Nicholas Caplan

Foot strike patterns and ground contact times during high-calibre middle-distance races

Abstract The aims of this study were to examine ground contact characteristics, their relationship with race performance, and the time course of any changes in ground contact time during competitive 800 m and 1500 m races. Twenty-two seeded, single-sex middle-distance races totalling 181 runners were filmed at a competitive athletics meeting. Races were filmed at 100 Hz. Ground contact time was recorded one step for each athlete, on each lap of their race. Forefoot and midfoot strikers had significantly shorter ground contact times than heel strikers. Forefoot and midfoot strikers had significantly faster average race speed than heel strikers. There were strong large correlations between ground contact time and average race speed for the womens events and men’s 1500 m (r = −0.521 to −0.623; P < 0.05), whereas the mens 800 m displayed only a moderate relationship (r = −0.361; P = 0.002). For each event, ground contact time for the first lap was significantly shorter than for the last lap, which might reflect runners becoming fatigued.

The effect of proprioceptive neuromuscular facilitation and static stretch training on running mechanics.

Caplan, N, Rogers, R, Parr, MK, and Hayes, PR. The effect of proprioceptive neuromuscular facilitation and static stretch training on running mechanics. J Strength Cond Res 23(4): 1175-1180, 2009-There is a long-standing belief that increased range of movement (RoM) at the hip or knee will improve running mechanics; however, few studies have examined the effect of such an increase in RoM. The aim of this study was to determine the influence of 2 methods of stretch training (static and proprioceptive neuromuscular facilitation [PNF]) on high-velocity running. Eighteen rugby league players were assessed for maximum sprinting velocity. They were randomly allocated into 2 stretch training groups: PNF or static. Each group trained their hamstrings 4 d·w−1 for 5 weeks. Pre- and posttraining subjects were videoed while running at 80% of maximum velocity. The video was digitized to identify biomechanical changes in hip flexion (HF), knee extension (KE), stride length (SL), stride rate (SR), and contact time (tc). Stretch training resulted in gains (p < 0.05) in HF for the static stretch (SS) (4.9%) and PNF (7.6%) groups. There were reductions in KE (p < 0.05) for SS (1.0%) and PNF (1.6%) groups. Stride mechanics were also altered after training. There were increases in SL (p < 0.05) for SS (7.1%) and PNF (9.1%) and a concomitant reduction in SR (p < 0.05) for SS (1.9%) and PNF (4.3%). No changes were observed in tc in either group. In conclusion, both SS and PNF training improved HF RoM and running mechanics during high-velocity running. These findings suggest that stretch training undertaken at the end of regular training is effective in changing running mechanics.

A fluid dynamic investigation of the Big Blade and Macon oar blade designs in rowing propulsion

Abstract The purpose of this investigation was to examine the fluid dynamic characteristics of the two most commonly used oar blades: the Big Blade and the Macon. Scaled models of each blade, as well as a flat Big Blade, were tested in a water flume using a quasi-static method similar to that used in swimming and kayaking research. Measurement of the normal and tangential blade forces enabled lift and drag forces generated by the oar blades to be calculated over the full range of sweep angles observed during a rowing stroke. Lift and drag force coefficients were then calculated and compared between blades. The results showed that the Big Blade and Macon oar blades exhibited very similar characteristics. Hydraulic blade efficiency was not therefore found to be the reason for claims that the Big Blade could elicit a 2% improvement in performance over the Macon. The Big Blade was also shown to have similar characteristics to the flat plate when the angle of attack was below 90°, despite significant increases in the lift coefficient when the angle of attack increased above 90°. This result suggests that the Big Blade design may not be completely optimized over the whole stroke.

A mathematical model of the oar blade – water interaction in rowing

Abstract Our aim was to present a mathematical model of rowing and sculling that allowed for a comparison of oar blade designs. The relative movement between the oar blades and water during the drive phase of the stroke was modelled, and the lift and drag forces generated by this complex interaction were determined. The model was driven by the oar shaft angular velocity about the oarlock in the horizontal plane, and was shown to be valid against measured on-water mean steady-state shell velocity for both a heavyweight mens eight and a lightweight mens single scull. Measured lift and drag force coefficients previously presented by the authors were used as inputs to the model, whichs allowed for the influence of oar blade design on rowing performance to be determined. The commonly used Big Blade, which is curved, and its flat equivalent were compared, and blade curvature was shown to generate a 1.14% improvement in mean boat velocity, or a 17.1-m lead over 1500 m. With races being won and lost by much smaller margins than this, blade curvature would appear to play a significant role in propulsion.

Optimization of oar blade design for improved performance in rowing

Abstract The aim of the present study was to find a more optimal blade design for rowing performance than the Big Blade, which has been shown to be less than optimal for propulsion. As well as the Big Blade, a flat Big Blade, a flat rectangular blade, and a rectangular blade with the same curvature and projected area as the Big Blade were tested in a water flume to determine their fluid dynamic characteristics at the full range of angles at which the oar blade might present itself to the water. Similarities were observed between the flat Big Blade and rectangular blades. However, the curved rectangular blade generated significantly more lift in the angle range 0 – 90° than the curved Big Blade, although it was similar between 90 and 180°. This difference was attributed to the shape of the upper and lower edges of the blade and their influence on the fluid flow around the blade. Although the influence of oar blade design on boat speed was not investigated here, the significant increases in fluid force coefficients for the curved rectangular blade suggest that this new oar blade design could elicit a practically significant improvement in rowing performance.

