Weeks Of Strength Training Research Articles

Response Of Il-4 And Il-4r Of Human Skeletal Muscle To Strength Training

Interleukin-4 (IL-4) is involved in the regulation of the myoblast fusion and IL-4 receptor (IL-4R) has significance for skeletal muscle growth in vitro and in mice. Taking into account that strength training can lead to muscle hypertrophy and/or regeneration and/or fiber type transformation, we hypothesized that IL-4 and IL-4R may play a role in these processes. PURPOSE To investigate the effects of strength training on IL-4R and IL-4 expression in skeletal muscle in humans. METHODS Twelve volunteers received a 6-week strength training with maximum contractions. Muscle samples were taken from triceps brachii before and after the total course of training. Total RNA was extracted from the muscle samples and Oligo primed synthesis of cDNA was performed using MuLV reverse transcriptase. MRNA levels of IL-4R and IL-4 expression were determined by quantitative real-time PCR and IL-4 protein expression by ELISA. RESULTS The expression of IL-4R was significantly increased after training from 0,19±0,10 to 1,38±0,36 mRNA copy number (p=0.004). There was a slight increase in IL-4 mRNA level of skeletal muscle after training from 654±268 to 1054±757 mRNA copy number (p=0,623) and a slight decrease in IL-4 protein expression from 0,35±0,06 to 0,26±0,04 OD (p=0,263). CONCLUSIONS We demonstrate for the first time that IL-4R is upregulated after strength training in human skeletal muscle. There were only slight effects on IL-4 protein and mRNA expression in skeletal muscle after strenght training. In conclusion, a possible role of IL-4 and IL-4R could be postulated for the adaptation of skeletal muscle in response to strength training in humans. This is supported by the established mitogenic effects of IL-4 and IL-4R in some cell types and tissues. The relevance of this findings has to be determined in further studies.

Effect of Exercise Training on Peak Aerobic Power, Left Ventricular Morphology, and Muscle Strength in Healthy Older Women

The effect that aerobic (AT) and/or strength training (ST) has on altering peak aerobic power (VO2peak), muscle strength, left ventricular (LV) morphology, and diastolic filling in healthy older women is not known. We assessed the effects of 12 weeks of AT, ST, combined aerobic and strength training (COMT), or no training (NT) on VO2peak, muscle strength, LV morphology, and diastolic filling in 31 healthy women (68 +/- 4 years). Relative VO2peak was significantly greater after 12 weeks of AT, ST, or COMT. Upper and lower extremity strength were significantly higher after 12 weeks of ST or COMT with no change after AT or NT. LV morphology and diastolic filling were not altered after 12 weeks of AT, ST, COMT, or NT. Twelve weeks of ST or COMT are as effective as 12 weeks of AT for increasing relative VO2peak, however, ST and COMT are more effective than AT for improving overall muscle strength.

Strength training: Isometric training at a range of joint angles versus dynamic training

Strength training with isometric contractions produces large but highly angle-specific adaptations. To contrast the contractile mode of isometric versus dynamic training, but diminish the strong angle specificity effect, we compared the strength gains produced by isometric training at four joint angles with conventional dynamic training. Thirty-three recreationally active healthy males aged 18 – 30 years completed 9 weeks of strength training of the quadriceps muscle group three times per week. An intra-individual design was adopted: one leg performed purely isometric training at each of four joint angles (isometrically trained leg); the other leg performed conventional dynamic training, lifting and lowering (dynamically trained leg). Both legs trained at similar relative loads for the same duration. The quadriceps strength of each leg was measured isometrically (at four angles) and isokinetically (at three velocities) pre and post training. After 9 weeks of training, the increase in isokinetic strength was similar in both legs (pooled data from three velocities: dynamically trained leg, 10.7%; isometrically trained leg, 10.5%). Isometric strength increases were significantly greater for the isometrically trained leg (pooled data from four angles: dynamically trained leg, 13.1%; isometrically trained leg, 18.0%). This may have been due to the greater absolute torque involved with isometric training or a residual angle specificity effect despite the isometric training being divided over four angles.

