Adding Vibration During Varied-Intensity Work Intervals Increases Time Spent Near Maximal Oxygen Uptake in Well-Trained Cyclists.

PURPOSE: Previous research suggests that the percentage of maximal oxygen uptake attained and the time it is sustained close to maximal oxygen uptake (eg, >90%) can serve as a good criterion to judge the effectiveness of a training stimulus. The aim of this study was to investigate the acute effects of adding vibration during varied high-intensity interval training (HIIT) sessions on physiological and neuromuscular responses. METHODS: Twelve well-trained cyclists completed a counterbalanced crossover protocol, wherein 2 identical varied HIIT cycling sessions were performed with and without intermittent vibration to the lower-intensity workloads of the work intervals (6 × 5-min work intervals and 2.5-min active recovery). Each 5-minute work interval consisted of 3 blocks of 40 seconds performed at 100% of maximal aerobic power interspersed with 60-second workload performed at a lower power output, equal to the lactate threshold plus 20% of the difference between lactate threshold and maximal aerobic power. Oxygen uptake and electromyographic activity of lower and upper limbs were recorded during all 5-minute work intervals. RESULTS: Adding vibration induced a longer time ≥90% maximal oxygen uptake (11.14 [7.63] vs 8.82 [6.90] min, d = 0.64, P = .048) and an increase in electromyographic activity of lower and upper limbs during the lower-intensity workloads by 20% (16%) and 34% (43%) (d = 1.09 and 0.83; P = .03 and .015), respectively. CONCLUSION: Adding vibration during a varied HIIT session increases the physiological demand of the cardiovascular and neuromuscular systems, indicating that this approach can be used to optimize the training stimulus of well-trained cyclists.

Comparison of two static methods of saddle height adjustment for cyclists of different morphologies.

Methods based on inseam length (IL) for saddle height adjustment in cycling are frequently employed. However, these methods were designed for medium-sized people. The aim of this study was to evaluate knee angle during pedalling by 2D video analysis and perceived comfort using a subjective scale under three saddle height conditions: (1) self-selected saddle height, (2) Genzling method (0.885 × IL) and (3) Hamley method (1.09 × IL minus crank arm length). Twenty-six cyclists of heterogeneous morphology were recruited. Three groups were determined based on IL: Short (IL < 0.8 m), Medium (0.8 m < IL< 0.88 m) and Long (IL > 0.88 m). The results showed that Medium and Long IL groups usually rode with saddle heights allowing knee angles consistent with those previously shown to prevent injuries (30°-40°). However, Short IL group, who were all children, self-selected a too low saddle height (knee angle was too large). Genzling and Hamley methods gave identical results for Medium IL group, permitting knee angles in the range of 30°-40°. However, both methods caused important differences between Short and Long IL groups. Hamley method was more suitable for short ILs, while Genzling method was more suitable for long ILs.

Physiological, biomechanical, and subjective effects of medio-lateral distance between the feet during pedalling for cyclists of different morphologies.

Improper medio-lateral distance between the feet in cycling can increase the risk of injuries and decrease performance due to hip/knee/ankle misalignment in the frontal plane. The objective of this study was to measure the impact of pedal spacing changes during pedalling on the biomechanical, physiological, and subjective variables of people with different morphologies. Twenty-two cyclists were divided into two groups according to their pelvis width (narrow and wide). They performed four submaximal pedalling tests with different pedal spindle lengths (+20 mm, +40 mm, and +60 mm compared to the pedal spindle lengths of standard road bikes). EMG activity, 3D joint kinematics of the lower limbs, comfort, and perceived exertion were measured during each test. Moreover, gas exchange data were collected to measure gross mechanical efficiency and cycling economy. No significant differences in muscular activity or joint kinematics were observed among the four experimental conditions. However, gross mechanical efficiency, cycling economy, and perceived comfort significantly improved while perceived exertion significantly reduced with the narrowest pedal spacing for the whole population, as well as for the narrow and wide pelvis groups. Therefore, the lowest medio-lateral distance between the feet seems more suitable for comfort and performance improvement, irrespective of the individual's morphology.

Immediate, short and medium-term effects of orthopedic insoles with a metatarsal retro-capital bar on biomechanical variables, plantar pressures and muscle activity in running.

