The effects of different speed training protocols on sprint acceleration kinematics and muscle strength and power in field sport athletes

A variety of resistance training interventions are used to improve field sport acceleration (e.g., free sprinting, weights, plyometrics, resisted sprinting). The effects these protocols have on acceleration performance and components of sprint technique have not been clearly defined in the literature. This study assessed 4 common protocols (free sprint training [FST], weight training [WT], plyometric training [PT], and resisted sprint training [RST]) for changes in acceleration kinematics, power, and strength in field sport athletes. Thirty-five men were divided into 4 groups (FST: n = 9; WT: n = 8; PT: n = 9; RST: n = 9) matched for 10-m velocity. Training involved two 60-minute sessions per week for 6 weeks. After the interventions, paired-sample t-tests identified significant (p ≤ 0.05) within-group changes. All the groups increased the 0- to 5-m and 0- to 10-m velocity by 9-10%. The WT and PT groups increased the 5- to 10-m velocity by approximately 10%. All the groups increased step length for all distance intervals. The FST group decreased 0- to 5-m flight time and step frequency in all intervals and increased 0- to 5-m and 0- to 10-m contact time. Power and strength adaptations were protocol specific. The FST group improved horizontal power as measured by a 5-bound test. The FST, PT, and RST groups all improved reactive strength index derived from a 40-cm drop jump, indicating enhanced muscle stretch-shortening capacity during rebound from impacts. The WT group increased absolute and relative strength measured by a 3-repetition maximum squat by approximately 15%. Step length was the major limiting sprint performance factor for the athletes in this study. Correctly administered, each training protocol can be effective in improving acceleration. To increase step length and improve acceleration, field sport athletes should develop specific horizontal and reactive power.     

The effect of assisted and resisted sprint training on acceleration and velocity in Division IA female soccer athletes

This investigation evaluated the effects of a 4-week, 12-session training program using resisted sprint training (RST), assisted sprint training (AST), and traditional sprint training (TST) on maximal velocity and acceleration in National Collegiate Athletic Association (NCAA) Division IA female soccer athletes (n = 27). The subjects, using their respective training modality, completed 10 maximal effort sprints of 20 yd (18.3 m) followed by a 20-yd (18.3 m) deceleration to jog. Repeated measures multivariate analyses of variance and analyses of variance demonstrated significant (p < 0.001) 3-way interactions (time × distance × group) and 2-way interactions (time × group), respectively, for both velocity and acceleration. Paired t-tests demonstrated that maximum 40-yd (36.6-m) velocity increased significantly in both the AST (p < 0.001) and RST (p < 0.05) groups, with no change in the TST group. Five-yard (4.6-m), 15-yd (13.7 m), 5- to 15-yd (4.6- to 13.7-m) acceleration increased significantly (p < 0.01) in the AST group and did not change in the RST and TST groups. Fifteen- to 25-yd (13.7- to 22.9-m) acceleration increased significantly (p < 0.01) in the RST group, decreased significantly (p < 0.01) in the AST group, and was unchanged in the TST group. Twenty-five to 40-yd (22.9- to 36.6-m) acceleration increased significantly (p < 0.05) in the RST group and remained unchanged in the AST and TST groups. It is purposed that the increased 5-yd (4.6-m) and 15-yd (13.7-m) accelerations were the result of enhanced neuromuscular facilitation in response to the 12-session supramaximal training protocol. Accordingly, it is suggested that athletes participating in short distance acceleration events (i.e., ≤15 yd; ≤13.7 m) use AST protocols, whereas athletes participating in events that require greater maximum velocity (i.e., >15 yd; > 13.7 m) should use resisted sprint training protocols.     

