Craig Williams

Publications (85) View all

• Article: A protocol to determine valid V˙O2max in young cystic fibrosis patients.

  Zoe L Saynor, Alan R Barker, Patrick J Oades, Craig A Williams
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  ABSTRACT: OBJECTIVES: Measuring aerobic fitness (V˙O2max) via a maximal cardiopulmonary exercise test is an important clinical tool in cystic fibrosis. This study sought to establish: (1) the validity of traditional criteria to verify maximal efforts during a ramp cardiopulmonary exercise test; and (2) whether V˙O2 measured during an exhaustive cardiopulmonary exercise test represents a valid V˙O2max in paediatric patients, using a subsequent exhaustive supramaximal (Smax) exercise test. DESIGN: Cross-sectional. METHODS: Fourteen patients (7-18 years; 10 males) completed an exhaustive ramp test to determine V˙O2max. Following 15-min recovery, Smax (110% ramp peak power output) was performed. RESULTS: Ramp test V˙O2peak was significantly higher than V˙O2 documented at traditional endpoint criteria, including a RER of 1.00 (0.99±0.47Lmin(-1) vs. 1.83±0.78Lmin(-1), p<0.001) and 1.10 (1.36±0.59Lmin(-1) vs. 1.83±0.78Lmin(-1), p<0.001), despite 100% of patients satisfying these two criteria. Only 23% and 75% of patients satisfied the 95% age-predicted heart rate (HR) maximum and 180bmin(-1) criteria. Whilst mean ramp and SmaxV˙O2peak were not significantly different (1.83±0.78Lmin(-1) vs. 1.82±0.67Lmin(-1); p=0.88), at the individual level Smax elicited a 'meaningful' (>9%) increase in V˙O2peak (range 9.9-38.3%) compared with V˙O2peak from the ramp test in 3 of 14 cases (21.4%). CONCLUSIONS: Traditional criteria significantly underestimate V˙O2max in young cystic fibrosis patients. Conversely, Smax can confirm when 'true'V˙O2max is achieved. The use of Smax following cardiopulmonary exercise test represents an appropriate method to measure V˙O2max in young cystic fibrosis patients.
  Journal of science and medicine in sport / Sports Medicine Australia. 03/2013;
• Article: Kicking velocity and physical, technical, tactical match performance for U18 female football players - Effect of a new ball.

  Thomas B Andersen, Mads Bendiksen, Jens M Pedersen, Christina Orntoft, João Brito, Sarah R Jackman, Craig A Williams, Peter Krustrup
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  ABSTRACT: We investigated kicking velocity and physical, technical, and tactical match performance for under-18 (U18) female football players and evaluated the effect of using a newly developed lighter smaller ball. Ten regional league teams participated. Maximal ball velocity was 4±1% higher when kicking the new ball (NB) compared with the standard ball (SB) in a laboratory testing situation (23.2±0.4 vs. 22.4±0.3ms(-1); p<.05). Mean HR was similar during games with NB and SB (169±2 vs. 170±2bmin(-1); p>.05), but lower-limb muscular RPE was lower with NB (4.2±0.4 vs. 5.2±0.3; p<.05). The number of activity changes (1387±76 vs. 1401±55), total distance covered (9.09±0.25 vs. 9.11±0.25km) and high-intensity running (1.04±0.08 vs. 1.11±0.07km) were not different between NB and SB (p>.05). High-intensity running decreased (p<.05) from 0-20 to 60-80min with NB (34%) and SB (37%). The number and success rate of long and short passes did not differ between NB and SB (p>.05). In conclusion, physiological demands were high in youth female football games, and decrements in running performance occurred towards the end of games. The players kicked faster and reported lower muscular exertion during games played with a lighter smaller ball, but locomotor activities, heart rate and overall technical-tactical game performance remained unaffected.
  Human movement science 11/2012; · 2.15 Impact Factor
• Article: Hydration Status, Fluid Intake and Electrolyte Losses in Youth Soccer Players.

