Physiological responses and time-motion characteristics of 4-a-side small-sided game in young soccer players: the influence of different team formation methods

ABSTRACT: K?klü, Y, Ers?z, G, Alemdaro?lu, U, A???, A, and ?zkan, A. Physiological responses and time-motion characteristics of 4-A-side small-sided game in young soccer players: The influence of different team formation methods. J Strength Cond Res 26(11): 3118-3123, 2012-The purpose of this study was to examine the influence of different team formation methods on the physiological responses to and time-motion characteristics of 4-a-side small-sided games (SSG4) in young soccer players. Thirty-two young soccer players (age 16.2 ± 0.7 years; height 172.9 ± 6.1 cm; body mass 64.1 ± 7.7 kg) voluntarily participated in this study. Anthropometric measurements, technical tests, and maximum oxygen uptake (V[Combining Dot Above]O2max) tests were carried out on the players. The SSG4 teams were then created using 4 different methods: according to the coaches' subjective evaluation (CE), technical scores (TS), V[Combining Dot Above]O2max (AP), and V[Combining Dot Above]O2max multiplied by TSs (CG). The teams thus created played 4 bouts of SSG4 at 2-day intervals. During the SSG4, heart rate (HR) responses, distance covered, and time spent in HRmax zones were recorded. In addition, rating of perceived exertion (RPE) and blood lactate level (La) were determined at the end of the last bout of each SSG4. Percent of HRmax (%HRmax), La, and RPE responses during SSG4 were significantly higher for teams chosen according to AP and CG compared with that according to CE and TS (p < 0.05). In addition, teams chosen by AP and CG spent significantly more time in zone 4 (>90% HRmax ) and covered a greater distance in the high-intensity running zone (>18 km·h) than did teams formed according to TS. Moreover, AP teams covered significantly greater total distance than TS teams did (p < 0.05). In conclusion, to spend more time in both the high-intensity HR zone and the high-intensity running zone, the teams in SSG4 should be formed according to the players' V[Combining Dot Above]O2max values or the values calculated using both the V[Combining Dot Above]O2max and technique scores.     

Achievement of v[combining dot above]o2max criteria during a continuous graded exercise test and a verification stage performed by college athletes

ABSTRACT: Mier, CM, Alexander, RP, and Mageean, AL. Achievement of V[Combining Dot Above]O2max criteria during a continuous graded exercise test and a verification stage performed by college athletes. J Strength Cond Res 26(10): 2648-2654, 2012-The purpose of this study was to determine the incidence of meeting specific V[Combining Dot Above]O2max criteria and to test the effectiveness of a V[Combining Dot Above]O2max verification stage in college athletes. Thirty-five subjects completed a continuous graded exercise test (GXT) to volitional exhaustion. The frequency of achieving various respiratory exchange ratio (RER) and age-predicted maximum heart rate (HRmax) criteria and a V[Combining Dot Above]O2 plateau within 2 and 2.2 ml·kg·min (<2SD of the expected increase in V[Combining Dot Above]O2) were measured and tested against expected frequencies. After 10 minutes of active recovery, 10 subjects who did not demonstrate a plateau completed a verification stage performed at supramaximal intensity. From the GXT, the number of subjects meeting V[Combining Dot Above]O2max plateau was 5 (≤2 ml·kg·min) and 7 (≤2.2 ml·kg·min), RER criteria 34 (≥1.05), 32 (≥1.10), and 24 (≥1.15), HRmax criteria, 35 (<85%), 29 (<10 b·min) and 9 (HRmax). The V[Combining Dot Above]O2max and HRmax did not differ between GXT and the verification stage (53.6 ± 5.6 vs. 55.5 ± 5.6 ml·kg·min and 187 ± 7 vs. 187 ± 6 b·min); however, the RER was lower during the verification stage (1.15 ± 0.06 vs. 1.07 ± 0.07, p = 0.004). Six subjects achieved a similar V[Combining Dot Above]O2 (within 2.2 ml·kg·min), whereas 4 achieved a higher V[Combining Dot Above]O2 compared with the GXT. These data demonstrate that a continuous GXT limits the college athlete's ability to achieve V[Combining Dot Above]O2max plateau and certain RER and HR criteria. The use of a verification stage increases the frequency of V[Combining Dot Above]O2max achievement and may be an effective method to improve the accuracy of V[Combining Dot Above]O2max measurements in college athletes.     

