A 10-week plyometrics-based intervention was carried out with a county-level hurler during preseason preparation. The intervention resulted in a number of physiological changes specific to hurling performance. Most notably, it enabled the athlete to complete repeated sprints with less decrement in performance compared with baseline scores.
Michael J. Duncan, Mark Lyons, and Joanne Hankey
This study examined the placebo effect of caffeine on number of repetitions (reps), rating of perceived exertion (RPE), blood pressure (BP), and peak heart rate (PHR) during resistance-training exercise with repetitions (reps) performed to volitional failure.
Following determination of 1-rep maximum in single-leg leg extension, 15 males performed reps to failure at 60% 1-RM in 3 conditions: control, perceived caffeine condition, and perceived placebo condition presented in a randomized order. Participants were informed they would ingest 250 mL of solution that contained either 3 mg·kg−1 caffeine or 3 mg·kg−1 placebo 1 h before each exercise trial. A deceptive protocol was employed and subjects consumed a placebo solution in both conditions. During each condition, total reps, RPE for the active muscle and overall body, and PHR were recorded.
Subjects completed 2 more reps when they perceived they had ingested caffeine. RPE was significantly (P = .04) lower in the perceived caffeine and control conditions and RPE for the active muscle was significantly higher across all conditions compared with RPE for the overall body. No substantial differences were evident in PHR across conditions.
Results of this study are similar to studies of actual caffeine ingestion. However, the perception of consuming a substance that purportedly enhances performance is sufficient enough to enable individuals to complete a greater number of reps to failure during short-term resistance exercise.
Neil D. Clarke and Michael J. Duncan
To investigate the effect of ingesting carbohydrate and caffeine solutions on measures that are central to success in badminton.
Twelve male badminton players performed a badminton serve-accuracy test, coincidence-anticipation timing (CAT), and a choice reaction-time sprint test 60 min before exercise. Participants then consumed 7 mL/kg body mass of either water (PLA), 6.4% carbohydrate solution (CHO), a solution containing a caffeine dose of 4 mg/kg, or 6.4% carbohydrate and 4 mg/kg caffeine (C+C). All solutions were flavored with orange-flavored concentrate. During the 33-min fatigue protocol, participants were provided with an additional 3 mL/kg body mass of solution, which was ingested before the end of the protocol. As soon as the 33-min fatigue protocol was completed, all measures were recorded again.
Short-serve accuracy was improved after the ingestion of CHO and C+C compared with PLA (P = .001, ηp 2 = .50). Long-serve accuracy was improved after the ingestion of C+C compared with PLA (P < .001, ηp 2 = .53). Absolute error in CAT demonstrated smaller deteriorations after the ingestion of C+C compared with PLA (P < .05; slow, ηp 2 = .41; fast, ηp 2 = .31). Choice reaction time improved in all trials with the exception of PLA, which demonstrated a reduction (P < .001, ηp 2 = .85), although C+C was faster than all trials (P < .001, ηp 2 = .76).
These findings suggest that the ingestion of a caffeinated carbohydrate solution before and during a badminton match can maintain serve accuracy, anticipation timing, and sprinting actions around the court.
Diego B. Souza, Michael Duncan, and Marcos D. Polito
Purpose: To examine the effects of acute caffeine (CAF) intake on physical performance in 3 sets of unilateral knee extensions with blood-flow restriction. Methods: In a double-blind crossover design, 22 trained men ingested 6 mg·kg−1 of CAF or a placebo (PLA), 1 h prior to performing unilateral knee-extension exercise with blood-flow restriction until exhaustion (30% of 1 maximal repetition). Results: There was a significant difference in the number of repetitions between the CAF and PLA conditions in the first set (28.3 [5.3] vs 23.7 [3.2]; P = .005), second set (11.6 [3.1] vs 8.9 [2.9]; P = .03), and total repetitions performed across the 3 sets (44.5 [9.4] vs 35.0 [6.6]; P = .001). Blood lactate was also significantly different (P = .03) after exercise between the CAF (7.8 [1.1] mmol·L−1) and PLA (6.0 [0.9] mmol·L−1). In regard to pain perception, there was a difference between the CAF and PLA in the second (6.9 [1.5] vs 8.4 [1.4]; P = .04) and third sets (8.7 [0.4] vs 9.5 [0.6]; P = .01). No differences were found for perceived effort. Conclusion: Acute caffeine intake increases performance and blood lactate concentration and reduces perception of pain in unilateral knee-extension exercise with blood-flow restriction.
Wesley O’Brien, Michael J. Duncan, Orlagh Farmer, and Diarmuid Lester
Recent research has shown that post-primary Irish youth are insufficiently active and fail to reach a level of proficiency across basic fundamental movement skills. The purpose of the current research was to gather cross-sectional data on adolescent youth, differentiated by gender, specifically to inform the development of a targeted movement-oriented intervention. Data were collected on adolescents (N = 219; mean age : 14.45 ± 0.96 years), within two, mixed-gender schools. Data collection included actual and perceived movement measurements comprised of fundamental movement skills, the functional movement screen, perceived movement confidence, and perceived functional confidence. Overall, levels of actual mastery within fundamental and functional movement were low, with significant gender differences observed. Adolescent males scored higher in the overall fundamental movement skill domain (male mean score = 70.87 ± 7.05; female mean score = 65.53 ± 7.13), yet lower within the functional movement screen (male mean score = 13.58 ± 2.59), in comparison to their female counterparts (female mean score = 14.70 ± 2.16). There were high levels of perceived confidence reported within fundamental and functional movement scales. Future intervention strategies should combat the low levels of actual movement skill proficiency, while identifying the reasons for higher perceived movement confidence within adolescents.
