Relationship between constant and variable practice and kinematic characteristics of the basketball free-throw

Abstract

This affiliated study is subject to the original objectives and study design of the project “Gaze behaviour and kinematics of especial skills”. The assessment and analysis of movements or parts of movements through kinematics has become a useful “tool” in movement analysis, where researchers believed that kinematics had recently become an important descriptor of performance in motor learning and control. The objectives of this study were to determine the differences and effect sizes of the differences in kinematic behavioural patterns and kinematic parameters (i.e. peaks in flexion, angular velocity and angular acceleration) between the basketball free throws (4.57 m) practised in constant and variable conditions. These kinematical differences and their effect sizes were observed on testing days and after intervention training days. The differences in shot proficiency from the free throw distance (4.57 m), were also observed to see the relevant effects that the applied intervention programme had relevant to, and within, constant and variable practice conditions groups. A five-day programme was conducted of which day one consisted of a pre-test, day two to four the intervention training days and day five a retention-test. Twenty (N=20) fit and healthy male participants (age 21.8 ± 1.8 years) were randomly divided into constant (n=10) and variable (n=10) practice groups. Informed consent was granted by participants, with the option to withdraw at any time. Each participant shot 20 free throws from five different distances (3.35 m, 3.96 m, 4.57 m, 5.18 m and 5.79 m – 20 shots per distance) resulting into 100 shots per day. During the three-day training programme, the constant group remained with 100 shots from the 4.57 m line, while the variable group shot 20 shots from each of the five distances. Participants were required to wear sleeveless shirts or no shirts to enable proper upper body analysis, whereas short trousers allowed adequate analysis of the lower body. For consistency, players had to be barefoot to allow an appropriate view of the ankle and foot. Nine reflective markers were used for analysis and put on the dominant side of the participant at the following locations: distal end of the fifth metatarsal of the toe, lateral malleolus of the ankle, lateral condyle of the femur and the greater trochanter of the femur. A further five landmarks were used on the upper extremity: distal end of the middle finger just below the nail, the hand about 1 cm below the middle finger, ulnar styloid of the wrist, lateral epicondyle of the elbow and the acromion process of the shoulder. Five different landmarks were attached within each recording, namely negative peak velocity (A), peak flexion (B), peak acceleration (C), peak velocity (D) and negative peak acceleration (E). Linear regression was computed for all the distances (except the free throw distance), for each participant and, based on the individual regressions, the predicted values at the free throw distance (4.57 m). The biggest difference between the constant- and variable groups in the pre-test was observed in landmark B (peak flexion). The variable group attained the highest value of the two groups, while in the post-test the biggest difference between the two groups was observed in landmark E (negative peak acceleration), this time with the constant group having the higher relative timing percentage. Since only one main effect was significant and the interaction was not, no additional posthoc analyses were performed. In relation to the objective, it is observed that the biggest difference between the predicted performance and the actual performance was at the 4.57 m free throw distance. This was the case in both the pre-test and retention-test of the constant group. However, the greatest difference was only noticed in the pre-test of the variable group, not in its retention-test.