Assessment of planarity of the golf swing based on the functional swing plane of the clubhead and motion planes of the body points

The purposes of this study were (1) to determine the functional swing plane (FSP) of the clubhead and the motion planes (MPs) of the shoulder/arm points and (2) to assess planarity of the golf swing based on the FSP and the MPs. The swing motions of 14 male skilled golfers (mean handicap = -0.5 +/- 2.0) using three different clubs (driver, 5-iron, and pitching wedge) were captured by an optical motion capture system (250Hz). The FSP and MPs along with their slope/relative inclination and direction/direction of inclination were obtained using a new trajectory-plane fitting method. The slope and direction of the FSP revealed a significant club effect (p < 0.001). The relative inclination and direction of inclination of the MP showed significant point (p < 0.001) and club (p < 0.001) effects and interaction (p < 0.001). Maximum deviations of the points from the FSP revealed a significant point effect (p < 0.001) and point-club interaction (p < 0.001). It was concluded that skilled golfers exhibited well-defined and consistent FSP and MPs, and the shoulder/arm points moved on vastly different MPs and exhibited large deviations from the FSP. Skilled golfers in general exhibited semi-planar downswings with two distinct phases: a transition phase and a planar execution phase.     

Validity of the X-factor computation methods and relationship between the X-factor parameters and clubhead velocity in skilled golfers

The purpose of this study was to assess the validity of the X-factor computation methods and to examine whether direct relationships exist between the X-factor parameters and the clubhead velocity in a group of skilled male golfers (n = 18, handicap = ? 0.6 ± 2.1). Five driver trials were captured from each golfer using an optical motion capture system (250 Hz). Two plane-based methods (conventional vs. functional swing plane-based) and one Cardan rotation-based method (relative orientation) were used to compute select X-factor (end of pelvis rotation, top of backswing, ball impact (BI), and maximum), X-factor stretch (stretch and maximum stretch), and X-factor velocity (BI and maximum) parameters. The maximum clubhead velocity was extracted and normalized to golfer's body height to eliminate the effect of body size. A one-way repeated MANOVA revealed that the computation methods generated significantly different X-factor parameter values (p < 0.001). The conventional method provided substantially larger X-factor values than the other methods in the untwisting phase and the meaningfulness of select X-factor parameters generated by this method was deemed questionable. The correlation analysis revealed that the X-factor parameters were not directly related to the maximum clubhead velocity (both unnormalized and normalized).     

Challenges of designing and carrying out laboratory experiments about Newton's second law

Science & Education - Experiment is understood as a core activity in science education as well as science in general. Despite many efforts to improve science education in the laboratory, a...     

Workshop on Friction: Understanding and Addressing Students’ Difficulties in Learning Science Through a Hermeneutical Perspective

Hermeneutics is useful in science and science education by emphasizing the process of understanding. The purpose of this study was to construct a workshop based upon hermeneutical principles and to interpret students’ learning in the workshop through a hermeneutical perspective. When considering the history of Newtonian mechanics, it could be considered that there are two methods of approaching Newtonian mechanics. One method is called the ‘prediction approach’, and the other is called the ‘explanation approach’. The ‘prediction approach’ refers to the application of the principles of Newtonian mechanics. We commonly use the prediction approach because its logical process is natural to us. However, its use is correct only when a force, such as gravitation, is exactly known. On the other hand, the ‘explanation approach’ could be used when the nature of a force is not exactly known. In the workshop, students read a short text offering contradicting ideas about whether to analyze a friction situation using the explanation approach or the prediction approach. Twenty-two college students taking an upper-level mechanics course wrote their ideas about the text. The participants then discussed their ideas within six groups, each composed of three or four students. Through the group discussion, students were able to clarify their preconceptions about friction, and they responded to the group discussion positively. Students started to think about their learning from a holistic perspective. As students thought and discussed the friction problems in the manner of hermeneutical circles, they moved toward a better understanding of friction.     

Evaluating the contribution of lower extremity kinetics to whole body power output during the power snatch

This study evaluated the contribution of lower extremity (hip, knee and ankle) net joint torques (NJT) to whole body power (WBP) output during the power snatch (PS). Ten experienced weightlifters (five males and five females) performed five trials of the PS with 60% of one repetition maximum. Lower extremity NJT and WBP were extracted through a three-dimensional motion analyses and used for data analyses. Pearson correlation coefficients were obtained to observe the relationship between lower extremity NJT and WBP. Multiple-regression (stepwise) analyses was also conducted to evaluate the contribution of lower extremity NJT to WBP during the PS with the hip, knee and ankle NJT being the independent variables. Hip NJT was characterised as a significant positive correlation with WBP (r = 0.47, p < 0.01), while knee NJT showed a significant negative correlation with WBP (r = ?0.34, p < 0.05). A significant inter-correlation was also observed between hip NJT and knee NJT (r = ?0.66, p < 0.01). Hip NJT was identified as a significant contributor to WBP during the PS. Practically, this study suggested that training skills allowing weightlifters to utilise hip extensor muscle action would help to improve WBP during the PS.     

Effects of the golfer–ground interaction on clubhead speed in skilled male golfers

The purposes of this study were to characterise the golfer–ground interactions during the swing and to identify meaningful associations between the golfer–ground interaction force/moment parameters and the maximum clubhead speed in 63 highly skilled male golfers (handicap ≤ 3). Golfers performed shots in 3 club conditions (driver, 5-iron and pitching wedge) which were captured by an optical motion capture system and 2 force plates. In addition to the ground reaction forces (GRFs), 3 different golfer–ground interaction moments (GRF moments, pivoting moments and foot contact moments) were computed. The GRF moment about the forward/backward (F/B) axis and the pivoting moment about the vertical axis were identified as the primary moments. Significant (p < 0.05) correlations of peak force parameters (all components in the lead foot and F/B component in the trail foot) and peak moment parameters (lead-foot GRF moment and trail-foot pivoting moment) to clubhead speed were found. The lead-foot was responsible for generating the GRF moment, while the trail foot contributed to the pivoting moment more. The instant the lead arm becomes parallel to the ground was identified as the point of maximum angular effort, and the loading onto the lead-foot near this point was critical in generating both peak moments.