How often should adults do strength training and aerobic exercise weekly?

Short answer
- Aerobic: at least 150–300 minutes of moderate-intensity aerobic activity per week (or 75–150 minutes of vigorous activity, or an equivalent combination).
- Strength (resistance) training: at least 2 nonconsecutive days per week working all major muscle groups.

Details and practical guidance
1. Aerobic exercise
- Goal: 150–300 min/week moderate (brisk walking, easy cycling) OR 75–150 min/week vigorous (running, fast cycling) — more gives greater benefit.
- Intensity guide: moderate = you can talk but not sing; vigorous = you can say a few words, not hold a conversation.
- Can be broken into sessions of any length (any activity counts); common schedules: 30 min × 5 days (moderate) or 25–30 min × 3–4 days (vigorous/intervals).

2. Strength training
- Minimum: 2 days/week, targeting all major muscle groups (legs, hips, back, chest, abdomen, shoulders, arms).
- Typical prescription: 2–4 sets of 8–12 reps for most adults for strength and hypertrophy; beginners can start with 1–2 sets.
- Leave ~48 hours before working the same muscle group hard again (e.g., full-body sessions on Mon/Thu or split routines).
- Include exercises such as squats, lunges, push-ups/bench press, rows, planks, overhead press, deadlifts — bodyweight, machines, free weights, or bands all work.

3. Putting it together — example weekly plans
- Option A (balanced): 30–40 min moderate aerobic × 4 days + strength training 2 days (full-body) = meets both targets.
- Option B (more vigorous): 25 min vigorous aerobic × 3 days + strength 2–3 days.
- Option C (daily movement): 20–30 min brisk walk most days + 2 strength sessions.

4. Older adults and fall prevention
- Same aerobic/strength targets, plus balance and functional training 2–3 days/week if at risk of falls.

5. Safety and progression
- Start gradually if inactive; increase duration first, then intensity.
- Warm up, use good technique, and allow recovery time.
- Consult a healthcare provider before starting or intensifying exercise if you have chronic health conditions, recent hospitalization, or symptoms like chest pain, dizziness, or uncontrolled medical issues.

Sources commonly used: U.S. Physical Activity Guidelines, World Health Organization, CDC. If you want, I can make a personalized weekly plan based on your current fitness, time availability, and goals.