Prior eccentric exercise reduces v[combining dot above]o2peak and ventilatory threshold but does not alter movement economy during cycling exercise

Exercise-induced muscle damage (EIMD) has been shown to reduce force production and result in delayed-onset soreness and pain in the damaged muscle(s). Cycling in the presence of EIMD reduces peak power output and time-trial performance. However, its effect on peak aerobic capacity has not been widely studied. The purpose of this study was to examine the impact of EIMD targeted specifically to the quadriceps muscle group on peak oxygen consumption (V[Combining Dot Above]O2peak) during cycling. Ten participants (4 men, 6 women) completed a V[Combining Dot Above]O2peak test on a cycle ergometer before and 48 hours after performing 24 eccentric contractions with their right and left quadriceps with a weight equal to 120% of 1-repetition maximal concentric strength (1RM). The EIMD was assessed using 1RM, and muscle soreness was assessed using a 100-mm visual analog scale. The presence of EIMD was confirmed by a 9% reduction in 1RM (p = 0.0001) and increased ratings of soreness from 2.4 ± 2.1 to 24.6 ± 10.8 mm (p = 0.001). The V[Combining Dot Above]O2peak was reduced from 46.2 ± 9.7 to 41.8 ± 10.7 ml·kg·min (10%; p = 0.01) with participants terminating exercise at lower heart rates 191 ± 9 vs. 186 ± 10 b·min (p = 0.02) and power output 248 ± 79 vs. 238 ± 81 W (p = 0.02) after EIMD. Additionally, ventilatory threshold decreased from 34.2 ± 7.8 to 30.5 ± 8.5 ml·kg·min (11%; p = 0.031). Despite the reduction in V[Combining Dot Above]O2peak, cycling economy (p = 0.17) did not differ pre-EIMD and post-EIMD. These findings indicate that EIMD reduced peak aerobic exercise capacity to an extent that could result in meaningful reductions in exercise performance. The reduction is likely attributable to a combination of reduced strength, earlier accumulation of lactic acid, and heightened muscle pain during exercise.     

Effects of isocaloric carbohydrate vs. carbohydrate-protein supplements on cycling time to exhaustion

The purpose of this study was to investigate the effects of isocaloric carbohydrate (CHO) and carbohydrate-protein (CHO-Pro) supplements on time to exhaustion. Eleven moderately aerobically fit adults (V[Combining Dot Above]O2max= 48.3 ± 6.5 ml·kg·min) performed a maximal cycle ergometer test for the determination of V[Combining Dot Above]O2max. At least 72 hours later, the participants performed a time-to-exhaustion test at a power output equivalent to the power output when subjects were at 75% of their V[Combining Dot Above]O2max. Either the CHO or the CHO-Pro supplement was administered at 0, 30, 60, 90, and 120 minutes after this test. After 3 hours of recovery and supplement ingestion, a second time-to-exhaustion test was performed. This testing protocol was repeated for the third visit, but the supplement not given during the second visit was administered. The results indicated that there was no significant difference in time to exhaustion after isocaloric CHO (pretest 22.4 ± 2.84 minutes, posttest 25.4 ± 4.45 minutes) and CHO-Pro (pretest 22.3 ± 3.46 minutes, posttest 24.0 ± 5.08 minutes) supplementation. Carbohydrate and CHO-Pro ingestion after exercise appear to have similar effects on short-term recovery.     

