[show abstract][hide abstract] ABSTRACT: The mechanisms for speed performance improvement from sprint (ST) and plyometrics (PT) training, especially relating to stance kinetics, require investigation in field sport athletes. This study determined the effects of ST and PT on 10-meter (m) sprint time (0-5, 5-10, 0-10 m intervals), step kinematics (step length and frequency, contact and flight time), and stance kinetics (first, second and last contact relative vertical [VF, VI], horizontal [HF, HI], and resultant [RF, RI] force and impulse; resultant ground reaction force angle [RFθ]; ratio of horizontal-to-resultant force [RatF]) during a 10-m sprint. Sixteen male field sport athletes were allocated into ST and PT groups according to 10-m sprint time; independent samples t-tests (p ≤ 0.05) indicated no between-group differences. Training involved two sessions per week for six weeks. A repeated measures analysis of variance (p ≤ 0.05) determined within- and between-subject differences. Both groups decreased 0-5 and 0-10 m time. The ST group increased step length by ∼15%, which tended to be greater than step length gains for the PT group (∼7%). The ST group reduced first and second contact RFθ and RatF, and second contact HF. Second contact HI decreased for both groups. Results indicated a higher post-training emphasis on VF production. VF changes were more pronounced for the PT group for the last contact, who increased or maintained last contact VI, RF, and RI to a greater extent than the ST group. Sprint and plyometrics training can improve acceleration, primarily through increased step length, and a greater emphasis on VF.
The Journal of Strength and Conditioning Research 10/2013; · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Field sport athletes must generate high velocities over short distances (10 meters [m] or less). The interaction between step kinematics (step length, step frequency, contact time, flight time) determines sprint velocity. This study determined the step kinematics that predicted 10-m sprint performance (0-5, 5-10, 0-10 m intervals) through stepwise multiple regression (p ≤ 0.05). Spearman's correlations (p ≤ 0.05) were also conducted between step kinematics and velocity for each interval. 0-5 m step length and 0-10 m contact time predicted 0-5 m velocity (R = 0.685; p = 0.006). 0-5 m contact time, and 5-10 m step length and step frequency predicted 5-10 m velocity (R = 0.715; p = 0.002). 5-10 m step length and step frequency predicted 0-10 m velocity (R = 0.606; p = 0.001). Correlations were found between 0-5 m velocity and step length in all intervals, and 0-5 m flight time (ρ = 0.406-0.515; p = 0.011-0.045). 0-10 m velocity correlated with 5-10 and 0-10 m step length, and 0-5 m flight time (ρ = 0.398-0.444; p = 0.026-0.048). Longer step lengths were integral for short sprint speed in field sport athletes. Step length should be developed in these athletes to improve short distance velocities.
[show abstract][hide abstract] ABSTRACT: The interaction between step kinematics and stance kinetics determines sprint velocity. However, the influence stance kinetics has upon effective acceleration in field sport athletes requires clarification. 25 men (age = 22.4 ± 3.2 years; mass = 82.8 ± 7.2 kilograms; height = 1.81 ± 0.07 m) completed 12 10-meter (m) sprints, 6 sprints each for kinematic and kinetic assessment. Pearson's correlations (p ≤ 0.05) examined relationships between: 0-5, 5-10, and 0-10 m velocity; step kinematics (mean step length [SL]; step frequency; contact time [CT]; flight time over each interval); and stance kinetics (relative vertical, horizontal, and resultant force and impulse; resultant force angle; ratio of horizontal to resultant force [RatF] for the first, second, and last contacts within the 10-m sprint). Relationships were found between 0-5, 5-10 and 0-10 m SL, and 0-5 and 0-10 m velocity (r = 0.397-0.535). 0-5 and 0-10 m CT correlated with 5-10 m velocity (r = -0.506 and -0.477, respectively). Last contact vertical force correlated with 5-10 m velocity (r = 0.405). Relationships were established between second and last contact vertical and resultant force, and contact time over all intervals (r = -0.398--0.569). First and second contact vertical impulse correlated with 0-5 m SL (r = 0.434 and 0.442, respectively). Subjects produced resultant force angles and RatF suitable for horizontal force production. Faster acceleration in field sport athletes involved longer steps, with shorter contact times. Greater vertical force production was linked with shorter contact times, illustrating efficient force production. Greater step lengths during acceleration were facilitated by higher vertical impulse, and appropriate horizontal force. Speed training for field sport athletes should be tailored to encourage these technique adaptations.
