Interval TRIMP Scores Predict Improvement in Maximal Oxygen Consumption in middle-aged, sedentary Individuals

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PURPOSE: The optimal training strategy to maximize increases in VO2 max is unclear. We sought to compare the contribution of different training loads from an exercise program combining interval and continuous training on improvements in VO2 max. Training load was objectively quantified by the Training Impulse (TRIMP). METHODS: We studied 30 healthy sedentary participants (53.21±4.70 years, 14 males). Each participant was prescribed a progressive exercise prescription consisting of endurance and interval training. Between month 1 and 6, the exercise progressed to reach a peak phase, which was maintained for 3 months (weekly prescription: interval x2; one 60 min base pace; one 30 min base pace; one recovery). VO2max was measured at baseline and after completion of the peak phase of training via Douglas Bag method and incremental treadmill protocol. The training load for each continuous (TRIMPc = t · k1 · x { ) and interval exercise session (TRIMPi =) was calculated using the relevant equation. Total TRIMP scores (for all exercise), TRIMPc and TRIMPi scores were summed for the peak phase of training. Regression analysis was performed to determine correlation between these scores and percent change in VO2max. RESULTS: VO2max increased from 28.73±4.8 ml/kg/min at baseline to 34.43±5.6 ml/kg/min after training (P< 0.01). Total TRIMP score was 4411±1127 for the peak phase, while TRIMPc score was 2353±699 and TRIMPi score was 2059±638. Total TRIMP score did not correlate with increase in relative VO2max (R2 = 0.04, P=0.31), nor did TRIMPc score (R2=0.00 P=0.92). However, TRIMPi score correlated with increased VO2max (R2=0.14, P=0.05). Moreover, there was a significantly greater percent increase in relative VO2max in individuals whose TRIMPi scores were in the top third of the group compared to those in the bottom third (24.70%±9.10 vs15.11%±7.33, P=0.0188). CONCLUSIONS: Our data suggests that interval TRIMP scores predict changes in relative VO2max in middle-aged, sedentary individuals undergoing exercise training. In conclusion, interval training may provide a greater stimulus for aerobic adaptation than continuous endurance training.