Table 3.

Recommendations for repeated muscle collections during short time frames

During Primary Vastus Lateralis Tissue Collection

1. Ensure patient safety by inquiring about medication use, bleeding risk, fasting status, etc.

2. Ensure anesthetic is 1% lidocaine with infused bicarbonate (1:10 bicarb to lidocaine ratio). This reduces the initial stinging sensation typically felt with lidocaine injection. Lidocaine with epinephrine should not be used.

3. Operator should be aware of the number of biopsies introduced in the study. Initial biopsy should be just frontal to the iliotibial band (approximately 1/3 distance of thigh from knee).

4. Have the participant flex their muscle to ensure proper placement.

5. Make sure not to introduce lidocaine into the muscle after the fascia is cut as infiltration of the lidocaine within the fascia will impact data and increase chances of fiber damage.

6. Gauge patient’s tolerance level and record the amount of lidocaine needed to completely remove the sensation of pain during the procedure.

7. Direction of the lidocaine insertion and biopsy needle angle should be held constant to be as local as possible.

8. Without epinephrine, there will be a propensity to bleed longer and have greater amounts of infiltrates. Make sure to hold pressure on the incision site for approximately 5–7 min and be consistent with each patient.

During Secondary Vastus Lateralis Tissue Collection (on same leg)

9. Move distally from the knee (up the leg) at least 3 cm from previous biopsy site. Further is better to prevent molecular changes due to trauma or anesthetic. We recommend distances >2 cm if possible as we saw inconsistent results at approximately this distance. Measure to confirm.

10. Same operator should be used when available.

11. Carefully inject similar amounts of lidocaine as previously given to ensure patient comfort.

12. Be aware and note the angle and opening of the trochar. The opening should be angled away from previous site of collection.

Other Considerations

13. Ultrasound-guided biopsies have been found to be a useful alternative when compared with open biopsies as it can guide the operator away from possible inflammation and takes the guesswork out of proper placement into the muscle (35).

14. Secondary samples might be obtained from the contralateral leg, although differences between legs do exist due to leg dominance and potential crossover effects of interventions. Therefore, this may not be possible for study designs using within-subject controls (intervention being applied to only one leg). Differences in leg or longitudinal orientation does not need to be considered when investigating muscle characteristics according to Horwath et al (36).

15. Regardless, the assessment of muscle damage should be included and reported in studies taking multiple samples within 1–2 wk.