Participants had randomly divided into two equal groups. Group (A) which is the study group will receive photobiomodulation session two times per week for four weeks. Group (B) will be the control group that will receive placebo photobiomodulation two times per week for four weeks.

group (A):

1. Each participant will sign a consent form after receiving a detailed explanation about the procedure.
2. submaximal exercise capacity using time up and go test will be assessed.
3. fatigability will be assessed using fatigue assessment scale.
4. hemodynamic variables including; Blood pressure, heart rate, oxygen saturation, maximum oxygen consumption will also be assessed.
5. After one month all the assessment procedure will be repeated again.

r group (B):

1. Each participant will sign a consent form after receiving a detailed explanation about the procedure.
2. submaximal exercise capacity using time up and go test will be assessed.
3. fatigability will be assessed using fatigue assessment scale.
4. hemodynamic variables including; Blood pressure, heart rate, oxygen saturation, maximum oxygen consumption will also be assessed.
5. After one month all the assessment procedure will be repeated again.

Inclusion Criteria:

• 60 to 75 years of age
• past history of covid 19 in the last year

Exclusion Criteria:

• ( history of a histologically demonstrated malignant carcinoma , hyperthyreosis , epilepsy, light sensitivity )

participants