Abstract
e of the present study was to examine the changes in the pedalling kinetics and in the ground reaction forces as a measure of the cycling stability during an incremental cycling exercise. Furthermore, we compared the effectiveness of the pedalling technique and postural stability between the high and low Functional Movement Screen score (FMS TM ) cyclists and analysed the relationships between the cycling specific postural stability, pedalling kinetics and cyclists FMS TM test scores. 31 competitive cyclists (18.5±2.1y; 1.81±0.06m; 73.7±7.5kg) were categorized based on the (FMS TM ) test results in a low (LS, n=19; FMS≤14) and a high (HS, n=12; FMS>14) score group. The pedalling effectiveness and absolute symmetry indexes, as well the ground reaction force (GRF) were measured during incremental cycling exercise. Cycling specific postural stability was expressed as the body mass corrected standard deviation of 3 linear and 3 angular GRF components during a 30sec cycling at four power levels. We found that during incremental cycling exercise the pedalling effectiveness, smoothness and cyclist’s swaying in all three planes increased according to the combined effect of the workload and fatigue. Cyclists with high FMS TM score showed a lower bilateral pedalling asymmetry and a greater cycling specific postural stability, but showed no differences in the pedalling effectiveness and smoothness compared with the LS cyclists. Cyclist’s FMS TM score were moderately related with the stability components acting along the horizontal plane. The pedalling effectiveness, smoothness and bilateral asymmetry were inversely related to the components acting perpendicularly to the horizontal plane. Key words: Core stability, Pedalling effectiveness, Bilateral Asymmetry, Ground Reaction Force
no differences in the pedalling effectiveness and smoothness compared with the LS cyclists. Cyclist’s FMS TM score were moderately related with the stability components acting along the horizontal plane. The pedalling effectiveness, smoothness and bilateral asymmetry were inversely related to the components acting perpendicularly to the horizontal plane. Key words: Core stability, Pedalling effectiveness, Bilateral Asymmetry, Ground Reaction Force
LASE Journal of Sport Science 2016 Vol 7, No. 1, Page | 2 Introduction Road cycling is a time and energy consuming sport where the training and competitions last up to 7 hours (Jeukendrup, Craig & Hawley, 2000), vary largely in the intensity levels (Ebert, Martin, Stephens & Withers, 2006) and the effective use of strength and energy are important factors for the successful performance (Lucía, Hoyos, & Chicharro, 2001) and injury preventation (Holmes, Pruitt & Whalen, 1994). The metabolic cost (Broker & Gregor, 1994; Ettema & Lorås, 2009), muscle activity (Duc, Bertucci, Pernin, & Grappe, 2008) and biomechanical effectiveness (Gonzales & Hull, 1989; Coyle, et al., 1991) are indicators that quantity the economy of cycling. No direct relationships between those parameters have been found (Castronovo, Conforto, Schmid, Bibbo, & D'Alessio, 2013), but they are all sensitive to bicycle set up according to cyclists, and to pedalling cadence, workload, road incline, cyclist experience, riding position and fatigue (Fonda & Sarabon 2010). The biomechanical rationality in cycling is mainly measured as a torque delivery effectiveness from the legs to the pedals using specially designed pedals (Gonzales & Hull, 1989; Coyle, et al., 1991) or commercially available equipment (Bini & Hume 2014). But these methods account mainly the work of the lower limbs and less of the upper body motion. It is known that with the increase in workload not only the amount of the force delivery, direction and efficiency on the pedals are changing, but also the application of the force to the saddle and handlebars (Stone & Hull, 1995). In other words, when the reaction forces on the pedals increase, then the body weight is less supported by the saddle. Furthermore, accelerations of the trunk center of mass, hips and shoulders will increase (Costes, Turpin, Villeger, Moretto & Watier, 2015). In line with this it has been found that stabilisation of the upper body (McDaniel, Subudhi, & Martin, 2005) and balancing of the bicycle (Miller, Heath, Bressel & Smith, 2013) bear additional metabolic cost. Stability of the cycling is also associated with the overuse injuries. Neck and back injuries are
