Purpose
Different strategies for near-infrared spectroscopy (NIRS)-derived muscle oxidative capacity assessment have been reported. This study compared and evaluated (I) approaches for averaging ...trials; (II) NIRS signals and blood volume correction equations; (III) the assessment of vastus lateralis (VL) and tibialis anterior (TA) muscles in two fitness levels groups.
Methods
Thirty-six participants 18 chronically trained (CT: 14 males, 4 females) and 18 untrained (UT: 10 males, 8 females) participated in this study. Two trials of twenty transient arterial occlusions were performed for NIRS-derived muscle oxidative capacity assessment. Muscle oxygen consumption (
V
˙
O
2
m
) was estimated from deoxygenated hemoglobin (HHb), corrected for blood volume changes following Ryan (HHbR) and Beever (HHbB) equations, and from oxygen saturation (StO
2
) in VL and TA.
Results
Superimposing or averaging
V
˙
O
2
m
or averaging the rate constants (
k
) from the two trials resulted in equivalent
k
values two one-sided tests (TOST) procedure with 5% equivalence margin—
P
< 0.001. Whereas HHbR (2.35 ± 0.61 min
−1
) and HHbB (2.34 ± 0.58 min
−1
) derived
k
were equivalent (
P
< 0.001), StO
2
derived
k
(2.81 ± 0.92 min
−1
) was greater (
P
< 0.001) than both.
k
values were greater in CT
vs
UT in both muscles (VL: + 0.68 min
−1
,
P
= 0.002; TA: + 0.43 min
−1
,
P
= 0.01).
Conclusion
Different approaches for averaging trials lead to similar
k
. HHb and StO
2
signals provided different
k
, although different blood volume corrections did not impact
k
. Group differences in
k
were detected in both muscles.
Decomposition of the surface electromyographic (sEMG) signal is commonly used to examine motor unit (MU) firing behavior. However, the intra- and inter-day reliability of these measurements has yet ...to be quantified or reported. This investigation 1) examined the effect of input excitation on the mean firing rate (MFR) vs. recruitment threshold (RT) relationship and 2) determined the inter- and intra-day reliability of the MFR vs. RT relationship at 30%, 50%, and 70% of maximum voluntary isometric strength (MVIC). Twenty-eight healthy males (23 ± 3 yr) completed two experimental visits, during which they performed MVIC testing and isometric ramp contractions at 30%, 50%, and 70% MVIC. sEMG signals were recorded from the vastus lateralis during the ramp contractions and decomposed to establish the MFR vs. RT relationship for the detected MUs. Intra- and inter-day reliability was then established for the slopes and y-intercepts of the MFR vs. RT relationship at each contraction intensity. All participants displayed significant MFR vs. RT relationships ( r range: -0.662 to -0.999; P ≤ 0.001-0.006). Intra- and inter-day intraclass correlation coefficients (ICCs) ranged from 0.766-0.824 and 0.867-0.919 for the slopes and from 0.780-0.915 and 0.804-0.927 for the y-intercepts, respectively. Furthermore, the slope coefficient was significantly greater at 70% than at 30% MVIC, and the y-intercepts increased with increasing contraction intensities. Changes in input excitation to the MU pool alter the magnitude, but not the reliability, of the slopes and y-intercepts of the MFR vs. RT relationship. NEW & NOTEWORTHY The firing behavior of the motor unit (MU) pool is often characterized using the mean firing rate vs. recruitment threshold relationship of the active MUs. Although this relationship has been widely used, this is the first study to report the effects of input excitation (contraction intensity) on the intra- and inter-day reliability of this relationship. The criteria used for MU analysis and the model utilized in this study allow for generalization to outside investigators and laboratories.
Quadriceps intramuscular anatomy is typically described in two dimensions. However, anatomical descriptions indicate fascicles in the quadriceps may have a three-dimensional orientation. The purpose ...of this investigation was to quantify the maximum force generating capacity of the individual quadriceps’ muscles in three dimensions. Muscle architectural parameters were obtained from three cadaver specimens (two female) and input into a geometry-based multiple fascicle muscle force model. Vastus lateralis, vastus medialis, and rectus femoris had partitions which could be defined based on differences in the sense and direction of fascicles between partitions. Vastus lateralis and rectus femoris were bipennate due to partitions sharing an aponeurosis. Vastus lateralis deep and superficial partitions exerted posterior- (maximum: −29 ± 5 N) and anterior-directed (maximum: 58 ± 15 N) forces on their shared distal aponeurosis. Rectus femoris medial and lateral partitions exerted medial- (maximum: −38 ± 17 N) and lateral-directed (maximum: 19 ± 12 N) forces on their shared proximal aponeurosis. All vastus medialis fascicles ran along the proximal–distal axis. However, fascicles arising near the lesser trochanter also ran along the superficial-deep axis, while fascicles arising from the linea aspera ran along the medial–lateral axis. Thus, vastus medialis could be divided into longus and oblique partitions. Due to the large pennation angle, vastus medialis oblique could exert maximum medial-directed (−219 ± 93 N) and proximal-directed (279 ± 168 N) forces at approximately −40° and −70° knee flexion, respectively, indicating dual roles for vastus medialis oblique dependent on knee flexion angle.
