Skeletal muscle adaptations during early phase of heavy-resistance training in men and women.

An 8-wk progressive resistance training program for the lower extremity was performed twice a week to investigate the time course for skeletal muscle adaptations in men and women. Maximal dynamic strength was tested biweekly. Muscle biopsies were extracted at the beginning and every 2 wk of the study from resistance-trained and from nontrained (control) subjects. The muscle samples were analyzed for fiber type composition, cross-sectional area, and myosin heavy chain content. In addition, fasting blood samples were measured for resting serum levels of testosterone, cortisol, and growth hormone. With the exception of the leg press for women (after 2 wk of training) and leg extension for men (after 6 wk of training), absolute and relative maximal dynamic strength was significantly increased after 4 wk of training for all three exercises (squat, leg press, and leg extension) in both sexes. Resistance training also caused a significant decrease in the percentage of type IIb fibers after 2 wk in women and 4 wk in men, an increase in the resting levels of serum testosterone after 4 wk in men, and a decrease in cortisol after 6 wk in men. No significant changes occurred over time for any of the other measured parameters for either sex. These data suggest that skeletal muscle adaptations that may contribute to strength gains of the lower extremity are similar for men and women during the early phase of resistance training and, with the exception of changes in the fast fiber type composition, that they occur gradually.

Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining.

Six women who had participated in a previous 20-wk strength training study for the lower limb detrained for 30-32 wk and subsequently retrained for 6 wk. Seven untrained women also participated in the 6-wk "retraining" phase. In addition, four women from each group volunteered to continue training an additional 7 wk. The initial 20-wk training program caused an increase in maximal dynamic strength, hypertrophy of all three major fiber types, and a decrease in the percentage of type IIb fibers. Detraining had relatively little effect on fiber cross-sectional area but resulted in an increased percentage of type IIb fibers with a concomitant decrease in IIa fibers. Maximal dynamic strength decreased but not to pretraining levels. Retraining for 6 wk resulted in significant increases in the cross-sectional areas of both fast fiber types (IIa and IIab + IIb) compared with detraining values and a decrease in the percentage of type IIb fibers. The 7-wk extension accentuated these trends such that cross-sectional areas continued to increase (nonsignificant) and no IIb fibers could be found. Similar results were found for the nonpreviously trained women. These data suggest that rapid muscular adaptations occur as a result of strength training in previously trained as well as non-previously trained women. Some adaptations (fiber area and maximal dynamic strength) may be retained for long periods during detraining and may contribute to a rapid return to "competitive" form.

Value of resistance training for the reduction of sports injuries.

Many competitive and recreational athletes perform resistance training as a part of their conditioning programmes. Resistance training in addition to increasing muscular strength and hypertrophy may also aid in the prevention of injuries. Research indicates that resistance training promotes growth and/or increases in the strength of ligaments, tendons, tendon to bone and ligament to bone junction strength, joint cartilage and the connective tissue sheaths within muscle. Studies involving humans and animal models also demonstrate resistance training can cause increased bone mineral content and therefore may aid in prevention of skeletal injuries. Investigations to date suggest resistance training can aid in injury prevention. The incidence of various types of overuse injuries, such as swimmers shoulder and tennis elbow, may be reduced by the performance of sport and/or motion specific resistance training activities. Screening of athletes for agonist and antagonist muscle strength imbalances can be utilised to identify possessing a predisposition for injury. Resistance training may then be performed to correct the imbalance and therefore reduce the incidence of injury.

Effect of blood pH on peripheral and central signals of perceived exertion.

