Changes to horizontal force-velocity and impulse measures during sprint running acceleration with thigh and shank wearable resistance (original) (raw)
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THE EFFECT OF LOWER LIMB WEARABLE RESISTANCE LOCATION ON SPRINT RUNNING STEP KINEMATICS
This study quantified changes in step kinematics between unloaded, thigh, and shank wearable resistance (WR) at 2% body mass (BM) during over ground sprint running. Eleven male athletes completed two maximal effort sprint trials over 52 m of in-ground force plates, for each condition. There were no significant (p > 0.05) changes in sprint times between all conditions. Compared to unloaded sprinting, shank WR significantly changed step frequency (SF) (-2.1% acceleration phase and-2.5% max velocity phase (MVP)), contact times (CT) (2.1% MVP) and flight times (3.3% MVP); thigh WR significantly changed SF (-1.4% MVP) and CT (2.9% MVP). It appears peripheral loading (2% BM) of the thigh and shank affects SF and CT but not step length and width. Such differential loading could be used to train different mechanical determinants of speed.
ACUTE KINEMATIC AND KINETIC ADAPTATIONS TO WEARABLE RESISTANCE DURING SPRINT ACCELERATION
Macadam, P, Simperingham, KD, and Cronin, JB. Acute kinematic and kinetic adaptations to wearable resistance during sprint acceleration. J Strength Cond Res 31(5): 1297–1304, 2017—Wearable resistance (WR) in the form of weighted vests and shorts enables movement-specific sprint running to be performed under load. The purpose of this study was to determine the acute changes in kinematics and kinetics when an additional load equivalent to 3% body mass (BM) was attached to the anterior or posterior surface of the lower limbs during sprint running. Nineteen male rugby athletes (age: 19.7 6 2.3 years; body mass: 96.1 6 16.5 kg; height: 181 6 6.5 cm) volunteered to participate in the study. Subjects performed six 20 m sprints in a randomized fashion wearing no resistance or 3%BM affixed to the anterior (quad-riceps and tibialis anterior) or posterior (hamstring and gas-trocnemius) surface of the lower limbs (2 sprints per condition). Optojump and radar were used to quantify sprint times, horizontal velocity, contact and flight times, and step length and frequency. A repeated measures analysis of variance with post hoc contrasts was used to determine differences (p # 0.05) between conditions. No significant differences were found between the anterior and posterior WR conditions in any of the variables of interest. There was no significant change in sprint times over the initial 10 m, however, the 10–20 m split times were significantly slower (22.2 to 22.9%) for the WR conditions compared with the unloaded sprints. A significant change in the relative force– velocity (F–v) slope (210.5 to 210.9%) and theoretical maximum velocity (V 0) (25.4 to 26.5%) was found, whereas a nonsignificant increase in theoretical maximum force (F 0) (4.9–5.2%) occurred. Wearable resistance of 3%BM may be a suitable training modality to enhance sprint acceleration performance by overloading the athlete without negatively affecting sprint running technique.
Acute changes in acceleration phase sprint biomechanics with lower body wearable resistance
Sports Biomechanics, 2020
The aim of this acute cross-sectional study was to quantify the kinematic and kinetic changes that occur during sprint acceleration when lower body WR is worn. Fifteen male rugby athletes (19 years; 181 cm; 91 kg) were assessed during maximal effort over−ground and treadmill sprinting over 20 m under three different loading conditions: 0%, 3% and 5% body mass (BM) added weight attached to the lower body. Treadmill data provided a convenient estimate of kinetic changes in the absence of in-ground force plates. The loaded conditions resulted in significantly increased ground contact time (5 to 6%) and decreased step frequency (−2 to −3%) during sprint accelerations (effect size = 0.32-0.72). Moderate WR loading (3% BM) resulted in increased (9%; effect size = 0.66) theoretical maximum horizontal force (relative to BM) and unchanged 20 m sprint times (p > 0.05). Heavier WR loading (5% BM) resulted in a significant decrease (−4%) in vertical ground reaction forces (relative to total system mass) and slower (1 to 2%) 20 m sprint times (effect size = 0.38-0.70). Lower body WR loading up to 5% BM can provide specific sprint training overload, while affecting sprint acceleration biomechanics by ≤ 6%.
