Comparison of concentric and eccentric bench press repetitions to failure.

Eccentric muscle actions (ECC) are characterized by muscle lengthening, despite actin-myosin crossbridge formation. Muscles acting eccentrically are capable of producing higher levels of force compared with muscles acting concentrically. The purpose of this study was to determine whether ECC bench press yields greater strength than concentric (CON) as determined by 1 repetition maximum (1RM). Additionally, a comparison was made examining differences in the number of repetitions to failure at different relative intensities of 1RM. Thirty healthy men (age = 24.63 ± 5.6 years) were tested for 1RM in CON and ECC bench press and the number of repetitions completed at 60, 70, 80, and 90% 1RM. For CON repetitions, the weight was mechanically lowered to the chest, and the participant pressed it up until the elbows were fully extended. The ECC bench press consisted of lowering a barbell from a fully extended elbow position to the chest in a continuous controlled manner for 3 seconds as determined by electronic metronome. Paired t-tests showed that ECC 1RM (115.99 ± 31.08 kg) was significantly (p ≤ 0.05) greater than CON 1RM (93.56 ± 26.56 kg), and the number of repetitions completed at 90% 1RM was significantly (p ≤ 0.05) greater in ECC (7.67 ± 3.24) as compared with CON (4.57 ± 2.21). There were no significant differences in number of completed repetitions during CON and ECC bench press at 60, 70, and 80% 1RM. These data indicate that ECC actions yield increased force capabilities (∼120%) as compared with CON in the bench press and may be less prone to fatigue, especially at higher intensities. These differences suggest a need to develop unique strategies for training eccentrically.

Effects of intensity and volume on insulin sensitivity during acute bouts of resistance training.

This study evaluated the effects of various resistance exercise protocols on 24-hour postexercise insulin sensitivity. Seventeen participants with impaired fasting glucose (100-125 mg/dL) completed 4 separate bouts of resistance exercise under moderate intensity (65% 1 repetition maximum [1RM]) or high intensity (85% 1RM) conditions within the confines of single set and multiple set protocols. Intravenous fasting blood was taken at baseline and 24 hours postexercise for each exercise condition to measure fasting plasma glucose (G0) and fasting serum insulin (I0) to calculate insulin sensitivity (homeostasis model assessment-insulin resistance = (G0*I0)/405). A minimum of 3 days washout was given between each exercise protocol. A 4 x 2 factorial analysis of variance was performed to compare insulin sensitivity and fasting glucose within subjects and between treatments. All of the exercise protocols improved subsequent insulin sensitivity (p = 0.002) and G0 (p = 0.001). In comparison with single set, there was a significantly greater decrease in G0 (p = 0.021) 24 hours after multiple set bouts. High intensity showed significant decreases in insulin sensitivity as compared with moderate intensity protocols (p = 0.046). Effect size data suggest a dose response relationship between program variables of volume and intensity and 24-hour postexercise insulin sensitivity. High-intensity protocols resulted in greater effect sizes for insulin sensitivity (0.83 multiple set; 0.53 single set) as compared with moderate-intensity protocols. The high-intensity, multiple set bout yielded the greatest treatment effect in both fasting glucose (0.61) and insulin sensitivity (0.83). Overall, single set protocols were less effective than multiple set protocols in lowering fasting blood glucose. Findings suggest a dose-response relationship between volume and intensity on insulin sensitivity and fasting blood glucose. Results indicate that resistance exercise is an effective treatment for acutely enhancing insulin sensitivity and regulating blood glucose in individuals with impaired fasting glucose.

The effect of warm-up with whole-body vibration vs. cycle ergometry on isokinetic dynamometry.

The purpose of this study was to compare the effects of warm-up protocols using either whole-body vibration (WBV) or cycle ergometry (CE) on peak torque at 3 different isokinetic speeds and on fatigue in the knee extension exercise. Twenty-seven recreationally trained (age = 23.59 ± 3.87 years) men (n = 14) and women (n = 13) were tested at 3 different isokinetic speeds (60, 180, 300°·s-1) after either WBV or CE warm-up. The WBV consisted of intermittent bouts of 30 seconds of isometric squats at various degrees of hip and knee flexion for a total of 5 minutes. The CE consisted of 5 minutes of pedaling a cycle ergometer at 65-85% of age-predicted max heart rate. Comparisons between the warm-up conditions were analyzed using repeated measures analysis of variance. For the fatigue comparison, subjects completed 50 continuous concentric knee extensions at 240°·s-1. Means from the first 3 repetitions were compared to means from the final 3 repetitions to establish a fatigue index. Conditions were compared through an independent T-test. No significant (p > 0.05) differences were discovered between warm-up conditions at any speed or on the fatigue index. Means were virtually identical at 60°·s-1 (WBV = 142.14 ± 43.61 ft lb-1; CE = 140.64 ± 42.72 ft lb-1), 180° s-1 (WBV = 93.88 ± 35.18 ft lb-1; CE = 96.36 ± 31.53 ft lb-1), and 300°·s-1 (WBV = 78.36 ± 26.04 ft lb-1; CE = 80.13 ± 26.08), and on fatigue percentage (WBV = 51.14 ± 10.06%; CE = 52.96 ± 9.19%). These data suggest that the more traditional 5-minute cycle ergometer warm-up elicits results comparable to a less common vibration warm-up. The findings of this study are that these modalities are comparable under the tested conditions.