Quantifying session ratings of perceived exertion for field-based speed training methods in team sport athletes

ABSTRACT: Lockie, RG, Murphy, AJ, Scott, BR, and Janse de Jonge, XAK. Quantifying session ratings of perceived exertion for field-based speed training methods in team sport athletes. J Strength Cond Res 26(10): 2721-2728, 2012-Session ratings of perceived exertion (session RPE) are commonly used to assess global training intensity for team sports. However, there is little research quantifying the intensity of field-based training protocols for speed development. The study's aim was to determine the session RPE of popular training protocols (free sprint [FST], resisted sprint [RST], and plyometrics [PT]) designed to improve sprint acceleration over 10 m in team sport athletes. Twenty-seven men (age = 23.3 ± 4.7 years; mass = 84.5 ± 8.9 kg; height = 1.83 ± 0.07 m) were divided into 3 groups according to 10-m velocity. Training consisted of an incremental program featuring two 1-hour sessions per week for 6 weeks. Subjects recorded session RPE 30 minutes post training using the Borg category-ratio 10 scale. Repeated measures analysis of variance found significant (p < 0.05) changes in sprint velocity and session RPE over 6 weeks. All groups significantly increased 0- to 5-m velocity and 0- to 10-m velocity by 4-7%, with no differences between groups. There were no significant differences in session RPE between the groups, suggesting that protocols were matched for intensity. Session RPE significantly increased over the 6 weeks for all groups, ranging from 3.75 to 5.50. This equated to intensities of somewhat hard to hard. Post hoc testing revealed few significant weekly increases, suggesting that session RPE may not be sensitive to weekly load increases in sprint and plyometric training programs. Another explanation, however, could be that the weekly load increments used were not great enough to increase perceived exertion. Nonetheless, the progressive overload of each program was sufficient to improve 10-m sprint performance. The session RPE values from the present study could be used to assess workload for speed training periodization within a team sports conditioning program.     

The effect of drag suit training on 50-m freestyle performance

Little research has evaluated the effects of drag suit training in swimming; these effects need to be explored further to optimize their use in training. For this 5-week training study, 18 subjects were divided evenly into 2 groups: control group and drag suit-trained group. Both groups performed weekly training routines that included 3 sprint sets. These sprint sets were performed by both the groups; however, the drag suit training group wore the drag suit, and the control group wore their typical training attire. We evaluated the swimmers' 50-m performance using a test set of six 50-m sprints on a 10-minute interval before and after the training program. The test set was performed twice (on 2 different days) where the swimmers were tested once in the drag suit and once in their regular training attire; the order of testing was randomized. Final time, stroke rate, and distance per stroke were collected. We observed that the drag suit-trained group exhibited a statistically significant decrease in distance per stoke while wearing the drag suit and the control group showed a significant increase in stroke rate and decrease in distance per stroke (in both suits). It is suggested to include some amounts of drag suit training in periods where swimming volume may decrease. Sets that are short in distance and performed at high intensity with sufficient rest to allow swimmers to maintain high stroke integrity should help athletes maintain techniques. We suggest incorporating the drag suit into the training regimen and should be considered a valuable resistive training device for swimming.     

A comparison of maximal squat strength and 5-, 10-, and 20-meter sprint times, in athletes and recreationally trained men

The purpose of this study was to identify whether there was a relationship between relative strength during a 1 repetition maximum (1RM) back squat and 5-, 10-, and 20-m sprint performances in both trained athletes and recreationally trained individuals. Professional rugby league players (n = 24) and recreationally trained individuals (n = 20) participated in this investigation. Twenty-meter sprint time and 1RM back squat strength, using free weights, were assessed on different days. There were no significant (p ≥ 0.05) differences between the well-trained and recreationally trained groups for 5-m sprint times. In contrast, the well-trained group's 10- and 20-m sprint times were significantly quicker (p = 0.004; p = 0.002) (1.78 + 0.06 seconds; 3.03 + 0.09 seconds) compared with the recreationally trained group (1.84 + 0.07 seconds; 3.13 + 0.11 seconds). The athletes were significantly stronger (170.63 + 21.43 kg) than the recreationally trained individuals (135.45 + 30.07 kg) (p = 0.01); however, there were no significant differences (p > 0.05) in relative strength between groups (1.78 + 0.27 kg/kg; 1.78 + 0.33 kg/kg, respectively). Significant negative correlations were found between 5-m sprint time and relative squat strength (r = -0.613, power = 0.96, p = 0.004) and between relative squat strength and 10- and 20-m sprint times in the recreationally trained group (r = -0.621, power = 0.51, p = 0.003; r = -0.604, power = 0.53, p = 0.005, respectively). These results, indicating that relative strength, are important for initial sprint acceleration in all athletes but more strongly related to sprint performance over greater distances in recreationally trained individuals.     

