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Biomedical subjects

Stephen P Sayers

Publications and source records attributed to Stephen P Sayers.

7 recordsLinked to original sources
PubMed2003

Neuromuscular variables affecting the magnitude of force loss after eccentric exercise.

The aim of this study was to examine neuromuscular variables contributing to differences in force loss after participants were exposed to the same relative bout of eccentric exercise. Thirty-six males performed 50 maximal eccentric contractions of the elbow flexors and were stratified into high responders (n = 10) and low responders (n = 10) based on force loss 36 h after exercise. Maximal voluntary isometric contractions (MVCs) and electromyography (EMG) were measured at baseline and 36 h after exercise. During eccentric exercise, mean peak torque, mean end-range torque from the final 25% of each trial and total angular impulse were computed over 25 contractions in each of two bouts. The slope of the change in these values for each 25 eccentric contractions was calculated for each participant using linear regression. At baseline, MVC was not different between groups (low responders: 97.0 +/- 9.6 N x m; high responders: 82.7 +/- 6.4 N x m; P = 0.08). High responders demonstrated a 68% (range 62-78%) reduction in MVC and low responders a 39% (29-48%) reduction after exercise. Peak torque, end-range torque and total angular impulse were 13%, 40% and 33% higher, respectively, in the low than in the high responders (peak torque: P = 0.0002; end-range torque: P < 0.0001; total angular impulse: P < 0.001). The rate of decline in peak torque slope was greater in high than in low responders (P = 0.044). In conclusion, lower peak torque, end-range torque and total angular impulse during eccentric contractions and a greater peak torque slope may identify high responders to eccentric exercise.

Adult↗
PubMed2003

Changes in function and disability after resistance training: does velocity matter?: a pilot study.

OBJECTIVE: To compare the effects of high- and low-velocity resistance training on functional performance and disability outcomes in physically limited older women. DESIGN: A total of 16 wk of high-velocity resistance training or traditional low-velocity resistance training consisting of knee extension and leg press exercises was performed three times per week by 30 women with self-reported disability to compare their effect on functional performance and disability. Tests of dynamic balance, stair-climb time, chair-rise time, and gait velocity were used to assess changes in functional performance. Changes in disability were assessed using the Medical Outcomes Study Short Form. RESULTS: Dynamic balance and stair-climb time improved 8% and 10%, respectively, with training. Self-reported disability, physical functioning, role physical, and mental health improved 11, 9, and 5% with training, respectively. There were no significant differences between high- and low-velocity training groups. CONCLUSIONS: High- and low-velocity training achieved similar improvements in functional performance and disability. Improvements in functional performance and disability were modest compared with robust increases in strength and power. Specific modes of training or behavioral strategies may be necessary to optimize improvements in these outcomes.

Aged↗
PubMed2003

Short-term immobilization after eccentric exercise. Part I: contractile properties.

PURPOSE: The purpose of this study was to examine the compound muscle action potential (M-wave) and evoked contractile properties of immobilized muscle after high-force eccentric exercise. We believed that changes in these variables would contribute to the enhanced recovery of maximal voluntary force observed after short-term immobilization of damaged muscle. We hypothesized that immobilization after eccentric exercise would result in an enhanced M-wave and a change in contractile properties toward characteristics of faster muscle fibers. METHODS: Twenty-five college-age males were matched according to force loss after 50 maximal eccentric contractions of the elbow flexors and placed into an immobilization (IMM, N = 12) or control (CON, N = 13) group. IMM had their arm immobilized at 90 degrees and secured in a sling during a 4-d treatment. Maximal isometric torque (MVC) was assessed at baseline and for 8 d after treatment. M-wave and evoked contractile properties of the muscle (twitch torque [TT], maximal rate of torque development [MRTD], time to peak torque [TPT], and one-half relaxation time [HRT]) were assessed at baseline and for the first 5 d after treatment. RESULTS: Immediately postexercise, MVC was reduced 43% and 42% in IMM and CON, respectively. Recovery of MVC was significantly greater in IMM during recovery (P < 0.05), 95% of baseline MVC compared with 83% in CON. M-wave was reduced 32%, and all contractile properties were altered immediately postexercise. M-wave, MRTD, TPT, and HRT were not significantly different between groups during recovery (P > 0.05). TT demonstrated enhanced recovery in IMM (P < 0.05). CONCLUSIONS: Short-term immobilization after eccentric exercise resulted in enhanced recovery of maximal voluntary force. However, enhanced force recovery cannot be explained by muscle activation and evoked contractile properties of the muscle.

Adult↗
PubMed2003

Short-term immobilization after eccentric exercise. Part II: creatine kinase and myoglobin.