The Journal of Strength and Conditioning Research 12/2012; · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leg stiffness (Kleg) is an important component to consider in both performance and injury in the Australian Football League (AFL). Kleg has not yet been examined longitudinally throughout an entire AFL season. A unilateral hop test was employed to measure Kleg in the left and right legs of 25 professional AFL players (24.9 ± 4.3 years, 86.8 ± 8.1 kg, 187.0 ± 7.3 cm). Kleg was assessed at least once per month for each participant. Further, the session RPE method was used to quantify the average weekly training loads experienced by the participants. One-way ANOVA revealed no significant difference between the average monthly bilateral Kleg scores, however, average weekly training loads varied between 1400 to 2000 AU, depending on the training period. Thirteen participants were randomly selected to perform hop tests on two consecutive weeks. Reliability tests revealed these measurements to have a typical error of measurement (TEM) of 4.15%, and an intra-class correlation (ICC) of 0.8, proving the methods to be reliable. Although training intensity appears to vary, Kleg does not fluctuate significantly across an entire AFL season, suggesting that weekly training loads between 1400 and 2000 AU may be prescribed without the risk of fluctuating stiffness levels.
The Journal of Strength and Conditioning Research 09/2012; · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this research was to investigate the validity and the reliability of 5-Hz MinimaxX global positioning system (GPS) units measuring athlete movement demands. A team sport simulation circuit (files collected from each unit = 12) and flying 50-m sprints (files collected from each unit = 34) were undertaken, during which the total distance covered; peak speed; player load; the distance covered; time spent and number of efforts performed walking, jogging, running, high-speed running, and sprinting were examined. Movement demands were also separately categorized into low-intensity activity, high-intensity running, and very high-intensity running. The results revealed that GPS was a valid and reliable measure of total distance covered (p > 0.05, percentage typical error of measurement [%TEM] < 5%) and peak speed (p > 0.05, %TEM 5-10%). Further, GPS was found to be a reliable measure of player load (%TEM 4.9%) and the distance covered, time spent, and number of efforts performed at certain velocity zones (%TEM <5% to >10%). The level of GPS error was found to increase along with the velocity of exercise. The findings demonstrated that GPS is capable of measuring movement demands performed at velocities <20 km·h(-1), whereas more caution is to be exercised when analyzing movement demands collected by using GPS velocities >20 km·h(-1).
The Journal of Strength and Conditioning Research 03/2012; 26(3):758-65. · 1.80 Impact Factor
[show abstract][hide abstract] 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 Journal of Strength and Conditioning Research 11/2011; 26(10):2721-8. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leg stiffness is a modifiable mechanical property that may be related to soft tissue injury risk. The purpose of this study was to examine mean leg stiffness and bilateral differences in leg stiffness across an entire professional Australian Football League (AFL) season, and determine whether this parameter was related to the incidence of lower body soft tissue injury. The stiffness of the left and right legs of 39 professional AFL players (age 24.4 ± 4.4 years, body mass 87.4 ± 8.1 kg, stature 1.87 ± 0.07 m) was measured using a unilateral hopping test at least once per month throughout the season. Injury data were obtained directly from the head medical officer at the football club. Mean leg stiffness and bilateral differences in leg stiffness were compared between the injured and non-injured players. There was no difference between the season mean leg stiffness values for the injured (219.3 ± 16.1 N x m(-1) x kg(-1)) and non-injured (217.4 ± 14.9 N x m(-1) x kg(-1); P = 0.721) groups. The injured group (7.5 ± 3.0%) recorded a significantly higher season mean bilateral difference in leg stiffness than the non-injured group (5.5 ± 1.3%; P = 0.05). A relatively high bilateral difference in leg stiffness appears to be related to the incidence of soft tissue injury in Australian football players. This information is of particular importance to medical and conditioning staff across a variety of sports.
