Steven T. McCaw

Perceived exertion, electromyography, and blood lactate during acute bouts of resistance exercise.

PURPOSEnThis study examined ratings of perceived exertion (RPE) during resistance exercise in women. In addition, changes in blood lactic acid and biceps muscle activity assessed using electromyography (EMG) were investigated as potential mediators of RPE during resistance exercise.nnnMETHODSnTwenty female volunteers (age, 25 +/- 4 yr) performed one set of biceps curl exercise at 30%, 60%, and 90% of their one-repetition maximum (1-RM). Total work was held constant by varying the number of repetitions during each of the three intensities. The three intensities were performed in random order. RPE responses were assessed for both the active muscle (RPE-AM) and the overall body (RPE-O) following each intensity. EMG data were collected from the biceps brachii muscle during each intensity. Blood samples were taken before and following the intensities and analyzed for blood lactic acid concentration.nnnRESULTSnA two-factor repeated-measures ANOVA showed a significant RPE (region) x intensity interaction (P < 0.02). Both RPE-AM and RPE-O increased as the intensity of exercise increased. EMG activity increased significantly (P < 0.01) as the intensity of exercise increased. A two-factor repeated measures ANOVA performed on the blood lactate data showed a significant (P < 0.04) time x intensity interaction. Postexercise [Hla] was significantly greater (P < 0.01) at 90% 1-RM than at 30% 1-RM. No significant differences were found in [Hla] between 30% and 60% 1-RM, or between 60% and 90% 1-RM.nnnCONCLUSIONnThese results indicate that monitoring RPE may be a useful technique for regulating resistance exercise intensity. Moreover, blood lactate and activity of the involved muscle may mediate the relation between RPE and resistance exercise intensity.

Stance width and bar load effects on leg muscle activity during the parallel squat.

PURPOSEnAltering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads.nnnMETHODSnNine male lifters served as subjects. Within 7 d of determining IRM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, alpha = 0.05).nnnRESULTSnFor rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase.nnnCONCLUSIONnThe results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.

Ratings of perceived exertion and muscle activity during the bench press exercise in recreational and novice lifters.

This study examined ratings of perceived exertion (RPE) and electro-myography (EMG) during resistance exercise in recreational and novice lifters. Fourteen novice (age = 21.5 ± 1.5 years) and 14 recreationally trained (age = 21.9 ± 2.2 years) women volunteered to perform the bench press exercise at 60 and 80% of their 1 repetition maximum (1RM). RPE and EMG were measured during both intensities. Statistical analyses revealed that active muscle RPE increased as resistance exercise intensity increased from 60% 1RM to 80% 1RM (12.32 ± 1.81 vs. 15.14 ± 1.74). Integrated EMG also increased as resistance exercise intensity increased from 60% 1RM to 80% 1RM (in the pectoralis major; 98.62 ± 17.54 vs. 127.98 ± 29.02). No significant differences in RPE or EMG were found between novice and recreational lifters. These results indicate that RPE is related to the relative exercise intensity lifted as well as muscle activity during resistance exercise for both recreational and novice lifters. These results support the use of RPE as a method of resistance exercise intensity estimation for both types of lifters.

Prophylactic ankle stabilizers affect ankle joint kinematics during drop landings.

PURPOSEnAnkle joint dorsiflexion contributes to energy absorption during landing, but wearing ankle stabilizers is known to restrict passive measures of dorsiflexion. This study compared the effects of various ankle stabilizers on ankle joint kinematics during soft and stiff landings.nnnMETHODSnSubjects (N = 14) performed two-legged landings off a 0.59-m platform. Kinematics of the right ankle were calculated from a sagittal plane video recording (120 Hz). Five soft and five stiff landings were performed in five ankle stabilizer conditions (no stabilizer, taping, Swede-O, AirCast, and Active Ankle), a total of 50 trials per subject. Style and stabilizer conditions were randomized across subjects. Each subjects five-trial mean value of selected kinematic variables for each landing style/stabilizer condition was entered into a two-way repeated MANOVA (alpha = 0.05).nnnRESULTSnDifferences between soft and stiff landing conditions were similar to those reported in the literature. Compared with the No stabilizer condition, most stabilizer conditions significantly reduced ankle dorsiflexion ROM and angular velocity during landing.nnnCONCLUSIONSnThe results indicate that some ankle stabilizers adversely affect ankle joint kinematics during landing.

The effect of comments about shoe construction on impact forces during walking

UNLABELLEDnComparisons of ground reaction forces (GRF) during gait are not typically conducted with blinding of the varied shoe characteristic, raising concerns related to the existence of a placebo effect, or a subject response based on a perceived expectation of change.nnnPURPOSEnTo determine whether investigator comments on shoe construction influenced GRF measures and ratings of shoe cushioning during walking.nnnMETHODSn19 female college students volunteered for a study presented as a test of a new shoe material. The study involved walking (2.5 m x s(-1)) under three shoe conditions (SC). Shoes in SC2 and SC3 were harder than those in SC1, but shoes in SC1 and SC3 looked similar. Subjects in a mislead group (N = 9) were told SC1 and SC3 were baseline measures in a standard shoe, with SC2 misleadingly described as a shoe constructed of unique new material. A control group performed the same three conditions without investigator description. GRF data were collected for 10 trials for each subject in each condition, and subjects rated the perceived cushioning of each shoe. GRF data and perceived cushioning scores were analyzed using mixed-factor (group by shoe) ANOVA.nnnRESULTSnA significant shoe main effect was found for loading rate. Post hoc tests identified the difference between SC1 and both SC2 and SC3. The group main effect was not significant for any dependent variable.nnnCONCLUSIONSnResults suggest that, as a group, GRF data and cushioning scores are not affected by investigator comments that do not match shoe construction characteristics. However, ratings of perceived shoe cushioning by some individual subjects reflected investigator comments and not the vertical GRF variables.