Penn State University, University Park, PA, USA.
University of Georgia, Athens, GA, USA.
Physiol Rep. 2021 Apr;9(8):e14826. doi: 10.14814/phy2.14826.
Non-invasive determination of mitochondrial capacity via near infrared spectroscopy (NIRS) typically involves voluntary exercise of a single muscle group followed by as many as 26 brief ischemic cuff occlusions to determine a single recovery rate constant (k).
To determine the within- and between-visit repeatability of a shortened bilateral NIRS protocol, and to establish the feasibility of hamstring k measurements.
Sixteen young (eight women, eight men; 22 ± 3 years) active adults underwent a bilateral electrical stimulation protocol in which multiple (n = 4) measurements of k for the vastus lateralis (VL) and medial hamstring (MH) muscles were determined on two visits. Repeatability (CV% and intraclass correlations, ICC) and equivalency across visits were assessed for both muscles.
Mean k values in the VL were consistent with published values and within-visit ICCs were moderately high for both muscles in both sexes. In men, average k values on visit 2 were within 1% (VL muscle) and 5% (MH muscle) of the values on visit 1 (all p > 0.78). In women, average k values were 10%-15% lower on visit 2 (p = 0.01 and p = 0.15 for MH and VL) with the largest between-visit differences in a subset of participants with the most days between visits.
This bilateral NIRS protocol is time efficient and provides valid estimates of k in both sexes and muscle groups with acceptable within-visit repeatability. Lower than expected between-visit repeatability in some participants reinforces the need for further investigation of this newly developed protocol to identify and control for experimental and behavioral sources of variation.
通过近红外光谱（NIRS）无创测定线粒体容量，通常需要对单个肌肉群进行自愿运动，然后进行多达 26 次短暂的缺血袖带闭塞，以确定单个恢复速率常数（k）。
确定缩短双侧 NIRS 方案的日内和日间可重复性，并确定腘绳肌 k 测量的可行性。
16 名年轻（8 名女性，8 名男性；22 ± 3 岁）活跃的成年人接受双侧电刺激方案，在两次就诊时对股外侧肌（VL）和内侧腘绳肌（MH）的 k 进行多次（n = 4）测量。评估了两种肌肉的日内和日间重复性（CV%和组内相关系数 ICC）和等效性。
VL 的平均 k 值与已发表的值一致，并且两种性别中两种肌肉的日内 ICC 均较高。在男性中，第二次就诊时的平均 k 值与第一次就诊时的 k 值相差 1%（VL 肌肉）和 5%（MH 肌肉）（均 p > 0.78）。在女性中，第二次就诊时的平均 k 值低 10%-15%（p = 0.01 和 p = 0.15 用于 MH 和 VL），在一些就诊间隔时间最长的参与者中，日间差异最大。
这种双侧 NIRS 方案省时，可提供两性和肌肉群中 k 的有效估计值，且日内重复性可接受。一些参与者的预期之外的日间重复性较差，这进一步强调需要进一步研究这个新开发的方案，以识别和控制实验和行为变异性源。
