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Effect of contralateral limb exercise on peripheral perfusion index in a resting limb
For correspondence: Dr Himel Mondal, Department of Physiology, All India Institute of Medical Sciences, Deoghar 814 152, Jharkhand, India e-mail: himelmkcg@gmail.com
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Received: ,
Accepted: ,
Abstract
Background & objectives
Following surgical treatment and subsequent immobilisation of one limb, physiological reductions in blood flow are expected due to limited or no movement. This study was designed to investigate the change in perfusion index in a resting limb when the contralateral limb exercises (active and passive).
Methods
This was a two-arm comparative study with 39 healthy participants (22 males, 17 females) with a mean (SD) age of 23.4 (5.2) years. One limb was set to exercise (active and passive in different sessions), and another limb rested with a pre-designed exercise protocol. We measured perfusion index in exercising and non-exercising limbs after 3, 4, 5, and 6 min of exercise.
Results
In resting upper limbs, there was an increase in the perfusion index during both active and passive exercise of the contralateral limb (achieved at 3 min in active and 4 min in passive exercise). In resting lower limbs, in active exercise, the increase in perfusion index occurred at 4 min and 6 min of exercise. In passive exercise, there was no significant change in perfusion index.
Interpretation & conclusions
Active exercise of one limb significantly increases blood flow in the opposite, resting limb. This effect is not found in passive exercise in the lower limb. Hence, when one limb undergoes surgery, for a higher perfusion on that limb, an active exercise or passive exercise in the upper limb, or active exercise in the lower limb may be beneficial.
Keywords
Blood flow
cross-transfer effect
exercise
perfusion
plethysmography
Plethysmographic peripheral perfusion index is a practical and simple metric for determining blood flow in peripheral tissues1. Perfusion index can be measured with a portable pulse oximeter. These meters analyse the ratio of pulsatile (arterial blood) and non-pulsatile blood (mainly venous blood) to calculate the perfusion index2.
There are various classifications of exercise according to various domains3,4. In active exercise, the individual does bodily movements with their effort. In contrast, passive exercise is described as the movement of body parts without voluntary effort and with the help of another person or devices5. During exercise, the local tissue metabolite helps in maintaining a high blood flow to the tissue that can be measured by the perfusion index6,7. However, these changes may be different in active and passive exercise8.
After any surgical treatment in a limb, physiologically, the blood flow would be reduced due to less or no movement of that limb9. Adequate blood flow is required for an early recovery. Hence, if exercise in the contralateral limb improves the perfusion in the immobilised limb, it would aid early recovery of the patient. There is a gap in the literature on the status of perfusion index in an immobilised limb during an exercise on the contralateral limb. We compared the perfusion index of exercising and non-exercising limbs during a protocol of active exercise and passive exercise.
Materials & Methods
Type and settings
This was a two-arm comparative study conducted at the department of Physiology, All India Institute of Medical Sciences, Deoghar, Jharkhand, India, from November 2023 to December 2023. The study was approved by the Institution Ethics Committee, and all participants provided written informed consent.
Participants
We recruited adult participants whose age was equal to or above 18 yr. As no previous similar study was available, we decided to recruit a convenience sample of 30 adults. A detailed history was taken and clinical examination with measurements of resting heart rate, blood pressure, and anthropometric measurements were carried out. Any patient with a history of diabetes, neuromuscular disorder, vascular disorder or malformation, hypertension, or a history of smoking or alcohol consumption was excluded. The capability of exercise was screened by the physical activity readiness questionnaire10.
Exercise protocol
A 6-min programme was applied for each type of exercise (active and passive) for the upper and lower limbs. This exercise programme was formulated for this study by considering the supine posture among the participants. For passive and active exercise, the same range of movements was done. For the upper limb, the dominant arm was exercised, and for the lower limb, the right limb was exercised. The exercise protocol for an active session has been shown in figure 1. Cadence was maintained by Android application Metronome - B'Metronome (sZpak, Bielsko-Biała, Poland) on a smartphone11. The exercise was continued for 6 min. After completing a session of passive exercise, participants rested for 15 min before proceeding with the active exercise session.
- Exercise protocol for upper and lower limb exercise.
Perfusion index measurement
The perfusion index was measured by two portable pulse oximeters - BPL Smart Oxy pulse oximeter (BPL Medical Technologies Pvt. Ltd., Bengaluru)12. The perfusion index was measured on the finger of the exercising and non-exercising limb (great toe for lower limb and middle finger for upper limb) after 3 min of exercise and then with a gap of 1 min for 6 min to observe the changes. The measurement interval is shown in figure 2. The resting perfusion index was measured with a full 5 min rest.
- Measurement of perfusion index from resting and exercising limb.
Data analysis
For comparing the perfusion index on the left and right upper and lower limbs, a paired t-test13 was used. For effect size calculation, Cohen’s d was calculated14. For observing changes in perfusion after 3, 4, 5, and 6 min, repeated measure ANOVA with post hoc analysis (Tukey’s multiple comparison test) was conducted. P value <0.05 was considered statistically significant. We used GraphPad Prism 9.5.0 (GraphPad Software, Boston, USA) for the statistical tests.
