Load rather than contraction type influences rate of perceived exertion and pain.

The purpose of the study was to determine whether muscle contraction type (concentric [CON] or eccentric [ECC]) or loading (relative or absolute) has a greater impact on the perceptual and metabolic responses to conventional resistance exercise. Additionally, overall effort, pain sensations, and specific pain descriptors were compared with physiological responses. Seven healthy men (mean +/- SE, 25.71 +/- 2.17 years) with resistance training experience completed 2 one-repetition maximum (1-RM) trials. Subsequently, 2 randomized, counterbalanced, experimental sessions were completed consisting of 4 sets of 10 repetitions for 6 exercises. These sessions were performed at 65% CON 1-RM for CON only contractions or 65% CON 1-RM + 20% for ECC contractions. Blood samples were taken pre, post, and 15 minutes postexercise. OMNI-RPE (OMNI-Res), CR-10 pain rating, McGill pain ratings, and heart rate (HR) were recorded after each set. A significant time effect occurred for OMNI-Res, pain, lactate, and HR (p < 0.05). No significant pattern emerged for the contraction type, except for higher HR and lactate immediately postexercise for the CON contractions. Physiological measures were not significantly related to perceptual measures. When considered with previous data, muscle loading rather than contraction type plays the primary role in perceptual alterations of effort sense and pain. Practical applications of the investigation are that strength and conditioning professionals may be able to load CON and ECC contractions in a relative fashion by increasing loads in the ECC portion by 20% above the CON load that would result in comparable perceptual experiences.

Maximal eccentric and concentric strength discrepancies between young men and women for dynamic resistance exercise.

Although research has demonstrated that isokinetic eccentric (ECC) strength is 20-60% greater than isokinetic concentric (CON) strength, few data exist comparing these strength differences in standard dynamic resistance exercises. The purpose of the study was to determine the difference in maximal dynamic ECC and CON strength for 6 different resistance exercises in young men and women. Ten healthy young men (mean +/- SE, 25.30 +/- 1.34 years), and 10 healthy young women (mean +/- SE, 23.40 +/- 1.37 years) who were regular exercisers with resistance training experience participated in the study. Two sessions were performed to determine CON and ECC 1 repetitions maximum for latissimus pull-down (LTP), leg press (LP), bench press (BP), leg extension (LE), seated military press (MP), and leg curl (LC) exercises. Maximal ECC and maximal CON strength were determined on weight stack machines modified to isolate ECC and CON contractions using steel bars and pulleys such that only 1 type of contraction was performed. Within 2 weeks, participants returned and completed a retest trial in a counterbalanced fashioned. Test-retest reliability was excellent (r = 0.99) for all resistance exercise trials. Men demonstrated 20-60% greater ECC than CON strength (LTP = 32%, LP = 44%, BP = 40%, LE = 35%, MP = 49%, LC = 27%). Women's strength exceeded the proposed parameters for greater ECC strength in 4 exercises, p < 0.05 (LP = 66%, BP = 146%, MP = 161%, LC = 82%). The ECC/CON assessment could help coaches capitalize on muscle strength differences in young men and women during training to aid in program design and injury prevention and to enhance strength development.

Similar hormonal responses to concentric and eccentric muscle actions using relative loading.

Conventional resistance exercise is performed using sequential concentric (CON) and eccentric (ECC) contractions, utilizing the same muscle load. Thus, relative to maximal CON and ECC resistance, the ECC contraction is loaded to a lesser degree. We have recently shown that at the same absolute load, CON contractions are associated with greater growth hormone (GH) but similar total testosterone (TT) and free testosterone (FT) responses compared with ECC contractions and attributed the larger GH response to greater relative CON loading. In the present study, we have examined the same endocrine parameters to six different upper and lower body exercises using relative loading rather than absolute loading, hypothesizing that GH responses would be similar for CON and ECC actions, but TT and FT responses would be greater after ECC contractions. Seven young men with recreational weight training experience completed an ECC and CON muscle contraction trial on two different occasions in a counterbalanced fashion. The exercises consisted of four sets of 10 repetitions of lat pull-down, leg press, bench press, leg extension, military press, and leg curl exercises at 65% of an ECC or CON 1-RM with 90 s between sets and exercises. CON and ECC actions were performed at the same speed. ECC 1-RMs were considered to be 120% of the CON 1-RM for the same exercise. Blood samples were collected before, immediately after, and 15 min after the exercise. GH significantly increased across both trials but was not different between the two trials. Total testosterone was not significantly altered in response to either trial; however, free testosterone concentrations increased in response to both ECC and CON trials. Data suggest that CON and ECC muscle contractions produce similar GH, T, and free testosterone responses with the same relative loading.