Blood Lactate Concentration Is Not Related to the Increase in Cardiorespiratory Fitness Induced by High Intensity Interval Training.

BACKGROUND: There is individual responsiveness to exercise training as not all individuals experience increases in maximal oxygen uptake (VO2max), which does not benefit health status considering the association between VO2max and mortality. Approximately 50% of the training response is genetic, with the other 50% accounted for by variations in dietary intake, sleep, recovery, and the metabolic stress of training. This study examined if the blood lactate (BLa) response to high intensity interval training (HIIT) as well as habitual dietary intake and sleep duration are associated with the resultant change in VO2max (ΔVO2max). METHODS: Fourteen individuals (age and VO2max = 27 ± 8 years and 38 ± 4 mL/kg/min, respectively) performed nine sessions of HIIT at 130% ventilatory threshold. BLa was measured during the first and last session of training. In addition, sleep duration and energy intake were assessed. RESULTS: Data showed that VO2max increased with HIIT (p = 0.007). No associations occurred between ΔVO2max and BLa (r = 0.44, p = 0.10), energy intake (r = 0.38, p = 0.18), or sleep duration (r = 0.14, p = 0.62). However, there was a significant association between training heart rate (HR) and ΔVO2max (r = 0.62, p = 0.02). CONCLUSIONS: When HIIT is prescribed according to a metabolic threshold, energy intake, sleep status, and BLa do not predict ΔVO2max, yet the HR response to training is associated with the ΔVO2max.

Change in VO2max and time trial performance in response to high-intensity interval training prescribed using ventilatory threshold.

Completion of high-intensity interval training (HIIT) leads to significant increases in maximal oxygen uptake (VO2max) and oxidative capacity. However, individual responses to HIIT have been identified as approximately 20-40% of individuals show no change in VO2max, which may be due to the relatively homogeneous approach to implementing HIIT. PURPOSE: This study tested the effects of HIIT prescribed using ventilatory threshold (VT) on changes in VO2max and cycling performance. METHODS: Fourteen active men and women (age and VO2max = 27 ± 8 year and 38 ± 4 mL/kg/min) underwent nine sessions of HIIT, and 14 additional men and women (age and VO2max = 22 ± 3 year and 40 ± 5 mL/kg/min) served as controls. Training was performed on a cycle ergometer at a work rate equal to 130%VT and consisted of eight to ten 1 min bouts interspersed with 75 s of recovery. At baseline and post-testing, they completed progressive cycling to exhaustion to determine VO2max, and on a separate day, a 5 mile cycling time trial. RESULTS: Compared to the control group, HIIT led to significant increases in VO2max (6%, p = 0.007), cycling performance (2.5%, p = 0.003), and absolute VT (9 W, p = 0.005). However, only 57% of participants revealed meaningful increases in VO2max and cycling performance in response to training, and two showed no change in either outcome. CONCLUSIONS: A greater volume of HIIT may be needed to maximize the training response for all individuals.

Acute Responses to the 7-Minute Workout.

Riegler, M, Stotz, G, Fitzgerald, K, Munoz, CK, Lewis, J, Ring, S, and Astorino, TA. Acute responses to the 7-minute workout. J Strength Cond Res 31(9): 2572-2578, 2017-A popular smartphone application called the 7-Minute Workout (7Min) claims to be scientifically proven to promote weight loss and improve cardiovascular function. The application has 10 million downloads and has been reviewed by 350,000 users. However, changes in metabolic and perceptual variables in response to 7Min are unknown. Our study compared acute responses between 7Min and a time-matched session of cycling-based high-intensity interval exercise (HIIE). Fourteen active men and women (age and V[Combining Dot Above]O2max = 25.4 ± 8.3 years and 40.5 ± 6.4 ml·kg·min) initially underwent V[Combining Dot Above]O2max testing. During 2 subsequent sessions separated by ≥48 hours, they completed 7Min or HIIE. During exercise, oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), blood lactate concentration (BLa), and rating of perceived exertion were measured. Peak V[Combining Dot Above]O2 was higher (p < 0.001) in HIIE vs. 7Min, and HIIE yielded greater (p < 0.001) mean V[Combining Dot Above]O2 (1.83 ± 0.41 L·min vs. 1.44 ± 0.32 L·min) and HR (159.0 ± 10.7 b·min vs. 140.7 ± 18.3 b·min, p < 0.001) vs. 7Min. Blood lactate concentration increased (p < 0.001) during exercise but was similar between bouts (p = 0.07). Rating of perceived exertion was higher (p = 0.008) in response to HIIE vs. 7Min. Although 7Min yields lower peak V[Combining Dot Above]O2 and HR than HIIE, it is characterized by bursts approaching 90 %HRmax and causes significant BLa accumulation, representing vigorous exercise. Nevertheless, 7Min is on the low end of the intensity spectrum, which questions whether it represents true HIIE and will confer similar benefits if performed long term.