1RM Load Research Articles

Association Of Vertical Jump Performance To Jump Squat Power Expressions

PURPOSE To establish the association in young men of vertical jump (VJ) displacement with various expressions of power obtained during parallel jump squats (PJS). METHODS Subjects were 48 men (age 22.9 ± 4.17 y; bwt 83.3 ± 14.55 kg) with resistance-training backgrounds. Subsequent to 3 practice sessions, displacement was determined for 4 different VJ styles: restricted (RVJ), non-counter movement (NCMVJ), standing (SVJ), and drop (DVJ). At a different time, each subject's 1RM parallel squat (≥ body wt) was determined for standardizing loading on subsequent tests. Within one week, subjects performed maximal PJS with an external load of 30% 1RM. A computer-interfaced dynamometer tethered to the barbell measured bar velocity while power was calculated based on load, acceleration, and velocity. The associations between displacement for the 4 styles of VJ and squat power expressions were determined using inter-class correlations. RESULTS ARPD is the aver rate of power devp from the onset of concentric movement to either peak or start position. Start gradient is the power @ 50% of time to start position/respective elapsed time, and acceleration gradient is the power @ start position/ respective elapsed time for the 2nd 50%. Means, std dev, and associations are reported in Table 1.Table 1: Means, standard deviations, and correlations of four styles of vertical jump and jump squat external power variable acquired at a 30% 1RM load.CONCLUSIONS When expressed relative to body wt, pk power, aver power to pk, and aver power to start position for jump squats performed with a 30% 1RM load were most highly associated (moderate) with the four styles of VJ. A myriad of other power expressions were less associated with VJ displacement. Table 1. Means, standard deviations, and correlations of four styles of vertical jump and jump squat external power variables acquired at a 30% 1RM load. load were most highly associated(moderate) with the four styles of VJ A myriad of other power expressions were less associated with VJ displacment.

Association Between Vertical Jump Displacement and Jump Squat Force Expressions

PURPOSE To determine the association between vertical jump (VJ) displacement and various expressions of concentric force during jump squats. METHODS Forty-eight male (body weight 83.3 ± 14.55 kg) heavy-resistance trained lifters, 18 to 36 (22.9 ± 4.17) years of age, participated in this study. Following 3 practice sessions, displacement was determined for 4 different VJ styles: restricted (RVJ), non-counter movement (NCMVJ), standing (SVJ), and drop (DVJ). In addition, each subject's 1RM parallel back squat (≥ body wt) was determined to standardize loading on subsequent tests. Within one week, subjects performed maximal jump squats with an external load of 30% 1RM. A computer-interfaced dynamometer measured barbell velocity while force was calculated based on load and acceleration. The association between VJ displacement and squatting concentric force was ascertained using Pearson product-moment correlations RESULTS ARFD is the average rate of force development from the onset of concentric movement to either the peak or start position. The start gradient is the force @ 50% of time to start position/respective elapsed time, and acceleration gradient is the force @ start position/ respective elapsed time for the 2nd 50%. Descriptives and associations are reported in Table 1.Table 1: Means, standard deviations, and correlations of four styles of vertical jump and jump squat external force variables acquired at a 30% 1RM load.CONCLUSIONS When expressed relative to body weight, peak force, average force to peak, and average force from bottom to original start position for jump squats performed with a 30% 1RM load were most highly associated (moderate) with the four styles of VJ. A myriad of other concentric force expressions are not as highly associated with VJ displacement.

Activation Of Satellite Cells In Human Skeletal Muscle In Response To Strength Training

