The relationships among endurance performance measures as estimated from VO2PEAK, ventilatory threshold, and electromyographic fatigue threshold: a relationship design.
BACKGROUND
The use of surface electromyography has been accepted as a valid, non-invasive measure of neuromuscular fatigue. In particular, the electromyographic fatigue threshold test (EMG(FT)) is a reliable submaximal tool to identify the onset of fatigue. This study examined the metabolic relationship between VO(2PEAK), ventilatory threshold (VT), and the EMGFT, as well as compared the power output at VO(2PEAK), VT, and EMG(FT).


METHODS
Thirty-eight college-aged males (mean +/- SD = 22.5 +/- 3.5 yrs) performed an incremental test to exhaustion on an electronically-braked cycle ergometer for the determination of VO(2PEAK) and VT. Each subject also performed a discontinuous incremental cycle ergometer test to determine their EMG(FT) value, determined from bipolar surface electrodes placed on the longitudinal axis of the vastus lateralis of the right thigh. Subjects completed a total of four, 2-minute work bouts (ranging from 75-325 W). Adequate rest was given between bouts to allow for subjects' heart rate to drop within 10 beats of their resting heart rate. The EMG amplitude was averaged over 10-second intervals and plotted over the 2-minute work bout. The resulting slopes from each successive work bout were used to calculate EMG(FT).


RESULTS
Power outputs and VO2 values from each subject's incremental test to exhaustion were regressed. The linear equations were used to compute the VO2 value that corresponded to each fatigue threshold. Two separate one-way repeated measure ANOVAs indicated significant differences (p < 0.05) among metabolic parameters and power outputs. However, the mean metabolic values for VT (1.90 +/- 0.50 l.min-1) and EMG(FT)VO2(1.84 +/- 0.53 l.min-1) were not significantly different (p > 0.05) and were highly correlated (r = 0.750). Furthermore, the mean workload at VT was 130.7 +/- 37.8 W compared with 134.1 +/- 43.5 W at EMG(FT) (p > 0.05) with a strong correlation between the two variables (r = 0.766).


CONCLUSIONS
Metabolic measurements, as well as the power outputs at VT and EMG(FT), were strongly correlated. The significant relationship between VT and EMG(FT) suggests that both procedures may reflect similar physiological factors associated with the onset of fatigue. As a result of these findings, the EMG(FT) test may provide an attractive alternative to estimating VT.
Graef
Jennifer L
JL
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Smith
Abbie E
AE
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Kendall
Kristina L
KL
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Walter
Ashley A
AA
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Moon
Jordan R
JR
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Lockwood
Christopher M
CM
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Beck
Travis W
TW
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Cramer
Joel T
JT
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Stout
Jeffrey R
JR
Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Ave., Norman, OK 73019, USA.
Ergonomics. 1982 Sep;25(9):783-91
7173165
Eur J Appl Physiol Occup Physiol. 1996;72(3):195-203
8820885
Clin Physiol Funct Imaging. 2003 Jul;23(4):208-14
12914560
Eur J Appl Physiol Occup Physiol. 1987;56(6):643-9
3119335
J Appl Physiol (1985). 2003 Nov;95(5):1901-7
12857763
Eur J Appl Physiol Occup Physiol. 1991;63(1):1-5
1915324
Jpn J Physiol. 1981;31(4):585-97
7328909
Res Q Exerc Sport. 1980 Mar;51(1):234-48
7394286
Eur J Appl Physiol Occup Physiol. 1998 Sep;78(4):315-23
9754971
J Appl Physiol Respir Environ Exerc Physiol. 1982 May;52(5):1349-52
7096157
J Appl Physiol Respir Environ Exerc Physiol. 1978 Mar;44(3):350-2
632175
Eur J Appl Physiol Occup Physiol. 1993;67(4):305-8
8299596
J Strength Cond Res. 2006 Nov;20(4):824-8
17149988
Biochem J. 1987 Jul 15;245(2):551-6
3663177
J Appl Physiol. 1975 Jun;38(6):1132-9
1141128
Br J Sports Med. 1999 Jun;33(3):178-85
10378070
J Appl Physiol (1985). 1993 Apr;74(4):1729-34
8514689
Circulation. 1990 Jan;81(1 Suppl):II14-30
2403868