James Bilzon

Characterization of the metabolic demands of simulated shipboard Royal Navy fire-fighting tasks

The purpose of this study was to quantify the metabolic demand of simulated shipboard fire-fighting procedures currently practised by men and women in the Royal Navy (RN) and to identify a minimum level of cardiovascular fitness commensurate with satisfactory performance. Thirty-four males (M) and 15 females (F) volunteered as subjects for this study (n = 49). Maximal oxygen uptake ([Vdot]O2max) and heart rate (fc max) of each subject was assessed during a standardized treadmill test. During the main trials, volunteers were randomly assigned to complete several 4-min simulated shipboard fire-fighting tasks (boundary cooling (BC), drum carry (DC), extinguisher carry (EC), hose run (HR), ladder climb (LC)), at a work rate that was endorsed as a minimum acceptable standard. Heart rate (fc) and oxygen uptake ([Vdot]O2) were recorded at 10-s intervals during rest, exercise and recovery. Participants completed all tasks within an allocated time with the exception of the DC task, where 11 subjects (all females) failed to maintain the endorsed work rate. The DC task elicited the highest (p< 0.01) group mean peak metabolic demand (PMD) in males (43 ml min-1 kg-1) and females (42 ml min-1 kg-1) who were able to maintain the endorsed work rate. The BC task elicited the lowest PMD (23 ml min-1 kg-1), whilst the remaining three tasks elicited a remarkably similar PMD of 38–39 ml min-1 kg-1. The human endurance limit while wearing a self-contained breathing apparatus (SCBA) dictates that RN personnel are only able to fire-fight for 20–30 min, while wearing a full fire-fighting ensemble (FFE) and performing a combination of the BC, HR and LC tasks, which have a group mean metabolic demand of 32.8 ml min-1 kg-1. Given that in healthy subjects fire-fighting can be sustained at a maximum work intensity of 80% [Vdot]O2max when wearing SCBA for this duration, it is recommended that all RN personnel achieve a [Vdot]O2max of 41 ml min-1 kg-1 as an absolute minimum standard. Subjects with a higher [Vdot]O2max than the above quoted minimum are able to complete the combination of tasks listed with greater metabolic efficiency and less fatigue.

Salivary immunoglobulin A response at rest and after exercise following a 48 h period of fluid and/or energy restriction

The aim was to investigate the effects of a 48 h period of fluid, energy or combined fluid and energy restriction on salivary IgA (s-IgA) responses at rest and after exercise. Thirteen healthy males (age 21 (sem 1) years) participated in four randomised 48 h trials. In the control trial participants received their estimated energy (12,154 (sem 230) kJ/d) and water (3912 (sem 140) ml/d) requirements. On fluid restriction (FR) participants received their energy requirements and 193 (sem 19) ml water/d to drink and on energy restriction (ER) participants received their water requirements and 1214 (sem 25) kJ/d. Fluid and energy restriction (F+ER) was a combination of FR and ER. After 48 h, participants performed a 30 min treadmill time trial (TT) followed by rehydration (0-2 h) and refeeding (2-6 h). Unstimulated saliva was collected at 0, 24 and 48 h, post-TT, and 2 and 6 h post-TT. Saliva flow rate (sflw) and s-IgA (ELISA) remained unchanged in control conditions and on ER. However, 48 h on FR decreased sflw (64 %) which most probably accounted for the increase in s-IgA concentration (P < 0.01). Despite a decrease in sflw (54 %), s-IgA concentration did not increase on F+ER, resulting in a decreased s-IgA secretion rate by 24 h (0 h: 20 (sem 2); 24 h: 12 (sem 2) microg/min; P < 0.01). Post-TT s-IgA secretion rate was not lower compared with 48 h on any trial. s-IgA secretion rate returned to within 0 h values by 6 h post-TT on F+ER. In conclusion, a 24-48 h period of combined F+ER decreased s-IgA secretion rate but normalisation occurred upon refeeding.

