Mean Cadence Research Articles

Power Output in Professional Cyclists during the Tour de France

Until present, workload in cycling competitions was mostly described through heart rate measurements and indirect estimation of exercise intensity. However, the most accurate variable to describe workload in cycling is to measure directly the power applied by the rider to propel his bicycle. PURPOSE: To illustrate direct power output of professional cyclist during a three-week stage race (Tour de France). METHODS: 143 Stage recordings of 15 riders of the 2005 Tour de France were monitored using a mobile power measurement device (SRM Trainingssystem, Julich, Germany), which recorded Power (W) and cadence (rpm). The studied riders were not contending for a high overall ranking but represented a broad range of skills from mountain specialists to team helpers. According to their topographic characteristics, stages were categorized into flat (7 stages/54 recordings), hilly (5/43) and mountain stages (6/46). Data was electronically processed, overall averages for power in different stage types, time in different power- and cadence bands and maximal mean power (MMP) for various durations were calculated. RESULTS: Power output averaged 218 +/− 21 W (3.1 +/− 0.3 W/kg) for flat, 234 +/−13 W (3.3 +/− 0.2W/kg) for mountain-, and 228 +/− 22 W (3.3 +/− 0.3 W/kg) for hilly stages. Mean cadence was 74 +/− 6.3 rpm for flat, 69 +/− 3.2 rpm for mountain-, and 70 +/− 5.2 rpm for hilly stages. Riders spent significantly more race time at medium- and high power output (76 % vs. 66 %) and lower cadence (56 % vs. 36 %) in mountain and hilly stages compared to flat stages. Mountain stages showed higher MMP (426 W vs. 385 W) for longer durations (1800 sec) and lower MMP (1046 W vs. 1179 W) for shorter durations (15 sec) compared to flat stages. CONCLUSION: Measurements of power output allow a direct description of the workload sustained by an athlete during cycling competition. Our data shows that different topographical characteristics of a race require distinct power output capacities with long, medium- to high intensity efforts at low cadence during mountain stages and short, high intensity power bursts during flat stages. As the presented data was obtained from riders without ambitions for a high overall ranking in the three week race, it can be speculated that riders aiming for a top overall finish display even higher average power outputs during decisive stages.

PHYSIOLOGICAL RESPONSES OF WELL-TRAINED CYCLISTS TO FIELD AND LABORATORY MOUNTAIN BIKE RACE SIMULATIONS

High power output (W.kg-1) of short duration is important in mountain bike (MTB) racing during the mass start, steep hill climbing, and sprints. Research examining the physiological demands of MTB racing is limited. PURPOSE To simulate a field MTB race in the laboratory to measure the physiological and metabolic responses associated with MTB racing. METHODS Five well-trained male MTB cross-country cyclists (VO2max 72.0 ± 4.6 ml.kg-1.min-1, maximum power output (MPO) 5.40 ± 0.30 W.kg-1, maximum heart rate (HRmax) 189 ± 7 bpm) performed two laps of a MTB course in the field using their race bikes with MTB SRM power cranks fitted. A laboratory MTB race simulation was performed using a wind braked ergometer. Cyclists attempted to match the average and peak power output (W.kg-1) achieved in the field trial in the laboratory. Power output, heart rate and cadence were measured during field and laboratory trials, while oxygen uptake (VO2) was determined only during the laboratory simulation. RESULTS Mean power output and heart rate between the field and laboratory trials were similar (4.18 ± 0.55 vs 4.22 ± 0.19 W.kg-1 respectively, 175 ± 9 vs 170 ± 8 bpm, p > 0.05). Time spent below 2 W.kg-1 and above 6 W.kg-1 for the field and laboratory trials accounted for ~32% and ~30% of the total time respectively. During field and laboratory trials cyclists utilised 77.4% vs 78.1% of MPO, 93.0% vs 90.1% of HRmax respectively. There was a significant difference between mean cadence in the field and laboratory trials (60.3 ± 9.1 vs 75.2 ± 7.0 rpm, respectively, p < 0.05). Mean and peak VO2 for the simulation were 57.5 ± 3.3 and 69.3 ± 4.4 ml.kg-1 · min-1 respectively, with cyclists sustaining an average of ~80% VO2max. CONCLUSION Although it is possible to reproduce the power output and heart rate responses of MTB racing in the laboratory, the power-cadence relationships appear more difficult to replicate.