Results
A total of 39 participants with mean (standard deviation, SD) age of 23.4 (5.2) years were recruited for this study. There were 22 males (56.4%) and 17 (43.6%) females. The age, weight, height, body mass index (BMI), resting heart rate (beats per minute), and blood pressure are shown in table I.
| Parameters | Overall (n=39) | Male (n=22) | Female (n=17) |
|---|---|---|---|
| Mean (SD) | |||
| Age (yr) | 23.4 (5.2) | 22.8 (4.8) | 24.1 (5.8) |
| Height (cm) | 165.3 (9.4) | 171.6 (5.8) | 157.3 (6.7) |
| Weight (kg) | 60.4 (11.6) | 66.6 (10.8) | 52.3 (7.6) |
| BMI (kg/m2) | 22 (3.5) | 22.6 (3.6) | 21.2 (3.2) |
| Resting HR (bpm) | 76.7 (9.8) | 75.6 (9.2) | 78.2 (10.5) |
| Resting systolic BP (mmHg) | 118 (10.2) | 121 (8) | 114.2 (11.7) |
| Resting diastolic BP (mmHg) | 76 (8) | 80 (5) | 70 (8) |
n, number; BMI, body mass index; HR, heart rate; bpm, beats per minute; BP, blood pressure; mmHg, millimetre of mercury, SD, standard deviation
The perfusion index in active exercise in exercising limb and resting limb is shown in Table II. In active exercise, in exercising limb, there was a significant increase in perfusion index after 3 min of exercise. Similarly, in the resting limb, there was a significant increase in perfusion index after 3 min of exercise. In passive exercise, in exercising limb, there was a significant increase in perfusion index after 3 min of exercise. In the resting limb, there was an increment of perfusion index at 4 min of exercise.
| Exercise mode | Time point | Exercising upper limb | Resting upper limb | P value* | Cohen’s d |
|---|---|---|---|---|---|
| Mean (SD) | |||||
| Active | Resting | 5.5 (4.3) | 5.8 (3.8) | 0.6 | 0.1 |
| At 3 min | 8.9 (3.9) | 7.4 (3.9) | 0.08 | 0.4 | |
| At 4 min | 9.7 (4.4) | 7.7 (3.8) | 0.03 | 0.5 | |
| At 5 min | 10 (4.5) | 8.1 (4) | 0.049 | 0.5 | |
| At 6 min | 10.3 (4.4) | 8 (4) | 0.02 | 0.3 | |
| P value† | <0.001; Rest-3 min, Rest-4 min, Rest-5 min, Rest-6 min | <0.001; Rest-3 min, Rest-4 min, Rest-5 min, Rest-6 min | - | - | |
| Passive | Resting | 6.4 (5.1) | 6.9 (4.8) | 0.5 | 0.1 |
| At 3 min | 8.9 (4.6) | 7.9 (4.4) | 0.2 | 0.2 | |
| At 4 min | 9.5 (4.6) | 8.6 (4.2) | 0.3 | 0.2 | |
| At 5 min | 9.4 (4.8) | 8.6 (4) | 0.4 | 0.2 | |
| At 6 min | 9.4 (4.7) | 8.5 (4) | 0.3 | 0.2 | |
| P value† | <0.001; Rest-3 min, Rest-4 min, Rest-5 min, Rest-6 min | <0.001; Rest-4 min, Rest-5 min, Rest-6 min | - | - | |
*P value of paired t-test. †P value of repeated measure analysis of variance (ANOVA) with post-hoc test, the pair mentioned along with P value showed significance difference. Cohen’s d interpretation: small (d ≤ 0.2), small-to-medium (d > 0.21 to=0.49), medium (d = 0.5 to <0.79), and large (d ≥ 0.8)
The perfusion index in rest and different time points in the lower limb in active and passive exercise is shown in table III. In active exercise, in exercising limb, there was an increment of perfusion index after 3, 4, and 5 min of exercise. In the resting limb, there was an increment of perfusion index at 4 and 6 min. In passive exercise, there was no increment of perfusion index in exercising or resting the lower limb.