Vastus lateralis tendon tear is an infrequent cause of lateral knee pain. Previously reported cases have described acute injury in middle-aged men after eccentric quadriceps contraction. This case ...report discusses 2 adolescent patients with longitudinal midsubstance tears diagnosed with MRI and dynamic ultrasound and treated successfully with operative intervention.
Whilst people typically choose to locomote in the most economical fashion, during bicycling they will, unusually, chose cadences that are higher than metabolically optimal. Empirical measurements of ...the intrinsic contractile properties of the vastus lateralis (VL) muscle during submaximal cycling suggest that the cadences that people self-selected might allow for optimal muscle fascicle shortening velocity for the production of knee extensor muscle power. It remains unclear, however, whether this is consistent across different power outputs where the self-selected cadence (SSC) varies. We examined the effect of cadence and external power requirements on muscle neuromechanics and joint power during cycling. VL fascicle shortening velocity, muscle activation and joint-specific power were measured during cycling between 60 and 120 rpm (including SSC), while participants produced 10%, 30% and 50% of peak maximal power. VL shortening velocity increased as cadence increased but was similar across the different power outputs. Although no differences were found in the distribution of joint power across cadence conditions, the absolute knee joint power increased with increasing crank power output. Muscle fascicle shortening velocity increased in VL at the SSC as pedal power demands increased from submaximal towards maximal cycling. A secondary analysis of muscle activation patterns showed minimized activation of VL and other muscles near the SSC at the 10% and 30% power conditions. Minimization of activation with progressively increasing fascicle shortening velocities at the SSC may be consistent with the theory that the optimum shortening velocity for maximizing power increases with the intensity of exercise and recruitment of fast twitch fibers.
Regional muscle architecture measures are reported widely; however, little is known about the variability of these measurements in the rectus femoris, vastus lateralis and anterior and lateral vastus ...intermedius. Quantifying this variability provides the purpose of this paper.
Regional muscle thickness (MT), pennation angle (PA) and calculated and extended field of view (EFOV) fascicle length (FL) were quantified using ultrasonography in 26 participants across 51 limbs, on three occasions. To quantify variability, the typical error of measurement (TEM) was multiplied by two, and thresholds of 0.2-0.6 (small), 0.6-1.2 (moderate), 1.2-2.0 (large), 2.0-4.0 (very large) and >4.0 (extremely large) applied. Additionally, variability was deemed large when the intraclass correlation coefficient (ICC) was <0.67 and coefficient of variation (CV) >10%; moderate when ICC>0.67 or CV<10% (but not both); and small when both ICC>0.67 and CV<10%.
MT of all muscles and regions had low to moderate variability (ICC=0.88-0.98, CV=2.4-9.3%, TEM=0.15-0.47). PA of the proximal and distal vastus lateralis (ICC=0.85-0.96, CV=3.8-8%) had low variability and moderate to large TEM (TEM=0.42-0.83). PA of the rectus femoris was found to have moderate to very large variability (ICC=0.38-0.74, CV=11.4-18.5, TEM=0.61-1.29) regardless of region. Extended field of view derived FL (ICC=0.57-0.94, CV=4.1-11.5%, TEM=0.26-0.88) was superior to calculated FL (ICC=0.37-0.84, CV=7.4-17.9%, TEM=0.44-1.33).
Variability of MT was low in all quadriceps muscles and regions. Only rectus femoris PA and FL measurements were highly variable. The EFOV technique should be utilized to assess FL where possible. Inferences based on rectus femoris architecture should be interpreted with caution.
