Resistance Exercise Alone Or In Conjunction With Caffeine On Measures Of Left Ventricular Workload In Women

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Resistance exercise alone or in conjunction with caffeine increases heart rate and blood pressure in resistance-trained women. While acute resistance exercise has been shown to increase measures of left ventricular workload, the addition of caffeine on these responses is unknown. PURPOSE: To evaluate alterations in left ventricular workload at rest, following acute caffeine supplementation or placebo, as well as during recovery from a fatiguing bout of resistance exercise in resistance-trained women. METHODS: Eleven resistance-trained women (Mean ± SD: Age: 24 ± 4 yrs) participated in a counterbalanced, double blind, placebo-controlled, crossover-design study. Each participant drank 4 mg/kg of caffeine mixed with water. Applanation tonometry was used to measure left ventricular workload at rest (Rest1), 45 minutes after caffeine ingestion (Rest2), immediately post-resistance exercise (Post 1), and 10 minutes post-resistance exercise (Post2). The acute bout of resistance exercise consisted of two sets at 75% 1-repetition maximum (1RM) for 10 repetitions, and one set at 70%1RM with repetitions to failure on the squat and bench press. Two minutes of rest were given between sets and exercises. A 2x4 two-way analysis of variance (ANOVA) was used to assess the effects of condition with a repeated measure of time. RESULTS: There were significant main effects of time for wasted left ventricular energy (Rest1: 608 ± 687dynes*s/cm2; Rest2: 529 ± 667dynes*s/cm2; Post1: 2154 ± 1164dynes*s/cm2; Post2: 1956 ± 1873dynes*s/cm2, p = 0.003), systolic pressure time index (Rest1: 1900 ± 290 mmHg*s; Rest2: 1937 ± 390 mmHg*s; Post1: 2769 ± 535 mmHg*s; Post2: 2652 ± 512 mmHg*s, p = 0.001), diastolic pressure time index (Rest1: 2827 ± 244 mmHg*s; Rest2: 2973 ± 294 mmHg*s; Post1: 2349 ± 319 mmHg*s; Post2: 2289 ± 402 mmHg*s, p = 0.001), and the subendocardial viability ratio (Rest1: 154 ± 34%; Rest2: 163 ± 44%; Post1: 90 ± 31%; Post2: 92 ± 33%, p = 0.001). While there were no significant differences from Rest1 to Rest2, there were significant increases for each of these variables such that Post1 and Post2 were augmented above Rest1 and Rest2. CONCLUSION: These data suggest that resistance exercise in conjunction with 4 mg/kg of caffeine does not mediate additional left ventricular workload compared to a placebo in resistance-trained women.