Effects of a Heavy and a Moderate Resistance Training on Functional Performance in Older Adults

Resistance training can improve strength and functional performance, but there is little information about the effect of training intensity on functional performance in older adults. The purpose of this study was to determine the effect of 12 weeks of heavy (80% of 1 repetition maximum [1RM]) and moderate (60% of 1RM) resistance training on functional performance in healthy, inactive older adults, ages 60-74 years. Volunteer subjects were assigned randomly to a control group (CS, n = 10), heavy resistance training group (HRT, n = 11), or moderate resistance training group (MRT, n = 12) and participated in 12 weeks of strength training, 3 times per week. Performance measurements included 1RM lower-body strength, chair-rising time, walking velocity, stair-climbing time, and flexibility. Significant differences between HRT and MRT were found for 1RM strength of the lower limbs after the training period. Functional performance improved similarly for both HRT and MRT after the training period. Functional performance can be improved significantly with either heavy or moderate resistance training, without significant differences in the effectiveness of the 2 training protocols.

Correlates of Strength Training in Older Rural African American and Caucasian Women

ABSTRACT This study examined factors influencing strength training (ST) in two convenience samples of older rural women. Focus group (FG) participants were 23 Caucasian and 16 African American women aged 67.5 ± 9.2 years. Survey participants were 60 Caucasian and 42 African American women, aged 70.59 ± 9.21 years. FG participants answered questions about the risks, benefits, and barriers to ST. Survey participants completed measures of demographics, physical activity (including ST), depression and stress, decisional balance for exercise (DBE), barriers to PA, and social support (SS). Regression modeling examined correlates of ST. FG participants identified physical health gains and improved appearance as ST benefits. African American women also included mental health benefits and “feeling good.” Both Caucasian and African American groups named physical health problems as risks of ST. Caucasian women identified time constraints, lack of ST knowledge, physical health problems, lack of exercise facilities, and the cost of ST as barriers. African American women cited being “too tired,” physical health problems, lack of support, and other family and work responsibilities. The linear regression model explained 23.2% of the variance in hours per week of ST; DBE and family SS were independent positive correlates. This study identified correlates to participation in ST in older rural women and provides a basis for developing ST interventions in this population.

Adults with cerebral palsy benefit from participating in a strength training programme at a community gymnasium

Purpose: This study examined whether a community-based progressive resistance strength training programme could improve muscle strength and functional activity in a group of adults with cerebral palsy with high support needs.Method: Using a single group pre-post clinical design, 10 adults (7 males, 3 females; mean age 47.8 SD 5.7 years) with cerebral palsy and high support needs completed 4 weeks of introduction and familiarization, followed by a 10-week progressive resistance strength training programme in a community gymnasium. Participants were measured for muscle strength, locomotion speed and timed sit-to-stand.Results: After establishment of a stable baseline from weeks 2 to 5 with no systematic change and a high degree of association (r > 0.86), participants increased leg strength by 22.0% (p = 0.02), arm strength by 17.2% (p = 0.01) and improved performance of sit-to-stand (p = 0.02) during the 10-week strength training intervention.Conclusions: This study adds to the accumulating evidence that strength training can be beneficial for people with cerebral palsy by demonstrating benefits for adults with cerebral palsy and high support needs who are subject to decline in physical function associated with the ageing process.

Effect of a 10-Week Strength Training Program and Recovery Supplement on Anaerobic Performance