Ischemic preconditioning (IPC) involves brief, repeated bouts of limb occlusion and reperfusion capable of improving exercise performance at least partially by enhancing local skeletal muscle ...oxygenation. This study sought to investigate the effect of a lower limb IPC protocol, with either a 5-min or 45-min post-application delay, on vastus lateralis tissue saturation index (TSI) and systemic cardiac hemodynamics at rest and during short-duration intense cycling. Twelve young adults randomly completed four interventions: IPC (at 220 mmHg) with 5-min delay (IPC5), IPC with 45-min delay (IPC45), SHAM (at 20 mmHg) with 5-min delay (SHAM5), and SHAM with 45-min delay (SHAM45). Following IPC intervention and recovery delay, participants completed 5, 60-s high-intensity (100% W
peak
) cycle sprints separated by 120-sec of active recovery (30% W
peak
). Compared to baseline, TSI immediately following IPC5, but pre-exercise, remained lower than the equivalent for IPC45 (−5.9 ± 1.5%, p = .002). IPC, imposed at least 45-min before the completion of five 60-s sprint cycling efforts, significantly enhanced TSI during active recovery between sprint intervals compared to a 5-min delay (6.6 ± 2.4%, p = .021), and identical SHAM conditions (SHAM5: 5.8 ± 2.2%, p = .024; SHAM45: 6.2 ± 2.5%, p = .029). A 45-min delay following IPC appears to provide heightened skeletal muscle metabolic rebound prior to intense sprint cycling as compared to a 5-min delay. Furthermore, IPC followed by a 45-min delay enhanced recovery of skeletal muscle oxygenation during low intensity active sprint recovery, despite an unchanged decline in skeletal muscle oxygenation during near-maximal sprinting efforts.
The vastus lateralis muscle is one of the four muscles that make up the quadriceps femoris muscle, and it is also the largest of them. Some studies have shown that patients experience lower quality ...of life and muscle weakness after surgical treatment of thigh muscles in order to perform reconstructive surgery of the head and neck. The aim of our study was to assess the quantitative and qualitative function of the lower extremities using an isokinetic dynamometer and a validated questionnaire on subjective difficulties in patients who underwent reconstructive surgery with the vastus lateralis free flap. Fourteen participants aged 20-70 years who suffered from malignant tumor in the head and neck region. The free vastus lateralis flap was used for reconstruction. All patients underwent isokinetic dynamometric measurement with the isokinetic dynamometer to test the isokinetic functions of the thigh muscles after surgery. In addition, subjective assessment of the lower extremities was performed using the validated questionnaire Lower Extremity Functional Scale. All isometric dynamometer measurements of the donor leg were compared with those of the unoperated leg. Peak torque and average power were significantly lower in the operated leg compared with the unoperated leg after 60°/s extension (p = 0.018 for peak torque, p = 0.021 for average power) and 180°/s extension (p = 0.019 for peak torque, p = 0.015 for average power). On the other hand, there was no statistically significant difference in dynamometer measurements after 60°/s flexion (p = 0.700 for peak torque, p = 0.854 for average power, and 180°/s flexion (p = 0.634 for peak torque, p = 0.571 for average power). The median value for the LEFS was 65.5 (40.00-71.25). The results of this study showed that there is a significant deterioration regarding the biophysical properties of the operated leg after harvesting vastus lateralis free flap.
The purpose of the present study was to compare the myosin heavy chain (MHC) isoform composition of the deltoid and vastus lateralis muscles of the dominant and non-dominant limbs in handball ...players. Eleven male Greek elite handball players (age 22.6 ± 1.9 yrs, training experience 10.6 ± 2.1 yrs, height 184.1 ± 4.1 cm, and weight 81.0 ± 12.5 kg) participated in the study. Four muscle biopsies were obtained from the dominant and non-dominant deltoid and vastus lateralis muscles during the in-season period. The MHC composition was determined using SDS-PAGE. No significant difference was found between the dominant and non-dominant muscles; Deltoid muscle: MHC I (95%CI = −1.22, 0.33), P = 0.228, MHC ΙΙa (95%CI = −0.32, 1.59), P = 0.168 and MHC IIx (95%CI = −1.49, 1.10), P = 0.749; Vastus lateralis muscle: MHC I (95%CI = −0.38, 0.63), P = 0.586, MHC ΙΙa (95%CI = −0.50, 0.65), P = 0.783 and MHC IIx (95%CI = −1.08, 0.42), P = 0.355. The findings of the present study indicate that the greater use of the dominant limbs for throwing actions and body movements in handball do not lead to altered MHC isoform composition compared to the non-dominant limbs.
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