Determinants of Heart Rate Variability Responses to High Intensity Interval Training in Healthy Women

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Presentation given at the National Strength and Conditioning Association National Conference, Washington, D.C.

Prior studies utilizing knee wraps (KWs) while performing a back squat have demonstrated a mechanical advantage that increases exercise volume and load. PURPOSE: To determine if knee wraps modify the immune response to resistance exercise. METHODS: 9 resistance trained men (22.6±3.6 yrs; 177.1±5.4cm; 83.2±17.3 kg) were recruited to participate in either a KW or control (CON) condition. During visit 1, participants performed a 1-repetition max (1-RM) and were required to attain a 1-RM between 1.5x-3.0x their body weight. Participants then returned to the Exercise Performance and Recovery Lab for visit 2 at least 72 hours later, having fasted at least 10 hours, abstained from caffeine for 16 hours, nicotine and alcohol for at least 24 hours, and exercise for 72 hours. During this visit, participants completed a 5-minute warm up on a cycle ergometer at a self-selected pace before completing eight sets of ten repetitions of the squat at 70% of their 1-RM, with 2 minutes rest between sets. Blood samples were obtained prior to exercise (PRE), immediately after (IP), 1-(1H), 24-(24H) and 48-(48H) hours after exercise. Blood was immediately analyzed for total leukocyte count (WBC), as well as the number (#) and ratio (%) of lymphocytes (LY), monocytes (MO), and granulocytes (GR) using an automated hematology analyzer. Differences between conditions were analyzed using a Mann-Whitney U test, while differences across time were assessed with a Friedman’s ANOVA, and post-hoc analysis with a Wilcoxon rank sum test. RESULTS: Friedman’s ANOVA demonstrated differences (p=0.005) in the KW group for WBC, with increases observed from PRE (5.74±1.41x103·µL-1) to IP (9.73±1.15x103·µL-1; p=0.043), with no differences at 1H (5.41±1.04x103·µL-1), 24H (5.17±1.13x103·µL-1), or 48H (5.12±1.07x103·µL-1). Friedman’s ANOVA also indicated differences (p=0.004) in the KW group for LY%, with increases from PRE (34.7±3.8%) at IP (40.9±4.48%; p=0.043) and a decrease at 1H (22.6 ±3.1%; p=0.043). Friedman’s ANOVA revealed differences (p=0.002) for the KW group in LY#, with an increase (p=0.043) from PRE (1.96±0.39 x103·µL-1) at IP (3.97±0.597 x103·µL-1). Friedman’s ANOVA indicated differences (p=0.015) in the KW group for MO#, with increases (p=0.043 ) at IP (0.67±0.17 x103·µL-1) compared to PRE (0.38±0.102 x103·µL-1), 1H (0.25±0.12 x103·µL-1), 24H (0.30±0.11 x103·µL-1) and 48H (0.32±0.08 x103·µL-1). Additionally, at IP, MO# were greater in KW (0.67±0.17x103·µL-1; p=0.036) versus CON (0.59± 0.13x103·µL-1). Friedman’s ANOVA demonstrated differences (p=0.004) in the KW group for GR% with increases (p=0.043 ) from PRE (58.1±5.1%) and IP (52.4±5.1%) at 1H (73.2 ±3.8%). Friedman’s ANOVA demonstrated differences (p=0.003) in the KW group for GR# with increases (p< 0.05) at IP (5.11±0.87x103·µL-1) compared to PRE (3.37±1.10 x103·µL-1), 1H(3.95±0.77 x103·µL-1), 24H(3.05±0.67 x103·µL-1) and 48H(2.79±0.60 x103·µL-1). CONCLUSION: A significant increase in circulating WBCs suggest KWs may increase the immune response possibly due to increased exercise volume. Additionally, the monocyte response to exercise with KW may be enhanced, especially immediately after exercise. PRACTICAL APPLICATIONS: KWs appear to increase the immune response to resistance exercise, which may increase post-exercise inflammation. Therefore, further research is necessary to determine if the use of KWs is beneficial to the athletes.


National Strength and Conditioning Association National Conference


Washington, D.C.