The Polar OH1 is an optical heart rate sensor on an elastic wristband, providing an alternative to training with a chest strap. Utilizing a high-quality optical sensor with 6 LEDs, it measures the heart rate directly on the upper or lower arm, ensuring flexible and easy use. The optical heart rate measurement allows users to determine how hard their body is working during exercise and how the training can be adjusted to meet individual goals. The lightweight and adjustable textile band offers a pleasant and comfortable wearing experience on the arm. A side button allows for starting the training session, and an LED signal indicates the status of the sensor. Training data is transmitted via Bluetooth to a smartphone or sports watch. The OH1 is compatible with many sports and fitness apps or products. With its built-in memory, it can also be used in training without additional products, storing up to 200 hours of training data.