Effects of creatine monohydrate supplementation on simulated soccer performance

Purpose: To determine the effects of acute short-term creatine (Cr) supplementation on physical performance during a 90-min soccer-specific performance test. Methods: A double-blind, placebo-controlled experimental design was adopted during which 16 male amateur soccer players were required to consume 20 g/d Cr for 7 d or a placebo. A Ball-Sport Endurance and Speed Test (BEAST) comprising measures of aerobic (circuit time), speed (12- and 20-m sprint), and explosive-power (vertical jump) abilities performed over 90 min was performed presupplementation and postsupplementation. Results: Performance measures during the BEAST deteriorated during the second half relative to the first for both Cr (1.2–2.3%) and placebo (1.0–2.2%) groups, indicating a fatigue effect associated with the BEAST. However, no significant differences existed between groups, suggesting that Cr had no performance-enhancing effect or ability to offset fatigue. When effect sizes were considered, some measures (12-m sprint, –0.53 ± 0.69; 20-m sprint, –0.39 ± 0.59) showed a negative tendency, indicating chances of harm were greater than chances of benefit. Conclusions: Acute short-term Cr supplementation has no beneficial effect on physical measures obtained during a 90-min soccer-simulation test, thus bringing into question its potential as an effective ergogenic aid for soccer players

Movement economy in soccer: Current data and limitations

Soccer is an intermittent team-sport, where performance is determined by a myriad of psychological, technical, tactical, and physical factors. Among the physical factors, endurance appears to play a key role into counteracting the fatigue-related reduction in running performance observed during soccer matches. One physiological determinant of endurance is movement economy, which represents the aerobic energy cost to exercise at a given submaximal velocity. While the role of movement economy has been extensively examined in endurance athletes, it has received little attention in soccer players, but may be an important factor, given the prolonged demands of match play. For this reason, the current review discusses the nature, impact, and trainability of movement economy specific to soccer players. A summary of current knowledge and limitations of movement economy in soccer is provided, with an insight into future research directions, to make this important parameter more valuable when assessing and training soccer players’ running performance

Does Caffeine Influence Salivary IgA Responses In A Dose-Dependent Manner Following High-Intensity Treadmill Exercise?

Introduction: Caffeine ingestion is associated with enhanced athletic performance, with doses as low as 2 mg.kg-1 body mass (BM) proving ergogenic. Bishop et al. (2006) have shown that ingesting a 6 mg.kg-1 BM dose of caffeine 1 h prior to 90 min of cycle exercise at 70%causes a transient increase in saliva Immunoglobulin A (IgA) concentration both during and immediately following exercise. However, no research has identified if the same response occurs with either lower or higher doses of caffeine. As such the purpose of this study was to examine the dose-response effects of caffeine ingestion on salivary IgA responses following high-intensity running. Methods: In a double blind randomised crossover design, 12 endurance trained male runners (age: 29 ± 3, 62.7 ± 5.1 mL·kg·min-1, mean ± SD) ran for 70 min at 80% 60 min after ingesting 0 (PLA), 2 (2CAF), 4 (4CAF), 6 (6CAF) or 8 (8CAF) mg·kg-1 BM of caffeine. For PLA, 6 mg·kg-1 BM of cornflour was ingested. Unstimulated whole saliva samples were obtained before supplementation, pre-exercise, after 35 min of exercise, immediately post-exercise and 1 h post-exercise. Saliva IgA was determined using ELISA, while caffeine concentrations were determined via HPLC. Results: Saliva caffeine concentrations were significantly increased at all time points (pre-, mid-, post- and 1 h post-exercise) when compared to pre-supplement in a dose-dependent manner (P\u3c0.001; peak concentration: PLA: 0 ± 0; 2CAF: 10 ± 3; 4CAF: 22 ± 8; 6CAF: 40 ± 9; 8CAF: 44 ± 9 μM). However, there was no dose-response effect of caffeine on either saliva IgA concentration or secretion rate before, during or after exercise. In fact neither caffeine nor exercise affected saliva IgA secretion rate or concentration. Conclusion: These findings suggest that caffeine ingestion (from 2-8 mg.kg-1 BM) 60 min prior to prolonged high-intensity treadmill running has no effect on saliva IgA responses following exercise. As such it can be suggested that athletes wanting to consume caffeine for ergogenic purposes can potentially do so (up to a dose of 8 mg.kg-1 BM) without reducing mucosal immunity

Pulmonary oxygen uptake kinetics in middle-and long-distance runners.