Dual Task Interference During Gait in People With Parkinson Disease: Effects of Motor Versus Cognitive Secondary Tasks

Exacerbation of movement disorders while doing 2 tasks (dual task performance) is a characteristic feature of Parkinson disease (PD). The aim of this investigation was to identify whether the type of secondary task (motor or cognitive) determined the severity of dual task interference. Footstep patterns for 15 people with PD and 15 comparison subjects without PD were compared when they walked: (1) at a self-selected speed, (2) while simultaneously performing a motor task (coin transference), and (3) while simultaneously performing a cognitive task (digit subtraction). Gait speed, stride length, cadence, and the percentage of the gait cycle in double-limb stance (DS) were examined with a computerized stride analyzer. When there was no second task, the mean stride length was less in the group with PD (1.29 m) than in the comparison group (1.51 m), and the mean gait speed was less in the group with PD (71.47 m/min) than in the comparison group (87.29 m/min). The mean cadence was less in the group with PD (110.79 steps/min) than in the comparison group (115.81 steps/min). The percentage of the gait cycle in DS was greater in the group with PD (33.38%) than in the comparison group (31.21%). Both groups reduced their stride length and speed when they had to change from unitask performance to dual task performance and DS increased. For the group with PD, cadence also decreased. For both groups, the type of secondary task had a negligible effect on the performance decrement. Although the performance of simultaneous motor or cognitive tasks compromised gait in people with PD, the type of secondary task was not a major determinant of the severity of dual task interference.

The validity of the GaitRite and the Functional Ambulation Performance scoring system in the analysis of Parkinson gait1

The purpose of this study was (1) to determine the validity of the GaitRite System in detecting footfall patterns and selected gait characteristics of person with early stage Parkinson's disease (PD) and (2) to investigate whether the Functional Ambulation Performance (FAP) scoring system is a valid tool to distinguish between selected gait characteristics of patients with early stage Parkinson's disease and similar age of non-impaired individuals. The FAP score is a quantitative means of assessing gait based on specific spatial and temporal gait parameters. 11 volunteers with idiopathic Parkinson's disease, (mean age = 74.3), and 11 age matched volunteers, (mean age = 70.3), with no history of neurological disorder participated in the study. The non-impaired control group were not matched in age and sex but of similar age and males and females were represented in the control group. Temporal and spatial parameters of gait were analyzed for both preferred- speed and fast-speed walking using the computerized GaitRite system. The system integrates specific components of locomotion to provide a single, numerical representation of gait, the Functional Ambulation Performance Score (FAP) score. The most powerful and discriminating variable between Parkinson's and non-impaired groups for both walking speeds was the mean normalized velocity (MNV). Which is velocity divided by leg length. The MNV was 0.83 for PD at preferred walking speed and 1.14 at fast speed, the non-impaired group preferred-speed group walking was 1.33, while fast-speed walking MNV was 1.70. Note the fast walking of PD was slower than the preferred velocity of the non-impaired group. For preferred-speed walking, all gait variables analyzed in the study were different between the two groups beyond the p < 0.05 level of confidence with the single exception of right stance percentage. For fast-speed walking, three of the entered variables did not discriminate between the two groups: the fast walking FAP score, left fast-walking cadence, and right fast-walking single support percentage. Our results indicate that persons with Parkinson's disease (PD) attain a significantly lower FAP score when ambulating at their preferred rate and demonstrate shorter step length and a longer step time than the age matched non-impaired group during both preferred and fast velocities of walking. Stance duration and double support duration were increased for the Parkinson's population, whereas single support duration, mean cadence, and heel-to-heel base of support were markedly reduced for both walking speeds. The FAP score was significantly different from the non-impaired control group for preferred-speed walking. These results indicate that the GaitRite system can be useful in detecting footfall patterns and selected time and distance measurements of persons with early stage Parkinson's disease and the FAP score discriminates between the PD population and the non-impaired controls when walking at preferred rate but not at fast walking.

Satisfaction with a New Community Stroke Rehabilitation Scheme

Discussion Mean velocity and cadence increased as the frequency of the cues increased; and decreased as the frequency of the cues decreased; except for 92.5% of preferred pace. Mean stride length remained stable regardless of the frequency of the cues. Therefore auditory cues appear to affect temporal parameters of gait and have little effect on spatial parameters. Auditory cues using a frequency at 85% of preferred pace appear to have a therapeutic effect by decreasing cadence and thus velocity of gait in subjects with Parkinson’s disease.

Effects of aerobic treadmill training on gait velocity, cadence, and gait symmetry in chronic hemiparetic stroke: a preliminary report.

