Kinetic Analysis of Swimming Flip-Turn Push-Off Techniques.

The aims of the present study were to examine the influences of different push-off techniques on kinetic and kinematic parameters both in and out of the water. The two techniques were: (1) a push off that was characterized by rapid extension of knees and hips towards the wall, prior to contact (i.e., no countermovement), and, (2) where the swimmer glides into the wall, letting the wall flex the knees in an approximate countermovement or eccentric phase. Twenty trained male and female freestyle swimmers (age 26.1 ± 9.9 years, height 1.61 ± 0.04 m, and weight 65.6 ± 19.3 kg) participated. Data were analyzed by employing two (i.e., land and water) 3 (variables of interest) x 2 (push-off type) repeated measures ANOVAs with the alpha level set a priori at 05. Results indicated that there were significant main effects for peak perpendicular force (p < 0.001), perpendicular impulse (p = 0.018), and velocity at 2.5 m (p = 0.005) on land. However, no significant effects were found between techniques in the water trials. As many of the participants were master swimmers, it is possible that they were unable to approach the wall in the water at the requisite speed to elicit a benefit from the countermovement.

Does T'ai Chi Gait Reduce External Knee Adduction Moment?

INTRODUCTION: T'ai chi chuan is a beneficial exercise of improving health and function. Biomechanical insights of t'ai chi chuan are less understood. OBJECTIVES: To study t'ai chi gait (TCG), a common form of t'ai chi chuan in order to quantify external knee adduction moment (EKAM) as a key indicator of mechanical loading of the medial compartment of the knee compared with normal walking (NW). DESIGN: A quantitative biomechanics approach to determine peak EKAM for NW and TCG. RESULTS: There were a tri-modal pattern of EKAM during TCG and a bimodal pattern of EKAM during normal walking. In addition, subsequent analysis showed a 25%-47% reduction in peak EKAM during double support phases of TCG compared with NW; the peak EKAM of TCG during single-limb support phase showed significantly higher magnitude than the other two double-support phases. CONCLUSION: These results indicate that t'ai chi chuan might be a beneficial intervention for reducing the medial mechanical load at the knee joint, particularly during the first double-support phases of TCG, but the special consideration of higher peak EKAM of single-limb support phase is needed during regular t'ai chi chuan practice.

Biomechanical comparison of frontal plane knee joint moment arms during normal and Tai Chi walking.

[Purpose] Medial knee osteoarthritis, a degenerative joint disease, affects adults. The external knee adduction moment, a surrogate knee-loading measure, has clinical implications for knee osteoarthritis patients. Tai Chi is a promising intervention for pain alleviation in knee osteoarthritis; however, the characteristics of external knee adduction moment during Tai Chi have not been established. [Subjects and Methods] During normal and Tai Chi walking, a gait analysis was performed to compare the external knee adduction moment moment-arm characteristics and paired t-tests to compare moment-arm magnitudes. [Results] A significant difference was observed in the average lateral direction of moment-arm magnitude during Tai Chi walking (-0.0239 ± 0.011 m) compared to that during normal walking (-0.0057 ± 0.004 m). No significant difference was found between conditions in average medial direction of moment-arm magnitude (normal walking: 0.0143 ± 0.010 m; Tai Chi walking: 0.0098 ± 0.014 m). [Conclusion] Tai Chi walking produced a larger peak lateral moment-arm value than normal walking during the stance phase, whereas Tai Chi walking and normal walking peak medial moment-arm values were similar, suggesting that medial knee joint loading may be avoided during Tai Chi walking.