This study investigated the movement preparation (reaction time) and movement execution (movement time) of children with and without ADHD by manipulating the uncertainty of occurrence. Participants performed a seated lower extremity choice response time protocol, which contained either 10% catch trials or 30% catch trials along with 27 empirical stimuli to one of three target directions. Results indicated that children with ADHD were significantly slower at processing lower extremity movements than their peers for the condition with increased number of catch trials, but not the condition with fewer catch trials. These findings suggest that children with ADHD are more affected by the uncertainty of an empirical stimulus during the preparation phase of a movement response than their age-matched peers are.
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Lower Extremity Movement Preparation and Children with Attention Deficit Hyperactivity Disorder
Scott J. Pedersen and Paul R. Surburg
Fractionated Lower Extremity Response Time Performance in Boys with and Without ADHD
Scott J. Pedersen, Paul R. Surburg, Matthew Heath, and David M. Koceja
The purpose was to investigate central and peripheral processing mechanisms through the use of electromyography (EMG) to determine differences between the performance of children with and without ADHD on a lower extremity choice response time task. Sixteen children with ADHD were tested on and off medication along with 19 children without ADHD. For premotor time, the comparison group performed significantly faster than children with ADHD. The longer latencies exhibited in central processing of children with ADHD were related to midline crossing inhibition (MCI). Medication improved the speed of processing for children with ADHD, but did not negate MCI.
Lower-Extremity Isokinetic Strength Profiling in Professional Rugby League and Rugby Union
Scott R. Brown, Matt Brughelli, Peter C. Griffiths, and John B. Cronin
Purpose:
While several studies have documented isokinetic knee strength in junior and senior rugby league players, investigations of isokinetic knee and hip strength in professional rugby union players are limited. The purpose of this study was to provide lower-extremity strength profiles and compare isokinetic knee and hip strength of professional rugby league and rugby union players.
Participants:
32 professional rugby league and 25 professional rugby union players.
Methods:
Cross-sectional analysis. Isokinetic dynamometry was used to evaluate peak torque and strength ratios of the dominant and nondominant legs during seated knee-extension/flexion and supine hip-extension/flexion actions at 60°/s.
Results:
Forwards from both codes were taller and heavier and had a higher body-mass index than the backs of each code. Rugby union forwards produced significantly (P < .05) greater peak torque during knee flexion in the dominant and nondominant legs (ES = 1.81 and 2.02) compared with rugby league forwards. Rugby league backs produced significantly greater hip-extension peak torque in the dominant and nondominant legs (ES = 0.83 and 0.77) compared with rugby union backs. There were no significant differences in hamstring-to-quadriceps ratios between code, position, or leg. Rugby union forwards and backs produced significantly greater knee-flexion-to-hip-extension ratios in the dominant and nondominant legs (ES = 1.49–2.26) than rugby union players.
Conclusions:
It seems that the joint torque profiles of players from rugby league and union codes differ, which may be attributed to the different demands of each code.
The Effects of Lower-Extremity Plyometric Training on Soccer-Specific Outcomes in Adult Male Soccer Players: A Systematic Review and Meta-Analysis
Peter A. van de Hoef, Jur J. Brauers, Maarten van Smeden, Frank J.G. Backx, and Michel S. Brink
stiffness, and increases peak torque and lower-extremity strength. Improved motor unit activation and increased joint stiffness improve acceleration, 43 and lower-extremity strength is strongly associated with maximum sprint speed. 44 Therefore, an increase in sprint speed over 20 m and longer distances
Soccer Footedness and Between-Limbs Muscle Strength: Systematic Review and Meta-Analysis
Matthew D. DeLang, Mehdi Rouissi, Nicola L. Bragazzi, Karim Chamari, and Paul A. Salamh
asymmetries. 9 Soccer, as a lower-extremity-dominant sport, terms lateral dominance footedness . The nature of an individual soccer kick is asymmetrical: the kicking limb is mobilized on a stable base provided by the plant limb. In this isolated portrayal, expected lower-limb tissue asymmetries attributable
Is Soleus Muscle-Tendon-Unit Behavior Related to Ground-Force Application During the Sprint Start?
Erik Schrödter, Gert-Peter Brüggemann, and Steffen Willwacher
Purpose:
To describe the stretch-shortening behavior of ankle plantar-flexing muscle–tendon units (MTUs) during the push-off in a sprint start.