0852 The purpose of this study was to determine whether post-exercise consumption of a supplement containing creatine, whey protein and amino acids, and carbohydrate (fructose and maltodextrin) during a 10-week strength training program promoted greater improvement in anaerobic performance compared with placebo and strength training. Methods. The study was double-blind and placebo controlled. Forty-three college-aged males were randomly assigned to receive supplement or placebo immediately after exercise. Subjects participated in a 10-week periodized strength training program with exercises for the legs and abdominal muscles on Monday and Thursday and exercises for the chest, back, arms and shoulders on Tuesday and Friday. Subjects had to complete at least 70% of the workouts and receive > of the supplement/placebo doses in order to remain in the study. Before and after the strength training program, anaerobic performance was assessed with a 30-second Wingate cycle test using an Excalibur cycle ergometer (Lode, Netherlands). Data were analyzed with a two-way ANOVA (time × group) with repeated measures on time. P < 0.05 was accepted as statistically significant. Results. Twenty-nine subjects (placebo: n = 12; supplement: n = 17) completed the study. Peak power, mean power and anaerobic power increased across groups over the 10-week strength training period, but there was no change for anaerobic capacity and fatigue rate. There were no significant time × group interactions for peak power (p = 0.056), mean power (p = 0.097), anaerobic power, anaerobic capacity or fatigue rate. There were trends for greater increases in peak and mean power for the supplement group. Effect sizes for peak power and mean power were large, Eta2 = 0.133 and 0.103, respectively. The supplement group had a 11.3 % improvement in peak power compared to a 3.5 % increase for the placebo group. The supplement group had a 5.8 % improvement in mean power compared to a 2.2 % increase for the placebo group. Conclusion. During a strength training program of short duration, consumption of a post-exercise supplement containing creatine, whey protein, amino acids and carbohydrate did not result in significantly greater improvement in anaerobic performance compared with placebo.

Effect of a 10-Week Strength Training Program and Recovery Supplement on Anaerobic Performance

0852 The purpose of this study was to determine whether post-exercise consumption of a supplement containing creatine, whey protein and amino acids, and carbohydrate (fructose and maltodextrin) during a 10-week strength training program promoted greater improvement in anaerobic performance compared with placebo and strength training. Methods. The study was double-blind and placebo controlled. Forty-three college-aged males were randomly assigned to receive supplement or placebo immediately after exercise. Subjects participated in a 10-week periodized strength training program with exercises for the legs and abdominal muscles on Monday and Thursday and exercises for the chest, back, arms and shoulders on Tuesday and Friday. Subjects had to complete at least 70% of the workouts and receive > of the supplement/placebo doses in order to remain in the study. Before and after the strength training program, anaerobic performance was assessed with a 30-second Wingate cycle test using an Excalibur cycle ergometer (Lode, Netherlands). Data were analyzed with a two-way ANOVA (time × group) with repeated measures on time. P < 0.05 was accepted as statistically significant. Results. Twenty-nine subjects (placebo: n = 12; supplement: n = 17) completed the study. Peak power, mean power and anaerobic power increased across groups over the 10-week strength training period, but there was no change for anaerobic capacity and fatigue rate. There were no significant time × group interactions for peak power (p = 0.056), mean power (p = 0.097), anaerobic power, anaerobic capacity or fatigue rate. There were trends for greater increases in peak and mean power for the supplement group. Effect sizes for peak power and mean power were large, Eta2 = 0.133 and 0.103, respectively. The supplement group had a 11.3 % improvement in peak power compared to a 3.5 % increase for the placebo group. The supplement group had a 5.8 % improvement in mean power compared to a 2.2 % increase for the placebo group. Conclusion. During a strength training program of short duration, consumption of a post-exercise supplement containing creatine, whey protein, amino acids and carbohydrate did not result in significantly greater improvement in anaerobic performance compared with placebo.

Effect of a Post-Exercise Recovery Supplement and 10-Week Strength Training Program on Muscle Strength and Endurance

0291 Optimizing the type and timing of nutrient intake may be essential for promoting maximal gains in muscle strength and endurance in conjunction with a resistance training program. Purpose. The purpose of this study was to determine whether consumption of a post-exercise recovery drink containing creatine, whey protein, amino acids, and carbohydrate (maltodextrin and fructose) combined with strength training resulted in greater improvements in muscular strength and endurance compared to placebo. Methods. Using a double-blind, placebo controlled design, 43 college-aged males were randomly assigned to receive supplement or placebo. Subjects completed a 10-week supervised, periodized strength training program with leg and abdominal exercises on Monday and Thursday and upper body exercises on Tuesday and Friday. Subjects had to complete > 70% of the workouts and receive at least 70% of the supplement/placebo doses in order to remain in the study. Before and after the 10-week program, 1-RM strength was determined for the free weight bench press and 45° leg press. Muscular endurance was measured as the repetitions completed with 80% of the 1-RM and as estimated external work (repetitions completed × resistance). Data were analyzed with a two-way ANOVA (time × group) with repeated measures on time. P < 0.05 was accepted as statistically significant. Results. Twenty-nine subjects (placebo: n = 12; supplement: n = 17) completed the study. Although 1-RM bench press and 45° leg press strength increased over the 10-week training period, there were no significant time × group interactions. Muscular endurance, whether determined as the number of repetitions completed with 80% of the 1-RM or as estimated external work, increased for the 45° leg press but not for the bench press over the 10-week strength training study. There were no time × group interactions for muscular endurance. Conclusion. During a short-term strength training program, consuming a recovery drink of creatine, whey protein, amino acids and carbohydrate post-exercise did not increase muscle strength and endurance compared with a placebo.

