bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological Demands of Competitive Sprint and Distance Performance in Elite Female Cross-Country Skiing
Authors: Carlsson Magnus , Carlsson Tomas , Wedholm Lars , Nilsson Mattias , Malm Christer , Tonkonogi Michail 
Published: January 2016

Abstract
Carlsson, M, Carlsson, T, Wedholm, L, Nilsson, M, Malm, C, and Tonkonogi, M. Physiological demands of competitive sprint and distance performance in elite female cross-country skiing. J Strength Cond Res 30(8): 2138–2144, 2016—The purpose was to investigate the relationship between elite females' competitive performance capability in sprint and distance cross-country skiing and the variables of gross efficiency (GE), work rate at the onset of blood-lactate accumulation (OBLA4mmol), maximal oxygen uptake (V̇o
2max), maximal speed (Vmax), and peak upper-body oxygen uptake (V̇o
2peak). Ten elite female cross-country skiers (age 24.5 ± 2.8 years) completed treadmill roller-skiing tests to determine GE, OBLA4mmol, and V̇o
2max using the diagonal-stride technique as well as Vmax and V̇o
2peak using the double-poling technique. International Ski Federations ranking points for sprint (FISsprint) and distance (FISdist) races were used as competitive performance data. There were correlations between the FISsprint and the V̇o
2max expressed absolutely (p = 0.0040), Vmax (p = 0.012), and V̇o
2peak expressed absolutely (p < 0.001) and as a simple ratio-standard (p = 0.049). The FISdist were correlated with OBLA4mmol (p = 0.048), V̇o
2max expressed absolutely (L·min−1) (p = 0.015) and as a simple ratio-standard (p = 0.046), and V̇o
2peak expressed absolutely (p = 0.036) and as a simple ratio-standard (ml·min−1·kg−1) (p = 0.040). The results demonstrate that the physiological abilities reflected by V̇o
2max and V̇o
2peak are indicators of competitive sprint and distance performance in elite female cross-country skiing. In addition, the ability to generate a high Vmax indicates the performance in sprint races, whereas the skier's OBLA4mmol reflects the performance capability in distance races. Based on the results, when evaluating the performance capacity of elite female cross-country skiers, it is recommended to use physiological variables that reflect competitive performance.
Barefoot Running Reduces the Submaximal Oxygen Cost in Female Distance Runners
Authors: Berrones Adam J. , Kurti Stephanie P. , Kilsdonk Korey M. , Cortez Delonyx J. , Melo Flavia F. , Whitehurst Michael 
Published: January 2016

Abstract
Berrones, AJ, Kurti, SP, Kilsdonk, KM, Cortez, DJ, Melo, FF, and Whitehurst, M. Barefoot running reduces the submaximal oxygen cost in female distance runners. J Strength Cond Res 30(8): 2348–2353, 2016—Being a competitive distance runner is, in part, attributable to a high V̇o
2max. However, running economy (RE) is a more robust indicator of distance running performance among endurance athletes of similar V̇o
2max levels. The purpose of this study was to examine the influence of unshod (barefoot) vs. shod (wearing shoes) running on RE (expressed as ml·kg−1·min−1) during three 5-minute submaximal running trials representing 65, 75, and 85% of V̇o
2max. Other physiologic and perceptual variables such as respiratory exchange ratio, lactate, heart rate, and ratings of perceived exertion were also chosen as dependent variables. We measured V̇o
2max in 14 recreationally active trained distance female runners (age = 27.6 ± 1.6 years; height = 163.3 ± 1.7 cm; weight = 57.8 ± 1.9 kg) who were completely inexperienced with unshod running. After initial testing, each subject was randomized to either unshod or shod for days 2 and 3. We analyzed the data with a 2-way (condition by intensity) repeated-measures analysis of variance. Submaximal oxygen consumption was significantly reduced at 85% of V̇o
2max (p = 0.018), indicating an improvement in RE, but not during the 65% or 75% trials (p > 0.05, both). No other dependent measure was different between unshod and shod conditions. Our results indicate that the immediate improvement to RE while barefoot occurs at a relatively high fraction of maximal oxygen consumption. For the recreational or competitive distance runner, training or competing while barefoot may be a useful strategy to improve endurance performance.
Comparison of Two Types of Warm-Up Upon Repeated-Sprint Performance in Experienced Soccer Players
Authors: van den Tillaar Roland , von Heimburg Erna 
Published: January 2016