The Effects of a 6-Week Strength Training on Critical Velocity,Anaerobic Running Distance, 30-M Sprint and Yo-Yo Intermittent Running Test Performances in Male Soccer Players

The objectives of this study were to examine the effects of a moderate intensity strength training on changes in critical velocity (CV), anaerobic running distance (D''), sprint performance and Yo-Yo intermittent running test (Yo-Yo IR1) performances. Methods: two recreational soccer teams were divided in a soccer training only group (SO; n = 13) and a strength and soccer training group (ST; n = 13). Both groups were tested for values of CV, D'', Yo-Yo IR1 distance and 30-m sprint time on two separate occasions (pre and post intervention). The ST group performed a concurrent 6-week upper and lower body strength and soccer training, whilst the SO group performed a soccer only training. Results: after the re-test of all variables, the ST demonstrated significant improvements for both, YoYo IR1 distance (p = 0.002) and CV values (p<0.001) with no significant changes in the SO group. 30-m sprint performance were slightly improved in the ST group with significantly decreased performance times identified in the SO group (p<0.001). Values for D'' were slightly reduced in both groups (ST -44.5 m, 95% CI = -90.6 to 1.6; SO -42.6 m, 95% CI = -88.7 to 3.5). Conclusions: combining a 6-week moderate strength training with soccer training significantly improves CV, Yo-Yo IR1 whilst moderately improving 30-m sprint performances in non-previously resistance trained male soccer players. Critical Velocity can be recommended to coaches as an additional valid testing tool in soccer.     

The effects of ten weeks of resistance and combined plyometric/sprint training with the Meridian Elyte athletic shoe on muscular performance in women

The purpose of this investigation was to examine the combined effects of resistance and sprint/plyometric training with or without the Meridian Elyte athletic shoe on muscular performance in women. Fourteen resistance-trained women were randomly assigned to one of 2 training groups: (a) an athletic shoe (N = 6) (AS) group or (b) the Meridian Elyte (N = 8) (MS) group. Training was performed for 10 weeks and consisted of resistance training for 2 days per week and 2 days per week of sprint/plyometric training. Linear periodized resistance training consisted of 5 exercises per workout (4 lower body, 1 upper body) for 3 sets of 3-12 repetition maximum (RM). Sprint/plyometric training consisted of 5-7 exercises per workout (4-5 plyometric exercises, 40-yd and 60-yd sprints) for 3-6 sets with gradually increasing volume (8 weeks) followed by a 2-week taper phase. Assessments for 1RM squat and bench press, vertical jump, broad jump, sprint speed, and body composition were performed before and following the 10-week training period. Significant increases were observed in both AS and MS groups in 1RM squat (12.0 vs. 14.6 kg), bench press (6.8 vs. 7.4 kg), vertical jump height (3.3 vs. 2.3 cm), and broad jump (17.8 vs. 15.2 cm). Similar decreases in peak 20-, 40-, and 60-m sprint times were observed in both groups (20 m: 0.14 vs. 0.11 seconds; 40 m: 0.29 vs. 0.34 seconds; 60 m: 0.45 vs. 0.46 seconds in AS and MS groups, respectively). However, when sprint endurance (the difference between the fastest and slowest sprint trials) was analyzed, there was a significantly greater improvement at 60 m in the MS group. These results indicated that similar improvements in peak sprint speed and jumping ability were observed following 10 weeks of training with either shoe. However, high-intensity sprint endurance at 60 m increased to a greater extent during training with the Meridian Elyte athletic shoe.     