Arm Muscle HSP70 Response to Strenght Training

2182 Heat shock protein 70 (HSP70) expression in skeletal muscle is involved in a variety of muscular changes including myopathy, muscle atrophy, muscle hypertrophy and ischemia.HSP70 plays an important role in muscular adaptation to training and can serve as an indicator for cellular stress. It is known that HSP70 expression and HSP70 response to exercise are related to muscle fiber type. Up to date, data on HSP70 response to training in human muscles have been derived from leg muscles and there is no study reporting HSP70 response in arm muscles. PURPOSE: To investigate HSP70 response to strength training in arm muscle. METHODS: Twelve male volunteers performed either a 6-week strength training (3d/w) with maximum contractions (Max group) or combination training of maximum contractions, ballistic and strech-shortening movements (Combi group). Muscle samples were taken from m. triceps brachii before and after training by fine needle biopsy technique. HSP70 (from 2.5 μg total protein loaded) was measured with Western Blot with reference to a series of standard HSP70. HSP70 mRNA was determined using quantitative real-time RT-PCR in relation to a house-keeping (HPRT) gene. RESULTS: Strength training produced a significant increase in 1 RM in both groups (5.6 kg for Max group and 5.0 kg for Combi group, respectively), and combined strength training led an additional improvement in maximum movement velocity (0.1 m/s, p<0.05). HSP70 (median) increased after training from 15.2 to 58.9 ng, (P<0.01) in Max group and 15.5 to 54.2 ng, (P<0.01) in Combi group. There was also a significant difference of the copy numbers of HSP70 mRNA before and after training in Max group (2.59 vs. 10.1, P<0.01) and Combi group (1.93 vs. 10.57, P<0.01). CONCLUSION: In response to physical training, HSP70 can be induced in human arm muscles. In our study different training programs with comparable training intensity and volume seem not to affect HSP70 expression. Based on its universal role as “molecular chaperone” HSP70 can have important impact on the adaptation to strength training in arm muscle composed predominantly of fast muscle fibers.

Short-Term Strength Training Does Not Alter Skeletal Muscle Capillarization In Young Or Older Women

0399 It is well-established that regular aerobic exercise training may increase skeletal muscle capillarization in young and older men and women. In addition, a number of studies have reported improved skeletal muscle capillarity in young and older men following strength training (ST). However, few studies have examined the effects of ST on skeletal muscle capillarization in women, especially in older women. PURPOSE: To examine the effects of ST on skeletal muscle capillarization in young (YW; n = 11; 26 ± 1 yr; 62 ± 12 kg) and older (OW; n = 11; 68 ± 3 yr; 68 ± 9 kg) women. METHODS: Needle biopsy samples of the vastus lateralis muscles of both legs were obtained before and after nine weeks of unilateral ST during which only the dominant leg was trained. Muscle samples were stained for capillary analyses using the PAS method. Baseline muscle samples and those obtained after ST were compared using ANOVA with repeated measures to examine the effects of age and ST on capillary density (CD), capillary per fiber ratio (CFR), and capillary contacts per fiber (CCF). RESULTS: Although ST led to significant increases in 1 RM strength and muscle fiber cross sectional area (CSA) in the trained leg of YW and OW, there were no significant changes in CD (YW: 259 ± 37 vs. 265 ± 16; OW: 267 ± 30 vs. 237 ± 27; cap/mm2), CFR (YW: 3.4 ± 0.4 vs. 3.5 ± 0.3; OW: 3.4 ± 0.5 vs. 3.6 ± 0.4; cap/fiber area/mm2), or CCF (YW: 4.9 ± 0.5 vs. 4.9 ± 0.7; OW: 4.8 ± 0.5 vs. 5 ± 0.2; cap/fiber) as a result of ST (all p > 0.05). There were also no significant differences in capillarization between YW and OW at baseline, and no changes in capillarization in the control leg. CONCLUSION: These data indicate that although short-term heavy-resistance ST may induce improvements in muscular strength and muscle fiber CSA in women, it does not result in significant alterations in skeletal muscle capillarity. Supported by NIA Research Contract #1AG-42148