Saliva indices track hypohydration during 48 h of fluid restriction or combined fluid and energy restriction

OBJECTIVE To investigate whether unstimulated whole saliva flow rate (UFR) and osmolality (Sosm) track changes in hydration status during 48h of restricted fluid intake (RF) or combined fluid and energy restriction (RF+RE). Following the 48h periods, UFR and Sosm were assessed after acute exercise dehydration and rehydration. DESIGN Thirteen healthy males completed three trials in a randomised order: control (CON) where participants received their estimated energy (12,154+/-230kJ/d: mean+/-S.E.M) and fluid (3912+/-140ml/d) requirements, RF trial where participants received their energy requirements and 193+/-19ml/d water to drink (total fluid 960+/-15ml/d) and RF+RE where participants received 1214+/-25kJ/d and 962+/-16ml/d. After 48h, participants completed 30min of maximal exercise followed by rehydration (0-2h) and refeeding (2-6h). RESULTS At 48h body mass loss exceeded 3% on RF and RF+RE. UFR decreased during 48h on RF (510+/-122 to 169+/-37microl/min) and RF+RE (452+/-92 to 265+/-53microl/min) and was lower than CON at 48h (441+/-90microl/min: P<0.05). Sosm increased during 48h on RF (54+/-3 to 73+/-5mOsmol/kg) and RF+RE (52+/-3 to 68+/-5mOsmol/kg) and was greater than CON at 48h (52+/-2mOsmol/kg: P<0.05). Unlike UFR, Sosm identified the additional hypohydration associated with exercise (P<0.05) and returned to within 0h values with rehydration. CONCLUSIONS Sosm, and to a lesser extent UFR, track hydration status during a 48h period of RF or RF+RE and after subsequent exercise and rehydration.

Foot Orthoses in the Prevention of Injury in Initial Military Training A Randomized Controlled Trial

Background: Overuse lower limb injury is common in incidence and morbidity. Many risk factors, gait related and biomechanical, have been identified, although little conclusive evidence has been found in terms of injury prevention to date. Hypothesis: Orthoses, as produced by proprietary software interpretation of plantar pressures, are able to reduce injury rates in an “at risk” military population. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Four hundred military officer trainees were assessed by means of pressure plate recording of their contact foot pressures during walking. Participants were risk assessed and randomized to receive or not receive customized orthoses using the D3D system. Both cohorts were followed up for injury through their basic training at the 7-week point. Results: The orthotic intervention group sustained 21 injuries in total (1 injury per 4666 hours of training), whereas the control group sustained 61 injuries in total (1 injury per 1600 hours of training) (P < .0001), thereby demonstrating an absolute risk reduction of 0.49 from use of the orthoses (P < .0001, chi square; confidence interval, 1.7, 2.4). Conclusion: In this military trainee population, orthoses were effective in the prevention of overuse lower limb injury. This is the first study to identify a positive preventive role of orthoses.

An investigation of a novel three-dimensional activity monitor to predict free-living energy expenditure

Abstract The aim of this study was to assess the capability of the 3dNX™ accelerometer to predict energy expenditure in two separate, free-living cohorts. Twenty-three adolescents and 14 young adults took a single dose of doubly labelled water and wore a 3dNX™ activity monitor during waking hours for a 10-day period while carrying out their normal routines. Multiple linear regression with backward elimination was used to establish the strength of the associations between various indices of energy expenditure, physical activity counts, and anthropometric variables. 3dNX™ output accounted for 27% and 35% of the variance in the total energy expenditure of the adolescent and young adult cohort, respectively. The explained variance increased to 78%, with a standard error of estimate of 7%, when 3dNX™ output was combined with body composition variables. The 3dNX™ accelerometer can be used to predict free-living daily energy expenditure with a standard error of estimate of 1.65 MJ in adolescents and 1.52 MJ in young adults. The inclusion of anthropometric variables reduces the error to approximately 1 MJ. Although it remains to cross-validate these models in other populations, early indications suggest that the 3dNX™ provides a useful method of predicting energy expenditure in free-living individuals.