Metabolic response of different high-intensity aerobic interval exercise protocols

ABSTRACT: Gosselin, LE, Kozlowski, KF, DeVinney-Boymel, L, and Hambridge, C. Metabolic response of different high-intensity aerobic interval exercise protocols. J Strength Cond Res 26(10): 2866-2871, 2012-Although high-intensity sprint interval training (SIT) employing the Wingate protocol results in significant physiological adaptations, it is conducted at supramaximal intensity and is potentially unsafe for sedentary middle-aged adults. We therefore evaluated the metabolic and cardiovascular response in healthy young individuals performing 4 high-intensity (～90% V[Combining Dot Above]O2max) aerobic interval training (HIT) protocols with similar total work output but different work-to-rest ratio. Eight young physically active subjects participated in 5 different bouts of exercise over a 3-week period. Protocol 1 consisted of 20-minute continuous exercise at approximately 70% of V[Combining Dot Above]O2max, whereas protocols 2-5 were interval based with a work-active rest duration (in seconds) of 30/30, 60/30, 90/30, and 60/60, respectively. Each interval protocol resulted in approximately 10 minutes of exercise at a workload corresponding to approximately 90% V[Combining Dot Above]O2max, but differed in the total rest duration. The 90/30 HIT protocol resulted in the highest V[Combining Dot Above]O2, HR, rating of perceived exertion, and blood lactate, whereas the 30/30 protocol resulted in the lowest of these parameters. The total caloric energy expenditure was lowest in the 90/30 and 60/30 protocols (～150 kcal), whereas the other 3 protocols did not differ (～195 kcal) from one another. The immediate postexercise blood pressure response was similar across all the protocols. These finding indicate that HIT performed at approximately 90% of V[Combining Dot Above]O2max is no more physiologically taxing than is steady-state exercise conducted at 70% V[Combining Dot Above]O2max, but the response during HIT is influenced by the work-to-rest ratio. This interval protocol may be used as an alternative approach to steady-state exercise training but with less time commitment.     

Modeling and relationship of respiratory exchange ratio to athletic performance

Previous research has related the results of tests of maximum aerobic capacity to performance for endurance athletes. These results are often only able to predict the running velocity of races such as the marathon. This investigation sought to determine the absolute V[Combining Dot Above]O2 at various respiratory exchange ratio (RER) values (0.85, 0.90, 0.95, 1.0, 1.05, and 1.10) by using a third-order polynomial regression to model the physiological responses for V[Combining Dot Above]O2 and RER obtained from an assessment of maximum aerobic capacity. The V[Combining Dot Above]O2 determined was subsequently correlated to race performance. The participants in the study were selected from a population of National Collegiate Athletic Association Division 1 crosscountry runners (male n = 7, female n = 7, age 20.5 ± 0.9 years; height 170.3 ± 8.2 cm; weight 59.7 ± 8.7 kg; V[Combining Dot Above]O2max 57.0 ± 7.8 ml O2·kg·min). Third-order regression analysis resulted in strong curve fitting between the variables (r = 0.949 ± 0.03). Partial correlations (controlled for weight) were used to assess the relationship between oxygen consumption at the desired points of RER and race performance. The partial correlations revealed that the absolute oxygen consumptions at all RER points of interest were significantly correlated to race performance (r > 0.740, p < 0.01). There was a significant difference in the strength of the correlations for the points RER 0.95 (t = 2.68957, p = 0.01), 1.0 (t = 2.18516, p = 0.03), and 1.05 (t = 1.85668, p = 0.04) and the correlations found for RER 0.85. After converting the oxygen consumption at the RER points to estimated horizontal running speeds, only the estimate at RER 1.05 was not statistically different from the actual speed achieved in the culminating XC race. It can be suggested based upon these results that coaches of collegiate crosscountry runners who engage in metabolic testing of athletes examine the estimated running pace at RER 1.05 to gain an insight into a runner's potential.     

The effects of ionized and nonionized compression garments on sprint and endurance cycling