The activation of satellite cells (SC) in the skeletal muscle may be attributed to muscle growth, hypertrophy and regeneration, and thus may have an important role in muscular adaptation to exercise. Our previous studies show that strength training led to a transformation of myosin heavy chain isoforms along with an upregulation of muscle growth factors. PURPOSE To investigate the activation of SC in human skeletal muscle in response to strength training with different strategies. METHODS 24 male volunteers (mean, age: 25 y; height: 183 cm; body mass: 81 kg) were divided into two groups with regard to the different trainings (6 weeks, 3d/w), in MAX-group (traditional strength training with maximum loads): 5 series, 3 reps (3 RM load); in COMBI-group: 1st day: 5 series, 3 reps; 2nd day: 3 series, 10 ballistic concentric-only throw movement (30%); 3rd day: 3 series, 7 reps, stretch-shorten-typed push-ups. Muscle samples were attained from m. triceps brachii before and at the end of the training using fine needle biopsy technique. The expression of the myogenic factors, MyoD and myogenin, were taken as the markers of activation of SC, and their mRNA levels were essesssed through reverse transcriptional PCR using quantitative real-time PCR technique. RESULTS Strength training resulted in a significant increase in 1RM in both groups, and the combined strength training led an additional improvement in maximum movement velocity. In comparison with that before training (100%), Myo D mRNA increased by 107% in MAX-group, but decreased slightly by 18% in the COMBI-group (NS). The expression level of myogenin mRNA was significantly increased by 90% in MAX-group, but did not change in COMBI-group (by −8%, NS). CONCLUSION A strength training with maximum contractions caused a significant activation of the satellite cells in human skeletal muscle, while strength training with combination strategy did not. The different effects on SC activation may be attributed to the fact that in MAX-group the upregulation of the growth factors (IGF-1 and MGF) war higher than that in COMBI-group. Since an upregulation of growth factors and a transformation of myosin heavy chain isoforms have been previously observed, the activation of SC in response to strength training suggests that the SC activation may have an important role in the muscular adaptation to exercise training.

Reliability of Knee Extenstion Mechanical Power Across a Load- Spectrum

2387 An inexpensive computer-interfaced dynamometer, incorporating what is essentially a linear position transducer, can be used to calculate instantaneous external power and related variables in situations in which the load is known, constant, and moved linearly. The device is tethered to the load while velocity and displacement are measured directly with a sampling rate of 100 HzFinewtonian physics are used for calculating acceleration, force and power. PURPOSE: To determine the stability reliability of external power data obtained from a single-joint lift using this dynamometer. METHODS: Maximum-acceleration, concentric-only knee extensions through 90° were performed at 40, 65, and 90% 1RM in a random sequence by 24 men who had been engaged in weight training for no less than the previous 3 months. Power was evaluated at 50, 100, 200, and 300 ms intervals as well as for peak and average. At each session, participants completed 2 single-repetition trials at each load interspersed by 3 min rest. The identical test battery was repeated 48 h later to assess reliability (intraclass correlation coefficient or ICC) and precision (standard error of measurement or SEm). RESULTS: ICC's ranged from .54 to .82 for peak power, between .74 and .85 for average power, and between −.03 and .79 for measurements taken between 50 and 300 ms over the load spectrum. Precision was ≤ 13.7 W except at 300 ms for the 40% 1RM load and at 50 ms for the 90% 1RM load (Table 1). CONCLUSIONS: For the dynamometer in question, reliable measures of knee extension peak power appear to be obtainable for young men at loads ranging from 40% to 65% 1RM, and to a lesser extent at 90% 1RM. When expressed as an average, reasonably reliable measures of power would be expected across the load spectrum. Knee extension instantaneous power appears to be a reliable measure up to about 200 ms. However, a transient software problem emerged at 50 ms for the 90% 1RM load that we have been unable to explain. Therefore, precise measures of power would be expected across the load spectrum for peak, average, and most time-dependent expressions.Table

Strength Training Induced Expressiom Of Mechano-growth Factor In Human Skeletal Muscle