The overall aim of this thesis was to evaluate the importance of pulmonary oxygen uptake (VO[2]) kinetics, in the moderate-domain, in the assessment of endurance-trained runners. Accordingly, there were five objectives: 1) to quantify the reproducibility of measures of VO[2] kinetics; 2) to characterise and compare VO[2] kinetics during the on-and off-transients in middle-distance (MD) and long-distance (LD) runners; 3) to assess the relationship between VO[2] kinetics and maximal VO[2] (VO[2Max]), ventilatory threshold (V[T]) and running economy (RE); 4) to determine the relationship between VO[2] kinetics and running performance and 5) to assess whether VO[2] kinetics is a determinant of running performance.Twelve participants performed two assessments of VO[2] kinetics on separate days to determine the reproducibility. Paired t-tests showed that parameters from test 1 and test 2 did not differ (P >0.05). Furthermore, narrow 95% limits of agreement (LOA), low measurement and method error suggested that the on- and off-transient time-constants (pion and pioff), mean response times (MRT[on] and MRT[off]) and amplitudes (A[on] and A[off]) were reproducible and could be used for the assessment of runners. Subsequently, VO[2] kinetics were compared in 10 MD and 10 LD runners. There was a tendency for pion (12.5 +/- 2.3 s vs. 14.2 +/- 3.1 s, P = 0.178) and pioff (24.1 +/- 2.3 s vs. 27.1 +/- 3.0 s, P = 0.023) to be shorter in LD than MD runners respectively, despite similar VO[2Max] (MD = 60.0 +/- 4.9 ml-kg[-1]min[-1]; LD = 59.0 +/- 6.3 ml-kg[-1]-min[-1], P = 0.689). Differences in VO[2] kinetics between MD and LD runners were attributed to approaches to training since the volume of training was greater in LD (64.0 +/- 15.7 km-wk[-1]) than MD (47.5 +/- 15.7 km-wk[-1]) runners (P = 0.047). To detail the relationships between VO[2] kinetics and other measures of aerobic function (VO[2max], V[t] and RE), 16 MD and 16 LD runners were assessed. Relationships existed between pion and VO[2max] (r = -0.72, P = 0.002), V[t] (r = -0.66, P = 0.006) and RE (r = -0.59, P = 0.016) in LD runners, but not in MD runners (P >0.05). In addition, pion was related to the volume of training in MD (r = -0.63 , P = 0.009) and LD runners (r = -0.65, P = 0.006).The importance of VO[2] kinetics for 5 km running performance was investigated in 36 endurance trained runners. Runners were categorised as high n=10), low (n=10) and combined [MD + LD (n=36)] performers according to running ability after performing a self-paced 5 km time-trial. Mean (+/-SD) speed for the 5 km time-trial was 5.2 +/-1.0 m-s[-1] (high), 4.5 +/- 0.2 m-s[-1] (low) and 4.9 +/- 0.3 m-s[-1] (combined). Measures of on- and off- transient VO[2] kinetics, VO[2max], V[t] and RE were also determined. Data were explored using bi-variate correlations, ANCOVA and multiple regression techniques. In high and low performers, V0[2] kinetic parameters were not related to running performance. In combined runners, pion, pioff, MRT[on] and MRT[off] were related (r = -0.54, P = 0.001; r = -0.36, P = 0.030; r = -0.50, P = 0.002; r = -0.63, P = 0.003) to running performance. Stepwise multiple regression models were used to identify the primary determinant(s) of 5 km running performance for each group. In high performers, VO[2Max] and RE were included in the model (r = 0.92, R = 0.85, SEE = 0.08 m-s[-1]; SEE% = 1.5). In low performers, VO[2Max] was included in the model (r = 0.76, R[2] = 0.57, SEE = 0.15 m-s[-1], SEE% = 3.3). In combined runners, V0[2Max] RE and MR[off] were included in the model (r = 0.87, R-2 = 0.75, SEE = 0.17 m-s[-1], SEE% = 3.5).Collectively, the results suggest that: 1) VO[2] kinetics can be reproducibly determined using a single visit protocol; 2) measures of VO[2] kinetics are sensitive enough to differentiate MD and LD runners; 3) relationships between VO[2] kinetics and other measures of aerobic function exist in LD runners, but not in MD runners; 4) VO[2] kinetics differ between high and low performers, but do not relate to running performance and 5) VO[2] kinetics discriminate between high and low performers but only contribute minimally to the prediction of running performance in a multiple regression model for combined MD and LD runners

