EFFECT OF BLOCK DESIGN ON ROTATIONAL CHARACTERISTICS OF A SWIM START

The purpose of this study was to examine the effect of start block design on the rotational characteristics of a swim start. Seven male and seven female university-level competitive swimmers (21.1±2.1 yrs, 1.79±0.08 m, 75.6±11.8 kg) completed three maximal effort swim starts under each of four conditions, flat block with no kick plate, flat block with a kick plate, inclined block with no kick plate and inclined block with a kick plate. Temporal and kinematic variables and angular momentum were determined for each start using a two-dimensional video analysis. Use of an inclined block significantly reduced block time by 4%, reduced time to 5m by 2.2% and reduced vertical velocity at entry by 4.9% compared to a flat block. Use of a kick plate significantly reduced block time by 3.4%, reduced time to 5m by 3.4%, increased horizontal velocity at takeoff by 3.7%, increased horizontal velocity at entry by 2.7% and increased the body orientation angle at takeoff by 2.7% compared to not using a kick plate. Neither block inclination nor use of a kick plate affected airborne whole body angular momentum. These data support using an inclined block platform and kick plate to improve start performance and suggest that experienced swimmers can adapt the rotational characteristics of their start to different conditions

Effect of Block Design on Rotational Characteristics of a Swim Start

Start block design in swimming had received little attention in the literature until the introduction of the kick plate. De Jesus et al. (2022) and Beretic et al. (2012) concluded that use of the kick plate provided advantages primarily in reducing block time and generating greater horizontal takeoff velocity and flight distance. This previous work has not considered how block design may affect the rotational characteristics of a swim start. PURPOSE: The purpose of this study was to examine the effect of start block design on the rotational characteristics of a swim start. METHODS: Fourteen university-level competitive swimmers (21.1±2.1 yrs, 1.79±0.08 m, 75.6±11.8 kg) completed three maximal effort swim starts under each of four conditions, flat block with no kick plate, flat block with a kick plate, inclined block with no kick plate and inclined block with a kick plate. Temporal and kinematic variables and angular momentum were measured for each start using a two-dimensional video analysis. RESULTS: Use of an inclined block significantly (pCONCLUSION: These data support using an inclined block platform and kick plate to improve start performance and suggest that experienced swimmers can adapt the rotational characteristics of their start to different conditions

Lower Extremity Muscle Activity When Walking on a Non-Motorized Treadmill

Effective interventions for increasing walking speed are important for improving health and quality of life in aging populations. Non-motorized treadmills (NMT) may enhance the ability to develop or improve motor control in gait by requiring the participant to produce and maintain speed as compared to use of a motorized treadmill (MT) which requires one to simply match speed. PURPOSE: The purpose of this project was to compare muscle activation patterns of lower extremity muscles between MT, NMT and overground (OG) walking. METHODS: Twenty healthy adults (24.4±7.2 yrs, 1.75±0.09 m, 75.4±13.1 kg) completed one trial of walking at each of three speeds (2.5, 3.5, 4.5 mph) and three modes (OG, MT, NMT). Surface EMG of the Biceps Femoris (BF), Tibialis Anterior (TA), Gastrocnemius (GA), and Vastus Medialis (VM) was collected at 1000 Hz using electrodes placed longitudinally at the midpoint of the muscle belly. After removing DC bias, EMG RMS was computed using a moving window of 250 ms. Peak EMG RMS within a stride was averaged across 8 consecutive gait cycles identified using vertical acceleration measured with a triaxial accelerometer. Separate 3x3 repeated measures ANOVA’s were used to compare muscle activity across walking speed and mode for each muscle. RESULTS: For all muscles, there was no significant interaction between walking mode and speed. Muscle activity significantly increased with walking speed (p\u3c0.05). TA, VM, and GA activity was not different between walking modes (p\u3c0.05). At 2.5 mph, GA muscle activity, was significantly (p\u3c0.001) higher for NMT (0.44±0.16 mV) than MT (0.33±0.13 mV) and OG (0.31±0.14 mV) but MT and OG were not different. At 3.5 mph, GA muscle activity, was significantly (p\u3c0.001) higher for NMT (0.49±0.19 mV) than MT (0.36±0.15 mV) and OG (0.36±0.17 mV) but MT and OG were not different. At 4.5 mph, GA muscle activity, was significantly (p\u3c0.001) higher for NMT (0.58±0.28 mV) than MT (0.47±0.19 mV) and OG (0.44±0.19 mV) but MT and OG were not different. CONCLUSIONS: These data suggest that use of NMT accentuates plantar flexor activity when walking. Given that reduced plantar flexor activity contributes to reduced gait speed in older adults, use of NMT has potential for clinical use in treatment of gait deficiencies in aging adults