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Philip F. Skiba, David Clarke, Anni Vanhatalo and Andrew M. Jones

Recently, an adaptation to the critical-power (CP) model was published, which permits the calculation of the balance of the work capacity available above the CP remaining (Wbal) at any time during intermittent exercise. As the model is now in use in both amateur and elite sport, the purpose of this investigation was to assess the validity of the Wbal model in the field. Data were collected from the bicycle power meters of 8 trained triathletes. Wbal was calculated and compared between files where subjects reported becoming prematurely exhausted during training or competition and files where the athletes successfully completed a difficult assigned task or race without becoming exhausted. Calculated Wbal was significantly different between the 2 conditions (P < .0001). The mean Wbal at exhaustion was 0.5 ± 1.3 kJ (95% CI = 0–0.9 kJ), whereas the minimum Wbal in the nonexhausted condition was 3.6 ± 2.0 kJ (95% CI = 2.1–4.0 kJ). Receiver-operator-characteristic (ROC) curve analysis indicated that the Wbal model is useful for identifying the point at which athletes are in danger of becoming exhausted (area under the ROC curve = .914, SE .05, 95% CI .82–1.0, P < .0001). The Wbal model may therefore represent a useful new development in assessing athlete fatigue state during training and racing.

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Gerard Carmona, Emma Roca, Mario Guerrero, Roser Cussó, Alfredo Irurtia, Lexa Nescolarde, Daniel Brotons, Josep L. Bedini and Joan A. Cadefau

Objective:

To investigate changes after a mountain ultramarathon (MUM) in the serum concentration of fast (FM) and slow (SM) myosin isoforms, which are fiber-type-specific sarcomere proteins. The changes were compared against creatine kinase (CK), a widely used fiber-sarcolemma-damage biomarker, and cardiac troponin I (cTnI), a widely used cardiac biomarker.

Methods:

Observational comparison of response in a single group of 8 endurance-trained amateur athletes. Time-related changes in serum levels of CK, cTnI, SM, and FM from competitors were analyzed before, 1 h after the MUM, and 24 and 48 h after the start of the MUM by 1-way ANOVA for repeated measures or Friedman and Wilcoxon tests. Pearson correlation coefficient was employed to examine associations between variables.

Results:

While SM was significantly (P = .009) increased in serum 24 h after the beginning of the MUM, FM and cTnI did not change significantly. Serum CK activity peak was observed 1 h after the MUM (P = .002). Moreover, serum peaks of CK and SM were highly correlated (r = .884, P = .004).

Conclusions:

Since there is evidence of muscle damage after prolonged mountain running, the increase in SM serum concentration after a MUM could be indirect evidence of slow- (type I) fiber-specific sarcomere disruptions.

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Robert F. Dyer and Rolando P. Irizarry

Safety is a growing concern in all sports, with the equestrian sector statistically more dangerous than most. Point Two USA hopes to make horse riding and competition a safer sport for all ages, riding levels, and disciplines with its innovative air vests, which use an inflatable air bag similar to those required in modern automobiles. Air vests are used to reduce the severity and frequency of injuries; however, no technology or equipment can eliminate all injuries associated with horse riding. After a strong entry in the United Kingdom in 2009, Point Two needs to formulate a comprehensive marketing plan for the larger U.S. market to expand its customer base to anyone getting on a horse who desires a safer ride. Its U.S. subsidiary has been primarily marketing with the same approaches used in the United Kingdom, heavily targeting English saddle riders in specific riding disciplines, such as eventing and dressage, both amateur and professional. The challenge for Point Two is how it can make headway in more mainstream riding markets, including recreation or pleasure riders, novice riders, and those who ride using Western saddles, which is very popular in the United States.

