Makeba Edwards by Makeba Edwards

Phase 2: Aerobic Efficiency Training

Before a client can begin phase 2, he or she must be able to, at a minimum, comfortably complete at least 20 to 30 minutes of consistent steady state exercise in zone 1.  Cardiorespiratory exercise in this phase introduces the use of intervals to improve aerobic efficiency, fitness, and health. The main focus is on increasing the duration of the cardiorespiratory training session, while introducing intervals to challenge clients at the lower end of zone 2 before progressing to the upper end.

By the time your client is ready to progress to Phase 2, he or she should have developed an aerobic base during Phase 1. For additional gains, you may need to evaluate your client’s particular cardiorespiratory goal. For clients seeking to achieve improved or maintenance of aerobic health and fitness, sticking with phase 2 training guidelines may be beneficial. For more competitive goals that prove to be more challenging, progressing to Phase 3 is appropriate. If your client does have a performance-based goal, there may not be a need to progress to the next phase. Always consider your clients’ goals when designing their programs and determining whether or not progression to another phase is warranted.

Important considerations for phase 2 training:

  • Before starting in phase 2, administer a submaximal talk test to determine the client’s heart rate (HR) at the first ventilatory threshold (VT1).
  • Utilize the HR found at VT1 for programming throughout this phase.
  • Reassess periodically as fitness improves to determine if HR has changed, and if adjustment in intensity is needed.
  • Objectives in this phase include enhancing aerobic efficiency, introducing zone 2 intervals, and increasing the duration and frequency of sessions, when necessary.
  • Warm-up and cool-down periods and recovery intervals are performed below VT1 to continue advancing fitness in the aerobic base.
  • When aerobic intervals above VT1 are introduced, it is with the intent of improving aerobic efficiency by increasing the intensity of exercise performed at VT1.
  • Intervals should start out brief--for about 60 seconds--with an approximate hard-to-recovery ratio of 1:3, and then progress to an equal hard-to-recovery ratio of 1:1.
  • Duration of intervals can be increased based on your client’s goals. Progress over several weeks, cautiously, taking into account the client’s fitness level.
  • Increase exercise load (i.e., distance, duration of interval, steady-state intensity, and/or duration of entire workout session) by no more than 10% per week.
  • Progress zone 2 intervals by increasing the time of each interval. Move toward a 1:1 ratio.
  • As the client progresses, intervals can progress to the upper end of zone 2. Progress first to longer intervals, then move to a 1:1 ratio.
  • Consider progressing your client to phase 3 once he or she has reached seven or more hours a week of cardiorespiratory training or if a performance goal is desired.
  • VT2 is not measured in this phase.

Remember, before your client can progress to phase 2 he or she must show success in the aerobic phase. Some clients may have no desire to accomplish performance-based goals, so they may choose to remain in phase 2. If your client has an advanced or performance-related goal, perform the second ventilatory threshold (VT2) test just prior to progressing to phase 3. 


Click here to learn about phase 1: aerobic base training.

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