ABSTRACT: Burden, RJ and Glaister, M. The effects of ionized and nonionized compression garments on sprint and endurance cycling. J Strength Cond Res 26(10): 2837-2843, 2012-The aim of this study was to examine the effects of ionized and nonionized compression tights on sprint and endurance cycling performance. Using a randomized, blind, crossover design, 10 well-trained male athletes (age: 34.6 ± 6.8 years, height: 1.80 ± 0.05 m, body mass: 82.2 ± 10.4 kg, V[Combining Dot Above]O2max: 50.86 ± 6.81 ml·kg·min) performed 3 sprint trials (30-second sprint at 150% of the power output required to elicit V[Combining Dot Above]O2max [pV[Combining Dot Above]O2max] + 3 minutes recovery at 40% pV[Combining Dot Above]O2max + 30-second Wingate test + 3 minutes recovery at 40% pV[Combining Dot Above]O2max) and 3 endurance trials (30 minutes at 60% pV[Combining Dot Above]O2max + 5 minutes stationary recovery + 10-km time trial) wearing nonionized compression tights, ionized compression tights, or standard running tights (control). There was no significant effect of garment type on key Wingate measures of peak power (grand mean: 1,164 ± 219 W, p = 0.812), mean power (grand mean: 716 ± 68 W, p = 0.800), or fatigue (grand mean: 66.5 ± 6.9%, p = 0.106). There was an effect of garment type on blood lactate in the sprint and the endurance trials (p < 0.05), although post hoc tests only detected a significant difference between the control and the nonionized conditions in the endurance trial (mean difference: 0.55 mmol·L, 95% likely range: 0.1-1.1 mmol·L). Relative to control, oxygen uptake (p = 0.703), heart rate (p = 0.774), and time trial performance (grand mean: 14.77 ± 0.74 minutes, p = 0.790) were unaffected by either type of compression garment during endurance cycling. Despite widespread use in sport, neither ionized nor nonionized compression tights had any significant effect on sprint or endurance cycling performance.     

Improved v[combining dot above]o2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist

ABSTRACT: St?ren, ?, Bratland-Sanda, S, Haave, M, and Helgerud, J. Improved V[Combining Dot Above]O2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist. J Strength Cond Res 26(10): 2705-2711, 2012-The present study investigated to what extent more high aerobic intensity interval training (HAIT) and reduced training volume would influence maximal oxygen uptake (V[Combining Dot Above]O2max) and time trial (TT) performance in an elite national cyclist in the preseason period. The cyclist was tested for V[Combining Dot Above]O2max, cycling economy (Cc), and TT performance on an ergometer cycle during 1 year. Training was continuously logged using heart rate monitor during the entire period. Total monthly training volume was reduced in the 2011 preseason compared with the 2010 preseason, and 2 HAIT blocks (14 sessions in 9 days and 15 sessions in 10 days) were performed as running. Between the HAIT blocks, 3 HAIT sessions per week were performed as cycling. From November 2010 to February 2011, the cyclist reduced total average monthly training volume by 18% and cycling training volume by 60%. The amount of training at 90-95% HRpeak increased by 41%. V[Combining Dot Above]O2max increased by 10.3% on ergometer cycle. TT performance improved by 14.9%. Cc did not change. In conclusion, preseason reduced total training volume but increased amount of HAIT improved V[Combining Dot Above]O2max and TT performance without any changes in Cc. These improvements on cycling appeared despite that the HAIT blocks were performed as running. Reduced training time, and training transfer from running into improved cycling form, may be beneficial for cyclists living in cold climate areas.     

IGF-I, IGFBPs, and inflammatory cytokine responses during gender-integrated Israeli Army basic combat training

Insulin-like growth factor 1 (IGF-I) is a robust metabolic and anabolic biomarker that has been demonstrated to be reflective of military training-induced body composition changes and influenced by initial aerobic fitness level. Greater mechanistic insight into the IGF-I response to physical training can potentially be gleaned by also examining other regulatory factors that influence IGF-I biological activity (i.e., insulin-like growth factor-binding proteins [IGFBPs] and inflammatory cytokine responses). The purpose of this study was to assess the influence of sex and initial fitness level on the IGF-I and inflammatory cytokine response to gender-integrated Israeli Defense Forces (IDF) basic combat training (BCT). Recruits (29 men, 19.1 ± 1.3 years; 93 women, 18.8 ± 0.6 years) were recruited from a 4-month gender-integrated BCT of the IDF. Blood was drawn and assayed for total IGF-I, free IGF-I, IGFBPs 1-6, tumor necrosis factor alpha (TNF-α), interleukin 6, and interleukin 1 beta. Body composition was determined via a 4-site skinfold (biceps, triceps, suprailiac, and subscapular) equation. Physical performance was assessed via a maximum volume of oxygen consumption (V[Combining Dot Above]O?max) test using a treadmill protocol. All measures were obtained pre- and posttraining. A 2-way (sex × time) analysis of variance was used to test for statistical differences (p ≤ 0.05). Additionally, subjects were further partitioned (men and women separately) by tertiles of initial V[Combining Dot Above]O?max to assess the influence of initial fitness level on the IGF-I system and inflammatory cytokine responses to physical training. Pearson product moment correlational analysis was also used to examine relationships between percent changes in blood measures and physical performance and body composition changes. All data are presented as mean ± SE. Time effects were observed only for total IGF-I, IGFBP-2, TNF-α, V[Combining Dot Above]O?max, fat-free mass, and fat mass. The only significant (p ≤ 0.05) correlations observed for percent changes were in men between total IGF-I and V[Combining Dot Above]O?max (r = 0.49) and body mass (r = -0.42) During gender-integrated Israeli Army BCT, men and women generally respond in a similar fashion with regard to blood measures (IGF-I system and inflammatory cytokines) and V[Combining Dot Above]O?max. Initial fitness level only influenced the IGF-I response to training in women. Although the training-induced changes in total IGF-I (increase), IGFBP-2 (decrease), and TNF-α (decrease) are all indicative of an enhanced circulating anabolic milieu, only total IGF-I for the men was correlated with body composition and fitness improvements.     