Maximal strength on different resistance training rowing exercises predicts start phase performance in elite kayakers

This study aimed to examine the relationship existing between maximum strength values in 2 common resistance training row exercises (bilateral bench pull [BBP] and one-arm cable row [OACR]) and short sprint performance in elite kayakers. Ten junior kayakers (5 women and 5 men) were tested on different days for 1 repetition maximum (1RM) and maximal voluntary isometric contraction in both exercises. Moreover, a 12-m sprint kayak was performed in a dew pond to record split times (2, 5, and 10 m), peak velocity, distance completed considering the first 8 strokes, and mean acceleration induced by right blade and left blade strokes. No differences (p > 0.05) were observed when right and left arms were compared in sprint testing or strength testing variables. Maximal strength values in BBP and OACR were significantly correlated with short sprint performance variables, showing the bilateral exercise with slightly stronger correlation coefficients than the unilateral seated row. Moreover, the relationship between strength testing and sprint testing variables is stronger when maximal force is measured through a dynamic approach (1RM) in comparison with an isometric approach. In conclusion, maximal strength in BBP and OACR is a good predictor of the start phase performance in elite sprint kayakers, mainly the 1RM value in BBP.     

Effects of sprint duration and exercise: rest ratio on repeated sprint performance and physiological responses in professional soccer players

The purpose of this study was to examine the physiological effects of different sprint repetition protocols on professional footballers. Of particular interest were the abilities of repeated sprint protocols to induce fatigue to an extent observed during competitive soccer. Six professional soccer players were assessed for fatigue rate and physiological responses of heart rate (HR), blood lactate (BLa), and rating of perceived exertion (RPE) during the performance of 4 repeated sprint drills, each totaling a sprint distance of 600 m. The 4 drills used 15- or 40-m sprints with 1:4 or 1:6 exercise: rest ratios. The 15-m sprint drill with 1:4 exercise:rest ratio induced the greatest fatigue (final sprint time 15% greater than initial sprint time) and greatest physiological responses. The 40-m sprint drill using a 1:4 exercise:rest ratio produced similar BLa and HR responses to the 15-m drill (13-14 mmol.L(-1) and 89% HRmax, respectively) but significantly lower RPE (mean +/- SD: 17.1 +/- 0.4 vs. 18.8 +/- 0.4, p < 0.05) and fatigue rates (11.1 vs. 15.0%, p < 0.01). Both sprint distance and exercise:rest ratio independently influenced fatigue rate, with the 15-m sprint distance and the 1:4 exercise:rest ratio inducing significantly (p < 0.01) greater fatigue than the 40-m sprint distance and the 1:6 exercise:rest ratio. The magnitude of fatigue during the 40- x 15-m sprint drill using a 1:6 exercise:rest ratio was 7.5%, which is close to the fatigue rate previously reported during actual soccer play. The present study is the first to examine both variations in sprint distances and rest ratios simultaneously, and the findings may aid the design of repeated sprint training for soccer.     

Force-velocity relationship and stretch-shortening cycle function in sprint and endurance athletes

This study examined the torque-velocity and power-velocity relationships of quadriceps muscle function, stretch shortening cycle function, and leg-spring stiffness in sprint and endurance athletes. Isokinetic maximal knee extension torque was obtained from 7 sprinters and 7 endurance athletes using a Con-trex isokinetic dynamometer. Torque and power measures were corrected for lean-thigh cross-sectional area and lean-thigh volume, respectively. Stretch-shortening cycle function and muscle stiffness measurements were obtained while subjects performed single-legged squat, countermovement, and drop-rebound jumps on an inclined sledge and force-plate apparatus. The results indicated that sprinters generated, on average, 0.15 +/- 0.05 N.m.cm(-2) more torque across all velocities compared with endurance athletes. Significant differences were also found in the power-velocity relationships between the 2 groups. The sprinters performed significantly better than the endurance athletes on all jumps, but there were no differences in prestretch augmentation between the groups. The average vertical leg stiffness during drop jumps was significantly higher for sprinters (5.86 N.m(-1)) compared with endurance runners (3.38 N.m(-1)). The findings reinforce the need for power training to be carried out at fast contraction speeds but also show that SSC function remains important in endurance running.     