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Edward C. Frederick, Jeremy J. Determan, Saunders N. Whittlesey and Joseph Hamill

Seven top amateur or professional skateboarders (BW = 713 N ± 83 N) performed Ollie maneuvers onto and off an elevated wooden platform (45.7 cm high). We recorded ground reaction force (GRF) data for three Ollie Up (OU) and Ollie Down (OD) trials per participant. The vertical GRF (VGRF) during the OU has a characteristic propulsive peak (M = 2.22 body weight [BW] ± 0.22) resulting from rapidly rotating the tail of the board into the ground to propel the skater and board up and forward. The anterior-posterior (A-P) GRF also shows a pronounced peak (M = 0.05 ± 0.01 BW) corresponding with this propulsive VGRF peak. The initial phase of landing in the OD shows an impact peak in VGRF rising during the first 30 to 80 ms to a mean of 4.74 ± 0.46 BW. These impact peaks are higher than expected given the relatively short drop of 45.7 cm and crouched body position. But we observed that our participants intentionally affected a firm landing to stabilize the landing position; and the Ollie off the platform raised the center of mass, also contributing to higher forces.

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Douglas J. Casa, Samuel N. Cheuvront, Stuart D. Galloway and Susan M. Shirreffs

The 2019 International Amateur Athletics Federation Track-and-Field World Championships will take place in Qatar in the Middle East. The 2020 Summer Olympics will take place in Tokyo, Japan. It is quite likely that these events may set the record for hottest competitions in the recorded history of both the Track-and-Field World Championships and Olympic Games. Given the extreme heat in which track-and-field athletes will need to train and compete for these games, the importance of hydration is amplified more than in previous years. The diverse nature of track-and-field events, training programs, and individuality of athletes taking part inevitably means that fluid needs will be highly variable. Track-and-field events can be classified as low, moderate, or high risk for dehydration based on typical training and competition scenarios, fluid availability, and anticipated sweat losses. This paper reviews the risks of dehydration and potential consequences to performance in track-and-field events. The authors also discuss strategies for mitigating the risk of dehydration.

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Kevin J. Beasley

Gaelic football is the second most popular team sport in Ireland in terms of participation. However, very little research exists on the nutritional considerations for elite male Gaelic footballers. Gaelic football is an intermittent type field game played by two teams of fifteen players. Although amateurs, elite players may train and compete 4–5 times per week and may play for several teams. Research suggests that elite footballers are similar anthropometrically and in fitness to professional soccer players. Work-rate analysis shows that footballers experience longer durations of high-intensity (HI) activity (5–7s) and shorter rest durations than soccer players. Recent data suggests that half-forward/backs perform a greater amount of HI work during games than players in other positions. Fatigue is apparent between the first and second halves and the first and fourth quarters. The limited amount of nutritional studies conducted implies that footballers may be deficient in energy intake and may be at the lower end of recommended carbohydrate intakes to support training. A wide variety of sweat rates have been measured during training, demonstrating the importance of individual hydration strategies. Ergogenic aids such as creatine and caffeine may prove beneficial to performance, although data are extrapolated from other sports. Due to the lack of research in Gaelic football, further population specific studies are required. Future areas of research on the impact of nutrition on Gaelic football performance are examined. In particular, the creation of a test protocol mimicking the activity patterns and intensity of a Gaelic football game is warranted.

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Jeremy Williams, Grant Abt and Andrew E. Kilding

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.

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Lachlan P. James, Emma M. Beckman, Vincent G. Kelly and G. Gregory Haff

Purpose:

To determine whether the maximal strength, impulse, and power characteristics of competitive mixed-martial-arts (MMA) athletes differ according to competition level.

Methods:

Twenty-nine male semiprofessional and amateur MMA competitors were stratified into either higher-level (HL) or lower-level (LL) performers on the basis of competition grade and success. The 1-repetition-maximum (1RM) squat was used to assess lower-body dynamic strength, and a spectrum of impulse, power, force, and velocity variables were evaluated during an incremental-load jump squat. In addition, participants performed an isometric midthigh pull (IMTP) and 1RM bench press to determine whole-body isometric force and upper-body dynamic strength capabilities, respectively. All force and power variables were expressed relative to body mass (BM).

