Papers by James L J Bilzon
European Journal of Applied Physiology, Aug 5, 2020
Purpose To examine the influence of post-exercise protein feeding upon the adaptive response to e... more Purpose To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training. Methods In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30-60 min at 70-75% maximal oxygen uptake (VO 2max ) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM -1 ) of carbohydrate (CHO) or an isocaloric carbohydrate-protein solution (CHO-P; 0.8 g carbohydrate kg BM -1 + 0.8 g protein kg BM -1 ) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up. Exercise training improved VO 2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min -1 and 3.0 ± 2 mL kg -1 min -1 , respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL -1 ) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL -1 ; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training. Conclusion Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO 2max was similar between groups.
European Journal of Applied Physiology, Aug 5, 2020
Purpose To examine the influence of post-exercise protein feeding upon the adaptive response to e... more Purpose To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training. Methods In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30-60 min at 70-75% maximal oxygen uptake (VO 2max ) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM -1 ) of carbohydrate (CHO) or an isocaloric carbohydrate-protein solution (CHO-P; 0.8 g carbohydrate kg BM -1 + 0.8 g protein kg BM -1 ) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up. Exercise training improved VO 2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min -1 and 3.0 ± 2 mL kg -1 min -1 , respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL -1 ) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL -1 ; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training. Conclusion Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO 2max was similar between groups.
International Journal of Sports Medicine, Dec 15, 2015
Little if any research has examined the variability in time to exhaustion (TTE) during submaximal... more Little if any research has examined the variability in time to exhaustion (TTE) during submaximal treadmill running. This study investigated the test-retest reliability of submaximal treadmill TTE as a measure of endurance capacity. Sixteen endurancetrained males (n=14) and females (n=2) completed a run to exhaustion at 70% (T1) and repeated the same run three weeks later (T2). At 30 min intervals during each run, expired gas, heart rate (HR) and ratings of perceived exertion (RPE) were collected. Mean ± SD TTE was 96 ± 20 min in T1 versus 101 ± 29 min in T2 (P=0.3). The mean ± 95% confidence intervals (CI) of the coefficient of variance (CV) was 5.4% (1.4 -9.6). The average intraclass correlation coefficient (±95% CI) was 0.88 (0.67 -0.96) between trials. The respiratory-exchange ratio was not different between trials, T1: 0.87±0.1 and T2: 0.89±0.1 (P>0.05) and neither was total whole-body carbohydrate oxidation (2.1±0.4 g•min -1 and 2.3±0.6 g•min -1 ), fat oxidation (0.6±0.2 g•min -1 ), HR (178±8 and 175±7 beats•min -1 ) or RPE (17±3 and 16±3). These results suggest that use of prolonged treadmill-based TTE can be a reliable research tool to assess human endurance capacity in aerobically-trained men and women.
International Journal of Sports Medicine, Dec 15, 2015
Little if any research has examined the variability in time to exhaustion (TTE) during submaximal... more Little if any research has examined the variability in time to exhaustion (TTE) during submaximal treadmill running. This study investigated the test-retest reliability of submaximal treadmill TTE as a measure of endurance capacity. Sixteen endurancetrained males (n=14) and females (n=2) completed a run to exhaustion at 70% (T1) and repeated the same run three weeks later (T2). At 30 min intervals during each run, expired gas, heart rate (HR) and ratings of perceived exertion (RPE) were collected. Mean ± SD TTE was 96 ± 20 min in T1 versus 101 ± 29 min in T2 (P=0.3). The mean ± 95% confidence intervals (CI) of the coefficient of variance (CV) was 5.4% (1.4 -9.6). The average intraclass correlation coefficient (±95% CI) was 0.88 (0.67 -0.96) between trials. The respiratory-exchange ratio was not different between trials, T1: 0.87±0.1 and T2: 0.89±0.1 (P>0.05) and neither was total whole-body carbohydrate oxidation (2.1±0.4 g•min -1 and 2.3±0.6 g•min -1 ), fat oxidation (0.6±0.2 g•min -1 ), HR (178±8 and 175±7 beats•min -1 ) or RPE (17±3 and 16±3). These results suggest that use of prolonged treadmill-based TTE can be a reliable research tool to assess human endurance capacity in aerobically-trained men and women.