Abstract
van den Tillaar, R and von Heimburg, E. Comparison of two types of warm-up upon repeated-sprint performance in experienced soccer players. J Strength Cond Res 30(8): 2258–2265, 2016—The aim of the study was to compare the effects of a long warm-up and a short warm-up upon repeated-sprint performance in soccer players. Ten male soccer players (age, 21.9 ± 1.9 years; body mass, 77.7 ± 8.3 kg; body height, 1.85 ± 0.03 m) conducted 2 types of warm-ups with 1 week in between: a long warm-up (20 minutes: LWup) and a short warm-up (10 minutes: SWup). Each warm-up was followed by a repeated-sprint test consisting of 8 × 30 m sprints with a new start every 30th second. The best sprint time, total sprinting time, and % decrease in time together with heart rate, lactate, and rate of perceived exertion (RPE) were measured. No significant differences in performance were found for the repeated-sprint test parameters (total sprint time: 35.99 ± 1.32 seconds [LWup] and 36.12 ± 0.96 seconds [SWup]; best sprint time: 4.32 ± 0.13 seconds [LWup] and 4.30 ± 0.10 seconds [SWup]; and % sprint decrease: 4.16 ± 2.15% [LWup] and 5.02 ± 2.07% [SWup]). No differences in lactate concentration after the warm-up and after the repeated-sprint test were found. However, RPE and heart rate were significantly higher after the long warm-up and the repeated-sprint test compared with the short warm-up. It was concluded that a short warm-up is as effective as a long warm-up for repeated sprints in soccer. Therefore, in regular training, less warm-up time is needed; the extra time could be used for important soccer skill training.
Caffeine Attenuates Decreases in Leg Power Without Increased Muscle Damage
Authors: Ribeiro Beatriz G. , Morales Anderson P. , Sampaio-Jorge Felipe , Barth Thiago , de Oliveira Marcio B.C. , Coelho Gabriela M.d.O. , Leite Tiago C. 
Published: January 2016

Abstract
Ribeiro, BG, Morales, AP, Sampaio-Jorge, F, Barth, T, de Oliveira, MBC, Coelho, GMdO, and Leite, TC. Caffeine attenuates decreases in leg power without increased muscle damage. J Strength Cond Res 30(8): 2354–2360, 2016—Caffeine ingestion has been shown to be an effective ergogenic aid in several sports. Caffeine administration may increase exercise capacity, which could lead to a greater degree of muscle damage after exercise. This was a randomized, double-blind, placebo-controlled crossover study. Six male handball athletes ingested placebo (PLA) or caffeine (CAF) (6 mg·kg−1 body mass) capsules on 2 different occasions. Sixty minutes after ingestion of the capsules, serum CAF levels were evaluated. Thereafter, all participants performed a protocol of vertical jumps (VJs). The protocol consisted of 4 sets of 30 seconds of continuous VJs with 60 seconds of recovery between sets. Blood lactate (LAC) and creatine kinase (CK) levels were determined before and after the protocol. We found significant differences in serum CAF levels between PLA (0.09 ± 0.18 µg·ml−1) vs. CAF (6.59 ± 4.44 µg·ml−1) (p < 0.001). Caffeine elicited a 5.23% (p ≤ 0.05) improvement in the leg power compared with PLA. The CAF trial displayed higher LAC (p ≤ 0.05) compared with PLA (6.26 ± 2.01 vs. 4.39 ± 2.42 mmol·L−1, respectively) after protocol of VJs, whereas no difference in CK was observed between trials (p > 0.05). These results indicate that immediate ingestion of CAF (6 mg·kg−1 body weight) can reduce the level of muscle fatigue and preserve leg power during the test, possibly resulting in increase in LAC. There was no increase in muscle damage, which indicates that immediate administration of (6 mg·kg−1 body weight) CAF is safe. Thus, nutritional interventions with CAF could help athletes withstand a greater physiological overload during high-intensity training sessions. The results of this study would be applicable to sports and activities that require repetitive leg power.
Movement Profiles, Match Events, and Performance in Australian Football
Authors: Johnston Richard J. , Watsford Mark L. , Austin Damien J. , Pine Matthew J. , Spurrs Robert W. 
Published: January 2016