PURPOSE: Although creatine kinase (CK) is commonly used as a marker of muscle damage, there is large variability in the response to exercise. We previously found short-term immobilization blunted the rise in plasma CK after eccentric exercise, suggesting subsequent movement of damaged muscle may contribute to variability. We hypothesized that immobilization decreases lymphatic transport of CK from damaged muscle, blunting the CK response. In this study, we compared changes in plasma CK and myoglobin (Mb), as Mb is released from damaged muscle directly into the bloodstream whereas CK is released first into the lymph. METHODS: Twenty-five college-age males were matched according to force loss after 50 maximal eccentric contractions of the elbow flexors and placed into an immobilization (IMM, N = 12) or control (CON, N = 13) group. IMM had their arm immobilized at 90 degrees and secured in a sling for 4 d (treatment). Venipuncture was performed during baseline, treatment, and for 5 d after treatment (recovery) to assess plasma CK activity and Mb. Urine specific gravity (USG) and muscle activity (ACT) were assessed. RESULTS: Immobilization significantly blunted increases in CK activity (IMM: 955 +/- 316 IU.L-1 vs CON: 2884 +/- 1083 IU.L-1; P < 0.05) but not increases in Mb (IMM: 712 +/- 278 ng.mL-1 vs CON: 891 +/- 253 ng.mL-1; P > 0.05). There were no differences in USG between groups over time (P > 0.05) and no group differences in ACT (P > 0.05). CONCLUSIONS: Short-term immobilization after eccentric exercise blunted the CK response but not the Mb response, suggesting lymphatic transport of CK may be responsible. Because hydration status and muscular activity after exercise were not different between groups, the blunted CK response was likely due to inactivation of CK activity before entering circulation.

Adult↗
PubMed2003

Treatment and prevention of delayed onset muscle soreness.

Eccentric exercise continues to receive attention as a productive means of exercise. Coupled with this has been the heightened study of the damage that occurs in early stages of exposure to eccentric exercise. This is commonly referred to as delayed onset muscle soreness (DOMS). To date, a sound and consistent treatment for DOMS has not been established. Although multiple practices exist for the treatment of DOMS, few have scientific support. Suggested treatments for DOMS are numerous and include pharmaceuticals, herbal remedies, stretching, massage, nutritional supplements, and many more. DOMS is particularly prevalent in resistance training; hence, this article may be of particular interest to the coach, trainer, or physical therapist to aid in selection of efficient treatments. First, we briefly review eccentric exercise and its characteristics and then proceed to a scientific and systematic overview and evaluation of treatments for DOMS. We have classified treatments into 3 sections, namely, pharmacological, conventional rehabilitation approaches, and a third section that collectively evaluates multiple additional practiced treatments. Literature that addresses most directly the question regarding the effectiveness of a particular treatment has been selected. The reader will note that selected treatments such as anti-inflammatory drugs and antioxidants appear to have a potential in the treatment of DOMS. Other conventional approaches, such as massage, ultrasound, and stretching appear less promising.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2002

Metabolic response to light exercise after exercise-induced rhabdomyolysis.

Inherent compromises in substrate metabolism, or impaired perfusion of muscle may contribute to the occurrence of exercise-induced rhabdomyolysis. In this study, the lactate response of the elbow flexor muscles to light exercise was examined in eight subjects (five males, three females) who previously demonstrated rhabdomyolysis with extreme swelling (ES; n = 4) or no swelling (NS; n = 4) of the upper arm after eccentric exercise. Subjects performed identical light exercise bouts (45 s of rapid isotonic biceps curls consisting of both concentric and eccentric actions at 25% of maximum voluntary contraction force) using their previously eccentrically exercised arm (E-ARM) and control arm, which was not used previously to perform eccentric exercise (C-ARM). Blood lactate concentration ([La]b) was assessed 1.5, 3, 4.5, 6, and 9 min post-exercise. Peak [La]b and the area under the curve (AUC) were compared between the E-ARM of the ES and NS groups and between the C-ARM and E-ARM of the ES group. The AUC did not differ between the E-ARM of the ES and NS groups (P > 0.05) or between the C-ARM and E-ARM of the ES group (P > 0.05). In the ES group, the increase in [La]b after light exercise with the C-ARM [mean (SD) change, delta: 1.98 (0.7) mmol/l] was not different from the increase after exercising the E-ARM [delta: 2.10 (0.7) mmol/l; P>0.05]. Comparing the response of the E-ARM between groups, the increase in [La]b of the NS group [delta: 1.40 (0.4) mmol/l] was not different than that observed in the ES group [delta: 2.10 (0.7) mmol/l; P>0.05). Thus, subjects who had previously exhibited signs of exercise-induced rhabdomyolysis did not show an abnormal response to low-intensity anaerobic exercise.

Adult↗