Overview: The article reviews the role of wearable devices and sensors in monitoring athletes' health and performance. It discusses how these non-intrusive devices revolutionize the sports industry by offering real-time data on vital health parameters. 

Because of advancements in the field of sensors and the internet, wearable technology has seen rapid development. It is widely used in various applications in everyday routine, including medicine, sports, defense, engineering, electronics, textiles, entertainment, etc.

What are wearable devices?

They are non-intrusive devices with battery-powered sensors, communication units, processors, and actuators that monitor and keep track of a person’s health conditions. These devices are directly or loosely worn on the body of the person and provide real-time data on vitals.

Revolutionizing Sport with Wearable Devices 

Wearable devices are a boon in the sports industry because they provide reliable monitoring of athletes' health conditions to improve training, enabling coaches to plan strategies and train the athletes accordingly. It improves the prowess of the athletes, enhancing their performance and safety.

Role of Sensors in Wearable Devices

Sensors play a vital role in obtaining real-time data from the human body and transmitting these signals to the processor. As shown in Fig. 1, the various sensors in wearable devices can be broadly classified as:

  • Physiological sensor
  • Biomechanics sensor
  • Location sensors
  • Environmental condition sensors

This article reviews various available physiological sensors, their working principles, advantages, and challenges.

Fig. 1: Sensor and Processor Layer of Wearable Technology. Source: MDPI

Physiological sensors

These sensors monitor the human body's biological parameters, which provide valuable information about overall health and performance. They find a wide range of applications, both in clinical and consumer applications, like wearable devices and fitness trackers, which provide valuable insights about a person’s health condition and can be used for diagnostics, monitoring, and improving health. More commonly used physiological sensors include:

  • Electromyography (EMG)
  • Electrocardiography (ECG)
  • Photoplethysmography (PPG)
  • Pulse oximeter
  • Blood pressure sensor
  • Respiratory sensors
  • Electroencephalography (EEG)
  • functional Near-Infrared Spectroscopy (fNIRS)
  • Galvanic skin response (GSR)
  • Electrochemical biosensors

Electromyography 

It measures the electrical activity of the muscle, which can be used to assess the health of the muscles and the neurons controlling them. It uses electrodes to measure the electrical signals in muscles. Needle and surface electrodes are the two commonly employed electrodes in measuring muscle activity. The neuron in the muscle fiber produces electrical signals during each muscle contraction and relaxation, which the electrodes measure. Amplifiers and recorders process and store them. This signal reflects the coordination of muscle contractions.

Electrocardiography

It measures the heart's electrical activity and provides information about the heart rate, arrhythmias, and cardiac health. Modern wearable devices enable continuous ECG monitoring in athletes during sports activity, which provides real-time data about the heart rate and severe arrhythmias, which are life-threatening. 

The electrodes are placed in the torso and limb and are used to measure the electrical signal generated during cardiac depolarisation and repolarisation, providing a comprehensive ECG report. For athletes, the conventional ECG with multiple electrodes can be inconvenient. Smartwatches and wristbands can also be used as single-lead ECGs to measure cardiac electrical activity during training for athletes. 

Photoplethysmography (PPG)

The photoplethysmography technique measures the heart rate by monitoring blood flow changes, which measure cardiovascular activities like heart rate, oxygen saturation (SpO2), blood pressure, and other pathological conditions. It is a more popular method in wearable technology that uses a light source and a photodetector to detect changes in blood volume.

Pulse oximeter

It measures the blood oxygen saturation and pulse rate and is worn on the fingertip. The working principle is based on two different light sources: red and infrared. The blood that is oxygenated absorbs red light, while the blood that is deoxygenated absorbs blue light. By measuring the amount of light being observed, a pulse oximeter provides real-time data on blood oxygen levels. They have widespread application in sports for detecting low blood oxygen levels, which are signs of cardiac and respiratory problems.