shoulders will increase (Costes, Turpin, Villeger, Moretto & Watier, 2015). In line with this it has been found that stabilisation of the upper body (McDaniel, Subudhi, & Martin, 2005) and balancing of the bicycle (Miller, Heath, Bressel & Smith, 2013) bear additional metabolic cost. Stability of the cycling is also associated with the overuse injuries. Neck and back injuries are described as the most common overuse injuries associated with the long distance road cycling (Weiss, 1985; Wilber, Holland, Madison, & Loy, 1995; Dannenberg, Needle, Mullady & Kolodner, 1996). Increased lumbar flexion and rotation with an associated loss of stabilization of the lumbar spine have been show to be related to the lower back pain (Burnett, Cornelius, Dankaerts, et al., 2004). It has been also shown that after strenuous cycling exercises during a test of closed- eyed standing there is a significant increase in the instability of the antero- posterior, but not in the medio-lateral direction (Wiest, Diefenthaeler, Mota
3 | Rannama et al: PEDALLING TECHNIQUE AND ... & Carpes, 2011), that indicates to the fatigue in the postural stabilisation muscles after an intensive cycling. Overuse problems in cycling can be attributed to a high number of pedalling repetitions produced by more or less asymmetric human body that is fixed as closed kinetic chain on the symmetrically designed bicycle (Holmes, Pruitt & Whalen, 1994). Existence of the asymmetry in the cycling kinematics (Edeline, et al., 2004), kinetics (Daly & Cavanagh 1976; Sanderson, 1990; Smak, Neptune & Hull, 1999; Carpes, et al., 2008) and muscle activation (Carpes, et al., 2011; Rannama & Port 2015) is well known. It seems that an increased effort improves the symmetry of pedalling kinetics and is also influenced by the pedalling rate (Carpes, Mota & Faria, 2010). At the same time the relationships between the pedalling symmetry and the cycling performance or the injury risk are not frequently discussed. The asymmetry in the strength of the bilateral knee extensors and the difference in the trunk motion kinematical between the left and right side during the pushing phases have been found to be negatively related with a short term sprint cycling performance (Rannama, Port, Bazanov, & Pedak, 2015), but there is also an opposite evidence that cyclists with a higher effectiveness in the bilaterally asymmetrical force delivery had better results in a 4 km time trial (Bini & Hume 2015). It has been proposed that the inclusion of the core stability training could have a beneficial effect in the terms of overuse injuries, and may also help to reduce the asymmetry of the movements, improve bike handling and stability (Fordham, Garbutt & Lopes, 2004; Asplund & Ross 2010). But there is a lack of empirical evidence of the relationships between the state of the core muscles and the variables of cycling performance and the injury incidence rate. Abt et al (2007) found that after fatiguing muscles of the torso the pedalling kinetics remained unchanged, but there was an alteration in the movement kinematics. Authors suggested that the training of the core strength for the greater torso
of the relationships between the state of the core muscles and the variables of cycling performance and the injury incidence rate. Abt et al (2007) found that after fatiguing muscles of the torso the pedalling kinetics remained unchanged, but there was an alteration in the movement kinematics. Authors suggested that the training of the core strength for the greater torso stability within the saddle helps to maintain the alignment of the lower extremity for the greater force transmission to the pedals (Abt, et al., 2007). In a last decade the Functional Movement Screen (FMS TM ) has become popular as a measurement method for the core stability and for the fundamental movement abilities in the monitoring of the training and in the scientific research (Kraus, Schütz, Taylor & Doyscher, 2014). The FMS TM test includes 7 fundamental movement exercises that are evaluated in the terms of the quality of movement patterns, bilateral asymmetry and existence of the compensatory movements in a scale from 0 to 3 with a maximal overall score of 21 points (Cook, Burton, Hoogenboom & Voight