Sport injuries in elite paralympic swimmers with visual impairment

CONTEXT Visually impaired athletes sustain overuse injuries in the lower limbs, but the pattern of injuries may vary according to the sport. The characteristics of sports injuries in visually impaired swimmers are unknown. OBJECTIVE To determine the characteristics and epidemiologic measures (prevalence, clinical incidence, and incidence rate) of sports injuries in visually impaired elite national swimmers and to assess differences among visual classes and between sexes. DESIGN Descriptive epidemiology study. SETTING International Paralympic competitions held between 2004 and 2008. PATIENTS OR OTHER PARTICIPANTS Twenty-eight elite, visually impaired swimmers (19 males, 9 females) from the Brazilian Paralympic Team participated in this study. Twelve were visual class S11 (blind swimmers), 12 were S12 (low-vision swimmers), and 4 were S13 (low-vision swimmers). INTERVENTION(S) A standardized report form was used to collect data during 5 competitions. This was endorsed by 2 Brazilian sports governing bodies. MAIN OUTCOME MEASURES The characteristics, prevalence, clinical incidence, and incidence rate of injuries were calculated. RESULTS Eighteen athletes reported 41 sports injuries, with a prevalence of 64%, clinical incidence of 1.5 injuries per athlete, and an incidence rate of 0.3 injuries per athlete per competition. Overuse injuries (80%) were more frequent than traumatic injuries (20%). The clinical incidence and prevalence varied according to sex and visual class, but no statistical differences were observed (P > .05). The highest proportion of injuries was in the trunk (46.34%), followed by the upper limbs (34.15%). The shoulders (29.27%) were most affected, followed by the thoracic (21.95%) and lumbar spine (17.07%). Spasm (36.59%) was the most frequent diagnosis, followed by tendinopathy (26.83%). CONCLUSIONS Visually impaired swimmers had a relatively high proportion of overuse injuries, predominantly associated with muscle spasm in the spine and tendinopathy in the shoulders. No differences were apparent in injury prevalence and clinical incidence among visual classes or between sexes.

Sports injuries in Brazilian blind footballers

The purpose of this study was to assess the characteristics and prevalence of sports-related injuries in visually disabled athletes of the Brazilian football 5-a-side team. The participants were 13 male athletes, all classified as B1 visual class, members of the Brazilian team, who played in five consecutive international competitions. Data were collected using the Brazilian Paralympic Committee and the Brazilian Confederation of Sports for the Blind report form. From the total of 13 athletes, 11 succumbed to some form of injury during the 5 competitions, which incorporated 23 matches, representing a prevalence of 84.6%. A total of 35 sports injuries were recorded, giving a clinical incidence of 2.7 injuries per athlete and an injury risk of 0.85 and an incidence rate of 0.12 injuries per match. Traumatic injuries (80%) were more common than overuse injuries (20%) (p<0.05). The highest distribution of injury was in the lower limbs (80%), followed by the head (8.6%), spine (5.7%) and upper limbs (5.7%). The body regions most affected were the knee (28.6%), feet (17.1%), ankle (11.4%) and thigh (11.4%). Contusions (31.4%), sprains (25.7%) and tendinopathy (8.6%) were the most frequent diagnoses. This is the first study to describe the nature and prevalence of sports-related injuries in 5-a-side football in blind athletes. The results are important in guiding strategies to inform the implementation of preventive pathways and provide a strong rationale for the compulsory use of additional protective equipment.

Predicting Physical Activity Energy Expenditure in Manual Wheelchair Users

PURPOSE This study aimed to assess the influence of anatomical placement of an accelerometer on physical activity energy expenditure prediction in manual wheelchair users. METHODS Ten accelerometer units (ActiGraph GT3X+) were attached to a multiaxis shaker table and subjected to a sinusoidal oscillation procedure to assess mechanical validity and reliability. Fifteen manual wheelchair users (mean ± SD: age, 36 ± 11 yr; body mass, 70 ± 12 kg) then completed five activities, including desk work and wheelchair propulsion (2, 4, 6, and 8 km·h). Expired gases were collected throughout. GT3X+ accelerometers were worn on the right wrist, upper arm, and waist. The relations between physical activity counts and metabolic rate were subsequently assessed, and bias ± 95% limits of agreement was calculated. RESULTS During mechanical testing, coefficients of variation ranged from 0.2% to 4.7% (intraunit) and 0.9% to 5.2% (interunit) in all axes. During human exercise testing, physical activity counts at each anatomical location was significantly (P < 0.01) correlated with metabolic rate (wrist, r = 0.93; upper arm, r = 0.87; waist, r = 0.73). The SEE for each correlation were 3.34, 4.38, and 6.07 kJ·min for the wrist, upper arm, and waist, respectively. The absolute bias ± 95% limits of agreement values were 0.0 ± 6.5 kJ·min, 0.0 ± 8.5 kJ·min, and 0.0 ± 11.8 kJ·min for the wrist, upper arm, and waist, respectively. CONCLUSIONS The ActiGraph GT3X+ is a reliable tool for determining mechanical movements within the physiological range of human movement. Of the three anatomical locations considered, a wrist-mounted accelerometer explains more of the variance and results in the lowest random error when predicting physical activity energy expenditure in manual wheelchair users.