Short-Term Strength Training Does Not Alter Skeletal Muscle Capillarization In Young Or Older Women

0399 It is well-established that regular aerobic exercise training may increase skeletal muscle capillarization in young and older men and women. In addition, a number of studies have reported improved skeletal muscle capillarity in young and older men following strength training (ST). However, few studies have examined the effects of ST on skeletal muscle capillarization in women, especially in older women. PURPOSE: To examine the effects of ST on skeletal muscle capillarization in young (YW; n = 11; 26 ± 1 yr; 62 ± 12 kg) and older (OW; n = 11; 68 ± 3 yr; 68 ± 9 kg) women. METHODS: Needle biopsy samples of the vastus lateralis muscles of both legs were obtained before and after nine weeks of unilateral ST during which only the dominant leg was trained. Muscle samples were stained for capillary analyses using the PAS method. Baseline muscle samples and those obtained after ST were compared using ANOVA with repeated measures to examine the effects of age and ST on capillary density (CD), capillary per fiber ratio (CFR), and capillary contacts per fiber (CCF). RESULTS: Although ST led to significant increases in 1 RM strength and muscle fiber cross sectional area (CSA) in the trained leg of YW and OW, there were no significant changes in CD (YW: 259 ± 37 vs. 265 ± 16; OW: 267 ± 30 vs. 237 ± 27; cap/mm2), CFR (YW: 3.4 ± 0.4 vs. 3.5 ± 0.3; OW: 3.4 ± 0.5 vs. 3.6 ± 0.4; cap/fiber area/mm2), or CCF (YW: 4.9 ± 0.5 vs. 4.9 ± 0.7; OW: 4.8 ± 0.5 vs. 5 ± 0.2; cap/fiber) as a result of ST (all p > 0.05). There were also no significant differences in capillarization between YW and OW at baseline, and no changes in capillarization in the control leg. CONCLUSION: These data indicate that although short-term heavy-resistance ST may induce improvements in muscular strength and muscle fiber CSA in women, it does not result in significant alterations in skeletal muscle capillarity. Supported by NIA Research Contract #1AG-42148

Effect of a Post-Exercise Recovery Supplement and 10-Week Strength Training Program on Muscle Strength and Endurance

Effect of a Post-Exercise Recovery Supplement and 10-Week Strength Training Program on Muscle Strength and Endurance

Effect of a 10-Week strength training program and recovery drink on body composition, muscular strength and endurance, and anaerobic power and capacity