Abstract
Johnston, RJ, Watsford, ML, Austin, D, Pine, MJ, and Spurrs, RW. Movement profiles, match events, and performance in Australian football. J Strength Cond Res 30(8): 2129–2137, 2016—This study examined the relationship between movement demands, match events, and match performance in professional Australian football. Data were collected from 19 players using global positioning system units during 2 Australian Football League seasons. A range of movement demands and instantaneous power measures were collected. The players were divided into high-caliber (HC, ≥17/20) and low-caliber (LC, ≤8/20) groups based on the rating score by their coaches. A Mann-Whitney U-test, independent samples t-test, and effect sizes were used to determine whether any differences existed between the 2 groups. The HC group had a significantly higher match duration (7.2%), higher total distance (9.6%), and covered more distance and spent more time high-speed running per minute (12.7 and 11.9%). Although not significant, the effect sizes revealed that the HC group tended to have a higher mean metabolic power output (2.6%) and spent more time at the high power zone (7.9%). For the match event data, the HC group had significantly more involvements with the football. The results demonstrated the higher physical demands placed on the HC group. The findings suggest that analyzing instantaneous power measures can provide valuable information about the physical demands placed on team sport athletes to coaches and conditioning staff.
Heart Rate and Energy Expenditure in Division I Field Hockey Players During Competitive Play
Authors: Sell Katie M. , Ledesma Allison B. 
Published: January 2016

Abstract
Sell, KM and Ledesma, AB. Heart rate and energy expenditure in Division I field hockey players during competitive play. J Strength Cond Res 30(8): 2122–2128, 2016—The purpose of this study was to quantify energy expenditure and heart rate data for Division I female field hockey players during competitive play. Ten female Division I collegiate field hockey athletes (19.8 ± 1.6 years; 166.4 ± 6.1 cm; 58.2 ± 5.3 kg) completed the Yo-Yo intermittent endurance test to determine maximal heart rate. One week later, all subjects wore a heart rate monitor during a series of 3 matches in an off-season competition. Average heart rate (AvHR), average percentage of maximal heart rate (AvHR%), peak exercise heart rate (PExHR), and percentage of maximal heart rate (PExHR%), time spent in each of the predetermined heart rate zones, and caloric expenditure per minute of exercise (kcalM) were determined for all players. Differences between positions (backs, midfielders, and forwards) were assessed. No significant differences in AvHR, AvHR%, PExHR, PExHR%, and %TM were observed between playing positions. The AvHR% and PExHR% for each position fell into zones 4 (77–93% HRmax) and 5 (>93% HRmax), respectively, and significantly more time was spent in zone 4 compared with zones 1, 2, 3, and 5 across all players (p ≤ 0.05). The kcalM reflected very heavy intensity exercise. The results of this study will contribute toward understanding the sport-specific physiological demands of women's field hockey and has specific implications for the duration and schedule of training regimens.
Changes in Contributions of Swimming, Cycling, and Running Performances on Overall Triathlon Performance Over a 26-Year Period
Authors: Figueiredo Pedro , Marques Elisa A. , Lepers Romuald 
Published: January 2016

Abstract
Figueiredo, P, Marques, EA, and Lepers, R. Changes in contributions of swimming, cycling, and running performances on overall triathlon performance over a 26-year period. J Strength Cond Res 30(9): 2406–2415, 2016—This study examined the changes in the individual contribution of each discipline to the overall performance of Olympic and Ironman distance triathlons among men and women. Between 1989 and 2014, overall performances and their component disciplines (swimming, cycling and running) were analyzed from the top 50 overall male and female finishers. Regression analyses determined that for the Olympic distance, the split times in swimming and running decreased over the years (r
2 = 0.25–0.43, p ≤ 0.05), whereas the cycling split and total time remained unchanged (p > 0.05), for both sexes. For the Ironman distance, the cycling and running splits and the total time decreased (r
2 = 0.19–0.88, p ≤ 0.05), whereas swimming time remained stable, for both men and women. The average contribution of the swimming stage (∼18%) was smaller than the cycling and running stages (p ≤ 0.05), for both distances and both sexes. Running (∼47%) and then cycling (∼36%) had the greatest contribution to overall performance for the Olympic distance (∼47%), whereas for the Ironman distance, cycling and running presented similar contributions (∼40%, p > 0.05). Across the years, in the Olympic distance, swimming contribution significantly decreased for women and men (r
2 = 0.51 and 0.68, p < 0.001, respectively), whereas running increased for men (r
2 = 0.33, p = 0.014). In the Ironman distance, swimming and cycling contributions changed in an undulating fashion, being inverse between the two segments, for both sexes (p < 0.01), whereas running contribution decreased for men only (r
2 = 0.61, p = 0.001). These findings highlight that strategies to improve running performance should be the main focus on the preparation to compete in the Olympic distance; whereas, in the Ironman, both cycling and running are decisive and should be well developed.
Effect of Vitamin D Supplementation on Training Adaptation in Well-Trained Soccer Players
Authors: Jastrzębska Maria , Kaczmarczyk Mariusz , Jastrzębski Zbigniew 
Published: January 2016

