 1.58 km·h-1), (iii) placebo IMW (PLA) comprising 5-min breathing using a sham device, (iv) AWU+IMW, and (v) AWU+PLA. Pooled baseline PImax was similar between trials and increased by 7% and 6% following IMW and AWU+IMW (P < 0.05). Relative to baseline, pooled PImax was reduced by 9% after the time-trial, which was not different between trials (P > 0.05). Time-trial performance was not different between any trials. Whole-body AWU and IMW performed alone or combination have no ergogenic effect upon high-intensity, short-duration performance when carrying a 25-kg load in a backpack.

Age-Specific Injury Risk Curves for Distributed, Anterior Thoracic Loading of Various Sizes of Adults Based on Sternal Deflections.

Injury Risk Curves are developed from cadaver data for sternal deflections produced by anterior, distributed chest loads for a 25, 45, 55, 65 and 75 year-old Small Female, Mid-Size Male and Large Male based on the variations of bone strengths with age. These curves show that the risk of AIS ≥ 3 thoracic injury increases with the age of the person. This observation is consistent with NASS data of frontal accidents which shows that older unbelted drivers have a higher risk of AIS ≥ 3 chest injury than younger drivers.

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

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. On separate days, 19 males (age 27±5years, height 180.0±7.4cm, mass 86.9±15.1kg) completed randomly ordered graded exercise tests to exhaustion in loaded (45kg) and unloaded conditions. On a third day, each subject completed four randomly ordered, 10-min bouts of treadmill walking at 1.34ms(-1) and 4% grade in the following conditions: unloaded, and with backpacks weighted to 15, 30, and 45kg. With 45-kg thoracic loading, absolute oxygen consumption ([Formula: see text]), 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, [Formula: see text] increased (P<0.05) by 11.0 (unloaded to 15kg), 14.5 (15-30kg), and 18.0% (30-45kg) showing that the increase in exercise [Formula: see text] was not proportional to load mass. These results provide further insight into the specificity of physiological responses to different types of load carriage.

Functional Inspiratory Muscle Training (IMT) Improves Load Carriage Performance Greater than Traditional IMT Techniques

The addition of 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 failed to attenuate RMF, potentially limiting the performance enhancement of IMT. It has been suggested that functional inspiratory muscle training (IMTF) may elicit adaptations above that of traditional IMT techniques as it targets the inspiratory muscles throughout the length-tension range adopted during exercise. PURPOSE: To investigate the use IMTF techniques on performance in exercise tasks with thoracic load carriage. METHODS: All participants (n=17) completed 4-week foundation IMT using a Powerbreathe device (2 x 30 breaths, daily at 50% maximal inspiratory pressure (MIP), either side of a pre-loaded time-trial (LCTT) while carrying a 25 kg thoracic load. Participants were randomly assigned to either IMTF (n=9) or a maintenance group (CON, n=8) and completed 4 additional weeks of training. IMTF consisted of 3 sessions per week whilst simultaneously breathing through the training device at 50% MIP and conducting 4 predetermined core exercises. CON, comprised of 30 breaths at 50% MIP, 3 times weekly. RESULTS: Baseline LCTT was 15.93 ± 2.30 and improved to 14.73 ± 2.40 min post 4 week IMT LCTT (P &lt0.01). Post IMTF, LCTT further improved (13.59 ± 2.33 min, P &lt0.05). Relative to baseline (151 ± 36 cmH2O), MIP was greater post IMT (172 ± 39 cmH2O, P<0.05) but was similar post IMTF (179 ± 25 cmH2O, P >0.05) and CON (P>0.05). The post exercise reduction in MIP in all trials remained unchanged. CONCLUSION: IMT improves MIP and exercise performance with thoracic load carriage and the improvement is enhanced by incorporating a period of IMTF, which provides an additional ergogenic effect to exercise performance. This appears to be the result of improved coordination between core and respiratory muscle groups that are tasked heavily via load carriage exercise and IMTF. However, it did not attenuate respiratory muscle fatigue after load carriage activities.

Physiological and performance consequences of heavy thoracic load carriage in females.

