Preloaded Time Trial to Assess Load Carriage Performance

Abstract

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.

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

“…Pre-intervention LC TT performance in both groups was consistent with previous literature using the same protocol (Faghy & Brown, 2014a, 2014b. In this double-blind placebo controlled study (see intervention above for more details); time-trial performance was significantly improved following IMT by 8 ± 4% with no change in PLA.…”

“…Following the intervention, participants performed two trials on separate days: (1) a shortened re-familiarisation trial: 20 min LC at 6.5 km h −1 , 0% gradient, and 15 min seated rest, followed by 2.4 km LC TT and (2) a post training experimental trial identical to the pre-intervention experimental trial detailed above. The shortened refamiliarisation trial performed has been shown to maximise reliability in between day LC assessments (Faghy & Brown, 2014a).…”

Blood lactate thresholds and walking/running economy are determinants of backpack-running performance in trained soldiers

“…In the present study, average blood lactate levels at this velocity were at resting values (∼1.2 mmol l −1 ) and the rating of perceived exertion (RPE) scores at 7-8 ('extremely light' on the Borg 6-20 scale). Moreover, the average completion time of 88.6 min (average speed: 8.71 km h −1 ) in the field test was less than ¾ of the time expected for conventional British troops to complete this distance, and is similar to the average velocity attained by trained men (VO2peak: 4.30 ± 0.46 l min −1 ; 53.03 ± 3.21 ml kg min −1 ) over shorter time trial distances (2.4 km) under controlled laboratory conditions (Faghy and Brown, 2014). These data underscore the advanced physiological capabilities of elite soldiers compared to both non-soldiers and conventional infantry soldiers, and also indicate that the physiological demands of backpack running performance across different subject groups should be interpreted with caution.…”

“…Despite the success and ubiquitous use of LTs, Vent T and running economy as predictors of endurance performance in athletes (Faude et al, 2009;Saunders et al, 2004), no previous studies have attempted to identify the efficacy of these variables as determinants of backpack load-carriage performance, or their effectiveness for predicting future success in field based load-carriage tasks. Moreover, while there is a large body of normative data available on the physiological responses to simulated backpack load-carriage tasks in conventional military troops (Beekley et al, 2007;Christie and Scott, Rayson et al, 2000) and recreationally active males (Faghy and Brown, 2014), comprehensive physiological data on elite soldiers are lacking (Simpson et al, 2006(Simpson et al, , 2010Wilkinson et al, 2008).…”

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

“…The increased PImax, prior to exercise reduces the relative work of the inspiratory muscles during exercise (Lomax et al 2011, Johnson et al 2014) and may attenuate dyspnoea, blood lactate accumulation and inspiratory muscle fatigue (Volianitis et al 2001, Lin et al 2007, Lomax et al 2011. However, no studies have investigated the effects of IMW upon load carriage performance which is surprising since carrying a thoracic load modifies breathing mechanics via an inspiratory volume limitation (Dominelli et al 2012), reducing respiratory muscle efficiency and accelerating respiratory muscle fatigue (~59% V̇O2peak, Faghy & Brown, 2014b) and impairs load carriage performance (Faghy and Brown 2014a). Accordingly, the aim of this study was to examine the effects of AWU with and without the addition of IMW upon a running 2.4 km load carriage (25 kg) time-trial performance (a specific performance model used within British Army infantry training programs).…”