Ergonomics, Feb 6, 2016
A minimum cardiorespiratory fitness standard was derived for firefighters following a metabolic d... more A minimum cardiorespiratory fitness standard was derived for firefighters following a metabolic demands analysis. Design and minimal acceptable performance of generic firefighting task simulations (i.e., hose running, casualty evacuation, stair climb, equipment carry, wild-land fire) were endorsed by a panel of operationally experienced experts. Sixty-two UK firefighters completed these tasks wearing a standard protective firefighting ensemble while being monitored for peak steady state metabolic demand and cardiovascular strain. Four tasks, endorsed as valid operational simulations by ≥90% of participants (excluding wild-land fire; 84%), were deemed to be a sufficiently valid and reliable basis for a fitness standard. These tasks elicited an average peak steady state metabolic cost of 38.1 ± 7.8 ml . kg -1. min -1 . It is estimated that healthy adults can sustain the total duration of these tasks (~16 min) at ≤90% maximum oxygen uptake and a cardiorespiratory fitness standard of ≥42.3 ml . kg -1. min -1 would be required to sustain work.
Ergonomics, Feb 6, 2016
A minimum cardiorespiratory fitness standard was derived for firefighters following a metabolic d... more A minimum cardiorespiratory fitness standard was derived for firefighters following a metabolic demands analysis. Design and minimal acceptable performance of generic firefighting task simulations (i.e., hose running, casualty evacuation, stair climb, equipment carry, wild-land fire) were endorsed by a panel of operationally experienced experts. Sixty-two UK firefighters completed these tasks wearing a standard protective firefighting ensemble while being monitored for peak steady state metabolic demand and cardiovascular strain. Four tasks, endorsed as valid operational simulations by ≥90% of participants (excluding wild-land fire; 84%), were deemed to be a sufficiently valid and reliable basis for a fitness standard. These tasks elicited an average peak steady state metabolic cost of 38.1 ± 7.8 ml . kg -1. min -1 . It is estimated that healthy adults can sustain the total duration of these tasks (~16 min) at ≤90% maximum oxygen uptake and a cardiorespiratory fitness standard of ≥42.3 ml . kg -1. min -1 would be required to sustain work.
Journal of Occupational and Environmental Medicine, Jul 1, 2018
Objective: To examine determinants of firefighting simulation task performance. Methods: Sixtyeig... more Objective: To examine determinants of firefighting simulation task performance. Methods: Sixtyeight (63 male; 5 female) firefighters completed a firefighting simulation (e.g. equipment carry, casualty evacuation) previously validated to test occupational fitness among UK firefighters. Multiple linear regression methods were used to determine physiological and physical attributes that best predicted completion time. Results: Mean (±SD) time taken to complete the simulation was 610 (±79) seconds. The prediction model combining absolute cardiorespiratory capacity (L.min -1 ) and fat mass explained the greatest variance in performance and elicited the least random error (R=0.765, R 2 =0.585, SEE: ±52 seconds). Higher fitness and lower fat mass were associated with faster performance. Conclusions: Firefighter simulation test performance is associated with absolute cardiorespiratory fitness and fat mass. Fitter and leaner individuals perform the task more quickly. Work-based interventions should enhance these attributes to promote safe and effective operational performance.
Journal of Occupational and Environmental Medicine, Jul 1, 2018
Objective: To examine determinants of firefighting simulation task performance. Methods: Sixtyeig... more Objective: To examine determinants of firefighting simulation task performance. Methods: Sixtyeight (63 male; 5 female) firefighters completed a firefighting simulation (e.g. equipment carry, casualty evacuation) previously validated to test occupational fitness among UK firefighters. Multiple linear regression methods were used to determine physiological and physical attributes that best predicted completion time. Results: Mean (±SD) time taken to complete the simulation was 610 (±79) seconds. The prediction model combining absolute cardiorespiratory capacity (L.min -1 ) and fat mass explained the greatest variance in performance and elicited the least random error (R=0.765, R 2 =0.585, SEE: ±52 seconds). Higher fitness and lower fat mass were associated with faster performance. Conclusions: Firefighter simulation test performance is associated with absolute cardiorespiratory fitness and fat mass. Fitter and leaner individuals perform the task more quickly. Work-based interventions should enhance these attributes to promote safe and effective operational performance.
