Sports Biomech. 2008 May;7(2):160-72.
In this study, we compared sprint kinematics of sled towing and vest sprinting with the same relative loads. Twenty athletes performed 30-m sprints in three different conditions: (a) un-resisted, (b) sled towing, and (c) vest sprinting. During sled towing and vest sprinting, external loads of 15% and 20% of body mass were used. Sprint times were recorded over 10 and 30 m. Sagittal-plane high-speed video data were recorded at 5, 15, and 25 m from the start. Relative to the un-resisted condition, sprint time increased (7.5 to 19.8%) in both resisted conditions, resulting mainly from decreased step length (-5.2 to -16.5%) with small decreases in step frequency (-2.7 to -6.1%). Sled towing increased stance phase duration (14.7 to 26.0%), trunk angle (12.5 to 71.5%), and knee angle (10.3 to 22.7%), and decreased swing phase duration (-4.8 to -15.2%) relative to the un-resisted condition. Vest sprinting increased stance phase duration (12.8 to 24.5%) and decreased swing phase duration (-8.4 to -14.4%) and trunk angle (-1.7 to -13.0%). There were significant differences between the two resisted conditions in trunk, thigh, and knee angles. We conclude that sled towing and vest sprinting have different effects on some kinematics and hence change the overload experienced by muscle groups.
Effects of three types of resisted sprint training devices on the kinematics of sprinting at maximum velocity.
J Strength Cond Res. 2008 May;22(3):890-7.
Resisted sprint running is a common training method for improving sprint-specific strength. For maximum specificity of training, the athlete's movement patterns during the training exercise should closely resemble those used when performing the sport. The purpose of this study was to compare the kinematics of sprinting at maximum velocity to the kinematics of sprinting when using three of types of resisted sprint training devices (sled, parachute, and weight belt). Eleven men and 7 women participated in the study. Flying sprints greater than 30 m were recorded by video and digitized with the use of biomechanical analysis software. The test conditions were compared using a 2-way analysis of variance with a post-hoc Tukey test of honestly significant differences. We found that the 3 types of resisted sprint training devices are appropriate devices for training the maximum velocity phase in sprinting. These devices exerted a substantial overload on the athlete, as indicated by reductions in stride length and running velocity, but induced only minor changes in the athlete's running technique. When training with resisted sprint training devices, the coach should use a high resistance so that the athlete experiences a large training stimulus, but not so high that the device induces substantial changes in sprinting technique. We recommend using a video overlay system to visually compare the movement patterns of the athlete in unloaded sprinting to sprinting with the training device. In particular, the coach should look for changes in the athlete's forward lean and changes in the angles of the support leg during the ground contact phase of the stride.
The effects of resisted sled-pulling sprint training on acceleration and maximum speed performance.
J Sports Med Phys Fitness. 2007 Mar;47(1):133. No abstract available.
The effects of resisted sprint training on acceleration performance and kinematics in soccer, rugby union, and Australian football players.
J Strength Cond Res. 2007 Feb;21(1):77-85.
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 effects of resisted sled-pulling sprint training on acceleration and maximum speed performance.
J Sports Med Phys Fitness. 2005 Sep;45(3):284-90.
