contribute to foot speed. 15 A primary mechanism is due to the interaction of the thigh and shank in creating a proximal-to-distal sequencing pattern of segmental angular velocities. If the strength of the knee extensor musculature is compromised by fatigue, the proximal–distal mechanism acting to generate
Thomas Haugen, Jørgen Danielsen, Leif Olav Alnes, David McGhie, Øyvind Sandbakk and Gertjan Ettema
Practitioners have, for many years, argued that athletic sprinters should optimize front-side mechanics (leg motions occurring in front of the extended line through the torso) and minimize back-side mechanics. This study aimed to investigate if variables related to front- and back-side mechanics can be distinguished from other previously highlighted kinematic variables (spatiotemporal variables and variables related to segment configuration and velocities at touchdown) in how they statistically predict performance. A total of 24 competitive sprinters (age: 23.1 [3.4] y, height: 1.81 [0.06] m, body mass: 75.7 [5.6] kg, and 100-m personal best: 10.86 [0.22] s) performed two 20-m starts from block and 2 to 3 flying sprints over 20 m. Kinematics were recorded in 3D using a motion tracking system with 21 cameras at a 250 Hz sampling rate. Several front- and back-side variables, including thigh (r = .64) and knee angle (r = .51) at lift-off and maximal thigh extension (r = .66), were largely correlated (P < .05) with accelerated running performance, and these variables displayed significantly higher correlations (P < .05) to accelerated running performance than nearly all the other analyzed variables. However, the relationship directions for most front- and back-side variables during accelerated running were opposite in comparison to how the theoretical concept has been described. Horizontal ankle velocity, contact time, and step rate displayed significantly higher correlation values to maximal velocity sprinting than the other variables (P < .05), and neither of the included front- and back-side variables were significantly associated with maximal velocity sprinting. Overall, the present findings did not support that front-side mechanics were crucial for sprint performance among the investigated sprinters.
Ross H. Sanders
A boost is a skill used in water polo to raise the body for the purpose of shooting for goal or passing, or defending against these. The purpose of this study was to investigate kinematic variables contributing to height achieved in a boost. The kinematics of the vertex, shoulders, and lower limbs of 16 players ranging in ability from novice to elite were quantified using three-dimensional videographic techniques. Maximum height of the vertex with respect to water level ranged from 0.50 m to 0.90 m. A multiple regression model comprising the squared maximum resultant foot speed, range of knee joint extension, and initial trunk angle with respect to the horizontal accounted for 74% of the variance in height achieved. Anteroposterior and medio-lateral motions assisted in maintaining foot speed throughout the period of knee extension. The foot orientations and direction of foot motion of the elite players suggested that effective technique involves the use of both drag and lift forces.
Nuno Oliveira, David H. Saunders and Ross H. Sanders
To investigate the effects of fatigue on the vertical force and kinematics of the lower limbs during maximal water polo eggbeater kicking.
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.
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.
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.
Paraskevi Giagazoglou, Athanasios Katis, Eleftherios Kellis and Christos Natsikas
The purpose of the current study was to examine the kinematic differences during instep soccer kicks between players who were blind and sighted controls. Eleven male soccer players who were blind and nine male sighted performed instep kicks under static and dynamic conditions. The results indicated significantly higher (p < .05) ball speed velocities (20.81m/sec) and ball/foot speed ratio values (1.35) for soccer players who were blind during the static kick compared with sighted players (16.16m/sec and 1.23, respectively). Significant group effect on shank and foot angular velocity was observed during the static kicking condition (p < .05), while no differences were found during the dynamic kicking condition (p > .05). Despite the absence of vision, systematic training could have beneficial effects on technical skills, allowing athletes who are blind to develop skill levels comparable to sighted athletes.
Kelly de Jesus, Ross Sanders, Karla de Jesus, João Ribeiro, Pedro Figueiredo, João P. Vilas-Boas and Ricardo J. Fernandes
Coaches are often challenged to optimize swimmers’ technique at different training and competition intensities, but 3-dimensional (3D) analysis has not been conducted for a wide range of training zones.
To analyze front-crawl 3D kinematics and interlimb coordination from low to severe swimming intensities.
Ten male swimmers performed a 200-m front crawl at 7 incrementally increasing paces until exhaustion (0.05-m/s increments and 30-s intervals), with images from 2 cycles in each step (at the 25- and 175-m laps) being recorded by 2 surface and 4 underwater video cameras. Metabolic anaerobic threshold (AnT) was also assessed using the lactate-concentration–velocity curve-modeling method.
Stroke frequency increased, stroke length decreased, hand and foot speed increased, and the index of interlimb coordination increased (within a catch-up mode) from low to severe intensities (P ≤ .05) and within the 200-m steps performed above the AnT (at or closer to the 4th step; P ≤ .05). Concurrently, intracyclic velocity variations and propelling efficiency remained similar between and within swimming intensities (P > .05).
Swimming intensity has a significant impact on swimmers’ segmental kinematics and interlimb coordination, with modifications being more evident after the point when AnT is reached. As competitive swimming events are conducted at high intensities (in which anaerobic metabolism becomes more prevalent), coaches should implement specific training series that lead swimmers to adapt their technique to the task constraints that exist in nonhomeostatic race conditions.
Mehdi Kordi, Campbell Menzies and Andy Galbraith
phases of muscle contraction), cadence/foot speed are not controlled for, and power cannot be accurately and reliably measured. 10 This means that speed is the measure of interest. However, speed is the summation of propulsion (mechanical power output) against resistance (running resistance and air
Bouwien Smits-Engelsman, Wendy Aertssen and Emmanuel Bonney
have excellent psychometric properties ( 11 ). The Ladder Agility Test Agility ladder drills are traditionally used for training players of team sports such as soccer, rugby, and netball. The purpose of these drills is to improve foot speed, foot placement, agility, and coordination, giving this item
biocultural explanations and to contend, as Cobb and Boas did before me, that culture exerts a powerful influence over not just our social but also our corporeal existence. A brief history of running cultures reveals that both popular audiences and “experts” frequently interpret feats of foot speed in