BACKGROUND: The aim of this study was to evaluate the effect of 12 weeks of use of orthopedic insoles equipped with a metatarsal retro-capital bar (MRCB) on plantar pressure under the feet and lower limb kinematic variables during running. METHODS: Two groups of 10 runners used for 12 weeks while running orthopedic insoles without correction or equipped with a MRCB. All participants performed successively a standing posture (CoP displacement) test and a running test at 11 km.h-1 (lower limb kinematic variables) using with flat insoles and orthopedic neutral or MRCB insoles at the beginning (T0), after 4 (T4) and 12 weeks (T12) of use. RESULTS: For the MRCB group, CoP moved backwards while forefoot plantar pressure was decreased during standing position at T4 and T12 compared to T0. During running, the plantar pressure under the 2nd, 3rd and 4th metatarsal heads was reduced with MRCB at T0, T4 and T12. The one under the 1st metatarsal head was decreased at T4 and T12, when MRCB or flat insoles were used. The maximal extension and the total amplitude of ankle were slightly increased at T4 and T12 with or without wearing MRCB insoles. Similar changes in knee joint kinematics were observed but only at T12. Any significant changes were found in runners that used orthopedic insoles without correction. CONCLUSIONS: Orthopedic insoles equipped with MRCB involve lower plantar pressure under the metatarsal heads, which may be of interest to treat forefoot injuries in runners.

Adding Whole-Body Vibration to Preconditioning Squat Exercise Increases Cycling Sprint Performance.

Duc, S, Rønnestad, BR, and Bertucci, W. Adding whole-body vibration to preconditioning squat exercise increases cycling sprint performance. J Strength Cond Res 34(5): 1354-1361, 2020-This study investigated the effect of performing a preconditioning exercise with or without whole-body vibration (WBV) on a subsequent cycling sprint performance. Fourteen trained subjects performed 2 separate test sessions in randomized order. After a warm-up, the preconditioning exercise (body-loaded half-squats) was applied: 30 seconds of half-squats with WBV (40 Hz, 2 mm) or 30 seconds of half-squats without WBV with a 10-second all-out sprint performed after 1 minute. Surface electromyography (EMG) was measured from the vastus medialis, vastus lateralis, and gastrocnemius medialis during the sprints. Blood lactate level (BL), heart rate (HR), and rating of perceived exertion (RPE) were determined immediately after the 10-second sprint. Performing preconditioning exercise with WBV resulted in superior peak (1,693 ± 356 vs. 1,637 ± 349 W, p ≤ 0.05) and mean power output (1,121 ± 174 vs. 1,085 ± 175 W, p ≤ 0.05) compared with preconditioning exercise without WBV. Effect sizes showed a moderate and large practical effect of WBV vs. no WBV on peak and mean power output, respectively. No differences were observed between the conditions for BL, HR, and RPE after the sprints and in EMG activity during the sprints. In conclusion, it is plausible to suggest that body-loaded half-squats with WBV acutely induce higher power output levels. The practical application of the current study is that body-loaded squats with WBV can be incorporated into preparations for specific sprint training to improve the quality of the sprint training and also to improve sprint performance in relevant competitions.

Comparison of static and dynamic methods based on knee kinematics to determine optimal saddle height in cycling.

PURPOSE: Bike-fitting methods based on knee kinematics have been proposed to determine optimal saddle height. The Holmes method recommends that knee angle be between 25° and 35° when the pedal is at bottom dead centre in static. Other authors advocate knee angle of 30-40° during maximum knee extension while pedalling. Although knee angle would be 5-10° greater at bottom dead centre during pedalling, no study has reported reference values in this condition. The purpose of this study was to compare these three methodologies on knee, hip, and ankle angles and to develop new dynamic reference range at bottom dead centre. METHODS: Twenty-six cyclists volunteered for this experiment and performed a pedalling test on their personal road or mountain bike. Knee, hip, and ankle angles were assessed by two-dimensional video analysis. RESULTS: Dynamic knee angle was 8° significantly greater than static knee angle when the pedal was at bottom dead centre. Moreover, dynamic knee angle with the pedal at bottom dead centre was 3° significantly greater than dynamic knee angle during maximum knee extension. The chosen methodology also significantly impacted hip and ankle angles under most conditions. CONCLUSIONS: The results allow us to suggest a new range of 33-43° when the pedal is at bottom dead centre during pedalling. Thus, this study defines clearly the different ranges to determine optimal saddle height in cycling according to the condition of measurement. These findings are important for researchers and bike-fitting professionals to avoid saddle height adjustment errors that can affect cyclists' health and performance.

Strategies for improving the pedaling technique.