Blood Pressure sensor

Pressure sensors measure blood pressure and detect changes in altitude. They are available as wristbands or cuffs that determine both systolic and diastolic blood pressure. Understanding blood pressure provides valuable insights into the athlete's cardiac condition and prevents hazardous health conditions. Modern wearable devices enable continuous monitoring of blood pressure with the help of wristbands or smartwatches.

Respiratory sensors

A respiration rate sensor is used to monitor breathing patterns and respiratory health conditions. The respiratory movement is measured with the help of various sensors, like:

  • Flowmeters and anemometers detect the rate of airflow entering and exiting the lungs.
  • Thermistors and thermocouples are used to measure the temperature of the inhaled air.
  • Capacitive and resistive sensors measure the changes in the movement of the chest wall.
  • Bioimpedance sensors measure the respiratory rate by tracking changes in electrical impedance caused by respiration.
  • Optical sensors use light to measure the blood oxygen level and respiratory rate.

Hence, with the help of various mechanical, electromagnetic, and optical sensors placed in the chest region, the respiratory pattern of the athlete is monitored. 

Smart masks are one of the most commonly available wearable devices to detect respiratory patterns. They incorporate gas sensors to detect the flow of carbon dioxide and oxygen gas. They provide precise and accurate data on various important parameters like respirator rate, aerobic capacity, anaerobic threshold, respiratory efficiency, lung function, etc. The real-time value of respiratory health conditions aids in improving performance and planning training intensity and time.

Electroencephalography

It measures the electrical activity of the brain cells and neurons with the help of electrodes placed in specific regions on the scalp. They provide reliable information regarding the athletes' brain activity, sleep quality, concentration, and mental health. They are more commonly used in sports as headbands to enhance the performance of athletes. They provide information about the cognitive and neural processes that can be used to optimize training, improve focus, and manage stress.

functional Near-Infrared Spectroscopy

It measures brain activity by monitoring the alteration in blood oxygenation and hemodynamics. They are non-invasive methods that use near-infrared light to measure athletes' cognitive load and brain activity.

Galvanic skin response

It measures the skin's electrical activity, which can vary during sweating. As sweating increases, electrical conductivity also increases. The sympathetic nervous system is in charge of controlling stress levels, emotional states, and physiological arousal. Sweat glands physiologically respond to changes in the nervous system via sweating, which are measured using galvanic skin responses.

Temperature sensor

Temperature sensors are the most commonly used sensors that detect body and environmental temperatures and are used in fitness devices and wearables. Thermistors, thermocouples, and infrared sensors can monitor the body temperature and detect fever.

Electrochemical biosensors

Electrochemical biosensors measure the chemical changes in body fluids and measure glucose, lactate, and other biomarker levels.

To conclude, all these sensors play a key role in obtaining real-time information from the human body, improving athletes’s training strategies, focusing, managing stress, and performance.

Summarizing the Key Points

  • Wearable technology has advanced significantly, with various sensors to monitor athletes' health and performance in real-time, enhancing training and safety during sports activities.
  • Physiological sensors, including ECG, EMG, and respiratory sensors, provide information about athletes' biological parameters, enabling training strategies and improved performance
  • Continuous monitoring of vital signs, such as heart rate and blood oxygen levels, through devices like pulse oximeters and blood pressure sensors helps in the early detection of potential health issues.
  • The integration of various sensor technologies in wearables not only enhances athletic performance but also contributes to overall health management.

Reference

Ahmet Çağdaş Seçkin, Bahar Ateş, and Mine Seçkin, “Review on Wearable Technology in Sports: Concepts, Challenges and Opportunities,” Applied Sciences 13, no. 18 (September 17, 2023): 10399, https://doi.org/10.3390/app131810399.

Vini Vijayan et al., “Review of Wearable Devices and Data Collection Considerations for Connected Health,” Sensors 21, no. 16 (August 19, 2021): 5589, https://doi.org/10.3390/s21165589.