No abstract

The SRM power measuring crank system is nowadays a popular device for cycling power output (PO) measurements in the field and in laboratories. The PowerTap (CycleOps, Madison, USA) is a more recent and less well-known device that allows mobile PO measurements of cycling via the rear wheel hub. The aim of this study is to test the validity and reliability of the PowerTap by comparing it with the most accurate (i.e. the scientific model) of the SRM system. The validity of the PowerTap is tested during i) sub-maximal incremental intensities (ranging from 100 to 420 W) on a treadmill with different pedalling cadences (45 to 120 rpm) and cycling positions (standing and seated) on different grades, ii) a continuous sub-maximal intensity lasting 30 min, iii) a maximal intensity (8-s sprint), and iiii) real road cycling. The reliability is assessed by repeating ten times the sub-maximal incremental and continuous tests. The results show a good validity of the PowerTap during sub-maximal intensities between 100 and 450 W (mean PO difference -1.2 +/- 1.3 %) when it is compared to the scientific SRM model, but less validity for the maximal PO during sprint exercise, where the validity appears to depend on the gear ratio. The reliability of the PowerTap during the sub-maximal intensities is similar to the scientific SRM model (the coefficient of variation is respectively 0.9 to 2.9 % and 0.7 to 2.1 % for PowerTap and SRM). The PowerTap must be considered as a suitable device for PO measurements during sub-maximal real road cycling and in sub-maximal laboratory tests.

This preliminary study examined, in a restricted randomized trial, the effects of a 6-week arm-crank rehabilitation training program in elderly osteoarthrosis patients after total hip arthroplasty, first on physiological and perceptual responses and second on physical function. Two groups of patients were studied: a training group (N = 7, mean age = 74.9 yr, standard deviation [SD] = 5.0 yr) who followed a training program in addition to traditional rehabilitation, and a control group who followed traditional rehabilitation only (N = 7 mean age = 75.4 yr, SD = 5.1 yr). At the beginning of the training program, the heart rate and the perceived exertion were not significantly correlated during the exercise session. However, at the end of the training program, five patients had a significant heart rate/perceived exertion relationship (p < 0.05). Furthermore, positive effects of the arm-crank rehabilitation training program were observed on cardioventilatory and functional responses in the training group compared with the control group. These results suggest that after an habituation period, most of our elderly osteoarthrosis patients experienced physical sensations that were connected to physiological responses. Therefore, perceived exertion could be useful in these patients to regulate exercise intensity, especially at the end of and after the rehabilitation period.

The aim of the present study was to investigate the influence of gear ratio (GR) and thus crank inertial load (CIL), on the activity levels of lower limb muscles. Twelve competitive cyclists performed three randomised trials with their own bicycle equipped with a SRM crankset and mounted on an Axiom ergometer. The power output ( approximately 80% of maximal aerobic power) and the pedalling cadence were kept constant for each subject across all trials but three different GR (low, medium and high) were indirectly obtained for each trial by altering the electromagnetic brake of the ergometer. The low, medium and high GR (mean +/- SD) resulted in CIL of 44 +/- 3.7, 84 +/- 6.5 and 152 +/- 17.9 kg.m(2), respectively. Muscular activity levels of the gluteus maximus (GM), the vastus medialis (VM), the vastus lateralis (VL), the rectus femoris (RF), the medial hamstrings (MHAM), the gastrocnemius (GAS) and the soleus (SOL) muscles were quantified and analysed by mean root mean square (RMS(mean)). The muscular activity levels of the measured lower limb muscles were not significantly affected when the CIL was increased approximately four fold. This suggests that muscular activity levels measured on different cycling ergometers (with different GR and flywheel inertia) can be compared among each other, as they are not influenced by CIL.