0390 It has been recently demonstrated that a variant of the insulin-like growth factor named mechano-growth factor (MGF) is upregulated in human skeletal muscle in response to mechanical load. Previous studies have shown that MGF may be involved in the cellular procedure of muscle hypertrophy and muslce regeneration, and therefore may play an important role in the muscular adaptation to physical training. PURPOSE: To investigate the expression of MGF at mRNA level in human skeletal muscle in response to strength training with different strategies. METHODS: 24 male sports students (mean, age: 25 y; height: 183 cm; body mass: 81 kg) were divided into two groups with regard to the different trainings (6 weeks, 3d/w), in MAX-group (traditional strength training with maximum loads): 5 series, 3 reps (3 RM load); in COMBI-group (different external force-speed and muscle-action requirements), 1st day: 5 series, 3 reps; 2nd day: 3 series, 10 ballistic concentric-only throw movement (30%); 3rd day: 3 series, 7 reps, stretch-shorten-typed push-ups. Muscls samples were attained from mfitriceps brachii before and at the end of the training using fine needle biopsy technique. Total RNA was extracted from the muscle samples and Oligo primed synthesis of cDNA was performed using MuLV reverse transcriptase. MGF mRNA level was determined using quantitative real-time PCR with relation to internal house-keeping gene (HPRT). RESULTS: Strength training produced a significant increase in 1RM in both groups (5.6 kg for MAX-group and 5.0 kg for COMBI-group, respectively), and the combined strength training led an additional improvement in maximum movement velocity (0.1 m/s, p < 0.05). In comparison with that before training (100%), MGF mRNA was significantly upregulated (565% for MAX-group and 171% for COMBI-group, respectively, p < 0.01). CONCLUSION: It can be demonstrated that MGF mRNA could be significantly upregulated in human skeletal muscle in response to the strength training, and MGF mRNA level can be affected by different training patterns. Because a transformation of myosin heavy chain isoforms has been observed in this study (JAP, 94:2282, 2003), MGF might be involved in this transformation and therefore play an important role in the muscle adaptation to strength training.

Postactivation Potentiation Response in Athletic and Recreationally Trained Individuals

To determine if training status directly impacted the response to postactivation potentiation, athletes in sports requiring explosive strength (ATH; n = 7) were compared to recreationally trained (RT; n = 17) individuals. Over the course of 4 sessions, subjects performed rebound and concentric-only jump squats with 30%, 50%, and 70% 1 RM loads. Jump squats were performed 5 minutes and 18.5 minutes following control or heavy load warm-ups. Heavy load warm-up consisted of 5 sets of 1 repetition at 90% 1 RM back squat. Jump squat performance was assessed with a force platform and position transducer. Heavy load warm-up did not have an effect on the subjects as a single sample. However, when percent potentiation was compared between ATH and RT groups, force and power parameters were significantly greater for ATH (p < 0.05). Postactivation potentiation may be a viable method of acutely enhancing explosive strength performance in athletic but not recreationally trained individuals.

STRENGTH TRAINING INDUCES UPREGULATION OF MHC I ALPHA MRNA IN HUMAN SKELETAL MUSCLE

Myosin heavy chain (MHC) Iα, a cardiac-like isoform of MHC, has been proven to be expressed in skeletal muscle in animals and is regarded as an intermediate between MHC Iα and MHC IIa. Studies on animals show that MHC Iα is expressed during muscle fiber transition, however, no study dealing with this issue in human skeletal muscle in terms of muscular adaptation to training has been reported. PURPOSE To investigate the expression of MHC Iα at mRNA level in human skeletal muscle in response to strength training with different strategies. METHODS 24 male subjects (mean, age:25 y; height:183 cm; body mass:81 kg) were divided into two groups with regard to the different trainings (6 weeks, 3d/w), in MAX-group (traditional strength training with maximum loads):5 series, 3 reps (3 RM load); in COMBI-group (different external force-speed and muscle-action requirements), 1st day:5 series, 3 reps; 2nd day:3 series, 10 ballistic concentric-only throw movement (30%); 3rd day:3 series, 7 reps, stretch-shorten-typed push-ups. Muscls samples were taken from m. triceps brachii before and at the end of the training using fine needle biopsy technique. Total RNA was extracted from the muscle samples and Oligo primed synthesis of cDNA was performed using MuLV reverse transcriptase. MHC Iα mRNA level was determined using real-time quantitative PCR with relation to internal reference (HPRT). RESULTS Strength training led to a significant increase in 1RM in both groups (5.6 kg for MAX-group and 5.0 kg for COMBI-group, respectively), but the combined strength training had an additional improvement on maximum movement velocity (0.1 m/s, p < 0.05). MHC Iα mRNA was significantly upregulated (308 ± 109% and 160 ± 49% for MAX- and COMBI-group, respectively, p < 0.01). CONCLUSION It can be demonstrated that an upregulation of MHC Iα mRNA could be induced in human skeletal muscle in response to training, and MHC Iα mRNA level can be affected by different training patterns. MHC Iα upregulation may suggest an active muscle fiber type transition.