No differences in O2-cost between V1 and V2 skating techniques during treadmill roller skiing at moderate to steep inclines

Elite crosscountry skiers use both the V1 and V2 techniques on moderate and steep inclines despite previous studies suggesting that the V1 technique is superior in terms of lower O2-cost and better performance on these inclines. However, this has not been studied in elite athletes, and therefore, the aim of this study was to compare O2-cost in these 2 main ski skating techniques in a group of 14 elite male crosscountry skiers (age: 24 ± 3 years, height: 184 ± 6 cm, weight: 79 ± 7 kg, V1 V[Combining Dot Above]O2max: 71.8 ± 3.5 ml·kg·min). With both techniques, the athletes performed submaximal trials for the determination of O2-cost on a roller ski treadmill at 4, 5, and 6° (3 m·s) and maximal trials at 8° (≥3 m·s) for the determination of V[Combining Dot Above]O2max. Video-based kinematic analyses on cycle length and cycle rate (CR) were performed to unravel if there was any relation between these variables and O2-cost. No significant differences in O2-cost or V[Combining Dot Above]O2max between techniques were found. However, large and significant individual variations in physiological response were observed. V2 had a longer cycle length and lower CR than V1 did. No significant correlation was found between CR and O2-cost. This study shows that both V1 and V2 are appropriate techniques for optimizing O2-cost on moderate to steep inclines in elite skiers. However, individual variation suggests that ski skating performance on moderate to steep inclines may be determined by technique preferences of the athletes.     

Effects of short-term quercetin supplementation on soldier performance

The purpose was to assess the short-term effects of quercetin supplementation on aerobically demanding soldier performance. In a double-blind crossover study, 16 male soldiers performed 3 days of aerobically demanding exercise under 3 conditions: Baseline (B), Placebo (P), and Quercetin (Q). Day 1 was a treadmill V[Combining Dot Above]O?peak test. Days 2 and 3 were identical, consisting of 75 minutes of loaded treadmill marching (LM) and a subsequent cycling time trial (TT) to complete 200 kJ of work. After B condition, the soldiers consumed 2 energy bars, each containing 0 mg (placebo) or 500 mg of quercetin (1,000 mg·d?1) for 8.5 days. Beginning day 6 of supplementation, the soldiers performed the 3 exercise days. There was a significant (p < 0.05) increase in plasma Q after Q supplementation. Repeated measures analyses of variance revealed no differences after P or Q supplementation as compared with B in V[Combining Dot Above]O?peak (B = 48.9 ± 1.1, P = 49.3 ± 1.1, Q = 48.8 ± 1.2 ml·kg?1·min?1) or TT time (B = 18.4 ± 1.0, P = 18.5 ± 1.1, Q = 18.3 ± 1.0 minutes [mean day 1 and day 2]). The respiratory exchange ratio during LM did not differ across treatments (B = 0.87 ± 0.03, P = 0.87 ± 0.03, Q = 0.86 ± 0.04 [mean day 1 and day 2]). Ratings of perceived exertion were not affected by Q supplementation during the V[Combining Dot Above]O?peak test, LM or TT. Supplementation of 1,000 mg·d?1 of quercetin for 8.5 days had no positive effect on aerobically demanding soldier performance. It is possible that a different dosing regimen, a combination of antioxidants or a different form of quercetin supplementation, may be needed to produce an increase in soldier performance.     