Medicina Sportiva, Mar 1, 2009
Introduction: Load carriage using backpacks is undertaken recreationally and as an occupational t... more Introduction: Load carriage using backpacks is undertaken recreationally and as an occupational task. We assessed physiological changes during 2 hours of load carriage during level and downhill treadmill walking. Methods: Ten male participants (age: 30±8 years, body mass: 79.4±8.3 kg, ¦O 2 max: 55.1±5.6 ml•kg -1 •min -1 ) completed randomly 3 walking tests (6.5 km•h -1 ) for 2 hours: (1) level walking no load (LW), (2) level walking with a 25 kg backpack (LWLC) and (3) downhill walking (-8%) with a 25 kg backpack (DWLC). Results: ¦O 2 was higher during LWLC compared to LW at baseline (minute 5) (23.0±2.7 vs.16.4±0.7 ml•kg -1 •min -1 , P<0.001) and 120 minute (26.9±3.3 vs. 17.9±0.5 ml•kg -1 •min -1 , P<0.001). The increase in ¦O 2 during LWLC was greater over the 120 minutes (3.9±2.3 vs.1.6±0.6 ml•kg -1 •min -1 , P=0.018). ¦O 2 during DWLC was lower than LWLC at baseline (17.1±1.6 vs. 23.0±2.7 ml•kg -1 •min -1 , P<0.001) and minute 120 (21.4±3.0 vs. 26.9±3.3 ml•kg -1 •min -1 , P<0.001), with no difference in ¦O 2 increase over time (4.3±2.5 vs. 3.9±2.3 ml•kg -1 •min -1 , P=0.411). Cardiovascular drift occurred between 5 and 120 minutes for LW (96±10 to 99±12 beats•min -1 , P=0.005), LWLC (116±13 to 141±23 beats•min -1 , P=0.001) and DWLC (103±9 to 126±21 beats•min -1 , P=0.001). RER decreased between 5 and 120 minutes during LWLC only (0.90±0.09 to 0.83±0.04, P=0.021). Stride frequency increased between 5 and 120 minutes during DWLC only (64±3 to 66±4 steps•min -1, P=0.043). Conclusion: Differences in ¦O 2 and cardiovascular drift between prolonged unloaded and loaded level treadmill walking and prolonged loaded level and downhill treadmill walking appear to relate to changes in substrate oxidation, muscle fatigue/damage and mechanical efficiency.
Medicina Sportiva, Mar 1, 2009
Introduction: Load carriage using backpacks is undertaken recreationally and as an occupational t... more Introduction: Load carriage using backpacks is undertaken recreationally and as an occupational task. We assessed physiological changes during 2 hours of load carriage during level and downhill treadmill walking. Methods: Ten male participants (age: 30±8 years, body mass: 79.4±8.3 kg, ¦O 2 max: 55.1±5.6 ml•kg -1 •min -1 ) completed randomly 3 walking tests (6.5 km•h -1 ) for 2 hours: (1) level walking no load (LW), (2) level walking with a 25 kg backpack (LWLC) and (3) downhill walking (-8%) with a 25 kg backpack (DWLC). Results: ¦O 2 was higher during LWLC compared to LW at baseline (minute 5) (23.0±2.7 vs.16.4±0.7 ml•kg -1 •min -1 , P<0.001) and 120 minute (26.9±3.3 vs. 17.9±0.5 ml•kg -1 •min -1 , P<0.001). The increase in ¦O 2 during LWLC was greater over the 120 minutes (3.9±2.3 vs.1.6±0.6 ml•kg -1 •min -1 , P=0.018). ¦O 2 during DWLC was lower than LWLC at baseline (17.1±1.6 vs. 23.0±2.7 ml•kg -1 •min -1 , P<0.001) and minute 120 (21.4±3.0 vs. 26.9±3.3 ml•kg -1 •min -1 , P<0.001), with no difference in ¦O 2 increase over time (4.3±2.5 vs. 3.9±2.3 ml•kg -1 •min -1 , P=0.411). Cardiovascular drift occurred between 5 and 120 minutes for LW (96±10 to 99±12 beats•min -1 , P=0.005), LWLC (116±13 to 141±23 beats•min -1 , P=0.001) and DWLC (103±9 to 126±21 beats•min -1 , P=0.001). RER decreased between 5 and 120 minutes during LWLC only (0.90±0.09 to 0.83±0.04, P=0.021). Stride frequency increased between 5 and 120 minutes during DWLC only (64±3 to 66±4 steps•min -1, P=0.043). Conclusion: Differences in ¦O 2 and cardiovascular drift between prolonged unloaded and loaded level treadmill walking and prolonged loaded level and downhill treadmill walking appear to relate to changes in substrate oxidation, muscle fatigue/damage and mechanical efficiency.