Ten male subjects underwent exercise testing in three modes, arms (A), legs (L), and arms + legs (A + L), after ingesting 0.3 g X kg-1 body weight of either NaHCO3 to induce alkalosis or CaCO3 as a placebo (i.e., six exercise trials). Ratings of perceived exertion (RPE: Borg, 15-pt scale) for the arms (RPE-A), legs (RPE-L), chest (REP-C), and overall body (RPE-O) did not differ between acid-base conditions at 20, 40, or 60% VO2max for all three exercise modes. At 80% VO2max, 1) RPE-A was lower (P less than 0.01) during A; 2) RPE-L was lower (P less than 0.01) during L; and 3) RPE-A and RPE-L were lower (P less than 0.01) during A + L under the NaHCO3 as compared to the CaCO3 condition. Differences were not found for RPE-L during A or for RPE-A during L. RPE-C and RPE-O were lower (P less than 0.01) under NaHCO3 during A, L, and A + L. Blood acid-base, VO2, and cardiorespiratory responses were not differentially influenced by exercise mode. Blood pH was significantly higher under NaHCO3 than CaCO3 at pre-exercise and 80% VO2max. VO2, heart rate, and tidal volume did not differ between acid-base conditions at any exercise intensity. VE and respiratory rate did not differ between acid-base conditions at 20, 40, or 60% VO2max but were significantly lower under NaHCO3 at 80% VO2max. RPE-A and L were positively related to blood [H+], and RPE-C was positively related to VE for all exercise modes.

Training responses of plasma beta-endorphin, adrenocorticotropin, and cortisol.

The purpose of this study was to examine the effects of three different run training programs on plasma responses of beta-endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol to maximal treadmill exercise. Subjects were randomly assigned to one of three training groups: sprint intervals (SI) (N = 8), endurance (E) (N = 10), or combination (C) (N = 7). Training was monitored for 10 wk, and maximal treadmill exercise tests were administered pre-training and after 2, 4, 6, 8, and 10 wk of training. Blood samples were obtained (pre-training and after 10 wk) before, immediately after, and 5 and 15 min following the maximal exercise tests. All groups significantly (P less than 0.05) increased maximal oxygen consumption values at 8 and 10 wk of the training period. Significant exercise-induced increase in plasma beta-EP, ACTH, cortisol, and blood lactate were observed for both pre- and post-training tests in all training groups. The SI group demonstrated significant post-training increases in beta-EP, ACTH, cortisol, and 5 min post-exercise blood lactate concentrations in response to maximal exercise. No training-induced hormonal changes were observed for the E group. While exercise-induced increases were observed, the C group exhibited significant post-training reductions in plasma responses of beta-EP, ACTH, and blood lactate concentrations in response to maximal exercise. Still, resting and post-exercise increases in plasma cortisol concentrations were significantly higher in magnitude in the post-training test. Lactate was significantly correlated with beta-EP (r = 0.72), ACTH (r = 0.70), and cortisol (r = 0.64).(ABSTRACT TRUNCATED AT 250 WORDS)

Amputation as a consequence of diabetes mellitus. An epidemiological review.

Amputation as a consequence of diabetes mellitus is becoming an increasingly serious public health problem and a problem that is commonly treated in the physical therapy clinic. Traditionally, physical therapists have devoted most of their efforts to treating the residual limb and have neglected caring for the other leg. This review examines the epidemiology of diabetic gangrene with consequent amputation and provides ideas for preventive measures and research directed at decreasing the occurrence of gangrene and its complications.

Effect of intermittent, supine cervical traction on the myoelectric activity of the upper trapezius muscle in subjects with neck pain.

This study was undertaken to compare the myoelectric activity of the upper trapezius muscle before, during, and after intermittent, supine cervical traction. Twelve people with diagnosed disease or injury of the cervical spine served as subjects. Electromyographic recordings were taken from the upper trapezius muscle with bipolar surface electrodes. The subjects were treated with 20 minutes of intermittent, cervical traction at a force of 8% of their body weight. Recordings were taken with the subjects in the supine position before the traction, during one pull and release phase of the 10th and 20th minutes of traction, and after completion of the traction treatment. An analysis of variance with repeated measures showed no significant differences in the myoelectrical activity during the six time periods measured. The results of this study do not support the clinical use of intermittent, supine traction to produce cervical muscle relaxation.

lsokinetic Evaluation of Tibial Rotation: Assessment of a Stabilization Technique*.