Perceptual and physiological responses to recovery from a maximal 30-second sprint

ABSTRACT: Glaister, M, Pattison, JR, Dancy, B, and McInnes, G. Perceptual and physiological responses to recovery from a maximal 30-second sprint. J Strength Cond Res 26(10): 2850-2857, 2012-The aims of this study were to evaluate perceptions of postexercise recovery and to compare patterns of perceived recovery with those of several potential mediating physiological variables. Seventeen well-trained men (age: 22 ± 4 years; height: 1.83 ± 0.05 m; body mass: 78.9 ± 7.6 kg; and body fat: 11.1 ± 2.2%) completed 10 sprint trials on an electromagnetically braked cycle ergometer. Trial 1 evaluated peak power via a 5-second sprint. The remaining trials evaluated (a) the recovery of peak power after a maximal 30-second sprint using rest intervals of 5, 10, 20, 40, 80, and 160 seconds; (b) perceived recovery via visual analog scales; and (c) physiological responses during recovery. The time point in recovery at which individuals perceived they had fully recovered was 163.3 ± 57.5 seconds. Power output at that same time point was 83.6 ± 5.2% of peak power. There were no significant differences between perceived recovery and the recovery processes of V[Combining Dot Above]O2 or minute ventilation (VE). Despite differences in the time courses of perceived recovery and the recovery of power output, individuals were able to closely predict full recovery without the need for external timepieces. Moreover, the time course of perceived recovery is similar to that of V[Combining Dot Above]O2 and VE.     

Performance changes following a field conditioning program in junior and senior rugby league players

This study investigated training loads, injury rates, and physical performance changes associated with a field conditioning program in junior and senior rugby league players. Thirty-six junior (16.9 [95% confidence interval: 16.7-17.1] years) and 41 senior (25.5 [23.6- 27.3] years) rugby league players participated in a 14-week preseason training program that included 2 field training sessions each week. Subjects performed measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility (L run), and maximal aerobic power (multistage fitness test) before and after training. Improvements in agility, muscular power, and maximal aerobic power were observed in both the junior and senior players following training; however, the improvement in maximal aerobic power and muscular power were greatest in the junior players. Training loads and injury rates were higher in the senior players. These findings demonstrate that junior and senior rugby league players adapt differently to a given training stimulus and that training programs should be modified to accommodate differences in training age.     

Role of energy systems in two intermittent field tests in women field hockey players

The energetics of 2 field tests that reflect physical performance in intermittent sports (i.e., the Interval Shuttle Sprint Test [ISST] and the Interval Shuttle Run Test [ISRT]) were examined in 21 women field hockey players. The ISST required the players to perform 10 shuttle sprints starting every 20 seconds. During the ISRT, players alternately ran 20-m shuttles for 30 seconds and walked for 15 seconds with increasing speed. Anaerobic and aerobic power tests included Wingate cycle sprints and a .V(O2)max cycle test, respectively. Based on correlation and regression analyses, it was concluded that for the ISST, anaerobic energetic pathways contribute mainly to energy supply for peak sprint time, while aerobic energetic pathways also contribute to energy supply for total sprint time. Energy during the ISRT is supplied mainly by the aerobic energy system. Depending on the aspect of physical performance a coach wants to determine, the ISST or ISRT can be used.     

