The Effect of Concurrent Training

Numerous recreational exercisers complete their
cardiovascular and strength training workouts either during the same training session or within hours of each other. This sequential exercise regime is referred to as “concurrent training.” The question often asked of personal fitness trainers (PFTs) is whether performing cardiovascular exercise prior to strength training will compromise the strength training performance. A recent publication by Sporer and Wenger (2003) addresses this question regarding concurrent training, as well as some related training issues.

Earlier Research on Concurrent Training

To date, little “basic” research (research performed to determine the underlying mechanism of a phenomenon) has been completed on concurrent training, so theories about how strength training is affected by preceding it with cardiovascular exercise are mostly speculative. One prevalent concept is the “fatigue hypothesis,” which theorizes that strength performance is reduced due to fatigue caused by the prior cardiovascular work. Muscle fatigue is a multifactorial phenomenon, however, caused by an increase in
cellular protons (due to acidosis), a decrease in energy-providing substrates and neural drive, and structural damage to the muscle cells (Sporer & Wenger 2003). More research is needed to identify the specific mechanism(s) determining how cardiovascular exercise performed prior to strength training may (or may not) affect performance.

Several investigations on concurrent training have demonstrated that strength improvements are impaired by prior cardiovascular exercise (Dudley & Djamil 1985; Green 1990; Hennessey & Watson 1994; Hickson 1980), while other studies on concurrent training have shown no impairments (Abernethy & Quigley 1993; McCarthy et al. 1995; Sale et al. 1990). Much of the inconsistency in the research reflects differences in one or all of the following study parameters:

• type of strength training performed
  (isokinetic or isotonic)

• intensity and/or duration of the
  cardiovascular exercise

• intensity and/or volume of the
  strength training

Some New Insights

A very sophisticated study recently conducted on concurrent training by researchers at the University of Victoria in British Columbia (Sporer & Wenger 2003) investigated three research questions:

1. Does prior aerobic exercise compromise strength training and, if so, for how long?

2. Does the intensity of aerobic training have a varying effect on strength
performance?

3. Does any effect on acute strength training depend on the muscle groups used in the aerobic exercise?

Study Methodology. Sixteen male athletes who had been strength training two to three times a week for 6 consecutive months in the 2 years prior to the study completed the testing conditions. Subjects were initially divided into a high-intensity interval training group and a submaximal continuous training group who did aerobic work on cycle ergometers. The cycle VO₂max and power output at VO₂max (MAPW) were determined for each subject.

Both groups performed a 5-minute warm-up and a 5-minute cool-down.
The high-intensity group performed six 3-minute exercise intervals from 85 to 100 percent of MAPW separated by
3-minute recovery periods performed at 40 percent of MAPW. The submaximal group performed 36 continuous minutes at approximately 70 percent of MAPW. Each of these groups also performed a strength training session under a control condition (no prior aerobic exercise) and under the following conditions:

• 4-hour recovery

• 8-hour recovery

• 24-hour recovery

Each strength training session was separated by a minimum of 72 hours. (See “Research Design Procedures” for a clear picture of the methodology.)

To mimic a typical strength training session, all subjects performed four sets of incline leg presses and four sets of bench presses at 75 percent of their one-repetition maximum. For each set, subjects performed as many repetitions as they could successfully execute.

Results. The different intensities of aerobic exercise made no significant difference on the subsequent strength training session. The researchers therefore combined the data from the high-intensity group and the submaximal group to
compare the results of both groups with different recovery periods. (See “Effects of Recovery Time on Performance.”)

With the leg press, for both the 4-hour and 8-hour recovery conditions, the repetitions were significantly lower than for the control condition (no aerobics) and the 24-hour recovery condition. There was no significant difference between the control group and the 24-hour group.

With the bench press, the average number of repetitions performed on each condition was 32, with no difference among the conditions.

Major Findings. This concurrent training study demonstrated three major practical findings:

1. The effect of recovery on strength performance following aerobic exercise on a cycle ergometer is similar regardless of the intensity of the aerobic exercise. In this study there was no difference in resistance training performance when subjects performed high-intensity intervals above 85 percent of maximum aerobic capacity or submaximal continuous training at 70 percent of maximum aerobic capacity.

2. Strength impairments are limited to the muscle groups used in the prior aerobic training. Cycle ergometry is a lower-body cardiovascular modality, which, in this study, had a negative effect on leg press performance after a short recovery period. Bench press output, on the other hand, was not impaired regardless of the recovery period or control condition. Thus, clearly, strength training work is not impaired when the prior aerobic exercise utilizes different muscle groups.

3. Incline leg press performance is dramatically influenced by prior cycle ergometer exercise. In this study, strength output was most noticeably weakened after the 4-hour recovery period, with the next highly affected condition being the 8-hour recovery period.

The researchers concluded that when aerobic training precedes strength training, the volume of training that can be performed can be diminished for up to 8 hours, but this impairment appears to be localized to the muscle groups involved in the aerobic training.

Practical Application

This well-designed concurrent training study reveals constructive insights for PFTs who train clients by using cardiovascular and resistance exercise within the same session. The results of this study suggest that when the sequence involves cardiovascular exercise followed by resistance training, different muscle groups should be emphasized during the two training modalities. On the other hand the decision about the intensity of the cardiovascular exercise completed prior to the strength workout can be based exclusively on the goals of the client for that workout. Should the trainer wish to ensure no compromise of strength training output in a concurrent workout session, another educated option is to perform the resistance exercise first, followed by the cardiovascular training.

One research question that remains to be addressed by future studies is whether long-term strength outcomes are truly affected by concurrent training.