Objective We investigated whether postexercise consumption of a supplement containing whey protein, amino acids, creatine, and carbohydrate combined with a strength training program promotes greater gains in fat-free mass (FFM), muscle strength and endurance, and anaerobic performance compared with an isocaloric, carbohydrate-only control drink combined with strength training. Methods The study was double blind and randomized, and the experimental supplement was compared with a carbohydrate-only control. Forty-one males ( n = 20 in control group, n = 21 in the supplement group; mean age, 22.2 y) participated in a 4 d/wk, 10-wk periodized strength training program. Subjects had to complete at least 70% of the workouts. Before and after 10 wk of strength training, subjects were tested for body composition by using hydrostatic weighing and skinfold thicknesses, one repetition maximum strength and muscular endurance for the bench press and 45-degree leg press, and anaerobic performance using a 30-s Wingate test. Thirty-three subjects (80.5%) completed the training program ( n = 15 in control group, n = 18 in the supplement); these 33 subjects also completed all post-training test procedures. Data were analyzed with two-way analysis of variance with repeated measures on time. P ≤ 0.05 was set as statistically significant. All statistical analyses, including calculation of effect size and power, were completed with SPSS 11.0. Results Across groups, FFM increased during 10 wk of strength training. Although there was no statistically significant time × group interaction for FFM, there was a trend toward a greater increase in FFM for the supplement group (+3.4 kg) compared with the control group (+1.5 kg; P = 0.077). The effect size (η 2 = 0.100) was moderately large. Percentage of body fat declined and fat mass was unchanged; there were no differences between groups. One repetition maximum strength for the bench press and 45-degree leg press increased, but there were no differences between groups. Muscular endurance expressed as the number of repetitions completed with 85% of the one repetition maximum was unchanged; external work, which was estimated as repetitions completed × resistance used, increased for the 45-degree leg press but not for the bench press over the 10-wk training period; there were no time × group interactions for either measurement. Anaerobic power and capacity improved, but there were no differences between groups for these variables or for fatigue rate. Conclusions Consumption of a recovery drink after strength training workouts did not promote greater gains in FFM compared with consumption of a carbohydrate-only drink; however, a trend toward a greater increase in FFM in the supplement group suggests the need for longer-term studies. Performance variables such as muscle strength and endurance and anaerobic performance were not improved when compared with the carbohydrate-only group.

BLOOD LIPIDS AND FIBRINOGEN LEVELS OF COLLEGE-AGED INDIVIDUALS FOLLOWING TWELVE WEEKS OF STRENGTH TRAINING

The effect of strength training (ST) on blood lipids and fibrinogen levels is not well documented. PURPOSE To examine the effects of 12 weeks of ST on blood lipids and fibrinogen in previously non-ST college-aged (n=20; age 23±3) women (n=10) and men (n=10). METHODS Subjects took part in a moderate intensity ST program (70–100% of measured 10-repetition maximum) three days per week; alternating between “push” (leg press, leg extension, triceps pushdown, shoulder press) and “pull” (lat pull-down, arm curl, upright row, leg curl, and bent-over row) exercises. Blood was collected at baseline and at four-week intervals for 12 weeks. Self-reported three-day dietary assessments were recorded to determine pre- and post-ST nutritional status. RESULTS All subjects improved strength (p < 0.05) in all of the ST exercises. Body weight was unchanged from pre to post, however a significant decrease in %body fat was observed (pre vs post; 24.3±7.2 vs 23.1±6.9%). Total caloric intake and macro-nutrient composition remained consistent throughout the ST program. HDL-C (43.4±10.3 vs 46.1±9.8 mg/dL) and HDL2-C (16.3±5.3 vs 18.0±5.2 mg/dL) increased, TC/HDL-C ratios (4.5±1.3 vs 4.2±1.3) decreased from pre to post and TC, LDL-C, HDL3-C and TG were unchanged with 12 weeks of ST. Although fibrinogen levels were reduced by 7.75% with 12 weeks of ST, this change was not found to be significant. CONCLUSION These data indicate 12 weeks of moderate intensity ST is an effective intervention to positively impact body composition and improve HDL-C, HDL2-C and TC/HDL-C ratios, but does not modify fibrinogen, TC, LDL-C, HDL3-C or TG in college-aged women and men.

