Analysis of the aerobic-anaerobic transition in elite cyclists during incremental exercise with the use of electromyography

To investigate the validity and reliability of surface electromyography (EMG) as a new non-invasive determinant of the metabolic response to incremental exercise in elite cyclists. The relation between EMG activity and other more conventional methods for analysing the aerobic-anaerobic transition such as blood lactate measurements (lactate threshold (LT) and onset of blood lactate accumulation (OBLA)) and ventilatory parameters (ventilatory thresholds 1 and 2 (VT1 and VT2)) was studied.Twenty eight elite road cyclists (age 24 (4) years; VO2MAX 69.9 (6.4) ml/kg/min; values mean (SD)) were selected as subjects. Each of them performed a ramp protocol (starting at 0 W, with increases of 5 W every 12 seconds) on a cycle ergometer (validity study). In addition, 15 of them performed the same test twice (reliability study). During the tests, data on gas exchange and blood lactate levels were collected to determine VT1, VT2, LT, and OBLA. The root mean squares of EMG signals (rms-EMG) were recorded from both the vastus lateralis and the rectus femoris at each intensity using surface electrodes. Results - A two threshold response was detected in the rms-EMG recordings from both muscles in 90% of subjects, with two breakpoints, EMG(T1) and EMG(T2), at around 60-70% and 80-90% of VO2MAX respectively. The results of the reliability study showed no significant differences (p > 0.05) between mean values of EMG(T1) and EMG(T2) obtained in both tests. Furthermore, no significant differences (p > 0.05) existed between mean values of EMG(T1), in the vastus lateralis and rectus femoris, and VT1 and LT (62.8 (14.5) and 69.0 (6.2) and 64.6 (6.4) and 68.7 (8.2)% of VO2MAX respectively), or between mean values of EMG(T2), in the vastus lateralis and rectus femoris, and VT2 and OBLA (86.9 (9.0) and 88.0 (6.2) and 84.6 (6.5) and 87.7 (6.4)% of VO2MAX respectively). Rms-EMG may be a useful complementary non-invasive method for analysing the aerobic-anaerobic transition (ventilatory and lactate thresholds) in elite cyclists.

Trace elements and electrolytes in human resting mixed saliva after exercise

Objectives—Exercise is known to cause changes in the concentration of salivary components such as amylase, Na, and Cl. The aim of this investigation was to evaluate the eVect of physical exercise on the levels of trace elements and electrolytes in whole (mixed) saliva. Methods—Forty subjects performed a maximal exercise test on a cycle ergometer. Samples of saliva were obtained before and immediately after the exercise test. Sample concentrations of Fe, Mg, Sc, Cr, Mn, Co, Cu, Zn, Se, Sr, Ag, Sb, Cs, and Hg were determined by inductively coupled plasma mass spectrometry and concentrations of Ca and Na by atomic absorption spectrometry. Results—After exercise, Mg and Na levels showed a significant increase (p<0.05) while Mn levels fell (p<0.05). Zn/Cu molar ratios were unaVected by exercise. Conclusions—Intense physical exercise induced changes in the concentrations of only three (Na, Mg, and Mn) of the 16 elements analysed in the saliva samples. Further research is needed to assess the clinical implications of these findings.

Determination of the maximum steady state of lactate (MLSS) in saliva: An alternative to blood lactate determination

Based on previous research which shows parallelism between the saliva and blood lactate response during incremental exercise, we hypothesized that a "maximum salivary lactate steady state" (saliva-MLSS) might exist. Thus, the aim of the present investigation was to establish 1) which lower limit for the increase in salivary lactate concentration during a constant workload (i.e., from the 10th to the 20th min) test could be used to determine the saliva-MLSS and 2) if the exercise intensity corresponding to the saliva-MLSS is identical to that evoking the (blood) MLSS. Twelve male amateur athletes of mean (+/-SD) age 24+/-5 year were selected for the study. Based on the results of a previous maximal cycle ergometer test for lactate threshold (LT) determination, each subject performed consecutive constant workload tests of 20-min duration on separate days for MLSS determination, Blood and saliva (25 mu l) samples were collected at 0, 10, and 20 min during the tests for lactate determination. A Student's t-test for paired data demonstrated that a salivary lactate increase of 0.8 mM corresponded to the saliva-MLSS. At this value, indeed, no significant differences were observed between the mean (V) over dot O-2, and W values corresponding to the MLSS and the saliva-MLSS. In conclusion, the present findings indicate that 0.8 mM is the lower limit for the increase in saliva lactate concentration during a constant load test and thus is that which might be used as a reference to determine saliva-MLSS. Furthermore, saliva-MLSS might be used as an alternative to MLSS determination in blood samples.