INTRODUCTION: Pedaling technique which can be defined as the way the cyclists pedal, has been mostly studied in lab conditions from pedal force kinetic, joints kinematic, and/or muscular activity patterns because it is considered as a main factor for gross efficiency (GE). Although this method is much controversial, its quality has extensively been evaluated from the index of pedal force effectiveness (IFE), i.e. the ratio between the effective to the total pedal force. Over the last thirty years, preferred pedaling technique has been compared between the experienced cyclists and non-cyclists and also often been manipulated by instructing these subjects to improve their effective force production during the downstroke phase ("pushing"), the upstroke phase ("pulling-up") or around top and bottom dead centers ("circling"). EVIDENCE ACQUISITION: It has been shown that PREF pedaling technique is much repeatable across crank cycles in experienced cyclists than in novice cyclists. PULL involves a significant increase of IFE compared to PREF, mainly attributed to the increase of the muscular work of hip (RF) and knee flexors muscles (BF) during the upstroke. This improvement is larger in non-cyclists than in experienced cyclists but it can be optimized in the latter after a short-term training (2-4 weeks) with pedal force feedback or uncoupled cranks. EVIDENCE SYNTHESIS: Despite that PULL enhances a lower muscular recruitment of contralateral knee extensors, GE and cycling performance variables are not significantly increased, probably due to the reversal effect of training with normal cranks and the highly robust pedaling technique of experienced cyclists. The question arises, as to whether or not, changes in pedaling technique can improve cycling efficiency if enough time is given for cyclists to adapt to a new pedaling technique. CONCLUSIONS: Further studies should investigate the pedaling techniques in more "ecological" conditions, as there is not probably one but several pedaling techniques that could optimize cycling efficiency according to the pedaling conditions (time-trial, uphill, road, off-road and track cycling), and should also focus on the potential effects of long-term training of PULL pedaling technique on cycling efficiency and cycling performance.

Analysis of muscular activity and dynamic response of the lower limb adding vibration to cycling.

Vibration in cycling has been proved to have undesirable effects over health, comfort and performance of the rider. In this study, 15 participants performed eight 6-min sub-maximal pedalling exercises at a constant power output (150W) and pedalling cadence (80 RPM) being exposed to vibration at different frequencies (20, 30, 40, 50, 60, 70 Hz) or without vibration. Oxygen uptake (VO2), heart rate (HR), surface EMG activity of seven lower limb muscles (GMax, RF, BF, VM, GAS, SOL and TA) and 3-dimentional accelerations at ankle, knee and hip were measured during the exercises. To analyse the dynamic response, the influence of the pedalling movement was taken into account. The results show that there was not significant influence of vibrations on HR and VO2 during this pedalling exercise. However, muscular activity presents a significant increase with the presence of vibration that is influenced by the frequency, but this increase was very low (< 1%). Also, the dynamic response shows an influence of the frequency as well as an influence of the different parts of the pedalling cycle. Those results help to explain the effects of vibration on the human body and the influence of the rider/bike interaction in those effects.

Transmission of whole body vibration to the lower body in static and dynamic half-squat exercises.

Whole body vibration (WBV) is used as a training method but its physical risk is not yet clear. Hence, the aim of this study is to assess the exposure to WBV by a measure of acceleration at the lower limb under dynamic and static postural conditions. The hypothesis of this paper is that this assessment is influenced by the frequency, position, and movement of the body. Fifteen healthy males are exposed to vertical sinusoidal vibration at different frequencies (20-60 Hz), while adopting three different static postures (knee extension angle: 180°, 120° and 90°) or performing a dynamic half-squat exercise. Accelerations at input source and at three joints of the lower limb (ankle, knee, and hip) are measured using skin-mounted accelerometers. Acceleration values (g) in static conditions show a decrease in the vibrational dose when it is measured at a more proximal location in the lower extremity. The results of the performed statistical test show statistically significant differences (p < 0.05) in the transmissibility values caused by the frequency, the position, and to the presence of the movement and its direction at the different conditions. The results confirm the initial hypothesis and justify the importance of a vibration assessment in dynamic conditions.

Effect of whole body vibration in energy expenditure and perceived exertion during intense squat exercise.