CLOSED AND OPEN KINETIC CHAIN STRENGTH TRAINING DOES NOT REDUCE LANDING FORCES IN FEMALE ATHLETES

Female athletes have a 4 times greater incidence of injury to the Anterior Cruciate Ligament (ACL) than males. Research has shown plyometric training can decrease landing forces and increase activity of the hamstring muscles when jumping and landing. Closed kinetic chain strength exercises for the lower extremities recruit both the quadriceps and hamstrings to stabilize the knee joint. When the foot is in contact with the ground, the hamstring muscles act to reduce stress on the ACL. Thus, a strong contraction of the hamstrings and a decrease in landing forces could diminish the likelihood of ACL injuries. PURPOSE The purpose of this study was to determine the effect of open kinetic chain (OKC) and closed kinetic chain (CKC) strength training on landing forces and corresponding electromyographical (EMG) activity of the quadriceps and hamstrings during a stabilization drop. METHODS Thirty female college volleyball players participated in a 6-week periodized training program consisting of either OKC or CKC exercises. Pre- and post-training, the subjects performed a drop stabilization from a 20-inch box onto a forceplate measuring ground reaction forces (GRF) and corresponding times at 200 Hz. Prior to testing, subjects were fitted with surface EMG electrodes on the Rectus Femoris (RF), Vastus Lateralis Oblique (VLO), Biceps Femoris (BF), and Gastrocnemius (GA). EMG data were filtered, rectified and integrated. Paired t-tests were used to compare dependent variables pre- and post-training and alpha was set at p <.05. RESULTS All GRF's remained unchanged in both groups. The time of foot contact to time of Fzpeak was unchanged. Integrated EMG signals increased in RF (.4 + .1v), VLO (.4+.1v), BF (.2+.1), and GA (.8+.3v) for the OKC and in the RF (.3+.1v), VLO (.6+.1v), and GA (.5+.2v) for the CKC. CONCLUSION Six weeks of strength training alone may not reduce landing forces or change neuromuscular patterns to protect the ACL in female athletes.

RELIABILITY OF DEOXYPYRIDINOLINE CROSSLINKS (DPD) MEASUREMENTS IN CHILDREN

Dpd has become routine in estimating bone resorption. In children, where bone is rapidly changing, it is important to determine the reliability of Dpd measurements because the ability to detect long-term changes in bone metabolism depends on the day-to-day variability of Dpd measurements. PURPOSE To determine the reliability of Dpd measurements in children ages 7 to 12 years. METHODS The present study included subjects taking part in an 8-week strength training study. Fasting first morning urine samples were collected from 14 girls and 26 boys twice within a 3 day period both at baseline and after 8 weeks. Eight girls and 7 boys did not collect a urine sample on at least one of the four data collection days. The present analyses include 65 observations because the baseline and follow-up samples were combined. Dpd, corrected for creatinine excretion (Cr), was measured by immunoassay using commercially avaliable kits (Quidel Corp., Mountain View, CA). Dpd on day 1 versus day 2 was compared using regression analysis and paired t-tests. Bland-Altman plots (day 2 minus day 1 regressed against the mean Dpd) were also performed to determine whether day 1 and 2 differences were affected by the magnitude of Dpd excretion. RESULTS Bone resorption [mean(SD)] for day 1 and day 2 was 25.9 (7.6) and 25.2 (7.3) nmol Dpd/mmol Cr, respectively. The mean difference was 0.63 (7.2) nmol Dpd/mmol Cr, which was not significant (p = 0.49). The day-to-day differences ranged from −15.5 to 14.3 nmol Dpd/mmol Cr. The correlation was 0.53 (p = 0.00) and the standard error of estimate was 6.5 nmol Dpd/mmol Cr. The Bland-Altman plot regression coefficient (r = 0.05) was not significant. CONCLUSION Though no significant mean differences existed between days and the differences were not affected by the magnitude of Dpd, the relationship between days 1 and 2 was only moderate. Reliability coefficients should be > 0.90 (vs 0.53). Therefore, a single urine sample may not provide a stable measurement of Dpd in children.

Effects of strength training on submaximal and maximal endurance performance capacity in middle-aged and older men.

Effects of a 16-week progressive strength-training program on blood lactate accumulation (LA), maximal workload (W(max)) attained during progressive cycling exercise, maximum half-squat (1RM(HS)), muscle cross-sectional area of the quadriceps femoris muscle group (CSA(QF)), and serum hormone concentrations were examined in 11 middle-aged (46 year old [M46]) and 11 older (64 year old [M64]) men. During the 16 weeks of training, significant increases were observed in 1RM(HS) in M46 and M64 (41-45%; p < 0.001). The muscle CSA(QF) increased (13-11%; p > 0.01) for both groups. The first 8 weeks of training led to significant increases in W(max) (6-11%; p < 0.001) and decreases in submaximal (LA) in both groups, but no further training-induced changes were observed during the subsequent 8 weeks of training. Statistically significant relationships were observed in M64 and in the combined group M46 + M64 between the training-induced changes observed in W(max) and serum testosterone-cortisol and free-testosterone-cortisol ratios, whereas in M46 the respective correlations values did not reach statistically significant levels. These data indicate that strength training results in a significant improvement in maximal and submaximal endurance during the first 8 weeks of strength training in both age groups, related in part to the intensity and the volume of resistance training used and to the training status of the subjects. The relationships found in this study between various indices of cycling testing and serum hormone concentrations after strength training suggest that maximal incremental cycling might be used as an additional test to detect anabolic-catabolic responses to prolonged strength training in middle-aged and older men.