AIM: The purpose of the present study was to examine the effects of resisted (RS) and un-resisted (US) sprint training programs on acceleration and maximum speed performance. METHODS: Twenty-two male students (age 20.1+/-1.9 y, height 1.78+/-7 cm, and weight 73+/-2 kg) completed RS (n=11) or US (n=11) sprint training programs. The RS group followed a sprint-training program with 5 kg sled pulling and the US group followed a similar sprint-training program without sled pulling. The training program consisted of 4x20 m and 4x50 m maximal runs, and was applied 3 times/week for 8 weeks. Before and after the training programs the subjects performed a 50 m run and the running velocity of 0-10 m, 10-20 m, 20-40 m and 40-50 m was measured. In addition, stride length and stride frequency were evaluated at the 3(rd) stride in acceleration phase and between 42-47 m in maximum speed phase. RESULTS: The RS improved running velocity in the run sections 0-10 m and 0-20 m, while in US group the running velocity in all run sections in acceleration phase remained unchanged. In contrast, RS training had no effect on running velocity in maximum speed phase, whereas US improved running velocity in 20-40 m, 40-50 m, and 20-50 m run sections. Stride rate increased only after RS in acceleration phase (+7.1%), whereas stride length increased only after US in maximum speed phase (+5.5%). CONCLUSION: Sprint training with 5 kg sled pulling for 8 weeks improves acceleration performance (0-20), while un-resisted sprint training improves performance in maximum speed phase (20-40) in non-elite athletes. It appears that each phase of sprint run demands a specific training approach.
Effects of resisted sled towing on sprint kinematics in field-sport athletes.
J Strength Cond Res. 2003 Nov;17(4):760-7.
Weighted sled towing is a common resisted sprint training technique even though relatively little is known about the effects that such practice has on sprint kinematics. The purpose of this study was to explore the effects of sled towing on acceleration sprint kinematics in field-sport athletes. Twenty men completed a series of sprints without resistance and with loads equating to 12.6 and 32.2% of body mass. Stride length was significantly reduced by approximately 10 and approximately 24% for each load, respectively. Stride frequency also decreased, but not to the extent of stride length. In addition, sled towing increased ground contact time, trunk lean, and hip flexion. Upper-body results showed an increase in shoulder range of motion with added resistance. The heavier load generally resulted in a greater disruption to normal acceleration kinematics compared with the lighter load. The lighter load is likely best for use in a training program.
Effect of elastic-cord towing on the kinematics of the acceleration phase of sprinting.
J Strength Cond Res. 2003 Feb;17(1):72-5.
We studied the specificity of elastic-cord towing by measuring selected kinematics of the acceleration phase of sprinting. Nine collegiate sprinters ran two 20-m maximal sprints (MSs) and towed sprints (TSs) that were recorded on high-speed video (180 Hz). Sagittal plane kinematics of a 4-segment model of the right side of the body were digitized for a complete stride at the 15-m point for the fastest trial. Significant differences were observed for horizontal velocity of the center of mass (CoM), stride length (SL), and horizontal distance from the CoM of the foot to the CoM of the body. There was no significant difference in stride rate between the MS and TS conditions. Omega-squared analysis showed that elastic-cord towing accounted for most of the variance in acute changes in horizontal velocity (73%), SL (68%), and horizontal position of the CoM at foot contact (64%). Elastic-cord tow training resulted in significant acute changes in sprint kinematics in the acceleration phase of an MS that do not appear to be sprint specific. More research is needed on the specificity of TS training and long-term effects on sprinting performance.
Velocity specificity in early-phase sprint training.
J Strength Cond Res. 2006 Nov;20(4):833-7.
ASSISTED AND RESISTED METHODS FOR SPEED DEVELOPMENT
PART II - RESISTED SPEED METHODS
By Adrian Faccioni
RESISTANCE TRAINING
Any athlete wishing to increase running velocity must overcome the inertia of the body through the acceleration phase. In this phase, it is the strong extensors of the hip (gluteals and hamstrings), knee (quadriceps) and ankle (Gastrocnemius and Soleus) that are actively involved in the process (Chu & Korchemny 1989).
By Adrian Faccioni
RESISTANCE TRAINING
Any athlete wishing to increase running velocity must overcome the inertia of the body through the acceleration phase. In this phase, it is the strong extensors of the hip (gluteals and hamstrings), knee (quadriceps) and ankle (Gastrocnemius and Soleus) that are actively involved in the process (Chu & Korchemny 1989).