Pedal force effectiveness in cycling: A review of constraints and training effects

Pedal force effectiveness in cycling is usually measured by the ratio of force perpendicular to the crank (effective force) and total force applied to the pedal (resultant force). Most studies measuring pedal forces have been restricted to one leg but a few studies have reported bilateral asymmetry in pedal forces. Pedal force effectiveness is increased at higher power output and reduced at higher pedaling cadences. Changes in saddle position resulted in unclear effects in pedal force effectiveness, while lowering the upper body reduced pedal force effectiveness. Cycling experience and fatigue had unclear effects on pedal force effectiveness. Augmented feedback of pedal forces can improve pedal force effectiveness within a training session and after multiple sessions for cyclists and non-cyclists. No differences in pedal force effectiveness were evident between summarized and instantaneous feedback. Conversely, economy/efficiency seems to be reduced when cyclists are instructed to improve pedal force effectiveness during acute intervention studies involving one session. Decoupled crank systems effectively improved pedal force effectiveness with conflicting effects on economy/efficiency and performance

Objective benefits, participant perceptions and retention rates of a New Zealand community-based, older-adult exercise programme

INTRODUCTION: Most exercise studies for older adults have been university- or hospital-based. Little is known about the benefits and factors influencing long-term participation in community-based exercise programmes, especially in New Zealand. AIM: To quantify the objective benefits, participant perceptions and retention rates of a New Zealand community-based exercise programme for adults (60 years or older). METHODS: Study 1 involved assessing the benefits of 12 weeks’ training on a convenience sample of 62 older adults commencing the never2old Active Ageing programme. Study 2 assessed the perceptions of 150 current participants on a variety of programme components that could act as barriers or facilitators to continued engagement. Study 3 assessed the retention rates of 264 participants in the programme over a two-year period. RESULTS: Significant improvements in many physical functional scores were observed in Study 1 (5–30 percentile points; p less than 0.05). Questionnaire responses from participants in Study 2 indicated many xsi:type=""benefits (positive responses from 67–95% on various questions) and that core components of the programme were rated very highly (64–99% on various components). Retention rates were high, with Study 3 finding 57% of participants still engaging in the programme at the end of the two-year period. DISCUSSION: A community-based exercise programme for older adults can improve many objective and subjective measures of physical fitness and functional performance and have good retention rates. General practitioners and other allied health professionals in New Zealand should consider promoting programmes, such as the never2old Active Ageing programme, to their older patients

Modulators of change-of-direction economy after repeated sprints in elite soccer players

Purpose: To investigate the acute effect of repeated-sprint activity (RSA) on change-of-direction economy (assessed using shuttle running economy [SRE]) in soccer players and explore neuromuscular and cardiorespiratory characteristics that may modulate this effect. Methods: Eleven young elite male soccer players (18.5 [1.4] y old) were tested on 2 different days during a 2-week period in their preseason. On day 1, lower-body stiffness, power and force were assessed via countermovement jumps, followed by an incremental treadmill test to exhaustion to measure maximal aerobic capacity. On day 2, 2 SRE tests were performed before and after a repeated-sprint protocol with heart rate, minute ventilation, and blood lactate measured. Results: Pooled group analysis indicated no significant changes for SRE following RSA due to variability in individual responses, with a potentiation or impairment effect of up to 4.5% evident across soccer players. The SRE responses to RSA were significantly and largely correlated to players’ lower-body stiffness (r = .670; P = .024), and moderately (but not significantly) correlated to players’ force production (r = −.455; P = .237) and blood lactate after RSA (r = .327; P = .326). Conclusions: In summary, SRE response to RSA in elite male soccer players appears to be highly individual. Higher lower-body stiffness appears as a relevant physical contributor to preserve or improve SRE following RSA