Journal of Sports Sciences 11/2011; 30(1):71-8. · 2.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: 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 Journal of Strength and Conditioning Research 09/2011; 26(6):1539-50. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Speed and acceleration are essential for field sport athletes. However, the mechanical factors important for field sport acceleration have not been established in the scientific literature. The purpose of this study was to determine the biomechanical and performance factors that differentiate sprint acceleration ability in field sport athletes. Twenty men completed sprint tests for biomechanical analysis and tests of power, strength, and leg stiffness. The sprint intervals analyzed were 0-5, 5-10, and 0-10 m. The subjects were split into a faster and slower group based on 0- to 10-m velocity. A 1-way analysis of variance determined variables that significantly (p ≤ 0.05) distinguished between faster and slower acceleration. All subject data were then pooled for a correlation analysis to determine factors contributing most to acceleration. The results showed that 0- to 5-m (∼16% difference) and 0- to 10-m (∼11% difference) contact times for the faster group were significantly lower. Times to peak vertical and horizontal force during ground contact were lower for the faster group. This was associated with the reduced support times achieved by faster accelerators and their ability to generate force quickly. Ground contact force profiles during initial acceleration are useful discriminators of sprint performance in field sport athletes. For the strength and power measures, the faster group demonstrated a 14% greater countermovement jump and 48% greater reactive strength index. Significant correlations were found between velocity (0-5, 5-10, and 0-10 m) and most strength and power measures. The novel finding of this study is that training programs directed toward improving field sport sprint acceleration should aim to reduce contact time and improve ground force efficiency. It is important that even during the short sprints required for field sports, practitioners focus on good technique with short contact times.
The Journal of Strength and Conditioning Research 08/2011; 25(10):2704-14. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Futsal is the Fédération de Internationale Football Association's officially recognized five-a-side indoor soccer, which although increasing in popularity worldwide, lacks the Australian or other English language research necessary to enable the growth of the sport. The purpose of this study was to establish a comprehensive overview of the demands of futsal by a time-motion analysis on 8 Australian National Team players and 10 State League Team players over 4 futsal matches. The study analyzed 6 locomotor activity categories, focusing on total distance covered, total duration of activities, total frequency of activities, effort distance, and effort duration. The national team covered a 42% greater overall distance than the state league team. In terms of relative data normalized for match duration, only the standing duration value was significantly different between the teams. Furthermore, futsal players of elite and subelite level in Australia perform a change in activity every 8-9 seconds on the court, and the national team athletes attained a higher, yet nonsignificant, average match-play velocity. This may be because of the national futsal athletes participating in an extended game duration, potentially suggesting that higher levels of competition facilitate a higher intensity of match play and greater physiological demands on individual players. Apart from the differences in timing structure and overall metabolic work, there was no real difference between the levels of competition within the Australian futsal analysis, although at higher levels of competition, there may be a need for more recovery because of the elevated intensity of the match. When comparing the data with other countries, however, Australian futsal players produce less distance and duration than Spanish futsal players.
The Journal of Strength and Conditioning Research 03/2011; 25(3):646-51. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Subjective notational analysis can be used to track players and analyse movement patterns during match-play of team sports such as futsal. The purpose of this study was to establish the validity and reliability of the Event Recorder for subjective notational analysis. A course was designed, replicating ten minutes of futsal match-play movement patterns, where ten participants undertook the course. The course allowed a comparison of data derived from subjective notational analysis, to the known distances of the course, and to GPS data. The study analysed six locomotor activity categories, focusing on total distance covered, total duration of activities and total frequency of activities. The values between the known measurements and the Event Recorder were similar, whereas the majority of significant differences were found between the Event Recorder and GPS values. The reliability of subjective notational analysis was established with all ten participants being analysed on two occasions, as well as analysing five random futsal players twice during match-play. Subjective notational analysis is a valid and reliable method of tracking player movements, and may be a preferred and more effective method than GPS, particularly for indoor sports such as futsal, and field sports where short distances and changes in direction are observed.
The Journal of Strength and Conditioning Research 03/2011; 25(3):852-9. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Hamstring strains remain one of the most prevalent injuries in Australian Rules football. The authors prospectively examined the relationship between musculotendinous stiffness of the hamstring and leg stiffness with hamstring injury in professional Australian Rules footballers during the 2006 season.
Higher hamstring stiffness and leg stiffness are related to noncontact, soft tissue hamstring injury risk in professional Australian Rules footballers.
