Studies show that: • Sitting still in 40°C hot water for 30 minutes can burn an additional 25–40 calories; • If the body's thermoregulation response is stronger (e.g., more sweating), it can reach 50–60 calories. In other words: A 30-minute hot tub bath can burn approximately 60–100 calories.

When the pH level in a swim spa tub is too high, the most direct impact is decreased water quality stability. A high pH level alters the chemical reaction environment in the water, making certain substances more prone to sedimentation or particle formation.

The water in spa equipment typically needs to maintain a stable chemical balance, such as pH, alkalinity, and disinfectant concentration. Rainwater has different chemical properties, so it may affect these parameters after entering the water.

Many people believe that weight loss after a spa hot tub bath is due to "burning fat." In reality, the temporary weight loss is due to the body losing water, not fat. Therefore, while a spa hot tub can slightly accelerate calorie burning, it cannot replace exercise.

If you experience the following symptoms after using a hot tub, you should suspect bacteria in the water: • Skin rash, itching, burning sensation; • Folliculitis or pimple-like red spots; • Localized skin infection or pustules. These are often signs of a hot tub rash caused by bacterial contamination.

For people with heart disease, using a spa hot tub carries potential risks. • Patients with coronary heart disease; • Those with a history of arrhythmia or heart failure; • Those who have had a myocardial infarction; • People with pacemakers (must have their device's safety range confirmed by a doctor).