High-Intensity Interval Training (HIT), Anaerobic Energy, Neuromuscular Load and Practical Applications - Notes

High-Intensity Interval Training (HIT)

  • Time-efficient method for improving cardiorespiratory and metabolic function.
  • Involves repeated bouts of high-intensity exercise with recovery periods.
  • Requires manipulation of variables like work/relief interval intensity/duration and exercise modality.

Metabolic System

  • Splitting of phosphagens (ATP and PCr).
  • Anaerobic glycolytic energy production.
  • Oxidative metabolism (aerobic system).

Anaerobic Glycolytic Energy Contribution

  • Assessed via accumulated O2 deficit and muscle lactate concentration.
  • Blood lactate accumulation is a surrogate marker (limitations exist).
  • Focus on post-HIT values and initial rate of blood lactate accumulation (first 5 min).

Long-Bout Duration HIT Sessions

  • Work Interval Intensity: Higher intensities lead to a greater rate of blood lactate increase.
  • Work Interval Duration: Doubling interval duration increases anaerobic glycolytic energy release.
  • Relief Interval Characteristics: Shorter recovery intervals increase anaerobic glycolytic energy contribution.
  • Work Interval Modality: Limited data, but hill sessions may result in lower blood lactate accumulation.

Short-Bout HIT Sessions

  • Can exercise at high intensity with relatively low blood lactate levels.
  • Relies on stored oxygen sources (myoglobin).
  • Higher work interval intensities elicit greater blood lactate responses.

Repeated-Sprint Sequences (RSS)

  • End-exercise blood lactate values can range widely.
  • Manipulating sprint distance/duration and recovery intensity/duration impacts anaerobic glycolic contribution.
  • Initial rate of blood lactate accumulation correlates with work/relief ratio.
  • Introducing COD and/or jumps influences blood lactate response.

Sprint Interval Session (SIT)

  • Involves near-maximal efforts with longer efforts and recovery periods than RSS.
  • Blood lactate levels generally reach high levels.
  • Shorter sprints and/or lower intensities may lower anaerobic glycolytic energy contribution.

Neuromuscular Responses to HIT

  • Neuromuscular load affects HIT performance, subsequent training sessions, and injury risk.
  • Fatigue induced by HIT tends to be primarily peripheral in origin.
  • Field-based measurements include CMJ height and sprint speed.
  • Endurance-trained athletes may show less impairment in muscular performance than explosive athletes.

Long-Bout HIT

  • No significant changes in CMJ height during 1 min/1 min vs. 2 min/2 min interval sessions.
  • Incline running lowers hamstring strain.

Short-Bout HIT

  • Surface should be considered (Table 3).
  • May be greater than long intervals due to higher intensity and frequent accelerations/decelerations.

Repeated-Sprint Sequences (RSS)

  • Reduction in running speed reflects increased locomotor stress.
  • Percentage of speed decrement (%Dec) is a commonly reported index.
  • COD can affect fatigue profile.
  • Adding jumps increases neuromuscular load.