Case-control study; Level of evidence, 3.
Unilateral hamstring stiffness and leg stiffness were assessed in 136 professional footballers in the month before the commencement of the competitive season. This information was then investigated relative to players who suffered noncontact, soft tissue hamstring injuries during either matches or training throughout the season to identify whether preseason stiffness was related to injury occurrence.
Fourteen tested players recorded acute, noncontact hamstring injuries, resulting in 3.3 ± 2.8 weeks of missed match play per injury. At preseason testing, the players who ended up sustaining a hamstring injury during the season recorded significantly higher mean hamstring stiffness (11%, P = .04) and leg stiffness (5%, P = .03). When considering the injured players, the leg stiffness of the involved limb was significantly higher than the noninjured players (P = .02), whereas hamstring stiffness was significantly higher on the noninvolved limb (P = .01). Further, those players who suffered a hamstring injury were significantly older than the noninjured players (P = .01).
It appears that a high bilateral hamstring stiffness and leg stiffness may be a determinant in the risk of sustaining a hamstring injury. Further, relatively lower hamstring stiffness in the involved limb of injured players appears to be associated with increased injury and may be related to a lack of strength. The information from stiffness assessment may allow medical staff to determine the hamstring risk status for individual players in team sports.
The American journal of sports medicine 10/2010; 38(10):2058-64. · 3.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this study was to investigate the effects of vibration exercise on postural steadiness performance in a healthy, older population. Forty-three healthy, older participants (23 men and 20 women, aged 73.5+/-4.5 yr) were randomly assigned to either a vibration group (VIB), an exercise without vibration group (EX) or a control group (CONT). The VIB and EX groups undertook static and dynamic bodyweight exercises three times per week for eight weeks. Static balance was assessed using a one-legged postural steadiness (OLPS) test. This test was performed prior to and immediately after the training period. OLPS improved significantly for the VIB intervention after eight weeks training (p<0.05) compared to the EX and CONT groups. The improvements in OLPS were significantly affected by the baseline values, with the largest changes evident for VIB participants with a poorer initial score (p<0.01). Vibration exercise can contribute to improved static one-legged balance in a healthy, older population. As improvements in OLPS were related to baseline values, vibration exercise as an intervention would appear to serve the most benefit for those that exhibit diminished postural control.
Journal of science and medicine in sport / Sports Medicine Australia. 06/2008; 12(4):440-4.
[show abstract][hide abstract] ABSTRACT: Vibration training is a relatively new exercise intervention. This study investigated the effects of vibration exercise on strength (force-producing capacity) and power in older adults who are healthy.
Thirty participants (mean age=73.7 years, SD=4.6) were randomly assigned to a vibration exercise training (VIB) group or an exercise without vibration training (EX) group. The interventions consisted of 3 sessions per week for 8 weeks. Outcome measures included isokinetic flexor and extensor strength and power of the hip, knee, and ankle.
The VIB group significantly improved ankle plantar flexor strength and power compared with the EX group. However, there were no significant differences between the VIB and EX groups for knee flexor or extensor strength.
Vibration training contributed to an increase in plantar flexor strength and power. However, the strength gains for the knee and hip flexors and extensors for the VIB group and the EX group were comparable. Future vibration protocols should explore different body positions to target muscles higher up on the leg.
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to examine the effect of proprioceptive neuromuscular facilitation (PNF) stretching on musculotendinous unit (MTU) stiffness of the ankle joint. Twenty active women were assessed for maximal ankle range of motion, maximal strength of planter flexors, rate of force development, and ankle MTU stiffness. Subjects were randomly allocated into an experimental (n = 10) group or control group (n = 10). The experimental group performed PNF stretching on the ankle joint 3 times per week for 4 weeks, with physiological testing performed before and after the training period. After training, the experimental group significantly increased ankle range of motion (7.8%), maximal isometric strength (26%), rate of force development (25%), and MTU stiffness (8.4%) (p < 0.001). Four weeks of PNF stretching contributed to an increase in MTU stiffness, which occurred concurrently with gains to ankle joint range of motion. The results confirm that MTU stiffness and joint range of motion measurements appear to be separate entities. The increased MTU stiffness after the training period is explained by adaptations to maximal isometric muscle contractions, which were a component of PNF stretching. Because a stiffer MTU system is linked with an improved the ability to store and release elastic energy, PNF stretching would benefit certain athletic performance due to a reduced contraction time or greater mechanical efficiency. The results of this study suggest PNF stretching is a useful modality at increasing a joint's range of motion and its strength.
The Journal of Strength and Conditioning Research 05/2007; 21(2):572-7. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: The reduced physiological capacity evident with ageing may affect the ability to perform many tasks, potentially affecting quality of life. Previous research has clearly demonstrated the reduced capacity of the respiratory system with ageing and described the effect that habitual physical activity has upon this decline. This research aimed to examine the influence of age on respiratory muscle (RM) function and the relationship between RM function and physical performance within the Australian population. Seventy-two healthy older adults (50-79 years) were divided into males (n=36) and females (n=36) and examined for pulmonary function, RM strength, inspiratory muscle endurance (IME) and 1.6 km walking performance. There were no significant age by gender effects for any variables; however, ageing was significantly related to reduced RM function and walking capacity within each gender. Furthermore, regression analysis showed that the RM strength could be predicted from age. Partial correlations controlling for age indicated that expiratory muscle strength was significantly related to walking performance in males (p=0.04), whilst IME contributed significantly to walking performance in all participants. These within-gender effects and relationships indicate that RM strength is an important physiological variable to maintain in the older population, as it may be related to functional ability.
Journal of Science and Medicine in Sport 03/2007; 10(1):36-44. · 2.90 Impact Factor
[show abstract][hide abstract] ABSTRACT: Acceleration is a significant feature of game-deciding situations in the various codes of football. However little is known about the acceleration characteristics of football players, the effects of acceleration training, or the effectiveness of different training modalities. This study examined the effects of resisted sprint (RS) training (weighted sled towing) on acceleration performance (0-15 m), leg power (countermovement jump [CMJ], 5-bound test [5BT], and 50-cm drop jump [50DJ]), gait (foot contact time, stride length, stride frequency, step length, and flight time), and joint (shoulder, elbow, hip, and knee) kinematics in men (N = 30) currently playing soccer, rugby union, or Australian football. Gait and kinematic measurements were derived from the first and second strides of an acceleration effort. Participants were randomly assigned to 1 of 3 treatment conditions: (a) 8-week sprint training of two 1-h sessions x wk(-1) plus RS training (RS group, n = 10), (b) 8-week nonresisted sprint training program of two 1-h sessions x wk(-1) (NRS group, n = 10), or (c) control (n = 10). The results indicated that an 8-week RS training program (a) significantly improves acceleration and leg power (CMJ and 5BT) performance but is no more effective than an 8-week NRS training program, (b) significantly improves reactive strength (50DJ), and (c) has minimal impact on gait and upper- and lower-body kinematics during acceleration performance compared to an 8-week NRS training program. These findings suggest that RS training will not adversely affect acceleration kinematics and gait. Although apparently no more effective than NRS training, this training modality provides an overload stimulus to acceleration mechanics and recruitment of the hip and knee extensors, resulting in greater application of horizontal power.
The Journal of Strength and Conditioning Research 03/2007; 21(1):77-85. · 1.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Two popular methods of assessing lower body musculotendinous stiffness include the hopping and oscillation tests. The disparity and paucity of reliability data prompted this investigation into leg musculotendinous stiffness (Kleg) and ankle musculotendinous stiffness (Kank) measures. Kleg and Kank were assessed on three separate occasions in 20 female subjects. Kleg was determined using bilateral hopping procedures conducted at 2.2 Hz and 3.2 Hz frequencies. Kank was assessed by perturbation of the subject's ankle musculotendinous unit on an instrumented calf raise apparatus at 70% of maximum isometric force (MIF). Excellent reliability was produced for all Kleg measures between all days, whereas Kank exhibited acceptable reliability after one session of familiarization. No relationship was evident between Kleg and Kank. It was concluded that no familiarization session was required for Kleg at the test frequencies and conditions tested, whereas at least one familiarization session was needed to ensure the reliable assessment of Kank.
Journal of applied biomechanics 12/2006; 22(4):296-304. · 1.26 Impact Factor