Marcus W. Kilpatrick

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.

Affective and Enjoyment Responses to High-Intensity Interval Training in Overweight-to-Obese and Insufficiently Active Adults

High-intensity interval training (HIIT) has many known physiological benefits, but research investigating the psychological aspects of this training is limited. The purpose of the current study is to investigate the affective and enjoyment responses to continuous and high-intensity interval exercise sessions. Twenty overweight-to-obese, insufficiently active adults completed four counterbalanced trials: a 20-min trial of heavy continuous exercise and three 24-min HIIT trials that used 30-s, 60-s, and 120-s intervals. Affect declined during all trials (p < .05), but affect at the completion of trials was more positive in the shorter interval trials (p < .05). Enjoyment declined in the 120-s interval and heavy continuous conditions only (p < .05). Postexercise enjoyment was higher in the 60-s trial than in the 120-s trial and heavy continuous condition (p < .05). Findings suggest that pleasure and enjoyment are higher during shorter interval trials than during a longer interval or heavy continuous exercise.

Comparisons of Rpe before, during, and after Self-regulated Aerobic Exercise

UNLABELLED Ratings of perceived exertion (RPE) were developed to provide a subjective estimation of exercise intensity during exercise but are also used to produce exercise intensities and to report the intensity of completed exercise sessions. PURPOSE To determine the relationship between RPE assessed before, during, and after trials of RPE-based self-regulated aerobic exercise. METHODS Twenty-six participants (10 males and 16 females) were tested for aerobic fitness. Participants completed three 30-min trials of treadmill exercise at a self-selected intensity corresponding to verbal prescriptions of light, moderate, and vigorous. Participants were instructed to adjust treadmill speed every 5 min to maintain the prescribed intensity. RPE using the OMNI picture system was taken immediately before, every 5 min during, immediately after, and 15 min after exercise. RESULTS Treadmill speed increased during the moderate trial, and HR increased during all trials (P < 0.05). Predicted RPE and session RPE were higher than the average RPE for all sessions (P < 0.05) but not different than RPE values obtained at the end of the 30-min trials (P > 0.05). CONCLUSIONS Findings suggest that predicted and session RPE are well matched to the exertion associated with the finishing minute of exercise sessions but are poorly matched to the majority of the exercise session. In-task RPE values tend to drift throughout exercise despite little or no change in treadmill speed and instructions to self-regulate exercise intensity. These findings indicate that RPE may be linked to exercise duration during self-regulated exercise. Additionally, session RPE ratings taken after exercise tend to reflect the close of exercise rather than the exertion associated with the exercise session as a whole.

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.

Impact of High-Intensity Interval Duration on Perceived Exertion

PURPOSE RPE is increasingly being considered as a viable tool beyond its original use for monitoring in-task exercise intensity. Research indicates that anticipated, in-task, and postexercise RPE values are often notably different from one another. An important new consideration is how perceptions are impacted by high-intensity interval training (HIT). This study aims to compare RPE responses before, during, and after continuous and HIT exercise trials. METHODS Twenty (11 females and 9 males; mean ± SD age, 22 ± 4 yr) overweight (mean ± SD body mass index, 29 ± 3 kg·m(-2)) and unfit (mean ± SD V˙O2peak, 28 ± 5 mL·kg·min(-1)) participants completed a 20-min heavy continuous (HC) trial and three 24-min severe-intensity interval trials that utilized 1:1 work-to-recovery ratios: 30 s (Severe Interval-30), 60 s (Severe Interval-60), and 120 s (Severe Interval-120). Exertion was assessed using the Borg CR10 Scale. Data were analyzed using repeated-measures ANOVA and pairwise comparisons. RESULTS Anticipated exertion was highest in the Severe Interval-120 trial (5.8 ± 2.0; P < 0.05) compared with other trials. Exertion increased from beginning to end in all trials (P < 0.05), with the greatest increases observed within the HC trial. Session RPE for the Severe Interval-120 trial (6.4 ± 2.3) was higher than those for all other trials (P < 0.05), and session RPE for the Severe Interval-30 trial (3.7 ± 1.8) was lower than that for the HC trial (4.9 ± 1.6; P < 0.05). CONCLUSIONS These findings suggest that 30-s HIT protocols limit the perceptual drift that occurs during exercise, in comparison to HC exercise. Moreover, performing more intervals of shorter durations appears to produce lower postexercise RPE values than performing fewer intervals of longer duration and equal intensity. Because effort perception may influence behavior, these results could have implications for the prescription of interval training in overweight sedentary adults.

Impact of Aerobic Exercise Intensity on Craving and Reactivity to Smoking Cues

Aerobic exercise can acutely reduce cigarette cravings during periods of nicotine deprivation. The primary aim of this study was to assess the differential effects of light and vigorous intensity aerobic exercise on cigarette cravings, subjective and physiological reactivity to smoking cues, and affect after overnight nicotine deprivation. A secondary aim was to examine cortisol change as a mediator of the effects of exercise on smoking motivation. 162 (55 female, 107 male) overnight nicotine-deprived smokers were randomized to one of three exercise conditions: light intensity, vigorous intensity, or a passive control condition. After each condition, participants engaged in a standardized cue reactivity assessment. Self-reported urges to smoke, affect, and salivary cortisol were assessed at baseline (i.e., before each condition), immediately after each condition, and after the cue reactivity assessment. Light and vigorous exercise significantly decreased urges to smoke and increased positive affect, relative to the control condition. In addition, those in the vigorous exercise condition demonstrated suppressed appetitive reactivity to smoking cues, as indexed by the startle eyeblink reflex. Although exercise intensity was associated with expected changes in cortisol concentration, these effects were not related to changes in craving or cue reactivity. Both light and vigorous exercise can reduce general cravings to smoke, whereas vigorous exercise appears especially well-suited for reducing appetitive reactions to cues that may precede smoking. Results did not support exercise-induced cortisol release as a mechanism for these effects.