The purpose of this study was to present a wide range of normative data on maximum active tibial rotation utilizing isokinetic resistance and a relatively new stabilization technique. Both legs of 25 healthy adult male subjects were tested at 30, 60, 120, and 180 degrees per second of angular velocity. Data were collected on total range of motion, component internal/external range of motion (via two different methods), joint position at peak torque production, peak torque production, and torque production as a percentage of body weight. The effect of weight and leg length on peak torque production and total range of motion was also determined. In light of recent studies which have shown the need for specific rotational rehabilitation for rotatory knee instabilities, this study serves to present normative data for practical use in either the clinical or research setting. J Orthop Sports Phys Ther 1984;6(1):46-51.

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women.

Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.

The effect of resistance training on blood pressure in normotensive women.

The purpose of the present study was to determine whether conventional resistance training alters 24-h ambulatory and manually determined casual blood pressure of normotensive women. Seven individuals (23 +/- 2 years old) trained 2 days week-1 for 20 weeks emphasizing the hip and knee extensor muscle groups. Three sets to exhaustion of the knee extension, squat, knee flexion and leg press exercises were performed. The load for each exercise represented approximately 80-85% of the one-repetition maximum. Average values for 24-h ambulatory blood pressure were not different (P greater than 0.05) pre- and post-training (systolic, 107 +/- 4 vs. 109 +/- 1 mmHg; diastolic, 73 +/- 2 vs. 71 +/- 2 mmHg). Ambulatory values over 8-h segments of the 24 h (day, evening, night) and casual resting determinations of blood pressure were also not affected. The lack of change in blood pressure cannot be explained by an insufficient training response. Knee extensor strength during dynamic or isokinetic actions increased (approximately 43%, P less than 0.05). In addition, biopsies from the vastus lateralis muscle showed an increase (P less than 0.05) in average muscle fibre cross-sectional area of 32%. This hypertrophic response was further substantiated by an increase (P less than 0.05) in lean body mass (41.2 +/- 1.3 kg to 43.4 +/- 1.5 kg). These results indicate that resistance training, which increases muscular strength, muscle fibre area and lean body mass, does not alter ambulatory or casual blood pressure. Thus, the concern that conventional resistance training may chronically elevate blood pressure does not appear warranted, at least in normotensive women.

Effect of induced erythrocythemia on hypoxia tolerance during physical exercise.

The effect of induced erythrocythemia on hypoxia tolerance during physical exercise was determined for five male mountain climbers. Treadmill testing was performed under four conditions: 1) prereinfusion, normoxia (Pre-N); 2) prereinfusion, hypoxia (Pre-H); 3) postreinfusion, normoxia (Post-N); and 4) postreinfusion, hypoxia (Post-H). An altitude of 3,566.2 m was simulated by having subjects breath a gas mixture of 13.5% O2-86.5% N2 at normal barometric pressure. Tests were administered immediately before and 24 h after autologous transfusion of 750 ml of red blood cells. Hematocrit increased from 43.3% at prereinfusion to 54.8% at postreinfusion. Hemoglobin concentration increased from 13.80 g X 100 ml-1 at prereinfusion to 17.63 g X 100 ml-1 at postreinfusion. Maximal O2 uptake (VO2 max, 1 X min-1) increased (P less than 0.05) by 12.8% (3.28 to 3.70) from Pre-N to Post-N and 13.0% (2.62 to 2.96) from Pre-H to Post-H. Treadmill performance time (s) increased (P less than 0.05) by 15.8% (793 to 918) from Pre-N to Post-N and 8.9% (687 to 748) from Pre-H to Post-H. VO2 max decreased by 20.1% from Pre-N to Pre-H and by 9.8% from Pre-N to Post-H. Treadmill time decreased by 13.4% from Pre-N to Pre-H and 5.7% from Pre-N to Post-H. The calculated change in hypoxia tolerance following reinfusion indicated that physiological altitude was improved by 463.6 m. It was concluded that induced erythrocythemia increased hypoxia tolerance during physical exercise.