Physical and energy demand of soccer: A brief review

Soccer is a complex and exhaustive team-sport requiring a high level of tactical, technical, and physical ability to succeed. During a competitive match, a random combination of explosive and powerful activities, together with technical and tactical gestures, is performed in an intermittent manner over a 90-minute game. This review presents a detailed analysis and up-to-date synthesis of the literature describing activities and energy system contribution during soccer to provide to strength and conditioning coaches a clear understanding of soccer players’ physical needs during competition

Pre-exercise carbohydrate or protein ingestion influences substrate oxidation but not performance or hunger compared with cycling in the fasted state

Nutritional intake can influence exercise metabolism and performance, but there is a lack of research comparing protein-rich pre-exercise meals with endurance exercise performed both in the fasted state and following a carbohydrate-rich breakfast. The purpose of this study was to determine the effects of three pre-exercise nutrition strategies on metabolism and exercise capacity during cycling. On three occasions, seventeen trained male cyclists (VO2peak 62.2 ± 5.8 mL·kg−1·min−1, 31.2 ± 12.4 years, 74.8 ± 9.6 kg) performed twenty minutes of submaximal cycling (4 × 5 min stages at 60%, 80%, and 100% of ventilatory threshold (VT), and 20% of the difference between power at the VT and peak power), followed by 3 × 3 min intervals at 80% peak aerobic power and 3 × 3 min intervals at maximal effort, 30 min after consuming a carbohydrate-rich meal (CARB; 1 g/kg CHO), a protein-rich meal (PROTEIN; 0.45 g/kg protein + 0.24 g/kg fat), or water (FASTED), in a randomized and counter-balanced order. Fat oxidation was lower for CARB compared with FASTED at and below the VT, and compared with PROTEIN at 60% VT. There were no differences between trials for average power during high-intensity intervals (367 ± 51 W, p = 0.516). Oxidative stress (F2-Isoprostanes), perceived exertion, and hunger were not different between trials. Overall, exercising in the overnight-fasted state increased fat oxidation during submaximal exercise compared with exercise following a CHO-rich breakfast, and pre-exercise protein ingestion allowed similarly high levels of fat oxidation. There were no differences in perceived exertion, hunger, or performance, and we provide novel data showing no influence of pre-exercise nutrition ingestion on exercise-induced oxidative stress

Activity profiles of elite netball umpires: A review

This review has outlined the existing literature relating to activity profiles in elite netball umpires. In particular, the physical (distance travelled), physiological (heart rate), and technical (movement classifications) characteristics have been described. The limited available literature report that on average elite netball umpires travel approximately 3850 m during a 60 min match. Up to approximately 50% of the match is spent standing, with only around 25% of the match in higher intensity movements such as jogging, sprinting, side stepping, or changing direction. Work:rest ratios are typically approximately 1:3 during match play, with additional recovery in the intervals between quarters. This includes an average of 140 sprints for a duration of 2.8 s. Elite umpires spend around 10% of the match at greater than 92% peak heart rate, with the majority (approximately 55%) between 75 and 92% peak heart rate. These characteristics may benefit umpires and strength and conditioning practitioners when designing training programmes. The literature also report a reduction in distance travelled by elite umpires as the match progresses. An accompanying decrease in heart rate suggests that this is not caused by physiological fatigue mechanisms but is a result of technical adjustments in the movement patterns utilised. Indeed, elite umpires tend to sidestep less and walk or stand more as the match progresses. Additionally, gaps in the existing literature have been highlighted, including the relationship between perceptual-cognitive processes and movement, and the application of fitness testing requirements to umpire activity profiles