The purposes of this experiment were to study physiological responses to graded exercise to exhaustion (Part I) and ventilatory responses during 45 min of exercise (Part II) with and without a 25-kg backpack. In Part I, on separate days, 24 females completed randomly ordered modified Balke treadmill tests. Analysis revealed significant decreases in absolute peak oxygen uptake (3.5%), peak power output (20%), and test duration (40%) under load. There was a significant but modest negative relationship between body mass and the change in test duration between conditions (r = -0.44). While physiological responses to peak exercise were similar, exercise performance was negatively impacted under load. On separate days in Part II, 14 females completed randomly ordered, loaded and unloaded exercise challenges of submaximal treadmill walking at matched oxygen demands. Under load, breathing frequency, dead space, and minute ventilation were increased by 19.9%, 29.8%, and 11.6% (P < 0.05), respectively, while tidal volume and end-inspiratory lung volume decreased by 13.6% and 6.0% (P < 0.05), respectively. After loaded exercise, maximal inspiratory pressure was decreased by 11.5% (P < 0.05) with no changes in maximal expiratory pressure in either condition. Despite matched oxygen uptake between loaded and unloaded exercise challenges, perceived exertion and breathing discomfort were higher (P < 0.05) under load. With heavy load carriage, the altered breathing pattern led to increased dead space and minute ventilation, which likely contributed to higher perceptions of exercise stress and breathing discomfort. These results are similar to previous research in males and underscore the impact of heavy load carriage during exercise.

The effects of thoracic load carriage on maximal ambulatory work tolerance and acceptable work durations.

Torso loads restrict chest-wall movement and ventilation, particularly during heavy exercise. Therefore, the differential impact of load carriage and chest-wall restriction was investigated during progressive treadmill exercise. In addition, acceptable work durations were derived across a wide range of submaximal, loaded exercise intensities. Twelve males participated in two research phases. Phase 1: Three incremental treadmill tests until exhaustion [control (clothing only), load carriage (clothing plus 22-kg vest), and clothing with chest strapping]. Phase 2: Five steady-state exercise trials (clothing plus 22-kg vest) at intensities from 30 to 80% of peak aerobic power to determine maximal acceptable work durations. Maximal work tolerance [control 17.21min (±0.93); loaded 13.44min (±0.68); strapped 17.00min (±0.83)] and the mass-specific peak aerobic power [control 61.61mLkg(-1)min(-1) (±2.28); loaded 45.42mLkg(-1)min(-1) (±1.41); strapped 59.99mLkg(-1)min(-1) (±1.61)] were reduced only when loaded (P<0.05). Peak minute ventilation was retained, although loading and chest strapping reduced the breathing reserve. The lower and upper acceptable work duration derivations when working at the 30% intensity were 133.40min (±23.77) and 220.10min (±48.69), but at 80% intensity, both durations were reduced to <7min. Thoracic loading significantly reduced exercise tolerance and the breathing reserve, but did not modify peak minute ventilation or the absolute peak aerobic power. Chest strapping, as used herein, exerted minimal impact. However, the projected maximal acceptable work durations were much less than derived using previously published methods.

A point-wise normalization method for development of biofidelity response corridors

An updated technique to develop biofidelity response corridors (BRCs) is presented. BRCs provide a representative range of time-dependent responses from multiple experimental tests of a parameter from multiple biological surrogates (often cadaveric). The study describes an approach for BRC development based on previous research, but that includes two key modifications for application to impact and accelerative loading. First, signal alignment conducted prior to calculation of the BRC considers only the loading portion of the signal, as opposed to the full time history. Second, a point-wise normalization (PWN) technique is introduced to calculate correlation coefficients between signals. The PWN equally weighs all time points within the loading portion of the signals and as such, bypasses aspects of the response that are not controlled by the experimentalist such as internal dynamics of the specimen, and interaction with surrounding structures. An application of the method is presented using previously-published thoracic loading data from 8 lateral sled PMHS tests conducted at 8.9m/s. Using this method, the mean signals showed a peak lateral load of 8.48kN and peak chest acceleration of 86.0g which were similar to previously-published research (8.93kN and 100.0g respectively). The peaks occurred at similar times in the current and previous studies, but were delayed an average of 2.1ms in the updated method. The mean time shifts calculated with the method ranged from 7.5% to 9.5% of the event. The method may be of use in traditional injury biomechanics studies and emerging work on non-horizontal accelerative loading.

