How Does Body Position Affect Skin Temperature and Blood Circulation?

In this article, we explore how body posture influences skin temperature, heart rate, and blood pressure. A study reveals key data for health, sports, and rehabilitation.

Infrared thermography (IRT) is a non-invasive tool used in sports medicine and human physiology to measure skin temperature (Tsk). Its application allows for the identification of thermal asymmetries, assessment of the autonomic nervous system response and recovery. However, most studies using infrared thermography have assumed that body posture does not influence thermal distribution, typically conducting measurements in a standing position.

But What Happens When We Sit or Lie Down?

The human thermoregulatory system adjusts skin temperature based on blood flow redistribution, which is regulated by sympathetic and parasympathetic activity. It is well known that body position influences heart rate (HR) and blood pressure, but its impact on skin temperature has been little studied.

How Does Posture Influence Skin Temperature?

The study conducted by Pereira Franco et al. (2024), published in the Journal of Thermal Biology, investigated how body posture (standing, sitting, and supine) affects skin temperature, heart rate, and blood pressure in physically active men.

The study results demonstrate that posture significantly modifies skin temperature, particularly in the upper limbs, which has important implications for the use of thermography in physiological, sports, and clinical studies.

Study Objective

The study aimed to analyze how posture affects three key physiological variables:

• Skin temperature (Tsk)
• Heart rate (HR)
• Blood pressure (systolic and diastolic)

The hypothesis was proposed that:

• Skin temperature will vary significantly between standing, sitting, and supine positions.
• Blood flow will influence the body's thermal redistribution.
• Heart rate and blood pressure will also change depending on posture.

Methodology

The study was conducted with 29 physically active men (age: 23.52 ± 0.34 years), who spent 10 minutes in each of the three positions:

• Standing (unsupported)
• Sitting (without back support)
• Supine (lying on their back with palms facing up)

During each posture, the following measurements were taken:

• Skin Temperature (Tsk), measured in 8 body regions:
  • Trapezius
  • Shoulder
  • Chest
  • Biceps
  • Lateral torso
  • Elbow
  • Abdomen
  • Forearm
• Heart Rate (HR)
• Blood Pressure (Systolic & Diastolic)

Instrumentation & variable control

• A FLIR T530 thermographic camera was used.
• Heart rate and blood pressure were measured using a high-precision digital sphygmomanometer.
• Breathing rate was controlled with a timer set to 10 breaths per minute.
• Analysis of covariance (ANCOVA) was performed to evaluate the relationship between heart rate and skin temperature.

Main Results

Skin Temperature Variations

Significant changes in skin temperature were found depending on body posture:

• The greatest variations were observed in the upper limbs:
  • Shoulder: 0.74 – 1.31%
  • Biceps: -0.36 – 1.33%
  • Elbow: 0.46 – 1.20%
  • Forearm: 0.58 – 1.41%
• The most pronounced differences were between the standing and supine positions, suggesting that blood flow redistribution influences skin temperature regulation.

Heart Rate Changes

• Standing position: Increase of 3.78 bpm
• Sitting position: Increase of 4.89 bpm
• Supine position: Decrease of 2.89 bpm

These changes correlated with temperature variations in chest (ES = 0.71), biceps (ES = 0.56) and abdomen (ES = 0.91)

Blood Pressure

• No significant changes in blood pressure were observed between different postures.

Measurement Reliability

The most reliable regions for thermographic assessment were:

• Chest (ICC = 0.91)
• Lateral torso (ICC = 0.91)
• Abdomen (ICC = 0.89)

Study Conclusions

The study by Pereira Franco et al. (2024) demonstrates that body posture significantly influences skin temperature, heart rate, and, to a lesser extent, blood pressure. The key findings include:

• Posture modifies skin thermal distribution, with greater variations in the upper limbs.
• Heart rate influences skin temperature, particularly in the chest, biceps, and abdomen.
• Blood pressure did not show significant changes, suggesting that thermal redistribution is more related to local blood circulation than systemic blood pressure variations.

Practical Applications

• Considerations for thermography studies
  • This study reinforces the need to standardize posture in thermography studies since body position can alter skin temperature and lead to misinterpretations if not properly controlled.
• Assessment and monitoring with athletes
  • In sports medicine, thermography is used to monitor fatigue and injury prevention.
  • Standardizing athlete posture before evaluation is crucial to avoid thermal variations unrelated to physiological status.
• Applications in medicine & rehabilitation
  • In physical therapy, the thermal variability observed in different postures can be used to assess blood circulation and autonomic nervous system activation.
  • This may be useful for monitoring patients with vascular or neurological disorders.

References

Pereira Franco, V. H., Vasquez-Bonilla, A. A., & Sillero-Quintana, M. (2024). Influence of body position on skin temperature, heart rate, and blood pressure in active men. Journal of Thermal Biology, 127, 104009. https://doi.org/10.1016/j.jtherbio.2024.104009