| Exercise mode | Time point | Exercising lower limb | Resting lower limb | P value* | Cohen’s d |
|---|---|---|---|---|---|
| Mean (SD) | |||||
| Active | Resting | 1.7 (1.1) | 0.9 (0.6) | <0.001 | 0.9 |
| At 3 min | 2.7 (2.3) | 1.5 (1.4) | 0.01 | 0.5 | |
| At 4 min | 2.7 (2.2) | 1.7 (1.6) | 0.01 | 0.5 | |
| At 5 min | 2.8 (2.5) | 1.5 (1.3) | 0.007 | 0.6 | |
| At 6 min | 2.8 (3) | 1.8 (1.7) | 0.04 | 0.4 | |
| P value† | 0.003; Rest-3 min, Rest-4 min, Rest-5 min | 0.015; Rest-4 min, Rest-6 min | - | - | |
| Passive | Resting | 1.9 (1.5) | 1.6 (1.5) | 0.3 | 0.2 |
| At 3 min | 2 (1.5) | 2.1 (2.1) | 0.9 | 0.02 | |
| At 4 min | 1.8 (1) | 1.8 (1.7) | 0.9 | 0.007 | |
| At 5 min | 1.9 (1) | 1.8 (1.8) | 0.8 | 0.06 | |
| At 6 min | 2 (1.2) | 1.7 (1.3) | 0.4 | 0.2 | |
| P value† | 0.8 | 0.4 | - | - | |
*P value of paired t-test. †P value of repeated measure analysis of variance (ANOVA) with post-hoc test, the pair mentioned along with P value showed significance difference. Cohen’s d interpretation: small (d ≤ 0.2), small-to-medium (d > 0.21 to=0.49), medium (d = 0.5 to <0.79), and large (d ≥ 0.8)
Discussion
We found that in the upper limb, both in active (movement of the arm with own will) and passive (movement of the arm with other assistance) exercise, there is an increase in the perfusion in both exercising and resting upper limb. In the lower limb, in active exercise, there was a change in the perfusion index, but there was no change in passive exercise.
In active exercise, the initial surge in perfusion index within the exercising limb may be attributed to the higher metabolic demands due to increased muscle activity associated with voluntary movement. This finding aligns with literature highlighting the role of muscle contraction in promoting vasodilation and enhancing blood flow to meet the metabolic needs of working tissues15,16. The maintenance of perfusion index at a plateau from 3 to 6 min of active exercise indicates a potential adaptation response. Here, the vasculature optimizes blood flow to sustain muscle performance over time as there is the same cadence of limb movement (e.g., same exercise intensity). This sustained elevation in perfusion index suggests effective vascular regulation and adaptation to prolonged same-intensity exercise activity17.
The phenomenon of increased perfusion index in a resting limb during contralateral limb exercise may be explained by the ‘cross-transfer effect’. Several mechanisms underlie this phenomenon18. There is a complex relationship among neural, humoral, and vascular factors. Neural mechanisms involve the activation of afferent nerves during exercise. Along with it, there is a central command that drives the voluntary will to do the exercise. This leads to reflex vasodilation and increased blood flow not only in the exercising limb but also in non-exercising tissues through nervous system modulation19. Additionally, humoral factors such as released metabolites, cytokines, and nitric oxide from the exercising limb can diffuse systemically and induce vasodilation in the resting limb. Furthermore, improved vascular responsiveness induced by acute exercise may increase the perfusion index in the body as whole20.
In passive exercise, where movement is facilitated by external assistance, the significant increase in perfusion index mirrors the response observed in active exercise. While in passive exercise, only the central command or voluntary is not there. Otherwise, all the factors responsible (e.g., neural, humoral, and vascular factors) for an increase in perfusion index in active exercise remain similar to that of active exercise8. The delay in perfusion index increase observed in the resting arm during passive exercise supports the phenomenon that there may be a delay due to a lack of or reduced central haemodynamic response in passive exercise8,21. The difference in results for upper and lower limbs during passive exercise could be attributed to variations in vascular structure, muscle mass, and autonomic innervation between the limbs. The lower limbs have a greater muscle mass and different sympathetic regulation, which might require a stronger physiological stimulus to induce significant changes in blood flow and perfusion in the resting limb22.
In this context, there is a method to improve perfusion called ‘preconditioning’. It uses a brief period of ischaemia (e.g., by inflating a cuff). It improves perfusion to the tissue. After surgery, it can help in increasing blood flow23. However, using it for improving perfusion to already damaged tissue is still not studied and needs further consensus on its applicability even in healthy tissue24. The current study shows how contralateral exercise increases perfusion immediately. Unlike preconditioning, it focuses on short-term effects, offering another way to improve blood flow after surgery.
The study findings not only deepen our understanding of the complex physiological adaptations to exercise but also have implications for optimising exercise interventions aimed at enhancing tissue perfusion after single-limb surgery. However, being a small-scale study, it has several limitations. The sample characteristics may limit the generalisability of the findings. Additionally, the use of perfusion index as a surrogate measure of tissue perfusion may not fully capture the intricacies of microvascular blood flow dynamics. Furthermore, only one limb (the dominant upper limb or the right lower limb) was exercised in this study. Future studies could explore these effects by alternating the exercising limb.
Acknowledgment
Authors acknowledge Ahana Aarshi (Dev Sangha National School, Deoghar), and Sarika Mondal (Medical Education and Research Association) for providing resources and helping in capturing the photographs for the images used in this article.
Financial support & sponsorship
The study received funding support from Indian Council of Medical Research as a short-term studentship programme (Reference number: STS-2023-149) awarded to the second author (MS). The devices used in this study were self-sponsored (HM).
Conflicts of Interest
None.
Use of Artificial Intelligence (AI)-Assisted Technology for manuscript preparation
The authors confirm that ChatGPT-4o (OpenAI) was used on September 25, 2024 between 8-11 PM, for assisting with grammar and language correction, ensuring that our findings were communicated clearly and effectively.
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