Borut Fonda

Validity and reliability of different kinematics methods used for bike fitting

Abstract The most common bike fitting method to set the seat height is based on the knee angle when the pedal is in its lowest position, i.e. bottom dead centre (BDC). However, there is no consensus on what method should be used to measure the knee angle. Therefore, the first aim of this study was to compare three dynamic methods to each other and against a static method. The second aim was to test the intra-session reliability of the knee angle at BDC measured by dynamic methods. Eleven cyclists performed five 3-min cycling trials; three at different seat heights (25°, 30° and 35° knee angle at BDC according to static measure) and two at preferred seat height. Thirteen infrared cameras (3D), a high-speed camera (2D), and an electrogoniometer were used to measure the knee angle during pedalling, when the pedal was at the BDC. Compared to 3D kinematics, all other methods statistically significantly underestimated the knee angle (P = 0.00; η2 = 0.73). All three dynamic methods have been found to be substantially different compared to the static measure (effect sizes between 0.4 and 0.6). All dynamic methods achieved good intra-session reliability. 2D kinematics is a valid tool for knee angle assessment during bike fitting. However, for higher precision, one should use correction factor by adding 2.2° to the measured value.

Effects of whole-body cryotherapy duration on thermal and cardio-vascular response

Whole-body cryotherapy (WBC) is the exposure of minimally dressed participants to very cold air, either in a specially designed chamber (cryo-chamber) or cabin (cryo-cabin), for a short period of time. Practitioners are vague when it comes to recommendations on the duration of a single session. Recommended exposure for cryo-chamber is 150s, but no empirically based recommendations are available for a cryo-cabin. Therefore the aim of this study was to examine thermal and cardio-vascular responses after 90, 120, 150 and 180s of WBC in a cryo-cabin. Our hypothesis was that skin temperature would be significantly lower after longer exposers. Twelve male participants (age 23.9±4.2 years) completed four WBC of different durations (90, 120, 150 and 180s) in a cryo-cabin. Thermal response, heart rate and blood pressure were measured prior, immediately after, 5min after and 30min after the session. Skin temperature differed significantly among different durations, except between 150 and 180s. There was no significant difference in heart rate and blood pressure. Thermal discomfort during a single session displayed a linear increase throughout the whole session. Our results indicate that practitioners and clinicians using cryo-cabin for WBC do not need to perform sessions longer than 150s. We have shown that longer sessions do not substantially affect thermal and cardio-vascular response, but do increase thermal discomfort.

Adjusted saddle position counteracts the modified muscle activation patterns during uphill cycling

The main aim of this project was to study muscle activity patterns during steep uphill cycling (UC) (i.e., with a gradient of 20%) with (1) normal saddle geometry and (2) with adjusted saddle position ASP (i.e., moving the saddle forward and changing the tilt of the saddle by 20%). Based on our preliminary case study, we hypothesized that: (1) during 20% UC muscle activity patterns would be different from those of level cycling (LC) and (2) during 20% UC with ASP muscle activity patterns would resemble those of LC. Twelve trained male cyclists were tested on an electromagnetically braked cycle ergometer under three conditions with the same work rate (80% of maximal power output) and cadence (90 rpm): level (LC), 20% UC and 20% UC with ASP. Electromyographic signals were acquired from m. tibialis anterior (TA), m. soleus (SO), m. gastrocnemius (GC), m. vastus lateralis (VL), m. vastus medialis (VM), m. rectus femoris (RF), m. biceps femoris (BF) and m. gluteus maximus (GM). Compared to LC, 20% UC significantly modified both the timing and the intensity of activity of the selected muscles, while muscles that cross the hip joint were the most affected (RF later onset, earlier offset, shorter range of activity and decrease in peak amplitude of 34%; BF longer range of activity; GM increase in peak amplitude of 44%). These changes in EMG patterns during 20% UC were successfully counteracted by the use of ASP and it was interesting to observe that the use of ASP during 20% UC was perceived positively by all cyclists regarding both comfort and performance. These results could have a practical relevance in terms of improving performance during UC, together with reducing discomfort.