LASE Journal of Sport Science 2016 Vol 7, No. 1, Page | 4 2014a and 2014b). This test complex is shown to have a good intra- and interrater reliability (Minick, et al., 2010; Teyhen, et al., 2012) and validity as a predictor of injury risk (Kiesel, Plisky, & Voight, 2007; Hotta, et al., 2015). Research is showing that the FMS TM score equal to or lower than 14 is associated with a bigger injury risk in the professional football players (Kiesel, Plisky, & Voight, 2007) and among the competitive male runners (Hotta, et al., 2015). Validity of the FMS to predict sport performance is not as clear as demonstrated with the risk of injuries (Kraus, Schütz, Taylor, & Doyscher, 2014). Some suggest that the core stability and FMS TM are not strong predictors of exercise performance (Okada, Huxel & Nesser, 2011), but there is evidence that high FMS TM scored track and field athletes have better results in a longer time perspective, as less injuries disturb the training process (Chapman, Laymon & Arnold, 2014). Authors of the present study have not found empirical evidence relating the FMS TM test results to the competitive road cyclist’s pedalling technique and cycling specific postural stability. We believe that current study is the first attempt to analyse the cycling specific stability by measuring the changes in the ground reaction force components during the various work intensity levels in the cycling. Purpose of the present study was to examine the changes in pedalling kinetics and ground reaction forces as a measure of the cycling stability during incremental cycling exercise, to compare the effectiveness of the pedalling technique and postural stability between high and low FMS TM score cyclists and to analyse the relationships between cycling specific postural stability, pedalling kinetics and cyclists FMS TM test scores. Material and methods Participants Participants of current study were 31 competitive junior (n=9) and U23 (n=22) class male road cyclists (18.5±2.1 years, 181.1±6.0cm, 73.7±7.5 kg, Vo2max – 64.6±4.6ml/min/kg). All athletes had had at least 4 years of focused endurance cycling training and competition experience and had annual cycling distance
specific postural stability, pedalling kinetics and cyclists FMS TM test scores. Material and methods Participants Participants of current study were 31 competitive junior (n=9) and U23 (n=22) class male road cyclists (18.5±2.1 years, 181.1±6.0cm, 73.7±7.5 kg, Vo2max – 64.6±4.6ml/min/kg). All athletes had had at least 4 years of focused endurance cycling training and competition experience and had annual cycling distance above 12000km during the last season. 30 cyclists were right and 1 left leg dominant, assessed as ball kicking preference. Study was performed after the end of a competitive season and before the start of a new preparation period. All participants were free of injuries and were informed of the research procedures and risks before the testing. All participants were told to avoid heavy or intensive trainings at least two days before the experiment. Procedures All experimental procedures for one person were made at same day. After arrival the cyclists performed following steps in the named order:
5 | Rannama et al: PEDALLING TECHNIQUE AND ... answered the questionnaire about training and health history of the past season; passed basic anthropometric measurement; performed Functional Movement Screen (FMS TM ) tests and completed incremental cycling exercise. The FMS TM consisted of the following sub-tests (Fig. 1): deep squat, hurdle step, in-line lunge, shoulder mobility test, active straight leg raise, trunk stability push-up and a rotary stability test, that assessing hip flexion, external and internal rotation strength and mobility, core stability and the mobility of shoulder joints (Cook, Burton, Hoogenboom & Voight, 2014a and 2014b) . All the sub-tests were performed at least three times and were registered from the different views, while the best trials were scored. All performed tests were captured by HD video camera (frame rate 60Hz). Figure 1. The FMS TM tests (A – deep squat, B – hurdle step, C – in-line lunge, D – active straight leg raise, E – shoulder mobility test, F – trunk stability push-up, G – rotary stability test) Experimental cycling exercise was performed using the personal racing bikes, which were mounted on the cycling ergometer Cyclus 2 (Avantronic, Cyclus 2, and Leipzig, Germany) that allows lateral inclination of the bike to matches the real life cycling. Exercise protocol consisted of a 10 minutes warm-up of steady ride at the power level of 100W and was followed by the incremental cycling exercise: target cadence 90±5 revolution/min (rpm), initial workload of 100W and the workload increased by 25W after every 2 minute until exhaustion. Exhaustion was defined as the point when the participant was no longer capable of maintaining a cadence of 70rpm. The cycling tests were conducted in sitting position hands on the drops (Fig. 2A).