Abstract
Jastrzębska, M, Kaczmarczyk, M, and Jastrzębski, Z. Effect of vitamin D supplementation on training adaptation in well-trained soccer players. J Strength Cond Res 30(9): 2648–2655, 2016—There is growing body of evidence implying that vitamin D may be associated with athletic performance, however, studies examining the effects of vitamin D on athletic performance are inconsistent. Moreover, very little literature exists about the vitamin D and training efficiency or adaptation, especially in high-level, well-trained athletes. The purpose of the current study was to investigate the effect of vitamin D supplementation on training adaptation in well-trained football players. The subjects were divided into 2 groups: the placebo group (PG) and the experimental group (SG, supplemented with vitamin D, 5,000 IU per day). Both groups were subjected to High Intensity Interval Training Program. The selection to the groups was based on peak power results attained before the experiment and position on the field. Blood samples for vitamin D level were taken from the players. In addition, total work, 5, 10, 20, and 30 m running speed, squat jump, and countermovement jump height were determined. There were no significant differences between SG and PG groups for any power-related characteristics at baseline. All power-related variables, except the 30 m sprint running time, improved significantly in response to interval training. However, the mean change scores (the differences between posttraining and pretraining values) did not differ significantly between SG and PG groups. In conclusion, an 8-week vitamin D supplementation in highly trained football players was not beneficial in terms of response to High Intensity Interval Training. Given the current level of evidence, the recommendation to use vitamin D supplements in all athletes to improve performance or training gains would be premature. To avoid a seasonal decrease in 25(OH)D level or to obtain optimal vitamin D levels, the combination of higher dietary intake and vitamin D supplementation may be necessary.
Acute Citrulline-Malate Supplementation and High-Intensity Cycling Performance
Authors: Cunniffe Brian , Papageorgiou Maria , O'Brien Barbara , Davies Nathan A. , Grimble George K. , Cardinale Marco 
Published: January 2016

Abstract
Cunniffe, B, Papageorgiou, M, O'Brien, B, Davies, NA, Grimble, GK, and Cardinale, M. Acute citrulline-malate supplementation and high-intensity cycling performance. J Strength Cond Res 30(9): 2638–2647, 2016—Dietary L-citrulline-malate (CM) consumption has been suggested to improve skeletal muscle metabolism and contractile efficiency, which would be expected to predispose exercising individuals to greater fatigue resistance. The purpose of this study was to examine the effects of CM supplementation on acid-base balance and high-intensity exercise performance. In a double-blind, placebo-controlled, crossover study, 10 well-trained males consumed either 12 g of CM (in 400 ml) or lemon sugar-free cordial (placebo [PL]) 60 minutes before completion of 2 exercise trials. Each trial consisted of subjects performing 10 (×15 seconds) maximal cycle sprints (with 30-second rest intervals) followed by 5 minutes recovery before completing a cycle time-to-exhaustion test (TTE) at 100% of individual peak power (PP). Significant increases in plasma concentrations of citrulline (8.8-fold), ornithine (3.9-fold), and glutamine (1.3-fold) were observed 60 minutes after supplementation in the CM trial only (p ≤ 0.05) and none of the subjects experienced gastrointestinal side-effects during testing. Significantly higher exercise heart rates were observed in CM condition (vs. PL) although no between trial differences in performance related variables (TTE: [120 ± 61 seconds CM vs. 113 ± 50 seconds PL]), PP or mean power, ([power fatigue index: 36 ± 16% CM vs. 28 ± 18% PL]), subjective rating of perceived exertion or measures of acid-base balance (pH, lactate, bicarbonate, base-excess) were observed (p > 0.05). This study demonstrated that acute supplementation of 12 g CM does not provide acute ergogenic benefits using the protocol implemented in this study in well-trained males.
Passive Recovery Promotes Superior Performance and Reduced Physiological Stress Across Different Phases of Short-Distance Repeated Sprints
Authors: Scanlan Aaron T. , Madueno Maria C. 
Published: January 2016

