Based on your history, the pain seems muscular due to strain while lifting weight and prolonged walking. Your MRI is normal, which is reassuring and suggests soft-tissue involvement rather than spinal damage.
IFT vs TENS
IFT is generally better for deep muscle pain and inflammation.
TENS works mainly for surface-level pain relief.
Since your pain is upper and middle back muscle strain, IFT would be more beneficial than TENS for long-term improvement.
Next Steps
Request treatment from a qualified physiotherapist, not a receptionist.
Start IFT + hot pack + gentle stretching for 7–10 days.
Add strengthening of upper back and posture training once pain reduces.
Health Tips
Avoid lifting heavy weight until recovery.
Maintain upright sitting posture, avoid long sitting.
Use hot fomentation at home 15 minutes twice a day.
Practice deep breathing to reduce chest tightness.
If pain does not improve in a week, get reassessment by a physiotherapist.
Let me know if you want home exercise suggestions.