Michelle Francois

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%). Womens 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.

Partial occlusion during resistance exercise alters effort sense and pain.

Hollander, DB, Reeves, GV, Clavier, JD, Francois, MR, Thomas, C, and Kraemer, RR. Partial occlusion during resistance exercise alters effort sense and pain. J Strength Cond Res 24(1): 235-243, 2010-The purpose of the study was to determine how manipulation of peripheral blood flow during resistance exercise using a light load affected perception and physiological measures compared with moderate load resistance exercise and a control trial. Seven subjects performed a 3 (session) by 2 (biceps curls and calf extensions) within-subjects study that was randomized and counterbalanced across 3 weeks. The 3 sessions included (a) light resistance exercise (3 sets to failure) at 30% of 1 repetition maximum (1RM) with partial occlusion (LRO), (b) moderate resistance at 70% of 1RM with no occlusion (MR), and (c) partial occlusion without exercise (OO). Ratings of perceived exertion (RPE), pain, and heart rate were assessed immediately after each set, whereas blood samples were taken before, immediately after, and 15 minutes after exercise. Results demonstrated that RPE and pain were lower in the OO condition than that in the MR and LRO conditions for biceps curls and calf extensions, Fs(2,24) = 22.75, 20.86, ps < 0.0001 and Fs(2,24) = 18.95, 24.52, ps < 0.01; however, no significant differences were noted between MR and LRO conditions. Heart rate was significantly higher for the LRO condition when compared with the MR trial, F(2,18) 20.12, p < 0.001. Results suggest that when partial vascular occlusion with a light load was applied, both pain and effort sense were altered to a similar degree as moderate loads but no occlusion. The practical application of results were that individuals may be better able to tolerate perceptual change at low loads with partial occlusion because joint stress may be minimized while local muscle metabolic demands increase, making resistance training maximally effective and minimally stressful on joints. Perceptual tracking of effort and pain may aid coaches who attempt this protocol.

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

Hollander, DB, Kilpatrick, MW, Ramadan, ZG, Reeves, GV, Francois, M, Blakeney, A, Castracane, VD, and Kraemer, RR. Load rather than contraction type influences rate of perceived exertion and pain. J Strength Cond Res 22: 1184-1193, 2008-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.

Amylin and Selective Glucoregulatory Peptide Alterations during Prolonged Exercise

UNLABELLED Amylin is a pancreatic β-cell peptide that facilitates the regulation of blood glucose concentration by inhibiting release of glucagon and modulating gastric emptying. Prolonged exercise may alter amylin and aid in the maintenance of blood glucose concentration; however, no studies have investigated the effects of prolonged exercise on amylin. PURPOSE This study aimed to determine the effects of 90 min of treadmill exercise on amylin and other glucoregulatory hormone responses in a postprandial state. METHODS Eight young healthy males completed a preliminary trial for VO2max and body composition determination and subsequent experimental and control trials in a counterbalanced manner. The experimental trial subjects arrived at the laboratory at 8:00 a.m., 1 h after consumption of a standard nutrient beverage (Ensure Plus®). At 9:50 a.m., subjects initiated 90 min of treadmill exercise at 60% of VO2max. Blood samples were collected twice before exercise, every 18 min during exercise, and every 20 min during 1 h of recovery. A resting control trial was conducted in an identical manner without VO2 assessment. RESULTS Plasma glucose and leptin concentrations remained stable across exercise, whereas lactate significantly increased to peak at 18 min of exercise then gradually declined. Amylin, insulin, and C-peptide values significantly declined over the trials, with no difference between exercise and control days. Glucagon area-under-the-curve concentrations were significantly greater during the exercise than the control trials. There was a significant time effect and trial effect for cortisol with a higher concentration during the experimental trial than during the control trial. CONCLUSIONS In a postprandial state, prolonged exercise stimulates glucagon and cortisol increases that are associated with stable blood glucose and leptin concentrations; however, similar to postprandial state control condition, insulin, C-peptide, and amylin concentrations decline.

Estrogen mediation of hormone responses to exercise.

The roles of estrogens extend from the regulation of reproduction to other functions involved in control of metabolism, fluid balance, as well as gastrointestinal, lung, and brain function, with a strong effect on other hormones that subsequently alter the physiology of multiple tissues. As such, alteration of endogenous estrogens across the menstrual cycle, or from oral contraception and estrogen replacement therapy, can affect these tissues. Due to the important effects that estrogens have on different tissues, there are many investigations concerning the effects of a human estrogenic environment on endocrine responses to exercise. The following review will describe the consequences of varying estrogen levels on pituitary, adrenal, gonadal, and endocrine function, followed by discussion of the outcomes of different estrogen levels on endocrine tissues in response to exercise, problems encountered for interpretation of findings, and recommended direction for future research.