LASE Journal of Sport Science 2016 Vol 7, No. 1, Page | 6 During and after 3 minute of the cycling exercise the heart rate and breath by breath pulmonary O2 (VO2), CO2 production ( CO2), and expired minute ventilation ( E) were measured continuously with the Cosmed Quark CPET metabolic analyser (Rome, Italy). Prior to each test, system was calibrated according to the manufacturer’s instructions. To measure the pedalling kinetics each participants bicycle was equipped with a pair of Garmin Vector power meter pedals (Garmin ector™). Same Vector pedals were used throughout and were calibrated before the each testing session according to manufacturer’s guidelines. Cycling specific postural stability was measured with two six component Kistler 9286B force plates (virtually combined surface of 0.6x1.4m plate) connected rigidly with Cyclus2 ergometer supports (Fig. 2) – one plate was under the bicycle front fork support (fixed with double side tape) and the other plate was under the ergometer load unit, connected with bicycle rear fork (fixed with special plate). The ergometer weight was set to zero before the cyclist sat on the bicycle, therefore only riders mass was counted. During the incremental test 6 GRF components were captured with frequency of 200Hz: 3 linear components along medio-lateral (Fx), anterior- posterior (Fy) and vertical axis (Fz) relative to bicycle direction and 3 rotational moments (Mx, My, Mz) around those axis (Fig. 2A). All data from Cyclus2 ergometer, Cosmed Quark CPET metabolic cart, Garmin Vector pedals and Kistler Force plates were synchronized in time and captured continuously. Data from the test was analysed after the test. Figure 2. The placement of force plates and GRF components (Figure A); computational parameters for Torque Effectiveness (TE) and Pedalling Smoothness (PS) (Figure B)
7 | Rannama et al: PEDALLING TECHNIQUE AND ... Measures Captured video of FMS TM tests were analysed with the video analysis software Kinovea 0.8.24 by an experienced (22 years of practice) physical therapist with 6 years of experience with the FMS. The movement quality of all 7 FMS TM were evaluated in four point ranking system: „3― – the correct performance of the movement pattern, „2― – the subject needs compensatory movements to solve the sub-test, „1― – the individual is not able to perform the movement pattern at all, „0― – subjects feel pain while performing a exercise. Five of the seven FMS TM items (hurdle step, shoulder mobility, active straight leg raise, trunk stability push-up and rotary stability test) are performed independently on the right and left sides of the body and the lowest score of the two sides were accounted. All of the seven sub-test scores were summed to a total FMS TM score, resulting in a maximum of possible 21 points. (Cook, Burton, Hoogenboom & Voight, 2014a and 2014b) According to a previous study cyclists were divided into low FMS score (LS – 4 or less point) and high FMS score (HS – over the 14 points) group (Kiesel, Plisky & Voight, 2007; Hotta, et al., 2015). The maximal aerobic power (VO2max) and ventilatory threshold levels assessment were performed using Cosmed PFT Ergo software independently by two experienced researchers. The first (aerobic level – AeL) and second ventilatory thresholds level (Anaerobic level – AnL) were estimated by methods described and validated by Weston and Gabbett (2001). The indicators for AeL were: the first nonlinear increases in the VE curve; the first increase VE/VO2 curve while the VE/VCO2 slope remains constant; the inflexion point between VO2 and VCO2. The AnL was determined by the second nonlinear increase in VE and the second nonlinear increase in VE/VO2 slope with simultaneous increase in VE/VCO2. The maximal aerobic oxygen uptake (VO2max) was determined as the highest 30sec average during the exercise. For the future analyses the AeL, AnL and VO2max power levels were determined as increments where the level
and VCO2. The AnL was determined by the second nonlinear increase in VE and the second nonlinear increase in VE/VO2 slope with simultaneous increase in VE/VCO2. The maximal aerobic oxygen uptake (VO2max) was determined as the highest 30sec average during the exercise. For the future analyses the AeL, AnL and VO2max power levels were determined as increments where the level moment was achieved. When the certain intensity level was achieved during first 30sec of the incremental step the previous increment was chosen. The kinetics of the pedalling were described by the pedalling power (POW), pedalling Torque Effectiveness (TE=(P+)/[(P+)+|P-|]*100(%)) and pedalling smoothness (PS=Pavg/Pmax*100(%)) collected from Garmin Vector pedals with 1sec interval, independently for the left and right sides throughout the experimental exercise(Fig. 2B). Also the absolute symmetry index (ASI (%)=100*|DO-ND|/0.5*(DO+ND)) was calculated (Robinson, Herzog & Nigg, 1987) for POW, TE and PS. Average values of the period