Waveform analysis of shank loaded wearable resistance during sprint running acceleration
Journal of Sports Sciences, 2021
Lower-limb wearable resistance (WR) provides a specific and targeted overload to the musculature involved in sprint running, however, it is unknown if greater impact forces occur with the additional limb mass. This study compared the contact times and ground reaction force waveforms between sprint running with no load and 2% body mass (BM) shank-positioned WR over 30 m. Fifteen male university-level sprint specialists completed two maximum effort sprints with each condition in a randomised order. Sprint running with shank WR resulted in trivial changes to contact times at 5 m, 10 m, and 20 m (effect size [ES] = < 0.20, p > 0.05) and a small, significant increase to contact time at 30 m by 1.94% (ES = 0.25, p = 0.03). Significant differences in ground reaction force between unloaded and shank loaded sprint running were limited to the anterior-posterior direction and occurred between 20−30% of ground contact at 10 m, 20 m, and 30 m. Shank WR did not result in greater magnitudes of horizontal or vertical forces during the initial impact portion of ground contact. Practitioners can prescribe shank WR training with loads ≤ 2% BM without concern for increased risk of injurious impact forces.
Force-velocity profile changes with forearm wearable resistance during standing start sprinting
European Journal of Sport Science, 2019
Horizontal force-velocity (F-V) profiling is a strategy to assess athletes' individual performance capabilities during sprinting. This study investigated the acute changes in F-V profiles during sprinting of fourteen collegiate male sprinters with a mean 100-m sprint time of 11.40 ± 0.39 s, from a split-stance starting position. The subjects sprinted 30-m with, and without, wearable resistance (WR) equivalent to 2% body mass, attached to their forearms. Sprinting time at 5, 10, 20, and 30-m was assessed using laser technology. External horizontal F-V relationships were calculated via velocity-time signals. Maximal theoretical velocity (V0), theoretical relative and absolute horizontal force (F0), and horizontal power (Pmax) were determined from the F-V relationship. Paired t-tests were used to determine statistical differences (p ≤ 0.05) in variables across conditions with Cohen's d as effect sizes (ES) calculated to assess practical changes. Sprint times at 10-m and beyond were significantly increased (1.9-3.3%, p 0.01-0.03, ES 0.46-0.60) with WR compared to unloaded sprinting. The only significant change in F-V with the WR condition was found in relative Pmax system (-6.1%, p 0.01, ES 0.66). A small decrease was reported in V0 (-1.0%, p 0.11, ES 0.27), with small to medium ES decreases reported in F0 (-4.
Forearm wearable resistance effects on sprint kinematics and kinetics
Objectives: Arm swing is a distinctive characteristic of sprint-running with the arms working in a con-tralateral manner with the legs to propel the body in a horizontal direction. The purpose of this study was to determine the acute changes in kinematics and kinetics when wearable resistance (WR) of 1 kg (equivalent to ∼1% body mass) was attached to each forearm during over ground short distance (20 m) maximal sprint-running. Design: Cross-sectional study. Methods: Twenty-two male amateur rugby athletes (19.4 ± 0.5 years; 97.0 ± 4.8 kg; 180.4 ± 7.2 cm) volunteered to participate in the study. Radar and Optojump were used to examine kinematic and kinetics between WR and unloaded sprint-running conditions. Results: No significant (p < 0.05) differences were found at 2 m or 5 m between conditions, however, the WR condition resulted in a significant increase in 10 m, 20 m and 10–20 m split time (all, ∼2%, small effect size) compared to the unloaded condition. Significant decreases were also found in theoretical maximum velocity (V 0) (−1.4%, small effect size) and relative peak horizontal power production (P max) (−5.5%, small effect size). Step length (2.1%, small effect size) and contact time (6.5%, medium effect size) were significantly increased, while step frequency (−4.1%, small effect size) and flight time (−5.3%, medium effect size) were significantly decreased. Conclusions: WR forearm loading provides a movement specific overload of the arms which significantly alters step kinematics and sprint times ≥10 m.
Journal of Strength and Conditioning Research, 2008
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.
Sports Biomechanics, 2020
This study determined the acute changes in rotational work with thigh attached wearable resistance (WR) of 2% body mass during 50-m sprint-running. Fourteen athletes completed sprints with, and without, WR in a randomised order. Sprint times were measured via timing gates at 10-m and 50-m. Rotational kinematics were obtained over three phases (steps 1-2, 3-6 and 7-10) via inertial measurement unit attached to the left thigh. Quantification of thigh angular displacement and peak thigh angular velocity was subsequently derived to measure rotational work. The WR condition was found to increase sprint times at 10-m (1.4%, effect size [ES] 0.38, p 0.06) and 50-m (1.9%, ES 0.55, p 0.04). The WR condition resulted in trivial to small increases in angular displacement of the thigh during all phases (0.6-3.4%, ES 0.04-0.26, p 0.09-0.91). A significant decrease in angular velocity of the thigh was found in all step phases (−2.5% to −8.0%, ES 0.17-0.51, p < 0.001-0.04), except extension in step phase 1 with the WR. Rotational work was increased (9.8-18.8%, ES 0.35-0.53, p < 0.001) with WR in all phases of the sprint. Thigh attached WR provides a means to significantly increase rotational work specific to sprinting.
Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production
Frontiers in Physiology, 2015
Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability.