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Gerhard Tschakert and Peter Hofmann

High-intensity intermittent exercise (HIIE) has been applied in competitive sports for more than 100 years. In the last decades, interval studies revealed a multitude of beneficial effects in various subjects despite a large variety of exercise prescriptions. Therefore, one could assume that an accurate prescription of HIIE is not relevant. However, the manipulation of HIIE variables (peak workload and peak-workload duration, mean workload, intensity and duration of recovery, number of intervals) directly affects the acute physiological responses during exercise leading to specific medium- and long-term training adaptations. The diversity of intermittent-exercise regimens applied in different studies may suggest that the acute physiological mechanisms during HIIE forced by particular exercise prescriptions are not clear in detail or not taken into consideration. A standardized and consistent approach to the prescription and classification of HIIE is still missing. An optimal and individual setting of the HIIE variables requires the consideration of the physiological responses elicited by the HIIE regimen. In this regard, particularly the intensities and durations of the peak-workload phases are highly relevant since these variables are primarily responsible for the metabolic processes during HIIE in the working muscle (eg, lactate metabolism). In addition, the way of prescribing exercise intensity also markedly influences acute metabolic and cardiorespiratory responses. Turn-point or threshold models are suggested to be more appropriate and accurate to prescribe HIIE intensity than using percentages of maximal heart rate or maximal oxygen uptake.

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Dietmar Wallner, Helmut Simi, Gerhard Tschakert and Peter Hofmann

Purpose:

To analyze the acute physiological response to aerobic short-interval training (AESIT) at various high-intensity running speeds. A minor anaerobic glycolytic energy supply was aimed to mimic the characteristics of slow continuous runs.

Methods:

Eight trained male runners (maximal oxygen uptake [VO2max] 55.5 ± 3.3 mL · kg−1 · min−1) performed an incremental treadmill exercise test (increments: 0.75 km · h−1 · min−1). Two lactate turn points (LTP1, LTP2) were determined. Subsequently, 3 randomly assigned AESIT sessions with high-intensity running-speed intervals were performed at speeds close to the speed (v) at VO2max (vVO2max) to create mean intensities of 50%, 55%, and 60% of vLTP1. AESIT sessions lasted 30 min and consisted of 10-s work phases, alternated by 20-s passive recovery phases.

Results:

To produce mean velocities of 50%, 55%, and 60% of vLTP1, running speeds were calculated as 18.6 ± 0.7 km/h (93.4% vVO2max), 20.2 ± 0.6 km/h (101.9% vVO2max), and 22.3 ± 0.7 km/h (111.0% vVO2max), which gave a mean blood lactate concentration (La) of 1.09 ± 0.31 mmol/L, 1.57 ± 0.52 mmol/L, and 2.09 ± 0.99 mmol/L, respectively. La at 50% of vLTP1 was not significantly different from La at vLTP1 (P = .8894). Mean VO2 was found at 54.0%, 58.5%, and 64.0% of VO2max, while at the end of the sessions VO2 rose to 71.1%, 80.4%, and 85.6% of VO2max, respectively.

Conclusion:

The results showed that AESIT with 10-s work phases alternating with 20 s of passive rest and a running speed close to vVO2max gave a systemic aerobic metabolic profile similar to slow continuous runs.