Mann & Sprague (1980), Mann (1981), Chapman & Caldwell (1983) and Chapmanet al (1984) all performed kinetic analyses on sprint performers and all concluded that the hip extensors produced the greatest muscle moments when analyzing hip, knee and ankle joint moments. (A muscle moment indicates the resultant muscle activity and details which muscle groups are dominating the activity). Therefore, to maximize horizontal velocity in both the acceleration and top running velocity phases, it is the hip extensor muscle groups that resistance training must target to increase their force output.
A second component of sprinting performance that can be targeted with resistance training is the minimizing of the drop of centre of gravity with each ground contact. The centre of gravity should not sink too low through the ground contact phase. The stronger the extensor muscle groups in the lower limb, the less drop in centre of gravity during the ground contact phase (Chu & Korchemny 1989). The less flexion of these joints, the greater the stretch reflex that will be activated, resulting in greater concentric contraction during the driving phase of each stride (Asmussen & Bond-Peterson 1974, Cavagna 1977).
The components of strength required for maximizing sprint performance are maximum -strength, and speed-strength components, explosive-strength, and reactive-strength (stretch-shortening cycle). It has been well documented that one of the best methods to increase maximal-strength is through low-repetition (1 to 10) and high-intensity (70 to 120%) weight training. (Berger, 1962a, b, Atha1981, Anderson & Kearney, 1982, Schmidtbleicher 1985).
It is from a sound strength base that the speed-strength components explosive- and reactive -strength can be developed through movement-specific training regimes using a variety of different methods. Each method is designed to increase the stress placed upon the major extensor muscle groups. The increased force production by these muscle groups is then transferred to greater stride length which, when combined with an optimal stride rate, will lead to an increase in horizontal velocity (m/s).
WEIGHTED VEST RUNNING
A study by Bosco et al (1986) looked at the effect of increasing body weight (7 to 8%) on sprint athletes over a three-week period, training 3 to 5 sessions per week. The added resistance through weighted vests was worn from morning to evening and the athletes were tested for jumping and running on a treadmill, pre and post experiment. The jump tests included squat jumps (SJ), counter-movement jump, drop jump and 15 seconds continuous jumps on a resistive platform. The SJ improved from 42.9cm to 47.4cm and as the correlation between maximal running velocity and SJ has been measured at 0.68 (Mero et al 1981), the increased loading would have a positive effect upon force production and running speed.
Another positive effect of weight vest running is that the added mass would increase the vertical force at each ground contact. This would increase the stress placed on the stretch-shortening cycle (reactive strength) function of the muscle and would improve muscle stiffness at ground contact (Komi 1986). This would improve the muscle’s capacity to tolerate greater stretch loads, store more elastic energy and improve power output, which may be seen in an increase in stride length. Whilst this study suggested the wearing of a weighted vest all day, it was only a three-week project, and over a longer period it could be assumed that loading only during training sessions would have a similar effect.
UPHILL RUNNING
Kunz & Kaufmann (1981) completed a biomechanical study on maximal running up a 3% incline. They found the velocity to be slower than that of level ground running (8.35m/s to 8.85m/s) and biomechanically the subjects performed the runs with shorter stride lengths and longer ground contact times. The authors feel that uphill running will increase the stress placed on the hip extensor muscle groups as the athlete will attempt to maximize stride length, therefore increasing this component on the flat surface.
They also feel this training method will develop a shorter ground contact time if the athlete emphasizes fast push off to conquer the effects of the positive grade. An incline of greater than 3% would still be beneficial in developing the forceful hip extensor movements required but will be less specific in the simulation of the specific technical movements of the sprint
action.
SAND AND WATER RUNNING
Whilst both environments are ideal to increase the resistance placed upon a running athlete, they both have limited application to increasing stride length (utilization of hip extensors). The resistance in running in these two conditions leads to a greater activation of the hip flexors rather than the hip extensors. In shallow water running (20 to 30cm), the main emphasis is to get the leg out of the water. When running in soft sand, the ability to apply great extension force is diminished and the increase in speed is through an increase in stride rate through a shorter stride and faster hip flexion activity.