The Influence of Volume of Exercise on Early Adaptations to Strength Training

The purpose of this investigation was to compare the effects of single-set strength training and 3-set strength training during the early phase of adaptation in 18 untrained male subjects (age, 20–30 years). After initial testing, subjects were randomly assigned to either the 3L-1U group (n = 8), which trained 3 sets in leg exercises and 1 set in upper-body exercises, or the 1L-3U group (n = 10), which trained 1 set in leg exercises and 3 sets in upper-body exercises. Testing was conducted at the beginning and at the end of the study and consisted of 2 maximal isometric tests (knee extension and bench press) and 6 maximal dynamic tests (1 repetition maximum [1RM] tests). Subjects trained 3 days per week for 6 weeks. After warm-up, subjects performed 3 leg exercises and 4 upper-body exercises. In both groups, each set consisted of 7 repetitions (reps) with the load supposed to induce muscular failure after the seventh rep (7RM load). After 6 weeks of training, 1RM performance in all training exercises was significantly increased (10–26%, p < 0.01) in both groups. The relative increase in 1RM load in the 3 leg exercises was significantly greater in the 3L-1U group than in the 1L-3U group (21% vs. 14%, p = 0.01). However, the relative increase in 1RM load in the 3 upper-body exercises was similar in the 3L-1U group (16%) and the 1L-3U group (14%). These results show a superior adaptation to 3-set strength training, compared with 1-set strength training, in leg exercises but not in upper-body exercises during the early phase of adaptation.

Power and maximum strength relationships during performance of dynamic and static weighted jumps.

The purpose of this study was to investigate the relationship of the 1 repetition maximum (1RM) squat to power output during countermovement and static weighted vertical squat jumps. The training experience of subjects (N = 22, 87.0 +/- 15.3 kg, 14.1 +/- 7.1% fat, 22.2 +/- 3.8 years) ranged from 7 weeks to 15+ years. Based on the 1RM squat, subjects were further divided into the 5 strongest and 5 weakest subjects (p <or= 0.05). Squat jumps were performed with a countermovement or statically at 2 different sessions spaced 1 week apart. Jumps were performed with weights ranging from 10 to 100% of the 1RM squat. A maximum effort was made for each trial; subjects performed jumps (feet left the floor) with weights up to approximately 90% of 1RM. Squat-jump power was determined using the V-scope 120. Results indicate strong correlations (r = 0.77-0.94) between the 1RM squat and both countermovement and static jump power up to 90% of 1RM. The highest power outputs for both jump conditions occurred at 10% of the 1RM and decreased as the relative intensity increased. Comparisons of weak and strong subjects indicate that as maximum strength increases the percentage of 1RM at which peak power occurs also increases (40 vs. 10% of 1RM). From a practical aspect, to improve jumping power output, these results suggest that improving maximum strength should be a primary component of training programs and that strength training should shift from lighter (10% 1RM) to heavier (40% 1RM) loads.

Effect of a submaximal half-squats warm-up program on vertical jumping ability.

The purpose of the current research was to study the effect of a warm-up program including submaximal half-squats on vertical jumping ability. Twenty physically active men participated in the study. Each subject performed 5 sets of half-squats with 2 repetitions at each of the following intensities: 20, 40, 60, 80, and 90% of the 1 repetition maximum (1RM) load. Prior to the first set and immediately after the end of the last set, the subjects performed 2 countermovement jumps on a Kistler force platform; the primary goal was to jump as high as possible. The results showed that mean vertical jumping ability improved by 2.39% after the warm-up period. Subjects were then divided into 2 groups according to their 1RM values for the half-squat. Subjects with greater maximal strength ability improved their vertical jumping ability (4.01%) more than did subjects with lower maximal strength (0.42%). A warm-up protocol including half-squats with submaximal loads and explosive execution can be used for short-term improvements of vertical jumping performance, and this effect is greater in athletes with a relatively high strength ability.