Online video-based resistance training improves the physical capacity of junior basketball athletes

ABSTRACT: Klusemann, MJ, Pyne, DB, Fay, T, and Drinkwater, EJ. Online Video-Based Resistance Training Improves the Physical Capacity of Junior Basketball Athletes. J Strength Cond Res 26(10): 2677-2684, 2012-Junior basketball athletes require a well-designed resistance training program to improve their physical development. Lack of expert supervision and resistance training in junior development pathways may be overcome by implementing an online video-based program. The aim of this study was to compare the magnitude of improvement (change) in physical performance and strength and functional movement patterns of junior basketball athletes using either a fully supervised or an online video-based resistance training program. Thirty-eight junior basketball athletes (males, n = 17; age, 14 ± 1 year; height, 1.79 ± 0.10 m; mass, 67 ± 12 kg; females, n = 21; age, 15 ± 1 year; height, 1.70 ± 0.07 m; mass, 62 ± 8 kg) were randomly assigned into a supervised resistance training group (SG, n = 13), video training group (VG, n = 13) or control group (CG, n = 12) and participated in a 6-week controlled experimental trial. Pre- and posttesting included measures of physical performance (20-m sprint, step-in vertical jump, agility, sit and reach, line drill, and Yo-Yo intermittent recovery level 1), strength (15 s push-up and pull-up), and functional movement screening (FMS). Both SG and VG achieved 3-5% ± 2-4% (mean ± 90% confidence limits) greater improvements in several physical performance measures (vertical jump height, 20-m sprint time, and Yo-Yo endurance performance) and a 28 ± 21% greater improvement in push-up strength compared with the CG. The SG attained substantially larger gains in FMS scores over both the VG (12 ± 10%) and CG (13 ± 8%). Video-based training appears to be a viable option to improve physical performance and strength in junior basketball athletes. Qualified supervision is recommended to improve functional movement patterns in junior athletes.     

Effects of sprint and plyometric training on muscle function and athletic performance

The purpose of this study was to evaluate the effects of sprint training on muscle function and dynamic athletic performance and to compare them with the training effects induced by standard plyometric training. Male physical education students were assigned randomly to 1 of 3 groups: sprint group (SG; n = 30), plyometric group (PG; n = 30), or control group (CG; n = 33). Maximal isometric squat strength, squat- and countermovement jump (SJ and CMJ) height and power, drop jump performance from 30-cm height, and 3 athletic performance tests (standing long jump, 20-m sprint, and 20-yard shuttle run) were measured prior to and after 10 weeks of training. Both experimental groups trained 3 days a week; SG performed maximal sprints over distances of 10-50 m, whereas PG performed bounce-type hurdle jumps and drop jumps. Participants in the CG group maintained their daily physical activities for the duration of the study. Both SG and PG significantly improved drop jump performance (15.6 and 14.2%), SJ and CMJ height ( approximately 10 and 6%), and standing long jump distance (3.2 and 2.8%), whereas the respective effect sizes (ES) were moderate to high and ranged between 0.4 and 1.1. In addition, SG also improved isometric squat strength (10%; ES = 0.4) and SJ and CMJ power (4%; ES = 0.4, and 7%; ES = 0.4), as well as sprint (3.1%; ES = 0.9) and agility (4.3%; ES = 1.1) performance. We conclude that short-term sprint training produces similar or even greater training effects in muscle function and athletic performance than does conventional plyometric training. This study provides support for the use of sprint training as an applicable training method of improving explosive performance of athletes in general.     

