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NEW: Effects of Work and Recovery Duration and Their Ratio on Cardiorespiratory and Metabolic Responses During Aerobic Interval Exercise

Myrkos, Aristides; Smilios, Ilias; Zafeiridis, Andreas; Iliopoulos, Stilianos; Kokkinou, Eleni M.; Douda, Helen; Tokmakidis, Savvas P.

Journal of Strength and Conditioning Research: August 2022 - Volume 36 - Issue 8 - p 2169-2175, doi: 10.1519/JSC.0000000000003578


To examine the effect of 1) work and recovery durations and 2) the work-to-rest ratio (WRR) on total exercise time and oxygen consumption (Vo2max), on exercise time above 80, 90, and 95% of Vo2max and heart rate maximum (HRmax), and on blood lactate concentrations during aerobic interval exercise.


Twelve men completed four interval protocols at an intensity corresponding to 100% of maximal aerobic velocity to the point of exhaustion.

Two protocols were performed with a total work time of 2:00 and recovery time of either a 2:00 (WRR: 1:1) or 1:00 (WRR: 2:1).

Another two protocols were performed with a total work time of 1:00 and a recovery time of either 1:00 (WRR: 1:1) or :30 WRR: 2:1).


When compared at equal exercise time, total Vo2 and exercise time at Vo2 above 80, 90, and 95% of Vo2max were:

  • 2:00:2:00 > 1:00:1:00.

  • 2:00:1:00 > 1:00:1:00.

  • 1:00::30 > 1:00:1:00.

When analyzed for total exercise time to the point of exhaustion, total Vo2 was:

  • 1:00:1:00 all other protocols.

  • 2:00:2:00 > 2:00:1:00.

  • Exercise time >95% of Vo2max and HRmax: 2:00:2:00 > 2:00:1:00.

  • There were no differences among protocols for exercise time >90% of Vo2max and HRmax.

  • Blood lactate: all other protocols > 1:00:1:00 and 2:00:1:00 > 1:00:30.

In conclusion, when interval exercise protocols are performed until exhaustion, the work and recovery durations generally do not affect exercise time at high oxygen consumption and HR rates.

However, as work duration decreases, a higher work-to-recovery ratio (such as 2:1) should be used to achieve and maintain high (>95% of maximum) cardiorespiratory stimulus.

Longer work bouts and higher work-to-recovery ratio seem to activate anaerobic glycolysis to a greater extent, as suggested by greater blood lactate concentrations.


First off, I would not consider any interval work period of <2:00 “aerobic” as the title of the experiment alluded to. In fact, it takes at least 2:00 for the aerobic system to get to full capacity, so anything performed at a high level of effort below 2:00 would more correctly be labeled anaerobic (relying more on stored ATP and ATP manufactured from the CK reaction and glycolysis).

So, short, high effort work bouts coupled with short recovery times between them result in a greater cardiovascular demand and greater metabolic accumulation.

Conversely, high effort work bouts again result in a greater cardiovascular demand but coupled with longer recovery time between them result in lesser metabolic accumulation and the ability to perform at a higher level during each work bout.

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