  Craig A Williams, Jamie Blackwell
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  ABSTRACT: The purpose of the study was to determine the hydration status, fluid intake and electrolyte losses of 21 male professional youth soccer players (age 17.1 ± 0.7 yr) training in a cool environment. Pre- and post training measurements of body mass, urine (freezing point osmolality method) and sweat concentration (flame emission spectroscopy) were collected. Fourteen players were found to be hypohydrated prior to training. The amount of fluid lost due to exercise equated to a 1.7 % loss in body mass, which equated to a gross dehydration loss of 0.5 %. Overall, the soccer players replaced 46 ± 88% of sweat loss during training and only four remained hypohydrated after training. No significant correlations between sweat loss and sweat concentrations of Na+ (r = -0.11, P = 0.67), K+ (r = 0.14, P = 0.58) were found, but there was a significant correlation with Mg2+ (r = -0.58, P < 0.009). This study found large variability in pre-training hydration status which the players were able to rehydrate during the training sessions. However, given the numbers starting training in a hypohydrated state, adequate hydration status prior to training should be considered by youth players, coaches and sports science support staff.
  International journal of sports physiology and performance 05/2012; · 1.80 Impact Factor
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  Available from: Kerry Mcgawley

  Article: A test to assess aerobic and anaerobic parameters during maximal exercise in young girls.

  Kerry McGawley, Erwan Leclair, Jeanne Dekerle, Helen Carter, Craig A Williams
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  ABSTRACT: The Wingate cycle test (WAnT) is a 30-s test commonly used to estimate anaerobic work capacity (AWC). However, the test may be too short to fully deplete anaerobic energy reserves. We hypothesized that a 90-s all-out isokinetic test (ISO_90) would be valid to assess both aerobic and anaerobic capacities in young females. Eight girls (11.9 ± 0.5 y) performed an exhaustive incremental test, a WAnT and an ISO_90. Peak VO2 attained during the ISO_90 was significantly greater than VO2peak. Mean power, end power, fatigue index, total work done and AWC were not significantly different between the WAnT and after 30 s of the 90-s test (i.e., ISO_30). However, 95% limits of agreement showed large variations between the two tests when comparing all anaerobic parameters. It is concluded that an ISO-90 may be a useful test to assess aerobic capacity in young girls. However, since the anaerobic parameters derived from the ISO_30 did not agree with those derived from a traditional WAnT, the validity of using an ISO_90 to assess anaerobic performance and capacity within this population group remains unconfirmed.
  Pediatric exercise science 05/2012; 24(2):262-74. · 1.71 Impact Factor
• Article: Cardiorespiratory fitness, fatness, and blood pressure associations in nigerian youth.

  Danladi I Musa, Craig A Williams
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  ABSTRACT: This study aimed to examine the independent associations of cardiorespiratory fitness (CRF) and body fatness with resting blood pressure (BP) in children (9-11 yr) and adolescents (12-15 yr) in Benue State of Nigeria. A total of 3243 children (n = 1017) and adolescents (n = 2226) were evaluated for aerobic fitness, body fatness, resting preexercise BP and recovery BP at minutes 1, 5, and 10 after a progressive aerobic cardiovascular endurance run test. Regression models, controlling for age and recovery BP at 1, 5, and 10 min after the progressive aerobic cardiovascular endurance run, determined the associations of independent variables with the dependent variables. Fatness and fitness were independent predictors of resting BP among participants, and the relationship of fatness with BP was more robust in adolescents than in children. In all cases, the relationships were stronger in boys than in girls. Combined fitness and fatness in predicting BP was modest (R = 1%-3%) after controlling for age and postexercise BP. Postexercise BP was a major determinant of resting BP in both groups (R = 23%-93%). In adolescents, fatter boys had 1.9 times likelihood of systolic HTN compared with leaner peers. Systolic and diastolic BP scores varied by fit-fat groups, the fit-low-fat group demonstrated the most favorable BP profiles, whereas the unfit-high-fat group showed the most adverse profiles. Irrespective of fatness, participants with higher CRF had more favorable BP profiles compared with their fat-unfit peers.
  Medicine and science in sports and exercise 04/2012; 44(10):1978-85. · 3.71 Impact Factor