Muscle coordination while pulling up during cycling.

The aim of this study was to determine the influence of the pull up action on the pedalling mechanics and muscle coordination during cycling. 9 elite cyclists pedalled at 320 watts with their preferred technique and while pulling up. The pull up action increased significantly the pedalling effectiveness during the upstroke and around the bottom dead centre. This was associated with a significant enhancement of the biceps femoris activity (48%), an earlier onset of activation of the tibialis anterior, i. e., 211 ± 83° vs. 259 ± 22° (crank angle) and a delayed offset of activation of the gastrocnemius lateralis, i. e., 244 ± 19° vs. 216 ± 39°. Consequently, co-activities between tibialis anterior and gastrocnemius lateralis muscles over 55 ± 65° (crank angle range), as well as between the biceps femoris and the tibialis anterior over 48 ± 57° were generated. These higher co-activities were necessary to stiffen the ankle joint and to power the pedal during the upstroke. Thus changes in muscle coordination improved the pedalling effectiveness during the upstroke phase but would probably lead to impairment of the oxygen consumption. Therefore, training the pull up action could be of interest to optimize this muscle coordination associated with better pedalling effectiveness by additionally relieving hip or knee extensors during the downstroke.

Effects of pedal type and pull-up action during cycling.

The aim of this study was to determine the influence of different shoe-pedal interfaces and of an active pulling-up action during the upstroke phase on the pedalling technique. Eight elite cyclists (C) and seven non-cyclists (NC) performed three different bouts at 90 rev . min (-1) and 60 % of their maximal aerobic power. They pedalled with single pedals (PED), with clipless pedals (CLIP) and with a pedal force feedback (CLIPFBACK) where subjects were asked to pull up on the pedal during the upstroke. There was no significant difference for pedalling effectiveness, net mechanical efficiency (NE) and muscular activity between PED and CLIP. When compared to CLIP, CLIPFBACK resulted in a significant increase in pedalling effectiveness during upstroke (86 % for C and 57 % NC, respectively), as well as higher biceps femoris and tibialis anterior muscle activity (p < 0.001). However, NE was significantly reduced (p < 0.008) with 9 % and 3.3 % reduction for C and NC, respectively. Consequently, shoe-pedal interface (PED vs. CLIP) did not significantly influence cycling technique during submaximal exercise. However, an active pulling-up action on the pedal during upstroke increased the pedalling effectiveness, while reducing net mechanical efficiency.

Effect of soccer shoe cleats on knee joint loads.

Noncontact injuries frequently occur during soccer matches and training. The purpose of this study was to examine the influences of different soccer shoe studs to kinematic, kinetic and electromyographic parameters in the knee joint. Six male soccer players performed complex turning movements (180 degrees ) with bladed and round studded soccer shoes. Ground reaction forces, 3-D kinematics and electromyographic activity of the lower leg muscles were recorded. Calculated external knee joint moments were similar with both stud configurations, although there was a trend towards increased vertical and anterior-posterior ground reaction forces with blades. Electromyography evidenced significantly higher activation of m. quadriceps femoris (p = 0.02) with round studs during initial phase of stance. In conclusion, comparison of soccer shoes with round and bladed studs showed no significant differences in externally applied knee joint loads during a complex injury related movement. The significant increased activation of m. quadriceps femoris with round studs during the critical weight acceptance can be associated with an additional internal load on the anterior cruciate ligament. Therefore, results revealed no higher risk of getting noncontact knee joint injuries with bladed soccer shoes.

Development and evaluation of a new bicycle instrument for measurements of pedal forces and power output in cycling.

Determination of pedal forces is a prerequisite to analyse cycling performance capability from a biomechanical point of view. Comparing existing pedal force measurement systems, there are methodological or practical limitations regarding the requirements of scientific sports performance research and enhancement. Therefore, the aim of this study was to develop and to validate a new bicycle instrument that enables pedal forces as well as power output measurements with a free choice of pedal system. The instrument (Powertec-System) is based on force transducer devices, using the Hall-Effect and being mounted between the crank and the pedal. Validation of the method was evaluated by determining the accuracy, the cross talk effect, the influence of lateral forces, the reproducibility and, finally, a possible drift under static conditions. Dynamic tests were conducted to validate the power output measurement in reference to the SRM-System. The mean error of the present system was -0.87 +/- 4.09 % and -1.86 +/- 6.61 % for, respectively, the tangential and radial direction. Cross talk, lateral force influence, reproducibility and drift mean values were < +/- 7 %, < or = 2.4 %, < 0.8 % and 0.02 N x min (-1), respectively. In dynamic conditions, the power output measurement error could be kept below 2.35 %. In conclusion, this method offers the possibility for both valid pedal forces and power output measurements. Moreover, the instrument allows measurements with every pedal system. This method has an interesting potential for biomechanical analyses in cycling research and performance enhancement.

Workload demands in mountain bike racing.

This study aims at describing the workload demands during mountain bike races using direct power measurements, and to compare these data to power output and physiological findings from laboratory exercise tests. Power output (P, Watt) from 11 national team cyclists (9 male, 2 female) was registered continuously during 15 races using mobile crank dynamometers (SRM System). To evaluate the intensity of racing, incremental exercise tests with determination of P at aerobic and anaerobic thresholds (AT, IAT) and at exhaustion (MAX) were performed. Intensity zones were determined (zone 1 < AT; AT < zone 2 < IAT; IAT < zone 3 < MAX; zone 4 > MAX) and time spent during racing in these zones was calculated. Based on power output measurements P during racing was 246 +/- 12 W (male) and 193 +/- 1 W (female). P showed high variation throughout the race. In contrast heart rate (HR) was relatively stable during racing (male 177 +/- 6 bpm, female 172 +/- 7 bpm). 39 +/- 6 % of race time were spent in zone 1, 19 +/- 6 % in zone 2, 20 +/- 3 % in zone 3 and 22 +/- 6 % in zone 4. MTB races are characterized by a high oscillation in P with permanently elevated HR. A highly developed aerobic and anaerobic system is needed to sustain the high variation in workload.