The Impact of Continuous and Interval Cycle Exercise on Affect and Enjoyment

Rates of physical activity remain low despite public health efforts. One form of physical activity that provides significant physiological benefit but has not been evaluated in terms of affective and enjoyment responses is interval exercise. Purpose: The purpose of this study was to compare affect and enjoyment assessed before, during, and after interval and continuous exercise sessions. Method: Twenty-four participants (12 men, 12 women; body mass index = 24 ± 4, maximal oxygen consumption = 41 ± 5 mL/kg/min) completed a maximal cycle ergometer test used to prescribe experimental trials: (a) moderate continuous, (b) heavy continuous, (c) heavy interval, and (d) severe interval. All trials were 20 min in length, and all intervals utilized 60-s segments and a 1:1 work-to-rest ratio. Results: Affective and enjoyment responses were significantly less positive for the heavy continuous trials in comparison with all other trials during exercise (p < .05; ES = .2–.8). Additionally, both severe and heavy interval exercise were more enjoyable than heavy continuous exercise (p > .05). Conclusion: Findings suggest that interval protocols produce affective and enjoyment responses that are equal to moderate continuous exercise and more positive than heavy continuous exercise. These results indicate that interval-based exercise may be a viable alternative to continuous exercise in the promotion of health and fitness.

Differential impact of acute high-intensity exercise on circulating endothelial microparticles and insulin resistance between overweight/obese males and females.

Background An acute bout of exercise can improve endothelial function and insulin sensitivity when measured on the day following exercise. Our aim was to compare acute high-intensity continuous exercise (HICE) to high-intensity interval exercise (HIIE) on circulating endothelial microparticles (EMPs) and insulin sensitivity in overweight/obese men and women. Methods Inactive males (BMI = 30 ± 3, 25 ± 6 yr, n = 6) and females (BMI = 28 ± 2, 21 ± 3 yr, n = 7) participated in three experimental trials in a randomized counterbalanced crossover design: 1) No exercise control (Control); 2) HICE (20 min cycling @ just above ventilatory threshold); 3) HIIE (10 X 1-min @ ∼90% peak aerobic power). Exercise conditions were matched for external work and diet was controlled post-exercise. Fasting blood samples were obtained ∼18 hr after each condition. CD62E+ and CD31+/CD42b- EMPs were assessed by flow cytometry and insulin resistance (IR) was estimated by homeostasis model assessment (HOMA-IR). Results There was a significant sex X exercise interaction for CD62E+ EMPs, CD31+/CD42b- EMPs, and HOMA-IR (all P<0.05). In males, both HICE and HIIE reduced EMPs compared to Control (P≤0.05). In females, HICE increased CD62E+ EMPs (P<0.05 vs. Control) whereas CD31+/CD42b- EMPs were unaltered by either exercise type. There was a significant increase in HOMA-IR in males but a decrease in females following HIIE compared to Control (P<0.05). Conclusions Overweight/obese males and females appear to respond differently to acute bouts of high-intensity exercise. A single session of HICE and HIIE reduced circulating EMPs measured on the morning following exercise in males but in females CD62E+ EMPs were increased following HICE. Next day HOMA-IR paradoxically increased in males but was reduced in females following HIIE. Future research is needed to investigate mechanisms responsible for potential differential responses between males and females.

Exertional responses to sprint interval training: a comparison of 30-sec. and 60-sec. conditions.

The purpose of this study was to assess the effect of sprint interval training on rating of perceived exertion. 20 healthy participants (11 men, 9 women; M age = 23 yr.) completed a maximal cycle ergometer test and two high-intensity interval training cycling sessions. Each session utilized the same work-to-rest ratio (1:1), work intensity (90% max), recovery intensity (10% work intensity), and session duration (16 min.). Trials differed on duration of the interval segment, with a 30-sec. trial and a 60-sec. trial. Sessions required the same amount of total work over the duration of the trial. Rating of perceived exertion assessed before, during, and after exercise were higher for the 60-sec. trial than the 30-sec. trial despite no difference in total work. High intensity interval training trials utilizing the same total external work but differing in interval length produced different ratings of perceived exertion. Perceived exertion is significantly higher for sessions of exercise that utilize longer work intervals. These findings suggest that shorter intervals may produce more favorable exertional responses that could positively affect future behavior.

Impact of aerobic exercise trials with varied intensity patterns on perceptions of effort: An evaluation of predicted, in-task, and session exertion

Abstract Perceptions of effort provide a sense of momentary exertion during exercise, but may have value when considered prior to and after exercise. The purpose of the present study was to determine the relationship between perceived exertion assessed before, during, and after trials of aerobic exercise fixed for total work but varied on intensity patterns. Twenty participants completed five trials of treadmill exercise that included planned intensity variations every 10 minutes to result in the same total work. Perceived exertion was taken before, during, and after exercise. Analyses confirmed each trial was similar in terms of average speed and heart rate (P > 0.05). Predicted and session exertion results indicated that the steady exercise bout was perceived as easier than many trials of varied speed (P < 0.05). Trials including an intense segment in the middle or end of the session were perceived as more difficult than sessions that varied intensity otherwise or remained constant. Similarly, trials that remained constant during the 30-minute period were perceived as less aversive than most other trials. These findings suggest that exercise sessions involving a steady intensity throughout are viewed as less taxing than sessions with variable intensity, especially when compared to sessions that conclude with a higher intensity finish.