PURPOSE: The purpose of this study was to investigate the effect of whole body vibration in oxygen uptake during intense squatting exercise with an added weight and whole body vibration compared with the same exercise without vibration. METHODS: Nine male sub- jects performed three trials of dynamic squatting with an additional load of 50% of their body weight during 3 min. One trial without vibration, one trial with the frequency of 40 Hz and amplitude of 2 mm and one trial with the frequency of 40 Hz and amplitude of 4 mm. RESULTS: The results showed no difference between the three experimental trials in relative and absolute oxygen uptake. However, the metabolic power and energy expended in whole body vibration (2 mm) were significantly different from exercise without vibration. The data analysis also showed a significant difference in rating of perceived exertion with whole body vibration (4 mm) compared with the exercise without vibration. Results showed that the addition of vibration stimulus has an increase in the energy expenditure particularly with 40 Hz and 2 mm amplitude, suggesting that the high metabolic power during heavy resistance training could be increased by the addition of vibration stimulation. CONCLUSIONS: Involuntary contractions generated by the vibration can be used by coaches to increase the intensity of heavy resistance training or to increase the energy expended during the workouts if the goal is a decrease of body mass.

Heart rate variability to assess ventilatory threshold in ski-mountaineering.

The capacity to predict the heart rate (HR) and speed at the first (VT1) and second (VT2) ventilatory thresholds was evaluated during an incremental ski-mountaineering test using heart rate variability (HRV). Nine skiers performed a field test to exhaustion on an alpine skiing track. VT1 and VT2 were individually determined by visual analysis from gas exchanges (VT1V and VT2V) and time-varying spectral HRV analysis (VT1fH, VT2fH and VT2H). VT1 could not be determined with the HRV methods used. On the contrary, the VT2 was determined in all skiers. No significant difference between HR and speed at VT2H and VT2V was observed (174.3 ± 5.6 vs. 174.3 ± 5.3 bpm, and 6.3 ± 0.9 and 6.3 ± 0.9 km h(-1), respectively). Strong correlations were obtained for HR (r = 0.91) and speed (r = 0.92) at VT2H and VT2V with small limits of agreement (±3.6 bpm for HR). Our results indicated that HRV enables determination of HR and speed at VT2 during a specific ski-mountaineering incremental test. These findings provide practical applications for skiers in order to evaluate and control specific training loads, at least when referring to VT2.

Gross efficiency and cycling economy are higher in the field as compared with on an Axiom stationary ergometer.

This study was designed to examine the biomechanical and physiological responses between cycling on the Axiom stationary ergometer (Axiom, Elite, Fontaniva, Italy) vs. field conditions for both uphill and level ground cycling. Nine cyclists performed cycling bouts in the laboratory on an Axiom stationary ergometer and on their personal road bikes in actual road cycling conditions in the field with three pedaling cadences during uphill and level cycling. Gross efficiency and cycling economy were lower (-10%) for the Axiom stationary ergometer compared with the field. The preferred pedaling cadence was higher for the Axiom stationary ergometer conditions compared with the field conditions only for uphill cycling. Our data suggests that simulated cycling using the Axiom stationary ergometer differs from actual cycling in the field. These results should be taken into account notably for improving the precision of the model of cycling performance, and when it is necessary to compare two cycling test conditions (field/laboratory, using different ergometers).

Validity and reproducibility of the ErgomoPro power meter compared with the SRM and Powertap power meters.

PURPOSE: The ErgomoPro (EP) is a power meter that measures power output (PO) during outdoor and indoor cycling via 2 optoelectronic sensors located in the bottom bracket axis. The aim of this study was to determine the validity and the reproducibility of the EP compared with the SRM crank set and Powertap hub (PT). METHODS: The validity of the EP was tested in the laboratory during 8 submaximal incremental tests (PO: 100 to 400 W), eight 30-min submaximal constant-power tests (PO = 180 W), and 8 sprint tests (PO > 750 W) and in the field during 8 training sessions (time: 181 +/- 73 min; PO: approximately 140 to 160 W). The reproducibility was assessed by calculating the coefficient of PO variation (CV) during the submaximal incremental and constant tests. RESULTS: The EP provided a significantly higher PO than the SRM and PT during the submaximal incremental test: The mean PO differences were +6.3% +/- 2.5% and +11.1% +/- 2.1% respectively. The difference was greater during field training sessions (+12.0% +/- 5.7% and +16.5% +/- 5.9%) but lower during sprint tests (+1.6% +/- 2.5% and +3.2% +/- 2.7%). The reproducibility of the EP is lower than those of the SRM and PT (CV = 4.1% +/- 1.8%, 1.9% +/- 0.4%, and 2.1% +/- 0.8%, respectively). CONCLUSIONS: The EP power meter appears less valid and reliable than the SRM and PT systems.