The effect of 40-m repeated sprint training on maximum sprinting speed, repeated sprint speed endurance, vertical jump, and aerobic capacity in young elite male soccer players

The purpose of this study was to examine the effect of 10 weeks' 40-m repeated sprint training program that does not involve strength training on sprinting speed and repeated sprint speed on young elite soccer players. Twenty young well-trained elite male soccer players of age (±SD) 16.4 (±0.9) years, body mass 67.2 (±9.1) kg, and stature 176.3 (±7.4) cm volunteered to participate in this study. All participants were tested on 40-m running speed, 10 × 40-m repeated sprint speed, 20-m acceleration speed, 20-m top speed, countermovement jump (CMJ), and aerobic endurance (beep test). Participants were divided into training group (TG) (n = 10) and control group (CG) (n = 10). The study was conducted in the precompetition phase of the training program for the participants and ended 13 weeks before the start of the season; the duration of the precompetition period was 26 weeks. The TG followed a Periodized repeated sprint training program once a week. The training program consisted of running 40 m with different intensities and duration from week to week. Within-group results indicate that TG had a statistically marked improvement in their performance from pre to posttest in 40-m maximum sprint (-0.06 seconds), 10 × 40-m repeated sprint speed (-0.12 seconds), 20- to 40-m top speed (-0.05 seconds), and CMJ (2.7 cm). The CG showed only a statistically notable improvement from pre to posttest in 10 × 40-m repeated sprint speed (-0.06 seconds). Between-group differences showed a statistically marked improvement for the TG over the CG in 10 × 40-m repeated sprint speed (-0.07 seconds) and 20- to 40-m top speed (-0.05 seconds), but the effect of the improvement was moderate. The results further indicate that a weekly training with repeated sprint gave a moderate but not statistically marked improvement in 40-m sprinting, CMJ, and beep test. The results of this study indicate that the repeated sprint program had a positive effect on several of the parameters tested. However, because the sample size in this study is 20 participants, the results are valid only for those who took part in this study. Therefore, we advice to use repeated sprint training similar to the one in this study only in periods where the players have no speed training included in their program. Furthermore, the participants in this study should probably trained strength, however, benefits were observed even without strength training is most likely to be caused by the training specificity.     

Comparison of two twelve week off-season combined training programs on entry level collegiate soccer players' performance

Olympic-style lifts (OSL) and plyometric exercises (PE) are frequently combined with traditional resistance training (TRT) to improve athletic performance. The goal of this study was to directly compare the performance effect of TRT (30 minutes) combined with either OSL or nondepth-jump PE (15 minutes) on entry level competitive collegiate athletes. Ten female and 5 male competitive soccer players, divided into 2 groups, completed 12 weeks of tri-weekly training during their off-season. Countermovement vertical jump, 4 repetition maximum squat, 25-m sprint, and figure-8 drill on a 5-dot mat were conducted pre-, mid-, and postintervention. Significant improvements were made by both groups in each performance parameter over the 12-week period (p < 0.05), with no significant differences found between the training groups. Although these training modalities may achieve their results through slightly different mechanisms, the performance-related improvements may not be significantly different for entry-level collegiate athletes with little resistance training experience.     

Development and validation of a core endurance intervention program: implications for performance in college-age rowers

The objective of this study was to examine the effectiveness of a core endurance exercise protocol. Forty-five college-age rowers (age 21 +/- 1.0) were assigned to either a core training group [core group] (n = 25), which took part in a core endurance intervention exercise protocol, or to a control training group [control group] (n = 20), which was not given any specialized core training. Training took place 2 days per week for 8 weeks. Trunk endurance was assessed using flexion, extension, and side flexion tests, whereas a variety of functional performance measures were assessed (vertical jump, broad jump, shuttle run, 40-m sprint, overhead medicine ball throw, 2,000-m maximal rowing ergometer test). The results revealed significant improvement in the two side flexion tests for the core group (p < 0.05). Interestingly, significant differences were noted in the trunk extension test endurance times for the control group (p < 0.05), but not for the core group. No significant differences were found for any of the functional performance tests. In summary, the 8-week core endurance training program improved selected core endurance parameters in healthy young men, but the effectiveness of the core intervention on various functional performance aspects was not supported.     