Methods:
Fifty-four male (100-m personal best: 9.58–12.07 s) and 34 female (100-m personal best: 11.05–14.00 s) sprinters were analyzed using an instrumented starting block and 2-dimensional high-speed video imaging. Analysis was performed separately for front and rear legs, while accounting for block obliquities and performance levels.
Results:
The results showed clear signs of a dorsiflexion in the upper ankle joint (front block 15.8° ± 7.4°, 95% CI 13.2–18.2°; rear block 8.0° ± 5.7°, 95% CI 6.4–9.7°) preceding plantar flexion. When observed in their natural block settings, the athletes’ block obliquity did not significantly affect push-off characteristics. It seems that the stretch-shortening-cycle-like motion of the soleus MTU has an enhancing influence on push-off force generation.
Conclusion:
This study provides the first systematic observation of ankle-joint stretch-shortening behavior for sprinters of a wide range of performance levels. The findings highlight the importance of reactive-type training for the improvement of starting performance. Nonetheless, future studies need to resolve the independent contributions of tendinous and muscle-fascicle structures to overall MTU performance.
Running Mechanics and Metabolic Responses With Water Bottles and Bottle Belt Holders
Heather K. Vincent, Laura A. Zdziarski, Kyle Fallgatter, Giorgio Negron, Cong Chen, Trevor Leavitt, MaryBeth Horodyski, Joseph G. Wasser, and Kevin R. Vincent
higher loads occurred, which can impact rates of oxygen use, energy expenditure, and injury risk while running. 11 Increasing loads (in the range of 30% of body weight in a weight vest) lengthen the stance time and magnitude of GRFs, thereby increasing the susceptibility to lower-extremity bony stress
The Effect of Fatigue-Induced Changes in Eggbeater-Kick Kinematics on Performance and Risk of Injury
Nuno Oliveira, David H. Saunders, and Ross H. Sanders
Purpose:
To investigate the effects of fatigue on the vertical force and kinematics of the lower limbs during maximal water polo eggbeater kicking.
Methods:
Twelve male water polo players maintained as high a position as possible while performing the eggbeater kick with the upper limbs raised out of the water until they were unable to keep the top of the sternum (manubrium) above water. Data comprising 27 complete eggbeater-kick cycles were extracted corresponding to 9 cycles of the initial nonfatigued (0%), 50% time point (50%), and final fatigued (100%) periods of the trial. Vertical force, foot speed, and hip-, knee-, and ankle-joint angles were calculated.
Results:
Mean vertical force (0%, 212.2 N; 50%, 184.5 N; 100%, 164.3 N) progressively decreased with time. Speed of the feet (0.4 m/s), hip abduction (2.9°), and flexion (3.6°) decreased with fatigue, while hip internal rotation (3.6°) and ankle inversion (4°) increased with fatigue. Average angular velocity decreased for all joint motions.
Conclusions:
Eggbeater-kick performance decreases with fatigue. Inability to maintain foot speeds and hip and ankle actions with progressing fatigue diminishes the ability of the player to produce vertical force during the cycle. Increased internal rotation of the hip when fatigued and the large eversion/abduction of the ankle during the cycle may be predisposing factors for the prevalence of patellofemoral pain syndrome observed among eggbeater-kick performers. Appropriate training interventions that can limit the effects of fatigue on performance and injury risk should be considered.
Improvement of Flutter-Kick Performance in Novice Surface Combat Swimmers With Increased Hip Strength
Anne Z. Beethe, Elizabeth F. Nagle, Mita Lovalekar, Takashi Nagai, Bradley C. Nindl, and Christopher Connaboy
flexion during maximal dolphin kick, reporting changes in lower-extremity kinematics and an overall decrease in swimming velocity of 0.32 m·s −1 . Bowes et al 16 examined accidental cold-water immersions investigating winter clothing or a swimsuit, finding winter clothing decreased total distance
The Impact of Blade Technology on Paralympic Sprint Performance Between 1996 and 2016: Bilateral Amputees’ Competitive Advantage
Yetsa A. Tuakli-Wosornu, Xiang Li, Kimberly E. Ona Ayala, Yinfei Wu, Michael Amick, and David B. Frumberg
lower-extremity amputee sprinter (Oliveira) winning against unilateral lower-extremity amputee sprinters in the same race. Adam Davy/PA Images via Getty Images. As Paralympic participation expands, it is important to clearly and definitively understand the impact of prosthetic technology on sprint