TOWING (RESISTED)
Towing either a sled, tire, speed chute or other weighted device over set distances are frequently used methods to develop running speed. The basis behind these methods is to increase the movement resistance requiring the athlete to increase force output (especially in the hip, knee and ankle extensors) to continue to run at speed. Studies by Behm (1991), Hakkinen et al (1985), Komi et al (1982) and Hakkinen & Komi (1985) all suggest that the improvement of a particular action (e.g. sprinting speed) is directly related to the similarity of movement in the training regime and the velocity specificity of the movement.
The two major towing methods used in Australia are that of tire or sled towing and the use of the speed chute (Speed Chute Australia). The benefits of using a tire or sled are that it is quite easy to change the size of the tire from small to large (thereby increasing the resistance), or using a tire with weights placed inside to increase resistance. A sled can be easily designed that allows weights to be secured, again making the resistance greater. It is important to have a long attachment to the towed device (10m), as shorter attachments can restrict the flat sliding of the device, leading to bouncing of the tire or sled as the athlete increases speed.
The second method, that of speed chute towing requires the use of a combination of small parachutes depending on the amount of resistance needed. Advantages of this device is that it is easily transported and the chute size can be changed very quickly. The chutes can be easily released mid-flight, allowing the athlete to finish a repetition with no increased resistance, giving the athlete the sensation of increased speed. A major disadvantage is that the chutes do not stay directly behind the athlete during the repetition. They move about from side to side (even more so in windy conditions) and can make it very difficult for the athlete to run at any great speed as he/she is trying to keep balance throughout each repetition. This may be of some use to team sport athletes, who are attempting to sprint whilst having to dodge and weave between opposing players, but for the purpose of purely increasing running speed, they have limited application.
SPEED-STRENGTH JUMPS (PLYOMETRICS)
Behm (1991), Hakkinen etal(1985), Komi et al (1982) and Hakkinen & Komi (1985) Smith & Melton (1981), Caiozzo et al (1981), Coyle et al (1981), and Kanehisa & Miyashita (1983a, b) all detailed research showing that high velocity, light resistance training led to a speed-specific enhancement of the neuromuscular system. This enhancement increased the subjects’ abilities to move small resistances with speed (such as own body weight) as shown by performance levels in the high velocity portion of a force- velocity curve.
These researchers measured squat jumps, counter-movement jumps, standing long jump, and isometric rate of force production with results indicating that adaptation was different to that achieved from heavy force to the ground, therefore requiring an increase in the early portion of the force production curve (increased rate of force production). The training modality can include long alternate leg bounds, double and single leg hops, hurdle jumps, and sandpit jumps. The movements can be dynamic in nature depending on the phase of training (Preparation phase — less intensity, Competition phase — more intensity, less volume).
WEIGHTED VEST RUNNING
A study by Bosco et al (1986) looked at the effect of increasing body weight (7 to 8%) on sprint athletes over a three-week period, training 3 to 5 sessions per week. The added resistance through weighted vests was worn from morning to evening and the athletes were tested for jumping and running on a treadmill, pre and post experiment. The jump tests included squat jumps (SJ), counter-movement jump, drop jump and 15 seconds continuous jumps on a resistive platform. The SJ improved from 42.9cm to 47.4cm and as the correlation between maximal running velocity and SJ has been measured at 0.68 (Mero et al 1981), the increased loading would have a positive effect upon force production and running speed.
Another positive effect of weight vest running is that the added mass would increase the vertical force at each ground contact. This would increase the stress placed on the stretch-shortening cycle (reactive strength) function of the muscle and would improve muscle stiffness at ground contact (Komi 1986). This would improve the muscle’s capacity to tolerate greater stretch loads, store more elastic energy and improve power output, which may be seen in an increase in stride length. Whilst this study suggested the wearing of a weighted vest all day, it was only a three-week project, and over a longer period it could be assumed that loading only during training sessions would have a similar effect.
UPHILL RUNNING
Kunz & Kaufmann (1981) completed a biomechanical study on maximal running up a 3% incline. They found the velocity to be slower than that of level ground running (8.35m/s to 8.85m/s) and biomechanically the subjects performed the runs with shorter stride lengths and longer ground contact times. The authors feel that uphill running will increase the stress placed on the hip extensor muscle groups as the athlete will attempt to maximize stride length, therefore increasing this component on the flat surface.
They also feel this training method will develop a shorter ground contact time if the athlete emphasizes fast push off to conquer the effects of the positive grade. An incline of greater than 3% would still be beneficial in developing the forceful hip extensor movements required but will be less specific in the simulation of the specific technical movements of the sprint
action.
SAND AND WATER RUNNING
Whilst both environments are ideal to increase the resistance placed upon a running athlete, they both have limited application to increasing stride length (utilization of hip extensors). The resistance in running in these two conditions leads to a greater activation of the hip flexors rather than the hip extensors. In shallow water running (20 to 30cm), the main emphasis is to get the leg out of the water. When running in soft sand, the ability to apply great extension force is diminished and the increase in speed is through an increase in stride rate through a shorter stride and faster hip flexion activity.
TOWING (RESISTED)
Towing either a sled, tire, speed chute or other weighted device over set distances are frequently used methods to develop running speed. The basis behind these methods is to increase the movement resistance requiring the athlete to increase force output (especially in the hip, knee and ankle extensors) to continue to run at speed. Studies by Behm (1991), Hakkinen et al (1985), Komi et al (1982) and Hakkinen & Komi (1985) all suggest that the improvement of a particular action (e.g. sprinting speed) is directly related to the similarity of movement in the training regime and the velocity specificity of the movement.
The two major towing methods used in Australia are that of tire or sled towing and the use of the speed chute (Speed Chute Australia). The benefits of using a tire or sled are that it is quite easy to change the size of the tire from small to large (thereby increasing the resistance), or using a tire with weights placed inside to increase resistance. A sled can be easily designed that allows weights to be secured, again making the resistance greater. It is important to have a long attachment to the towed device (10m), as shorter attachments can restrict the flat sliding of the device, leading to bouncing of the tire or sled as the athlete increases speed.
The second method, that of speed chute towing requires the use of a combination of small parachutes depending on the amount of resistance needed. Advantages of this device is that it is easily transported and the chute size can be changed very quickly. The chutes can be easily released mid-flight, allowing the athlete to finish a repetition with no increased resistance, giving the athlete the sensation of increased speed. A major disadvantage is that the chutes do not stay directly behind the athlete during the repetition. They move about from side to side (even more so in windy conditions) and can make it very difficult for the athlete to run at any great speed as he/she is trying to keep balance throughout each repetition. This may be of some use to team sport athletes, who are attempting to sprint whilst having to dodge and weave between opposing players, but for the purpose of purely increasing running speed, they have limited application.
SPEED-STRENGTH JUMPS (PLYOMETRICS)
Behm (1991), Hakkinen etal(1985), Komi et al (1982) and Hakkinen & Komi (1985) Smith & Melton (1981), Caiozzo et al (1981), Coyle et al (1981), and Kanehisa & Miyashita (1983a, b) all detailed research showing that high velocity, light resistance training led to a speed-specific enhancement of the neuromuscular system. This enhancement increased the subjects’ abilities to move small resistances with speed (such as own body weight) as shown by performance levels in the high velocity portion of a force- velocity curve.
These researchers measured squat jumps, counter-movement jumps, standing long jump, and isometric rate of force production with results indicating that adaptation was different to that achieved from heavy force to the ground, therefore requiring an increase in the early portion of the force production curve (increased rate of force production). The training modality can include long alternate leg bounds, double and single leg hops, hurdle jumps, and sandpit jumps. The movements can be dynamic in nature depending on the phase of training (Preparation phase — less intensity, Competition phase — more intensity, less volume).
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