Many people resolve to start using a treadmill, but from a Traditional Korean Medicine perspective, it's crucial to first assess your body's condition. There are two main scenarios. First, those who sweat a lot but only feel tired and don't lose weight—often this indicates Spleen Deficiency (脾虛) or Phlegm-Fluid (痰飲). Spleen Deficiency means the spleen's function is weakened, failing to properly process food and leading to water metabolism dysfunction. Dampness (濕) accumulates, causing swelling, and exercise depletes Qi (氣) further, resulting in fatigue. For such individuals, rather than strenuous cardio, it's better to first strengthen the Spleen-Stomach (脾胃) with herbal medicine, moxibustion, or dietary adjustments. Second, those who eat well, are active, and stressed may have Liver Qi Stagnation (肝氣鬱結) or Blood Stasis (瘀血). Cardio can help with blood circulation and stress relief. However, if knees hurt, avoid joint strain: set the incline to 1–2 degrees, keep speed under 5–6 km/h, and start with under 20 minutes. Consistency at 20 minutes is better than an hour of overexertion, as it prevents worsening Spleen Deficiency. If after exercise your hands and feet feel cold or you remain breathless for a long time, that is a signal from your body. On such days, rest or substitute with light stretching. Ultimately, the answer is not 'good exercise' but 'exercise that suits your body.' Do not feel pressured; first check your condition.