Aerobic efficiency is essential to all cardio training.  Long gone is the notion that anaerobic athletes can forego aerobic training given the benefits derived from first developing an aerobic base.  For example, aerobic training expands blood volume which in turn allows blood to hold greater quantities of our lactate buffer.  Additionally, improved aerobic efficiency (using fats as a fuel at higher intensities) allows the body to switch back over to fats sooner in recovery and facilitate greater re-conversion of lactate back to usable forms of energy like glucose.

AI, popularized by programs such as the Jeff Galloway method (run-walk) has allowed many individuals to achieve their aerobic goals.  The overall goal with AI is to systematically alternate the overload placed upon the various physiological systems (e.g., energy pathways, cardiopulmonary, neuromuscular) while reducing fatigue, potential repetitive overuse and tissue damage.  The application of science to this training modality can yield impressive results when programs are designed around unique metabolic markers.  The ACE Integrated Fitness Training^TM (ACE IFT™) Model is the first cardio training model to move away from the antiquated models of % MHR and % HRR in favor of Ventilatory Threshold One (VT1) and Ventilatory threshold Two (VT2).  Recent research demonstrates how these markers reflect significant events occurring within the energy pathways and with fuel utilization.

• VT1 represents the transition in one’s primary fuel from fats to carbohydrates, representing the onset of our loss in aerobic efficiency (caloric quality) and a noticeable increase in blood lactate levels.
• VT2 represents the point where carbohydrates contribute exclusively to energy production via the aerobic and fast glycolytic pathways, and where we begin to overwhelm our capacity to tolerate lactate spillover into the blood (scientifically defined as OBLA, although most refer to it as lactate threshold).

Ideally, while many cardio programs strive to maximize caloric quantity (burn more calories per unit of time), they should also strive to build caloric quality (representing greater fat utilization per unit of time, and faster recoveries).  Essentially, this implies training your body to continue to burn fat into higher intensities of exercise.  As many individuals seek health and general fitness goals, building VT1 (aerobic efficiency) is a primary goal.  ACE’s 4^th edition Personal Trainer Manual provides field tests to measure VT1.  Once heart rate or RPE at VT1 is established, a simple 2-zone AI model can be created to build aerobic efficiency with one zone on either side of the VT1-HR as illustrated in figure one below.  Develop a 4 - 6 week microcycle spanning 12 – 15 sessions, after which we re-assess VT1 -assessed to identify improvement (new VT1-HR).  Your AI training program should systematically increase the volume of work performed in Zone two by manipulating several variables (RIVR):

• Number of repetitions or intervals (R)
• Intensity of the interval (I) – Zone 2
• Volume of work (V) – total amount of time in Zone 2
• Length of the recovery interval (R)

As AI is aerobic in nature, steady-state must be achieved in Zone 2 to effectively induce the appropriate overload upon the cardiopulmonary and energy systems.  Consequently, the intervals should be no shorter than 3 minutes and can progress to any duration, pending individual needs, desires and available time.  Structure you work-to-recovery intervals to progress from longer-to-shorter recoveries over the microcycle period as illustrated below in table one (using 4-minute intervals).

Table One: Work-to-recovery Intervals

Using a VT1-HR of 142 bpm as an example, table two illustrates a sample program to improving VT1.

Figure One: General structure of a 2-zone model

Table Two: Sample 2-zone training model to improve VT1