Abstract
Scanlan, AT and Madueno, MC. Passive recovery promotes superior performance and reduced physiological stress across different phases of short-distance repeated sprints. J Strength Cond Res 30(9): 2540–2549, 2016—Limited research has examined the influence of recovery modalities on run-based repeated-sprint (RS) performance with no data available relative to the sprint phase. This study compared run-based RS performance across various sprint phases and underlying physiological responses between active and passive recoveries. Nine students (21.8 ± 3.6 years; 171.3 ± 6.4 cm; 72.8 ± 12.2 kg) completed 2 bouts (active and passive recoveries) of 10 × 20 m sprints interspersed with 30 s recoveries in a randomized crossover fashion. Sprint times and decrements were calculated for each split (0–5, 5–15, 15–20, and 0–20 m) across each sprint. Blood lactate concentration ([BLa−]), heart rate (HR), and rating of perceived exertion (RPE) were measured at various time-points. Passive recovery promoted improved performance times (p ≤ 0.005) and decrements (p ≤ 0.045) across all splits, and lower post-test [BLa−] (p ≤ 0.005), HR (bout 3 onwards) (p ≤ 0.014), and RPE (bout 4 onwards) when compared with active recovery. Performance differences between recoveries were less pronounced across the 0–5 m split. Temporal analyses showed significant (p ≤ 0.05) increases in sprint times and decrements primarily with active recovery. The present data indicate that passive recovery promoted superior performance across run-based RS, with earlier performance deterioration and greater physiological load evident during active recovery. These findings can aid the manipulation of interbout activity across RS drills to promote physiological overload and adaptation during training. Further, coaches may develop tactical strategies to overcome the detrimental effects of active recovery and optimize sprint performance in athletes during game-play.
Off-Ice Anaerobic Power Does Not Predict On-Ice Repeated Shift Performance in Hockey
Authors: Peterson Ben J. , Fitzgerald John S. , Dietz Calvin C. , Ziegler Kevin S. , Baker Sarah E. , Snyder Eric M. 
Published: January 2016

Abstract
Peterson, BJ, Fitzgerald, JS, Dietz, CC, Ziegler, KS, Baker, SE, and Snyder, EM. Off-ice anaerobic power does not predict on-ice repeated shift performance in hockey. J Strength Cond Res 30(9): 2375–2381, 2016—Anaerobic power is a significant predictor of acceleration and top speed in team sport athletes. Historically, these findings have been applied to ice hockey although recent research has brought their validity for this sport into question. As ice hockey emphasizes the ability to repeatedly produce power, single bout anaerobic power tests should be examined to determine their ability to predict on-ice performance. We tested whether conventional off-ice anaerobic power tests could predict on-ice acceleration, top speed, and repeated shift performance. Forty-five hockey players, aged 18–24 years, completed anthropometric, off-ice, and on-ice tests. Anthropometric and off-ice testing included height, weight, body composition, vertical jump, and Wingate tests. On-ice testing consisted of acceleration, top speed, and repeated shift fatigue tests. Vertical jump (VJ) (r = −0.42; r = −0.58), Wingate relative peak power (WRPP) (r = −0.32; r = −0.43), and relative mean power (WRMP) (r = −0.34; r = −0.48) were significantly correlated (p ≤ 0.05) to on-ice acceleration and top speed, respectively. Conversely, none of the off-ice tests correlated with on-ice repeated shift performance, as measured by first gate, second gate, or total course fatigue; VJ (r = 0.06; r = 0.13; r = 0.09), WRPP (r = 0.06; r = 0.14; r = 0.10), or WRMP (r = −0.10; r = −0.01; r = −0.01). Although conventional off-ice anaerobic power tests predict single bout on-ice acceleration and top speed, they neither predict the repeated shift ability of the player, nor are good markers for performance in ice hockey.