Leg stiffness decreases during a run to exhaustion at the speed at VO2max.

Abstract Vertical and leg stiffness are related to running speed. In endurance running, the ability to maintain stiffness might be more important than the absolute stiffness magnitude. The purpose of this study was to examine changes in vertical and leg stiffness during an exhaustive. Six sub-elite runners (24.2, s = 4.2 years; 1.81, s = 0.03 m; 73.4, s = 4.4 kg) participated in this study. They performed preliminary tests to determine lactate threshold, lactate turnpoint, O2max, sO2max and a series of isokinetic endurance tests. During the run to exhaustion runners were videoed (50 Hz) to determine contact and flight times, from which leg (Kleg) and vertical (Kvert) stiffness were calculated. During the run Kleg showed a significant decrease [P = 0.030, effect size statistics (ES) = 0.74], however, the decrease in Kvert was non-significant and of a small magnitude (P = 0.051, ES = 0.32). The distance covered during the run was correlated with ΔKleg (r = −0.868) but not ΔKvert (r = 0.684). ΔKleg was very strongly related to Δ ground contact time (r = −0.937) and Δ step length (r = −0.957). The Δ ground contact time had a near perfect relationship with Δ step length (r = 0.995). Isokinetic measures were not significantly correlated with either ΔKleg. The ability to maintain a short ground contact time appears to be a key determinant of maintaining performance during a run to exhaustion. Minimising this is important for maintaining Kleg. Kleg was not significantly related to isokinetic measures.

Numerical Modelling of the Flow Around Rowing Oar Blades (P71)

Recent experimental studies have presented the lift and drag coefficients for a range of oar blades. However, these studies were not able to provide insight into the mechanisms of lift and drag generation. The aims of this study, therefore, were to model the flow around an oar blade using computational fluid dynamics (CFD), and to validate this model against experimental data.

The influence of stretcher height on posture in ergometer rowing

Abstract The aim of this investigation was to determine the effect on rower posture of raising the stretchers. Nine male university rowers completed a single 30-s trial at each of three stretcher heights on an ergometer, at 30 strokes min−1. The first ten strokes with complete data were averaged and data for four time points during the stroke extracted: catch, mid-drive, finish, and mid-recovery. Ankle angle was shown to increase significantly at all points during the stroke (P<0.01) as the stretchers were raised. Knee angle was only significantly increased into a more extended posture at mid-drive (P<0.05) and mid-recovery (P<0.01) for the higher stretcher positions, hip angle was significantly reduced into a more flexed posture at the catch (P<0.05) and at mid-recovery (P<0.05), and the trunk was significantly extended at the catch (P<0.01), finish (P<0.01), and mid-recovery (P<0.05) as the stretchers were raised. Our results show that the increase in stretcher height caused the rowers body to rotate posteriorly in the sagittal plane. This we suggest reduced the vertical component of stretcher force, thus achieving a more mechanically effective position, which could have led to the slower rate of fatigue reported previously for the two raised stretcher positions (Caplan & Gardner, 2005). The increased flexion of the hip should not be ignored, however, as this may lead to overstretching of the hip extensors if the stretchers are raised too high. Further research is required to determine the extent to which the stretchers can be raised in on-water rowing.

A Simulation of Outrigger Canoe Paddling Performance (P19)

The main performance variable in outrigger canoeing is boat velocity. The aims of this study were to derive a model of the mechanics of the outrigger canoeing (O1) stroke and to perform a sensitivity analysis to determine the key variables for increasing boat velo city.

Textured insoles reduce vertical loading rate and increase subjective plantar sensation in overground running

Abstract The effect of textured insoles on kinetics and kinematics of overground running was assessed. 16 male injury-free-recreational runners attended a single visit (age 23 ± 5 yrs; stature 1.78 ± 0.06 m; mass 72.6 ± 9.2 kg). Overground 15-m runs were completed in flat, canvas plimsolls both with and without textured insoles at self-selected velocity on an indoor track in an order that was balanced among participants. Average vertical loading rate and peak vertical force (Fpeak) were captured by force platforms. Video footage was digitised for sagittal plane hip, knee and ankle angles at foot strike and mid stance. Velocity, stride rate and length and contact and flight time were determined. Subjectively rated plantar sensation was recorded by visual scale. 95% confidence intervals estimated mean differences. Smallest worthwhile change in loading rate was defined as standardised reduction of 0.54 from a previous comparison of injured versus non-injured runners. Loading rate decreased (−25 to −9.3 BW s−1; 60% likely beneficial reduction) and plantar sensation was increased (46–58 mm) with the insole. Fpeak (−0.1 to 0.14 BW) and velocity (−0.02 to 0.06 m s−1) were similar. Stride length, flight and contact time were lower (−0.13 to −0.01 m; −0.02 to−0.01 s; −0.016 to −0.006 s) and stride rate was higher (0.01–0.07 steps s−1) with insoles. Textured insoles elicited an acute, meaningful decrease in vertical loading rate in short distance, overground running and were associated with subjectively increased plantar sensation. Reduced vertical loading rate could be explained by altered stride characteristics.