Rocker-bottom, profile-type shoes do not increase lower extremity muscle activity or energy cost of walking

The purpose of this study was to determine if wearing rocker-bottom shoes with compliant midsoles (RB) influences muscle activity and metabolic cost of walking. Furthermore, we sought to determine if weight differences between shod conditions accounted for any potential change. Twenty-eight subjects (17 women, 11 men, age 22.8 ± 6.6 years; weight 72 ± 20 kg; height 170 ± 6.7 cm; percent body fat 23.0 ± 11.7) walked on a treadmill (0% grade) for 10 minutes at a self-selected speed plus 10% (1.3 ± 0.2 m·s) in each of the following laboratory-provided shoes: flat-bottomed shoe (W), flat-bottomed shoe weight-matched to RB (WM), and RB. Muscle activity of the right side biceps femoris (BF), rectus femoris (RF), gastrocnemius (GA), and tibalis anterior (TA) was recorded for 30 seconds at the beginning, middle, and ending of the 10-minute walk using an electromyography (EMG) system. The average (AVG) and root mean square (RMS) were calculated from full-wave rectified EMG data at each interval. The rate of oxygen consumption (V[Combining Dot Above]O2) was measured for 10 minutes during each condition. A 3 (shoe) × 3 (time) repeated-measures analysis of variance (ANOVA) was used to compare each EMG-dependent variable (AVG and RMS EMG of each muscle), and repeated measures ANOVA was used to test V[Combining Dot Above]O2. Muscle activity (for any muscle) was not influenced by the interaction of shoe and time (p > 0.05). The AVG and RMS for RF, BF, and GA, including V[Combining Dot Above]O2, were not different among shod conditions (W: 9.7 ± 0.6 ml·kg·min; WM: 10.0 ± 0.5 ml·kg·min; RB: 10.1 ± 0.5 ml·kg·min), whereas TA AVG and RMS were lower during RB (p < 0.05). It seems that there is no increase in muscle activity or metabolic cost while wearing RB beyond the flat-bottomed shoe despite there being the rocker-profile design and mass differences.     

Performance changes following training in junior rugby league players

The purpose of this study was to investigate the time course of adaptations to training in young (i.e., <15 years) and older (i.e., <18 years) junior rugby league players. Fourteen young (14.1 +/- 0.2 years) and 21 older (16.9 +/- 0.3 years) junior rugby league players participated in a 10-week preseason strength, conditioning, and skills program that included 3 sessions each week. Subjects performed measurements of standard anthropometry (i.e., height, body mass, and sum of 7 skinfolds), muscular power (i.e., vertical jump), speed (i.e., 10-m, 20-m, and 40-m sprint), agility (505 test), and estimated maximal aerobic power (i.e., multistage fitness test) before and after training. In addition, players underwent a smaller battery of fitness tests every 3 weeks to assess the time course of adaptation to the prescribed training stimulus. During the triweekly testing sessions, players completed assessments of upper-body (i.e., 60-second push-up, sit-up, and chin-up test) and lower-body (i.e., multiple-effort vertical jump test) muscular endurance. Improvements in maximal aerobic power and muscular endurance were observed in both the young and the older junior players following training. The improvements in speed, muscular power, maximal aerobic power, and upper-body muscular endurance were greatest in the young junior players, while improvements in lower-body muscular endurance were greatest in the older junior players. These findings demonstrate that young (i.e., <15 years) and older (i.e., <18 years) junior rugby league players adapt differently to a given training stimulus and that training programs should be modified to accommodate differences in maturational and training age. In addition, the results of this study provide conditioning coaches with realistic performance improvements following a 10-week preseason strength and conditioning program in junior rugby league players.     

Repeated-sprint ability and aerobic fitness

The purpose of this study was to reinvestigate the relationship between aerobic fitness and fatigue indices of repeated-sprint ability (RSA), with special attention to methodological normalization. Soldiers were divided into low (n = 10) and high (n = 9) fitness groups according to a preset maximal aerobic speed (MAS) of 17 km·h(-1) (～60 ml O2·kg(-1)·min) measured with the University of Montreal Track Test (UMTT). Subjects' assessment included the RSA test (3 sets of 5 40-m sprints with 1-minute rest between sprints and 1.5 minutes between sets), a 40-m sprint (criterion test used in the computation of fatigue indices for the RSA test), strength and power measurement of the lower limbs, and the 20-m shuttle run test (20-m SRT) and the UMTT, which are measures of maximal aerobic power. The highest correlation with the RSA fatigue indices was obtained with the 20-m SRT (r = 0.90, p = 0.0001, n = 19), a test with 180° direction changes and accelerations and decelerations. The lower correlation (r = 0.66, p < 0.01, n = 19) with the UMTT (continuous forward running) suggests that some aerobic tests better disclose the importance of aerobic fitness for RSA and that aerobic power is not the sole determinant of RSA. However, neither strength nor vertical jumping power was correlated to the RSA fatigue indices. Subjects with greater MAS were able to maintain almost constant level of speed throughout series of repeated sprints and achieved better recovery between series. A MAS of at least 17 km·h(-1) favors constant and high speed level during repeated sprints. From a practical point of view, a high aerobic fitness is a precious asset in counteracting fatigue in sports with numerous sprint repetitions.     