International Journal of Sport Nutrition and Exercise Metabolism, Jun 1, 2011
The purpose of the study was to determine the effects of carbohydrate (CHO) intake, with and with... more The purpose of the study was to determine the effects of carbohydrate (CHO) intake, with and without protein (PRO), immediately after prolonged strenuous exercise on circulating bacterially stimulated neutrophil degranulation. Twelve male runners completed 3 feeding interventions, 1 week apart, in randomized order after 2 hr of running at 75% VO 2max . The feeding interventions included a placebo solution, a CHO solution equal to 1.2 g CHO ∼ /kg body mass (BM), and a CHO-PRO solution equal to 1.2 g CHO/kg BM and 0.4 g PRO/kg BM (CHO+PRO) immediately postexercise. All solutions were flavor and water-volume equivalent (12 ml/kg BM). Circulating leukocyte counts, bacterially stimulated neutrophil degranulation, plasma insulin, and cortisol were determined from blood samples collected preexercise, immediately postexercise, and every 30 min until 180 min postexercise. The immediate postexercise circulating leukocytosis, neutrophilia, and lymphocytosis (p < .01 vs. preexercise) and the delayed lymphopenia (90 min postexercise, p < .05 vs. preexercise) were similar on all trials. Bacterially stimulated neutrophil degranulation decreased during recovery in control (23% at 180 min, p < .01 vs. preexercise) but remained above preexercise levels with CHO and CHO+PRO. In conclusion, CHO ingestion, with or without PRO, immediately after prolonged strenuous exercise prevented the decrease in bacterially stimulated neutrophil degranulation during recovery.
International Journal of Sport Nutrition and Exercise Metabolism, Jun 1, 2011
The purpose of the study was to determine the effects of carbohydrate (CHO) intake, with and with... more The purpose of the study was to determine the effects of carbohydrate (CHO) intake, with and without protein (PRO), immediately after prolonged strenuous exercise on circulating bacterially stimulated neutrophil degranulation. Twelve male runners completed 3 feeding interventions, 1 week apart, in randomized order after 2 hr of running at 75% VO 2max . The feeding interventions included a placebo solution, a CHO solution equal to 1.2 g CHO ∼ /kg body mass (BM), and a CHO-PRO solution equal to 1.2 g CHO/kg BM and 0.4 g PRO/kg BM (CHO+PRO) immediately postexercise. All solutions were flavor and water-volume equivalent (12 ml/kg BM). Circulating leukocyte counts, bacterially stimulated neutrophil degranulation, plasma insulin, and cortisol were determined from blood samples collected preexercise, immediately postexercise, and every 30 min until 180 min postexercise. The immediate postexercise circulating leukocytosis, neutrophilia, and lymphocytosis (p < .01 vs. preexercise) and the delayed lymphopenia (90 min postexercise, p < .05 vs. preexercise) were similar on all trials. Bacterially stimulated neutrophil degranulation decreased during recovery in control (23% at 180 min, p < .01 vs. preexercise) but remained above preexercise levels with CHO and CHO+PRO. In conclusion, CHO ingestion, with or without PRO, immediately after prolonged strenuous exercise prevented the decrease in bacterially stimulated neutrophil degranulation during recovery.