HUMAN SKELETAL MUSCLE MYOSIN HEAVY CHAIN EXPRESSION IN RESPONSE TO STRENGTH TRAINING

In response to physical exercise, structural, metabolic and functional changes can occur in skeletal muscle. Alteration of the myosin heavy chain (MHC) composition is one of the important mechanisms for skeletal muscle to adapt to cellular stress caused by exercise. PURPOSE: To investigate human skeletal muscle adaptation to strength training (classic vs. combination with ballistic concentric movement) in terms of myosin heavy chain isoform expression. METHODS: 24 male students (age: 25 y; height: 183 cm; body mass: 81 kg) were divided into two groups with regard to different trainings (6 weeks, 3d/w), in MAX-group (traditional strength training with maximum loads): 5 series, 3 reps (3 RM load); in COMBI-group (different external force-speed and muscle-action requirements), 1st day: 5 series, 3 reps; 2nd day: 3 series, 10 ballistic concentric-only throw movement (30%); 3rd day: 3 series, 7 reps, stretch-shorten-typed push-ups. Muscls samples were taken from m. triceps brachii before and at the end of the training using fine needle biopsy technique. MHC analysis followed SDS-PAGE with silver staining. The percentage of each MHC isoform (MHC I, IIa and IId) was calculated based on the densitometric values of the corresponding protein bands. The mRNA level of each MHC isoform was estimated by RT-PCR. RESULTS: MHC IIa increased significantly in both groups (from 48. ± 9.9% to 64.7 ± 18.6%) and there was a significant decrease of MHC I in COMBI-group (from 18.2 ± 7.0% from 9.2 ± 10.1%) whereas in MAX-group MHC IId decreased (from 33.4 ± 5.7% 19.5 ± 13.0%, P < 0.01). RT-PCR showed that MHC Ia mRNA was significantly upregulated (308 ± 109% and 160 ± 49% for MAX- and COMBI-group, respectively, P < 0.01), and the changes of mRNAs for MHC 16, IIa and IId were not statistically significant. CONCLUSION: The strength training led to an increase of MHC IIa, this increase was accompanied by a decrease of MHC IId during a traditional strength training with maximum loads, whereas the increase of MHC IIa during a strength training programme with different external force-speed and muscle-action requirements was accompanied by a decrease of MHC I. The upregulation of MHC Ia mRNA may suggest an active muscle fiber type transition and may have impact on preserving MHC I during the traditional strength training with maximum loads.

Power absorption and production during slow, large-amplitude stretch-shorten cycle motions.

The purpose of this study was to determine the important predictors of power absorption and power production during slow, large-amplitude stretch-shorten cycle (SSC) motions. The relationship between power absorption (mean eccentric power output) and production (mean concentric power output) across different inertial loads was also investigated. Fifty-four subjects with a sporting background performed concentric (CBP) and rebound bench-presses (RBP) at 40% and 80% of their one-repetition maximum (1RM). The relationship between kinematic and kinetic variables and mean eccentric power and RBP mean power output was determined using correlation and multiple regression analysis. Maximal strength was found to be the best single predictor of power absorption, explaining between 44.2% and 69.1% of the variability that was associated with mean eccentric power output for 40% and 80% 1RM loads. Stretch velocity in combination with maximal strength was found to be the best two-predictor model of power absorption ( R(2)=83.7-97.3%). The best single predictor of SSC power production was found to be concentric mean power output ( R(2)=49.2-88.0%). The utilisation of the power absorbed during the power production phase differed across loads. It was suggested that as maximal strength is more trainable than speed, training to improve power absorption might emphasise maximal strength development. It was also suggested that SSC power output might benefit from training methods that focus on concentric force development. Further research is needed to evaluate these hypotheses and whether the findings of this study are similar for fast SSC motion.

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work.

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Effect of strenuous strength training on the Na-K pump concentration in skeletal muscle of well-trained men.