Michael J. Duncan, Joanne Hankey, and Alan M. Nevill
This study examined the efficacy of peak-power estimation equations in children using force platform data and determined whether allometric modeling offers a sounder alternative to estimating peak power in pediatric samples. Ninety one boys and girls aged 12–16 years performed 3 countermovement jumps (CMJ) on a force platform. Estimated peak power (PPest) was determined using the Harman et al., Sayers SJ, Sayers CMJ, and Canavan and Vescovi equations. All 4 equations were associated with actual peak power (r = 0.893−0.909, all p < .01). There were significant differences between PPest using the Harman et al., Sayers SJ, and Sayers CMJ equations (p < .05) and actual peak power (PPactual). ANCOVA also indicated sex and age effect for PPactual (p < .01). Following a random two-thirds to one-third split of participants, an additive linear model (p = .0001) predicted PPactual (adjusted R 2 = .866) from body mass and CMJ height in the two-thirds split (n = 60). An allometric model using CMJ height, body mass, and age was then developed with this sample, which predicted 88.8% of the variance in PPactual (p < .0001, adjusted R 2 = .888). The regression equations were cross-validated using the one-third split sample (n = 31), evidencing a significant positive relationship (r = .910, p = .001) and no significant difference (p = .151) between PPactual and PPest using this equation. The allometric and linear models determined from this study provide accurate models to estimate peak power in children.
Amanda Santos, Sandra Silva-Santos, Michael Duncan, Maria João Lagoa, Susana Vale, and Jorge Mota
Purposes: To examine the association between sedentary time (ST) and light physical activity (LPA), moderate- to vigorous-intensity physical activity (MVPA), and body mass index (BMI), and to track these behaviors over a 3-year follow-up in young schoolchildren. Methods: The final sample was 64 children (female: n = 36 or 56.3%), enrolled in schools in Porto, Portugal. Height and mass of children were measured by standard methods, and BMI was then calculated. ST, LPA, and MVPA were measured by accelerometer. Changes (Δ) and relative changes (Δ%) between 2009/2010 and 2012/2013 of ST, LPA, MVPA, and BMI were computed. Multiple linear regression analyses were fit to predict Δ%ST (outcome variable), by Δ%LPA, Δ%MVPA, and Δ%BMI (exposure variables). Results: ST increased and LPA decreased significantly for whole sample (both Ps < .05). No statistically significant difference was found for MVPA over time. There were no differences for ΔST, ΔLPA, ΔMVPA, and ΔBMI between boys and girls. The Δ%LPA and Δ%MVPA were negatively associated with Δ%ST, whereas Δ%BMI was positively associated. Tracking coefficients varied from moderate to strong. Conclusions: Time spent in ST increases due to displacement of time in LPA. This reinforces public health measures and suggests the need for interventions focusing on offsetting the decline ST and increasing MVPA during childhood.
Nadia Cristina Valentini, Glauber Carvalho Nobre, Mariele Santayana de Souza, and Michael J. Duncan
Background: Higher levels of actual and perceived motor competence are purported to lead to participation in physical activity (PA). Whereas considerable work has been published regarding motor and perceived competence and body mass index (BMI), much less is known about the association of these variables considering PA and engagement in physical education settings—the focus of the present study. Method: In 600 children (aged 3–10 y), PA during physical education lessons, locomotor skills, object control skills, perceived competence, and BMI (study 1) were assessed. In a subsample of 149 children, PA, engagement, and health-related fitness were assessed (study 2). Results: Structural equation model showed that in study 1, locomotor skills were the strongest variable in the early years, and object control skills were the strongest later, in explained PA. The regression analysis, in study 2, showed that BMI, object control skills, and engagement were significantly associated with PA and that appropriate motor engagement was the best predictor of PA. Conclusion: The authors extended previous research by providing evidence that motor competence varies across childhood in explaining participation in PA, and appropriate motor engagement plays a critical role in being active during lessons and was the strongest predictor of PA. BMI and self-perception were not significant in the models.
Michael J. Duncan, Lorayne Woodfield, Yahya Al-Nakeeb, and Alan M. Nevill
The purpose of this study was to compare physical activity levels between white and South Asian children in the UK. The data were obtained from 606, 11–14 year old schoolchildren (397 white; 209 Asian). Physical activity was assessed using the ‘four by one day’ recall questionnaire from which the time spent in moderate and vigorous physical activity was calculated. Boys were significantly more active than girls (p = .0001), and white children reported significantly greater physical activity than south Asian children (p = .001). Mean ± SD of time spent in moderate and vigorous activity was 90.2 ± 65.4 mins and 68.2 ± 49.3 mins for white and south Asian children and 103.5 ± 63.4 mins and 65.6 ± 53.5 mins for boys and girls respectively. These findings indicate that south Asian children are significantly less active than their white peers and there may be a need for specific interventions to target South Asian children particularly.
Lorayne Woodfield, Michael Duncan, Yahya Al-Nakeeb, Alan Nevill, and Charles Jenkins
The present study examines the relationship of sex, ethnicity, and socio-economic status to physical activity levels of young people. Participants were 301 males and females (12.9 – 0.81 years). Physical activity was measured using the four by one-day physical activity recall questionnaire. ANOVA revealed that high socio-economic status children reported greater average daily energy expenditure levels than low socio-economic status children (p < .01). The daily energy expenditure of white-Caucasian children was significantly higher than black or Asian children. White boys were significantly more active than white girls, but no such sex differences were observed among black and Asian children. Although activity was always greater at weekends, a decline in activity by school year was observed on Saturdays and Sundays but with no such decline observed on weekdays.