bioRxiv (Cold Spring Harbor Laboratory), Jan 19, 2023
This study examined if occluded joint locations from markerless motion capture produced 2D joint ... more This study examined if occluded joint locations from markerless motion capture produced 2D joint angles with reduced accuracy compared to visible joints, and if 2D frontal plane joint angles were usable for practical applications. Fifteen healthy participants performed over-ground walking whilst recorded by fifteen marker-based cameras and two machine vision cameras (frontal and sagittal plane). Repeated measures Bland-Altman analysis illustrated that markerless standard deviation of bias (random differences) for the occluded-side hip and knee joint angles in the sagittal plane were double that of the camera-side (visible) hip and knee. Camera-side sagittal plane knee and hip angles were near or within marker-based error values previously observed. While frontal plane random differences accounted for 35-46% of total range of motion at the hip and knee, systematic and random differences (-4.6-1.6 ± 3.7-4.2˚) were actually similar to previously reported marker-based error values. This was not true for the ankle, where random difference (±12˚) was still too high for practical applications. Our results add to previous literature, highlighting shortcomings of current pose estimation algorithms and labelled datasets. As such, this paper finishes by reviewing markerbased methods for creating anatomically accurate markerless training data.
bioRxiv (Cold Spring Harbor Laboratory), Jan 19, 2023
This study examined if occluded joint locations from markerless motion capture produced 2D joint ... more This study examined if occluded joint locations from markerless motion capture produced 2D joint angles with reduced accuracy compared to visible joints, and if 2D frontal plane joint angles were usable for practical applications. Fifteen healthy participants performed over-ground walking whilst recorded by fifteen marker-based cameras and two machine vision cameras (frontal and sagittal plane). Repeated measures Bland-Altman analysis illustrated that markerless standard deviation of bias (random differences) for the occluded-side hip and knee joint angles in the sagittal plane were double that of the camera-side (visible) hip and knee. Camera-side sagittal plane knee and hip angles were near or within marker-based error values previously observed. While frontal plane random differences accounted for 35-46% of total range of motion at the hip and knee, systematic and random differences (-4.6-1.6 ± 3.7-4.2˚) were actually similar to previously reported marker-based error values. This was not true for the ankle, where random difference (±12˚) was still too high for practical applications. Our results add to previous literature, highlighting shortcomings of current pose estimation algorithms and labelled datasets. As such, this paper finishes by reviewing markerbased methods for creating anatomically accurate markerless training data.
Journal of Sports Sciences, Nov 20, 2015
Journal of Sports Sciences, Nov 20, 2015
Systematic Reviews, Aug 2, 2019
Systematic Reviews, Aug 2, 2019
Background: Experiencing a lower limb amputation (LLA) or spinal cord injury (SCI) is a life-chan... more Background: Experiencing a lower limb amputation (LLA) or spinal cord injury (SCI) is a life-changing event, affecting physical and systemic function as well as having psychological and social impacts. However, the severity of the physical impairment and/or motor disability demonstrates a poor relationship with patient-reported quality of life, suggesting that other factors determine such outcomes. As such, holistic health-related quality of life (QoL) assessment is an important tool to monitor long-term outcomes. While there are some studies that have assessed the influence of variables such as age at time of injury occurrence and time since injury on changes in QoL, there are no systematic reviews which synthesise this evidence. Methods/design: All follow-up study designs will be included, where data from multiple time points are presented. Searches will target both SCI and LLA populations where a validated measure of QoL has been used: Medical Outcome Study Short-Form 36/12 or the World Health Organization Quality of Life instruments 100 and BREF. Studies must include adult participants (≥ 18 years at time of injury) and detail time since injury event and patient age. The primary objective is to establish the effects of participant age and time since injury on QoL scores. Secondary objectives include determining between-group effects (i.e. LLA vs. SCI). We will search PubMed, Embase and Web of Science databases, supplemented by hand-searching references within existing review articles and experimental studies. Reviewer pairs will conduct screening and quality assessment of included papers. Results will be stratified by impairment, QoL tool, age/time since injury and additional variables such as sex, race, comorbidity or disease aetiology, as appropriate. If sufficient high-quality data exist, a meta-analysis will be conducted. Discussion: The results of this systematic review will summarise evidence of how QoL changes across the life course, relative to both patient age and time since injury, for both LLA and SCI populations. By enabling a direct comparison of different chronic conditions, disability-specific differences in QoL changes over the life course can be identified. Systematic review registration: PROSPERO CRD42018096633.
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Papers by James L J Bilzon