Comparison of 1 and 2 Days per Week of Strength Training in Children

The purpose of this study was to compare the effects of 1 and 2 days per week of strength training on upper body strength, lower body strength, and motor performance ability in children. Twenty-one girls and 34 boys between the ages of 7.1 and 12.3 years volunteered to participate in this study. Participants strength trained either once per week (n = 22) or twice per week (n = 20) for 8 weeks at a community-based youth fitness center. Each training session consisted of a single set of 10–15 repetitions on 12 exercises using child-size weight machines. Thirteen children who did not strength train served as age-matched controls. One repetition maximum (1RM) strength on the chest press and leg press, handgrip strength, long jump, vertical jump, and flexibility were assessed at baseline and posttraining. Only participants who strength trained twice per week made significantly greater gains in 1RM chest press strength, compared to the control group (11.5 and 4.4% respectively, p < .05). Participants who trained once and twice per week made gains in 1RM leg press strength (14.2 and 24.7%, respectively) that were significantly greater than control group gains (2.4%). On average, participants who strength trained once per week achieved 67% of the 1RM strength gains. No significant differences between groups were observed on other outcome measures. These findings support the concept that muscular strength can be improved during the childhood years and favor a training frequency of twice per week for children participating in an introductory strength training program.

EFFECT OF STRENGTH TRAINING ON CYTOKINE MRNA LEVELS IN SKELETAL MUSCLE OF DIABETIC HISPANIC ELDERS

There is evidence that the cytokines tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, interleukin (IL)-1β, and insulin-like growth factor-I (IGF-I) have roles in muscle regenerative and anabolic processes. PURPOSE: To examine the effects of progressive strength training (ST) on mRNA levels of TNF-α, TGF-β1, IL-1β, and the two muscle IGF-I isoforms, liver-like IGF-I (L.IGF-I) and the mechanically sensitive IGF isoform, MGF, in skeletal muscle of older individuals with type 2 diabetes (T2D). METHODS: Thirty men (n = 15) and women (n = 15), aged 67.0 ± 7.3 yrs with T2D were randominzed to 16 weeks of ST (EX) or to their usual diabetic care only (CON). All subjects underwent biopsy of the vastus lateralis at baseline. A post-intervention biopsy was performed 48 hrs after 1RM testing in EX and CON subjects. Cytokine and growth factor mRNA levels were determined by semi-quantitative real-time PCR. Leukocyte infiltration was monitored via the β2 integrin CD18, a pan-leukocyte marker. RESULTS: ST increased type I and II muscle fiber cross-sectional areas (CSA)(P < 0.05), fat free mass measured by DXA (P < 0.001), and strength (P < 0.001). TNF-α, TGF-β1, L.IGF-I, MGF and CD18 mRNA levels increased with ST (P < 0.05). All cytokines were significantly correlated with one another and all correlated with CD18. There were no associations between L.IGF-I or MGF and any cytokines. Increased TNF-α, TGF-β1, IL-1β, and CD18 mRNA levels correlated with the increase in muscle fiber CSA (P < 0.05), but L.IGF-I and MGF mRNA did not. CONCLUSION: The ST-induced hypertrophy of type I and II fibers appears to be related to increases in gene expression of cytokines known to be associated with muscle injury and regeneration (TNF-α, TGF-β1 and IL-β1), but not with increased gene expression of either IGF-I isoform. The increase in CD18, and its correlation with increased cytokine mRNA levels suggests that leukocytes recruited into skeletal muscle contribute directly or indirectly to the increased cytokine gene expression. Supported by the Brookdale Foundation, ARS contract 58-1950-9-001, and NIH GCRC grant M01 RR000054.