Biomechanics of Cycling

Biomechanics of Cycling The aim of this review paper is to outline the effects of several biomechanical factors on cycling efficiency and safety. The paper begins with a short introduction and listing of basic concepts important for understanding the biomechanics of cycling, followed by an explanation of mechanical forces and torques that are created during pedaling. Workloads and joint movement are detailed in chapter three, which is augmented by chapter four on muscle activation patterns. Throughout the text we have paid careful attention in interpreting the results of research studies into changes in bicycle geometry, feet position, terrain incline and other cycling-related factors. The paper closes with an overview of all issues and solutions as well as presenting proposals for additional research.

Effects of intermittent lower-body negative pressure on recovery after exercise-induced muscle damage.

UNLABELLED It has been reported in practice that the application of lower-body negative pressure (LBNP) to elite athletes during periods of intense training can help aid recovery. PURPOSE To examine the effects of LBNP on biochemical, pain, and performance parameters during a 5-d recovery period after a damaging plyometric-exercise bout. DESIGN Randomized controlled study. METHODS 24 healthy young female adults were randomly allocated into 2 groups. Before and 1, 24, 48, and 96 h after the damaging exercise for hamstrings (50 drop jumps and 50 leg curls), participants underwent a series of tests (blood samples, pain sensation, countermovement jump, maximal isometric torque production, maximal explosive isometric torque production, and 10-m sprint). After the damaging exercise, the experimental group was exposed to intermittent LBNP therapy daily for 60 min. RESULTS There was a statistically significant interaction (P<.05) between the experimental and control groups for maximal strength, explosive strength, pain sensation, and vertical jumps (maximal power and force). No statistically significant interaction was present for the biochemical markers, jump height, and 100-m sprint. CONCLUSIONS LBNP therapy could improve recovery by limiting the loss in muscle strength and power and limiting the presence of pain.

Bicycle rider control skills: expertise and assessment

Abstract Research on how human balance and control bicycles are inconclusive, largely due to the small number of participants in the previous studies. Therefore, the aim of this study was to test the hypotheses that 1) cycling lateral deviation amplitude will reliably show differences between more and less experienced cyclists and 2) more experienced will exhibit slower and smaller steering motions compared to the less experienced cyclists. Twenty-eight experienced and inexperienced cyclists rode a bicycle in a straight line. Lateral deviation, steering and roll were measured. Intersession reliability of the deviation was high with Cronbach’s alpha values higher than 0.75. The amplitude, variability and rate of steering and roll parameters showed statistically significant differences between the groups. The test used in this study is sensitive to detect differences between more and less experienced cyclists and can be used for further research that aims to test the effect of a specific intervention addressing rider control. We also showed that steering and roll angle, which were described before as two of the main motor control actions in bicycle control, differ in the variability, amplitude and rate between more and less experienced cyclists. The results of the present study have practical implications for improving bicycle rider control and increasing the safety of cyclists.

Effects of whole-body cryotherapy on recovery after hamstring damaging exercise

The purpose of this study was to examine the effects of whole-body cryotherapy (WBC) on biochemical, pain, and performance parameters during the 5-day recovery period after damaging exercise for hamstrings. Participants completed a bout of damaging exercise for the hamstring muscles on two separate occasions (control and experimental condition) separated by 10 weeks. During the control condition, subjects received no treatment after the damaging exercise. The experimental condition consisted of WBC everyday during the recovery period. WBC included single 3-min daily exposures to low temperatures (-140 to -195 °C) in the cryo-cabin. During the recovery period, subjects were tested for biochemical markers, perceived pain sensation, and physical performance (squat jump, counter movement jump, maximal isometric torque production, and maximally explosive isometric torque production). Majority of the observed variables showed statistically significant time effects (P < 0.05) in control group, which indicates the presence of muscle damage. Significant interaction between the control and WBC condition was evident for the rate of torque development (P < 0.05). Pain measures substantially differed between the WBC and the control condition after the exercise. Results of this study are not completely supportive of the use of WBC for recovery enhancement after strenuous training