Physiological and anthropometric characteristics of elite women rugby league players

This study investigated the physiological and anthropometric characteristics of elite women rugby league players and developed physical performance standards for these athletes. Thirty-two elite women rugby league players underwent measurements of standard anthropometry (body mass, height, sum of 7 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility (505 test), glycolytic capacity (glycolytic agility test), and estimated maximal aerobic power (multistage fitness test). The skinfold thickness, speed, agility, vertical jump height, glycolytic capacity, and estimated maximal aerobic power results were 6.0-38.1% poorer than previously reported for elite women team sport athletes (e.g., rugby union, soccer, and hockey). Although no significant differences (p > 0.05) were detected between selected and nonselected players for any of the physiological or anthropometric characteristics, significant differences (p < 0.05) were detected between forwards and backs for body mass, skinfold thickness, 10-, 20-, and 40-m speed, and estimated maximal aerobic power. When data were analyzed according to positional similarities, it was found that the hit-up forwards positional group were heavier, had greater skinfold thickness, and had lower 10-, 20-, and 40-m speed, muscular power, glycolytic capacity, and estimated maximal aerobic power than the adjustables and outside backs positional groups. The results of this study show that elite women rugby league players have slower speed and agility, lower muscular power, glycolytic capacity, and estimated maximal aerobic power, and greater body mass and skinfold thickness than previously reported for other elite women team sport athletes. These findings show the need to develop all physiological parameters to allow elite women rugby league players to more effectively tolerate the physiological demands of competition, reduce fatigue-related errors in skill execution, and decrease the risk of injury.     

Physical responses of different small-sided game formats in elite youth soccer players

A major use of small-sided games (SSGs) in soccer training is the concomitant development of game-specific aerobic fitness. We hypothesize that the SSG formats of 2 vs. 2, 3 vs. 3, and 4 vs. 4 players reveal game-like intensities and therefore are most adequate to increase game-specific aerobic fitness. Heart rate (HR), percentage of maximum heart rate (HRmax), blood lactate concentration (La), and time-motion characteristics of 17 elite male youth soccer players (aged 14.9 ± 0.7 years, V[Combining Dot Above]O2max 61.4 ± 4.5 ml·kg·min, HRmax 199.6 ± 7.3 b·min) were collected by global positioning systems while performing the SSG formats. Repeated-measures analysis of variance and effect sizes were calculated to demonstrate the differences between SSG formats. Highest physiological responses were obtained in 2 vs. 2 (HR: 186 ± 7 b·min, HRmax: 93.3 ± 4.2%, La: 5.5 ± 2.4 mmol·L) followed by 3 vs. 3 (HR: 184 ± 8 b·min, HRmax: 91.5 ± 3.3%, La: 4.3 ± 1.7 mmol·L) and 4 vs. 4 (HR: 179 ± 7 b·min, HRmax 89.7 ± 3.4%, La: 4.4 ± 1.9 mmol·L). Pronounced differences were found for most physiological parameters and for time spent in the speed zones "walking" (<5.3 km·h), "moderate-speed running" (10.3-13.9 km·h), and "maximum sprinting" (≥26.8 km·h). The findings suggest that all the formats reveal game-like intensities and are suitable for aerobic fitness improvements. However, we found pronounced demands on the anaerobic energy supply in 2 vs. 2, whereas 3 vs. 3 and 4 vs. 4 remain predominantly on an aerobic level and differ mainly in the HR response. We suggest using 3 vs. 3 for soccer-specific aerobic fitness training.