Assessment of Bilateral Thoracic Loading on the Near-Side Occupant Due to Occupant-to-Occupant Interaction in Vehicle Crash Tests

Objective: This study aims, by means of the WorldSID 50th percentile male, to evaluate thoracic loading and injury risk to the near-side occupant due to occupant-to-occupant interaction in combination with loading from an intruding structure.Method: Nine vehicle crash tests were performed with a 50th percentile WorldSID male dummy in the near-side (adjacent to the intruding structure) seat and a THOR or ES2 dummy in the far-side (opposite the intruding structure) seat. The near-side seated WorldSID was equipped with 6 + 6 IR-Traccs (LH and RH) in the thorax/abdomen enabling measurement of bilateral deflection. To differentiate deflection caused by the intrusion, and the deflection caused by the neighboring occupant, time history curves were analyzed. The crash tests were performed with different modern vehicles, equipped with thorax side airbags and inflatable curtains, ranging from a compact car to a large sedan, and in different loading conditions such as car-to-car, barrier, and pole tests. Lateral delta V based on vehicle tunnel acceleration and maximum residual intrusion at occupant position were used as a measurement of crash severity to compare injury measurements.Result: In the 9 vehicle crash tests, thoracic loading, induced by the intruding structure as well as from the far-side occupant, varied due to the size and structural performance of the car as well as the severity of the crash. Peak deflection on the thoracic outboard side occurred during the first 50 ms of the event. Between 70 to 150 ms loading induced by the neighboring occupant occurred and resulted in an inboard-side peak deflection and viscous criterion. In the tests where the target vehicle lateral delta V was below 30 km/h and intrusion less than 200 mm, deflections were low on both the outboard (20–40 mm) and inboard side (10–15 mm). At higher crash severities, delta V 35 km/h and above as well as intrusions larger than 350 mm, the inboard deflections (caused by interaction to the far-side occupant) were of the same magnitude or even higher (30–70 mm) than the outboard deflections (30–50 mm).Conclusion: A WorldSID 50th percentile male equipped with bilateral IR-Traccs can detect loading to the thorax from a neighboring occupant making injury risk assessment feasible for this type of loading. At crash severities resulting in a delta V above 35 km/h and intrusions larger than 350 mm, both the inboard deflection and VC resulted in high risks of Abbreviated Injury Scale (AIS) 3+ injury, especially for a senior occupant.

Training the inspiratory muscles improves running performance when carrying a 25 kg thoracic load in a backpack

Load carriage (LC) exercise in physically demanding occupations is typically characterised by periods of low-intensity steady-state exercise and short duration, high-intensity exercise while carrying an external mass in a backpack; this form of exercise is also known as LC exercise. This induces inspiratory muscle fatigue and reduces whole-body performance. Accordingly we investigated the effect of inspiratory muscle training (IMT, 50% maximal inspiratory muscle pressure (PImax) twice daily for six week) upon running time-trial performance with thoracic LC. Nineteen healthy males formed a pressure threshold IMT (n = 10) or placebo control group (PLA; n = 9) and performed 60 min LC exercise (6.5 km h–1) followed by a 2.4 km running time trial (LCTT) either side of a double-blind six week intervention. Prior to the intervention, PImax was reduced relative to baseline, post-LC and post-LCTT in both groups (pooled data: 13 ± 7% and 16 ± 8%, respectively, p < .05) and similar changes were observed post-PLA. Post-IMT only, resting PImax increased +31% (p < .05) and relative to pre-IMT was greater post-LC (+19%) and post-LCTT (+18%, p < .05), however, the relative reduction in PImax at each time point was unchanged (13 ± 11% and 17 ± 9%, respectively, p > .05). In IMT only, heart rate and perceptual responses were reduced post-LC (p < .05). Time-trial performance was unchanged post-PLA and improved 8 ± 4% after IMT (p < .05). In summary, when wearing a 25 kg backpack, IMT attenuated the cardiovascular and perceptual responses to steady-state exercise and improved high-intensity time-trial performance which we attribute in part to reduced relative work intensity of the inspiratory muscles due to improved inspiratory muscle strength. These findings have real-world implications for occupational contexts.