Relationships between repeated sprint testing, speed, and endurance

Repeated sprint testing is gaining popularity in team sports, but the methods of data analysis and relationships to speed and endurance qualities are not well described. We compared three different methods for analyzing repeated sprint test results, and we quantified relationships between repeated sprints, short sprints, and endurance test scores. Well-trained male junior Australian Football players (n = 60, age 18.1 +/- 0.4 years, height 1.88 +/- 0.07 m, mass 82.0 +/- 8.1 kg; mean +/- SD) completed a 6 x 30-m repeated sprint running test on a 20-second cycle, a 20-m sprint test (short sprint), and the 20-m multistage shuttle run for endurance. Repeated sprint results were evaluated in three ways: total time for all six sprints (TOTAL), percent change from predicted times (PRED) from the fastest 30-m sprint time, and percent change from first to last sprint (CHANGE). We observed a very large decrement (CHANGE 6.3 +/- 0.7%, mean +/- 90% confidence limits) in 30-m performance from the first to last sprint (4.16 +/- 0.10 to 4.42 +/- 0.11 seconds, mean +/- SD). Results from TOTAL were highly correlated with 20-m sprint and 20-m multistage shuttle run tests. Performance decrements calculated by PRED were highly correlated with TOTAL (r = 0.91), but neither method was directly comparable with CHANGE (r = -0.23 and r = 0.12 respectively). TOTAL was moderately correlated with fastest 20-m sprint time (r = 0.66) but not the 20-m multistage shuttle run (r = -0.20). Evaluation of repeated sprint testing is sensitive to the method of data analysis employed. The total sprint time and indices of the relative decrement in performance are not directly interchangeable. Repeated sprint ability seems more related to short sprint qualities than endurance fitness.     

Is fiber mitochondrial volume density a good indicator of muscle fatigability to isometric exercise?

The relationship between the ratio of interfibrillar mitochondrial volume density (Vvmit) to myofibrillar volume density (Vvmyo) and isometric fatigue characteristics of the human triceps surae was determined in six bodybuilders, six endurance athletes, and six active controls before and after 16 wk of isometric training at 30 or 100% maximal voluntary contraction (MVC) in six sedentary subjects in a unilateral exercise model. Time to fatigue at 30% MVC was significantly less in sedentary subjects before training than in the other subject groups, but it was similar to the other groups posttraining. Stereological analyses of type I fibers indicated that Vvmit/Vvmyo was less in bodybuilders than in other subjects. Training at 30% MVC increased type I fiber Vvmit/Vvmyo of the soleus by 11% but did not affect the gastrocnemii. Training at 100% MVC did not alter Vvmit/Vvmyo in any muscle, nor was this ratio changed in type II fibers by either training program. Despite the morphological differences, both training protocols increased relative endurance, although greater fatigue resistance was seen after training at 30% MVC. Correlation analyses indicated that isometric endurance and improvements in muscle endurance by isometric exercise were not dependent on increasing interfibrillar Vvmit or Vvmit/Vvmyo in either fiber type.     

beta-Alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters.