Results:

The HL competitors produced significantly superior values across a multitude of measures. These included 1RM squat strength (1.84 ± 0.23 vs 1.56 ± 0.24 kg BM; P = .003), in addition to performance in the incremental-load jump squat that revealed greater peak power (P = .005–.002), force (P = .002–.004), and velocity (P = .002–.03) at each load. Higher measures of impulse (P = .01–.04) were noted in a number of conditions. Average power (P = .002–.02) and velocity (P = .01–.04) at all loads in addition to a series of rate-dependent measures were also superior in the HL group (P = .005–.02). The HL competitors’ 1RM bench-press values approached significantly greater levels (P = .056) than the LL group’s, but IMTP performance did not differ between groups.

Conclusions:

Maximal lower-body neuromuscular capabilities are key attributes distinguishing HL from LL MMA competitors. This information can be used to inform evidenced-based training and performance-monitoring practices.

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Tom G.A. Stevens, Cornelis J. de Ruiter, Cas van Niel, Roxanne van de Rhee, Peter J. Beek and Geert J.P. Savelsbergh

Purpose:

A local position measurement (LPM) system can accurately track the distance covered and the average speed of whole-body movements. However, for the quantification of a soccer player’s workload, accelerations rather than positions or speeds are essential. The main purpose of the current study was therefore to determine the accuracy of LPM in measuring average and peak accelerations for a broad range of (maximal) soccerspecific movements.

Methods:

Twelve male amateur soccer players performed 8 movements (categorized in straight runs and runs involving a sudden change in direction of 90° or 180°) at 3 intensities (jog, submaximal, maximal). Position-related parameters recorded with LPM were compared with Vicon motion-analysis data sampled at 100 Hz. The differences between LPM and Vicon data were expressed as percentage of the Vicon data.

Results:

LPM provided reasonably accurate measurements for distance, average speed, and peak speed (differences within 2% across all movements and intensities). For average acceleration and deceleration, absolute bias and 95% limits of agreement were 0.01 ± 0.36 m/s2 and 0.02 ± 0.38 m/s2, respectively. On average, peak acceleration was overestimated (0.48 ± 1.27 m/s2) by LPM, while peak deceleration was underestimated (0.32 ± 1.17 m/s2).

Conclusion:

LPM accuracy appears acceptable for most measurements of average acceleration and deceleration, but for peak acceleration and deceleration accuracy is limited. However, when these error margins are kept in mind, the system may be used in practice for quantifying average accelerations and parameters such as summed accelerations or time spent in acceleration zones.

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Damir Zubac, Drazen Cular and Uros Marusic

Purpose: To determine the reliability and diagnostic accuracy of noninvasive urinary dehydration markers in field-based settings on a day-to-day basis in elite adolescent amateur boxers. Methods: Sixty-nine urine samples were collected daily from 23 athletes (17.3 ± 1.9 y) during their weight-stable phase and analyzed by field and laboratory measures of hydration status. Urine osmolality (UOSM), urine specific gravity (USG), total protein content (TPC), and body-mass stability were evaluated to determine fluid balance and hydration status. Overall macronutrient and water intake were determined using dietary records. According to their anthropometric characteristics, athletes were assigned into 2 groups: lightweight (LWB) and heavyweight (HWB) boxers. Results: Data presented on UOSM demonstrated a uniform increment by 11.2% ± 12.8% (LWB) and 19.9% ± 22.7% (HWB) (P < .001) over the course of the study, even during the weight-stable phase (body mass, ICC = .99) and ad libitum fluid intake (42 ± 4 mL · kg−1 · d−1). The intraclass correlation coefficients (ICCs) ranged from .52 to .55 for USG and .38 to .52 for UOSM, further indicating inconsistency of the urinary dehydration markers. Poor correlations were found between USG and TPC metabolites (r = .27, P = .211). Conclusions: Urinary dehydration markers (both USG and UOSM) exhibit high variability and seem to be unreliable diagnostic tools to track actual body-weight loss in real-life settings. The ad libitum fluid intake was apparently inadequate to match acute fluid loss during and after intense preparation. The applicability of a single-time-point hydration-status assessment concept may preclude accurate assessment of actual body-weight deficits in youth boxers.