It is widely assumed that only limited improvement in functional mobility is possible beyond the subacute period following ischemic stroke. Contrary to this notion, we studied "neurologically plateaued" stroke patients with chronic hemiparesis to assess whether a "task-oriented" treadmill-training regimen would improve walking speed, cadence, and gait cycle symmetry on a modified "Get-Up and Go" task. Five male patients with a mean age of 60.4 +/- 2.7 years (mean +/- S.D.) status post ischemic stroke (> 6 months prior) participated in this nonrandomized low-intensity treadmill exercise pilot study three times/week for 3 months. All patients had mild to moderate gait asymmetries due to residual hemiparesis. Patients were videotaped before and after 3 months of treadmill aerobic exercise (AEX) while performing a functional task consisting of arising from a chair, walking 3.1 m without an assistive device as fast as safely possible, and returning to sit. Gait events were timed using a 2-D Peak Motus video analysis system. After 3 months AEX training, times for the overall "get-up and return-to-sit" (GURS) task and the "straight-away walk" (SAW) segment decreased from 8.2 +/- 1.4 sec to 6.5 +/- 0.8 sec (mean +/- SEM) (p < 0.05), and from 3.7 +/- 1 sec to 2.8 +/- 0.7 sec (p < 0.05), respectively. These data represent improvements of 21% and 24% for the GURS and SAW segments, respectively. Mean velocity increased from 0.9 +/- 0.2 to 1.2 +/- 0.21 m/sec, a 33% improvement (p < 0.01). Mean cadence (steps/min) increased from 89 +/- 9 to 97 +/- 8, a 9% increase (p < 0.05). Mean stance and swing duration diminished for both paretic (P) and nonparetic (NP) limbs, and the intralimb stance/swing ratio values moved toward normal for both the paretic and nonparetic limbs. However, these latter changes reached significance only for the P limb. Interlimb stance symmetry was unchanged. The more impaired subjects experienced the greatest gains in gait velocity and temporal measures. Collectively, these findings indicate that treadmill exercise improves functional overground mobility in individuals with chronic, stable hemiparesis.

Lower Extremity Electromyographic Analysis of Running Gait

Onset of firing for the quadriceps, hamstrings, and gastroc soleus groups during running, both on a treadmill and over ground, was determined in seven normal adult male subjects. Surface and wire electrode data were collected simultaneously from 959 individual gait cycles. The mean velocity over ground was 274 +/- 38 m/minute, with a mean cadence of 171 +/- 14 steps/minute. The treadmill was set at 107 m/minute (4 miles/hour), and the subjects' mean cadence was 147 +/- 11 steps/minute. Over ground, the mean swing/stance ratio was 70/30 +/- 3%, and that for the treadmill was 60/40 +/- 6%. Like muscle groups on the right and left showed a mean difference in onset of muscle activity of 1.3% (+/- 4.6%) when measured during a minimum of ten cycles per subject for each test condition. The average difference in time of onset between the surface and wire electrodes was 2% (SD +/- 4.9%) on the treadmill and 1.5% (SD +/- 3.7%) for over-ground running. These differences are not statistically significant. Surface and wire electrode data have been determined to be equivalent only for regional synergistic muscle groups and should not be extrapolated to compare functions of individual muscles within those groups.

INTERFACE PRESSURES IN BELOW-KNEE (B-K) PROSTHESIS UPON RAMP WALKING

Ten B-K amputees were studied for stump-socket interface pressure changes upon ramp walking.Five miniature pressure transducers were placed on the patellar tendon, kickpoint, medial and lateral tibial condyle and the calf. Flexion of the hip and knee joint was evaluated by electric goniometers and the gait pattern was analysed through foot switches.Upon the level walking, the mean maximum pressure was 1.67kg/cm2 at the patellar tendon and 0.86kg/cm2 at the kick-point. The maximum pressures on the medial and lateral condyle and the calf were 1.01, 1.09, and 0.32kg/cm2 respectively.On the ramp walking, a remarkable pressure change was noted on the kick-point where the pressure was increased up to 1.40kg/cm2 on 3 degree descending and decreased to 0.65kg/cm2 on 3 degree ascending. On the patellar tendon, the pressure was decreased to 1.22kg/cm2 on 3 degree descending. There was little change noted during the ramp walking in the lateral and medial tibial condyle and the calf.On the level walking, flexion of the hip and the knee joint was 27.9 and 51.2 degree respectively and flexion of the joint was increased as the subject ascended.The mean cadence was 80 per minute with the stance phase of 57.8% on the prosthetic leg and 62.5% on the nomal leg. This may indicate some instability of the prosthetic leg.Finally, the computer analysis was compared with the conventional pen-recorder polygraph and future research is contemplated using the computer system.