The purpose of this observational study is to examine how slowing down blood flow to the legs- a practice called blood flow restriction (BFR)- during exercise by applying compression to the legs affects the way stem cells are released into the blood stream. This will be determined by drawing 6 cubic centimeters (ccs) of blood immediately post-exercise after the Delfi Personalized Tourniquet System (PTS) has been removed. 6 ccs of blood will also be taken prior to exercise and at the 20-, 40-, and 60-minute marks after exercise. The main question of this study is:

• Will the levels of stem cells extracted before and after exercise be the same if blood flow is restricted during exercise?

In this study, participants will undergo the following:

• 6 ccs of blood extracted from the forearm prior to exercise to establish a baseline
• 3 exercises- seated leg extension, semi-reclined leg press, and seated hamstring curl- consisting of 4 sets of 30-15-15-15 repetitions per exercise; resistance will be set to 30% of one-rep maximum (1-RM)
• Additional 6 cc blood draws will be performed immediately post-exercise and after 20, 40, and 60 minutes have elapsed

The proposed study is a prospective, quasi-experiment, dual-center (exercise facility and laboratory) study involving 15 healthy, male and female volunteers. A potential subject must clear the screening, consent to the procedures of this study, and complete the medical interview before proceeding with the familiarization session. The familiarization process will include an introduction to the Delfi BFR Tourniquet System (Delfi Medical Innovations Inc., Vancouver, BC) and the exercises (seated leg extension, semi-reclined leg press, seated hamstring curl) that the subject will complete. The weight each subject will use for each exercise will be determined during this time. All familiarization procedures must be completed prior to the scheduling and execution of the first of twelve experimental testing sessions.

The experimental testing sessions will occur twice a week for six weeks (12 sessions) and will involve the BFR training utilizing the Delfi BFR Tourniquet System, as further described in the Experimental Testing Session section of the treatment plan (6.2). At the beginning of the first, the sixth, and the twelfth testing sessions there will be a blood draw requiring 6 cc of blood to be taken prior to exercise. Post-exercise, at each testing session, additional 6cc blood draws will be conducted immediately post exercise (time point 0), as well as 20- , 40- , and 60 minutes after the conclusion of the workout. Following every testing session workout, finger-prick blood samples for lactate testing will be taken. These blood samples are to be taken at Time point 0- (T 0), 10-, 20-, 30-, 40-, 50-, and 60-minutes following exercise. Once the twelfth experimental testing session has been completed, the subjects will have one final session that is to take place no more than five days following the twelfth testing session. This final session will include one final blood draw of 6 cc. Throughout the duration of the study, the blood drawn will be used for obtaining a complete blood count (CBC) and for cellular analysis to quantify peripheral hematopoietic progenitor cell concentration. The blood samples collected from subject's fingers throughout the study will be used for analysis using a portable lactate analyzer. Lactate analysis will allow researchers insight into each subject's exertion level reflected by the amount of lactate found within the samples collected.

Inclusion Criteria

1. Volunteer population of healthy males and females aged 18-45.
2. Subjects consent to attending a total of 14 visits over a time span of seven to nine weeks. The breakdown of the 14 visits is as follows: 1 familiarization session, 12 experimental testing sessions, 1 final session.

Exclusion Criteria

Volunteers who have medical history involving one or more of the following medical conditions:

1. Diabetes
2. Uncontrolled hypertension
3. Autoimmune disorders
4. Blood disorders
5. Ongoing infectious disease
6. Cancer
7. Any disorder requiring immunosuppression treatment
8. Steroid usage
9. Significant cardiovascular, pulmonary, hepatic, or renal disease.
10. Volunteers where 20 minutes of intense exercise is contra-indicated will also be excluded from the study.
11. Positive pregnancy test