This study examined how strenuous strength training affected the Na-K pump concentration in the knee extensor muscle of well-trained men and whether leg muscle strength and endurance was related to the pump concentration. First, the pump concentration, taken as 3H-ouabain binding, was measured in top alpine skiers since strength training is important to them. Second, well-trained subjects carried out strenuous eccentric resistance training either 1, 2, or 3 times.week-1 for 3 months. The Na-K pump concentration, the maximal muscle strength in a full squat lift (one repetition maximum, 1 RM), and the muscle endurance, taken as the number of full squat lifts of a mass of 70% of the 1 RM load, were measured before and after the training period. The mean pump concentration of the alpine skiers was 425 (SEM 11) nmol.kg-1 wet muscle mass. The subjects in part two increased their maximal strength in a dose-dependent manner. The muscle endurance increased for all subjects but independently of the training programme. From a mean starting value of 356 (SEM 6) nmol.kg-1 the mean Na-K pump concentration increased by 54 (SEM 15) nmol.kg-1 (+15%, P < 0.001) when the results for all subjects were pooled. The effect was larger for those who had trained twice a week than for those who had trained only once a week (P = 0.025), suggesting that the effect of strength training depended on the amount of training carried out. The muscle strength and endurance were not related to the pump concentration, suggesting that the pumping power of this enzyme did not limit the performance during heavy lifting. However, the individual improvements in the endurance test during the training period correlated with the individual changes in the pump concentration (rSpearman = 0.5; P = 0.01) which could mean that a common factor both increases the pump concentration and makes the muscles more adapted to repeated heavy lifting.

Effects of Different Resistance Training Protocols on Upper-Body Strength and Endurance Development in Children

This study examined the effects of 4 different resistance training protocols on upper-body strength and local muscle endurance development in children. Untrained boys and girls (mean +/- SD age, 8.1 +/- 1.6 years) trained twice per week for 8 weeks using child-sized weight machines and medicine balls weighing 1-2.5 kg. In addition to general conditioning exercises, subjects in each exercise group performed 1 set of the following exercise protocols for upper-body conditioning: 6-8 repetitions with a heavy load on the chest press exercise (HL, n = 15); 13-15 repetitions with a moderate load on the chest press exercise (ML, n = 16); 6-8 repetitions with a heavy load on the chest press exercise immediately followed by 6-8 medicine ball chest passes (CX, n = 12); or 13-15 medicine ball chest passes (MB, n = 11). Twelve children served as nontraining controls (CT). After training, only the ML and CX groups demonstrated significant (p < 0.05) improvements in 1RM chest press strength (16.8% and 16.3%, respectively) as compared with the CT group. Local muscle endurance, as determined by the number of repetitions performed posttraining on the chest press exercise with the pretraining 1RM load, significantly increased in the ML group (5.9 +/- 3.2 repetitions) and CX group (5.2 +/- 3.6 repetitions) as compared with the CT group. In terms of enhancing the upper-body strength and local muscle endurance of untrained children, these findings favor the prescription of higher-repetition training protocols during the initial adaptation period.

STRENGTH TRAINING IMPROVES THE STEADINESS OF SLOW ECCENTRIC CONTRACTIONS IN OLDER ADULTS.

1103 When older adults participate in a heavy-load, strength-training program, they experience an increase in muscle strength and in the steadiness of submaximal contractions. The purpose of this study was to determine the effect of light- (10% 1RM) and heavy-load (80% 1RM) strength training on the ability of older adults to perform steady slow movements. Twelve older adults (62-90 yrs; 5 control, 4 light, 3 heavy) participated in a four-week training program designed to strengthen the first dorsal interosseous muscle. Before and after training, subjects performed slow (6 s for 10 °) abduction (concentric) and adduction (eccentric) movements with the index finger against an adduction load of 20% MVC. Index finger position was recorded with a low-friction, linear-displacement transducer. A least squares regression was used to determine average movement velocity. The smoothness of the movement(fluctuations about the average velocity for the middle 4 s) was determined by subtracting the regression (trend) from the data. There was no effect of training on the MVC force for either group. Both training groups had significant gains in 1RM load (% change: low = 29 ±12%; high = 47±14%). There were no changes in the steadiness of the concentric contractions for any group. However, both training groups experienced significant improvements in the steadiness of the eccentric contractions (% change: control = 1.8 ±.0.1%; low = 42.4 ±.0.1%; high = 57.5±.0.1%). It appears that the improvement in steadiness experienced by older adults who perform strength training is similar whether they train with light or heavy loads.