Carnosine (beta-alanyl-l-histidine) is present in high concentrations in human skeletal muscle. The ingestion of beta-alanine, the rate-limiting precursor of carnosine, has been shown to elevate the muscle carnosine content. We aimed to investigate, using proton magnetic resonance spectroscopy (proton MRS), whether oral supplementation with beta-alanine during 4 wk would elevate the calf muscle carnosine content and affect exercise performance in 400-m sprint-trained competitive athletes. Fifteen male athletes participated in a placebo-controlled, double-blind study and were supplemented orally for 4 wk with either 4.8 g/day beta-alanine or placebo. Muscle carnosine concentration was quantified in soleus and gastrocnemius by proton MRS. Performance was evaluated by isokinetic testing during five bouts of 30 maximal voluntary knee extensions, by endurance during isometric contraction at 45% maximal voluntary contraction, and by the indoor 400-m running time. beta-Alanine supplementation significantly increased the carnosine content in both the soleus (+47%) and gastrocnemius (+37%). In placebo, carnosine remained stable in soleus, while a small and significant increase of +16% occurred in gastrocnemius. Dynamic knee extension torque during the fourth and fifth bout was significantly improved with beta-alanine but not with placebo. Isometric endurance and 400-m race time were not affected by treatment. In conclusion, 1) proton MRS can be used to noninvasively quantify human muscle carnosine content; 2) muscle carnosine is increased by oral beta-alanine supplementation in sprint-trained athletes; 3) carnosine loading slightly but significantly attenuated fatigue in repeated bouts of exhaustive dynamic contractions; and 4) the increase in muscle carnosine did not improve isometric endurance or 400-m race time.     

The relationship between kinematic determinants of jump and sprint performance in division I women soccer players

The purpose of this study was to determine the relationship between measures of unilateral and bilateral jumping performance and 10- and 25-m sprint performance. Fifteen division I women soccer players (height 165 ± 2.44 cm, mass 61.65 ± 7.7 kg, age 20.19 ± 0.91 years) volunteered to participate in this study. The subjects completed a 10- and 25-m sprint test. The following jump kinematic variables were measured using accelerometry: sprint time, step length, step frequency, jump height and distance, contact time, concentric contact time, and flight time (Inform Sport Training Systems, Victoria, BC, Canada). The following jumps were completed in random order: bilateral countermovement vertical jump, bilateral countermovement horizontal jump, bilateral 40-cm drop vertical jump, bilateral 40-cm drop horizontal jump, unilateral countermovement vertical jump (UCV), unilateral countermovement horizontal jump, unilateral 20-cm drop vertical jump (UDV), and unilateral 20-cm drop horizontal jump (UDH). The trial with the best jump height or distance, reactive strength (jump height or distance/total contact time), and flight time to concentric contact time ratio (FT/CCT) was recorded to analyze the relationship between jump kinematics and sprint performance. None of the bilateral jump kinematics significantly correlated with 10- and 25-m sprint time, step length, or step frequency. Right-leg jump height (r = -0.71, p = 0.006, SEE = 0.152 seconds), FT/CCT (r = -0.58, p = 0.04, SEE = 0.176 seconds), and combined right and left-leg jump height (r = -0.61) were significantly correlated with the 25-m sprint time during the UCV. Right-leg FT/CCT was also significantly related to 25-m step length (r = 0.68, p = 0.03, SEE = 0.06 m) during the UDV. The combined right and left leg jump distance to standing height ratio during the UDH significantly correlated (r = -0.58) with 10-m sprint time. In comparison to bilateral jumps, unilateral jumps produced a stronger relationship with sprint performance.     

Effect of creatine supplementation on intermittent sprint running performance in highly trained athletes

This study examined the impact of short-term (7-day), high-dose (0.35 g.kg(-1).d(-1)) oral creatine monohydrate supplementation (CrS) on single sprint running performance (40 m, <6 seconds) and on intermittent sprint performance in highly trained sprinters. Nine subjects completed the double-blind cross-over design with 2 supplementation periods (placebo and creatine) and a 7-week wash-out period. A test protocol consisting of 40-m sprint runs was performed, and running velocity was continuously recorded over the total distance. The maximal sprint performance, the relative degree of fatigue at the end of intermittent sprint exercise (6 x 40 m, 30-second rest interval), as well as the degree of recovery (120-second passive rest) remained unchanged following CrS. There were no significant changes related to CrS in absolute running velocity at any distance between start and finish (40 m). It was concluded that no ergogenic effect on single or repeated 40-m sprint times with varying rest periods was observed in highly trained athletes.