Sports injuries in Paralympic track and field athletes with visual impairment

PURPOSE The aims of this study were to determine the epidemiology, nature, and pattern of sports injuries in Brazilian Paralympic track and field athletes with visual impairment and to assess differences between visual classes and sex. METHODS Forty visually impaired elite Paralympic athletes participated in this study (28 males and 12 females). All athletes competed in International Paralympic competitions between 2004 and 2008. According to the visual classification, 14 athletes were T/F11, 15 were T/F12, and 11 were T/F13. A standardized report form was used to collect injury data during five competitions. RESULTS Thirty-one athletes reported 77 sports injuries, with a prevalence of 78%, a clinical incidence of 1.93 injuries per athlete, and an incidence rate of 0.39 injuries per athlete per competition. Overuse injuries accounted for 82% and traumatic injuries 18% (P < 0.05). Small variations in the prevalence and clinical incidence of injury between sexes and visual classes were observed, but these were not statistically different (P > 0.05). The highest distribution of injury was in the lower limbs (87%), followed by spine (12%) and upper limbs (1%). The body regions most affected were the thighs (33.8%), lower legs (16.9%), and knees (9.1%). The most frequent diagnoses were spasms (26%), tendinopathies (23.4%), and strains (13%). CONCLUSIONS Elite visually impaired track and field Paralympic athletes present a pattern of overuse injuries predominantly affecting the lower limbs, particularly the thighs, lower legs, and knees. These injuries are associated with tendinopathies, muscle spasms, and strains. There were no apparent differences in injury characteristics between visual classes or sex.

Short-term recovery from prolonged constant pace running in a warm environment: the effectiveness of a carbohydrate-electrolyte solution.

Abstract Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. This study examined the influence of drinking a carbohydrate-electrolyte solution on short-term recovery and subsequent exercise capacity in a warm environment. Thirteen healthy male volunteers completed two trials, at least 7 days apart. On each occasion subjects performed an initial treadmill run at 60% of maximal oxygen uptake (VO2max), for 90 min or until volitional fatigue (T1), in a warm environment (35 °C, 40% relative humidity, RH). Volitional ingestion of water was permitted during each of the exercise trials. During a subsequent 4-h recovery period (REC) subjects consumed either a 6.9% carbohydrate-electrolyte solution (CES) or a sweetened placebo (P), in a volume equivalent to 140% of body mass loss. Following REC, subjects ran to exhaustion at the same %VO2max in order to assess their endurance capacity (T2). Mean (SEM) run times during T1 did not differ between the CES [74.8 (4.6) min] and P [72.5 (5.2) min] trials. Body mass was reduced (P < 0.01) by 1.9 (0.2)% (CES) and 1.7 (0.2)% (P), and plasma volume (P < 0.01) by 6.0 (0.9)% (CES) and 5.4 (1.0)% (P) during the T1 trials. During REC 2006 (176) ml and 1830 (165) ml of fluid was ingested, providing 138 (12) g and 0 g of carbohydrate in the CES and P trials, respectively. Prior to T2, plasma volume and net fluid balance were similarly restored [CES +58 (26) g; P −4 (68) g] in both trials. During T2 the exercise duration was longer (P < 0.01) in the CES compared to the P trial [CES 60.9 (5.5) min; P 44.9 (3.0) min]. Thus, provided that an adequate hydration status is maintained, inclusion of carbohydrate within an oral rehydration solution will delay the onset of fatigue during a subsequent bout of prolonged submaximal running in a warm environment.