Effects of High and Low Intensity Weight Training on iEMG and Force 1139

To test the hypothesis that the EMG to Force relationship is a function of training intensity, thirteen weight trained college-age males were divided into two groups for 8 weeks of periodized training on the bench press. Prior to the study, subjects trained regularly for at least 1 year on the bench press. Subjects performed two 1RM tests separated by 48-96 hours for the pretest and posttest. After the pretest, subjects were assigned to either a High Repetition (HiRep) or Low Repetition (LoRep) group. There were no pretest differences in 1RM between groups. Subjects trained twice per week with 3-4 sets. HiRep trained at 10RM to 15RM per set while LoRep trained at 6RM to 2RM per set. Pretest and posttest EMG was measured on the lateral head of the triceps, the anterior deltoid and the pectoralis major. EMG was rectified, filtered and integrated. The iEMG was adjusted for the duration of the 1RM and averaged across the 3 muscles. A repeated measures ANOVA showed similar increases (p<.05) in 1RM for LoRep (112.9 ± 6.53 kg to 117.0± 7.07 kg) and HiRep (107.7 ± 7.42 kg to 114.5 ± 6.2 kg). The ratio of iEMG to 1RM increased (p<.05) for LoRep and decreased(p<.05) for HiRep from pretest to posttest. In summary, low RM loads increase activation and strength leading to an increased iEMG/1RM ratio. Conversely, high RM loads increase strength but not activation leading to a decreased iEMG/1RM ratio. In conclusion, the mechanism of strength increase by experienced weight lifters is dependent on the RM loads.

Effects of low-volume resistive exercise on beta-endorphin and cortisol concentrations.

It has been recently suggested that high and sustained lactate levels may elicit increases in peripheral B-EN concentrations (16). We have observed elevated and sustained lactate concentrations in response to a low-volume resistive exercise protocol (14) that were similar to those from other exercise protocols that produced elevated beta-endorphin (B-EN) concentrations. Thus, the purpose of the study was to determine the effects of a low-volume (21,700 J) resistive exercise repetition maximum (RM) protocol using weight machines on peripheral lactate, B-EN and cortisol concentrations. Subjects completed 3 sets of bench press, lat-pull, leg extension, and leg curl exercise at a 10-RM load. Blood samples were collected and rating of perceived exertion (RPE, 15-point Borg scale) was assessed before exercise (-40 and -10 min), after each exercise, and after the exercise session (+ 35 min); blood samples were collected at 7 additional post-exercise times. RPE increased significantly throughout the exercise. Lactate concentrations rose significantly to peak at 8.54 mM at LE. B-EN and cortisol concentrations (-10) of 4.63 +/- 0.54 pmol.l-1 and 12.09 +/- 1.44 micrograms.dl-1, respectively, were not significantly elevated over time. The data suggest that a low-volume resistive exercise protocol using weight machines elevates lactate concentrations without altering B-EN and cortisol concentrations.

Growth hormone, IGF-I, and testosterone responses to resistive exercise

It has been suggested that growth hormone (GH), testosterone (T), and insulin-like growth factor I (IGF-I) play large roles in muscle tissue growth; however, in only two investigations IGF-I responses to resistive exercise have been examined. Eight young males who had not weight trained for a minimum of 5 months participated in the study. Three sets of bench press (BP), lat-pull (LP), leg extension (LE), and leg curl (LC) exercises were performed at a 10-RM load for 10 repetitions or until failure. Blood samples were collected from an IV catheter before exercise (-30 min and -10 min), after each individual exercise (BP, LP, LE, LC), and after the exercise session (+5, +15, +25, +35, +95 min; +5:35, +22:30, and +23:30 h). GH, IGF-I, and T determinations were corrected for plasma volume change. GH significantly increased (P < 0.05), but IGF-I did not change. Correction for plasma volume accounted for significant increases in T, but did not account for GH and IGF-I results. These data suggest that moderate resistive exercise may increase GH concentrations, whereas elevated T levels can be accounted for by exercise-induced alteration of plasma volume.

Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance Exercise in Males and Females

To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i.e. P-1 and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-1 utilized a 5 RM load, 3-min rest periods and had lower total work than P-2. P-2 utilized a 10 RM load, 1-min rest periods and had a higher total work than P-1. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C [SM-C] (i.e. insulin-like growth factor 1, IGF-1) were determined pre-exercise, mid-exercise (i.e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 min post-exercise. Males demonstrated significant (p less than 0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all time points than corresponding P-1 values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-1 exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs.(ABSTRACT TRUNCATED AT 250 WORDS)