Lower Resistance Exercise Research Articles

Blood flow restriction training as a prehabilitation concept in total knee arthroplasty: A narrative review about current preoperative interventions and the potential impact of BFR

Osteoarthritis of the knee is one of the most commonly diagnosed joint ailments and responsible for increased rates of total knee arthroplasty surgeries worldwide. Whereas the surgical approach is able to diminish the perceived knee pain of concerned patients’, the postoperative recovery is often accompanied by persistent skeletal muscle dysfunctions and atrophy, which is responsible for functional deficits for up to several years. Recent findings indicate that surgery induced adverse effects on skeletal muscles are largely associated with the use of pneumatic tourniquets, wherefore several studies try to reduce tourniquet use in orthopedic surgery. However, due to comparable incidence of muscle impairment and increased surgical challenge, the most frequently applied surgical technique in TKA is still associated with the use of tourniquets. When attenuating TKA induced adverse effects, the preoperative preparation of patients by specific exercises (called prehabilitation) was able to enhance preoperative overall fitness through associated accelerated recovery. Based on patients’ limited functional activity, prehabilitation techniques have to be particularly designed to allow regular adherence. The present paper is based on a narrative review of current literature, and provides a novel hypothesis by which blood flow restriction exercises (BFR) are able to improve patients’ compliance to prehabilitation. BFR training is characterized by the application of low-resistance exercise with similar intensities as daily living tasks in association with a suppression of venous blood flow in an extremity, achieving significant morphological and neuromuscular adaptations in skeletal muscles. In addition, preoperative enhancements in muscle health with corresponding benefits in overall fitness, BFR induced molecular alterations could also be able to interfere with TKA induced pathological signaling. Therefore, based on the known major impact of BFR on skeletal muscle physiology, the present paper aims to illustrate the potential beneficial impact of BFR training as a prehabilitation concept to promote patients regular adherence to preoperative exercises and thus achieve an accelerated recovery and increases in patients’ satisfaction.

Early strength training using theraband exercises for phase-1 cardiac rehabilitation in a patient with a fractured femur: a case report

The effectiveness of exercise-based cardiac rehabilitation (CR) following an acute coronary syndrome (ACS) is well established. However, ACS complicated by an orthopedic limitation, poses greater challenges to early mobilization. Thus, there is a need for an alternative rehabilitation approach to improving exercise capacity and in preventing and reducing associated complications during convalescence. This case report highlights the value and utility of using low level resistance exercises to the upper limb with theraband exercise during an inpatient or phase-1 CR program. A low intensity theraband regimen for the upper limb was administered basedon the number of repetitions performed to fatigue. The functional improvements observed and the ability of the patient to tolerate the therapy suggests a potential role for theraband exercises in phase-1 CR in ACS patients with selected orthopedic limitations.

Feasibility Of 2D Strain For Assessing Myocardial Function In Trained And Not-trained Renal Transplant Recipients

Table: No title available.PURPOSE: Deformation parameters are normally employed to early discover a possible myocardial damage. This aspect is particularly important in post-renal- transplant syndrome where cardiovascular mortality remains elevated and where physical activity is normally allowed. This study aims to verify the role of Longitudinal (Lo) Strain in two groups of renal transplant recipients at different level of physical training. METHODS: A group of 8 transplant recipients (aged 45±5 yrs) following a program of moderate (75% of the max effort) aerobic exercise added to a low resistance exercise for at least 3 times a week for 1 year was compared to a group of 6 subjects not trained. All participants underwent an echocardographic exam with the evaluations of the standard 2D parameters and by Lo Strain calculation by a dedicated software (ESAOTE XStrain). RESULTS: All parameters were within the normal range. Lo Strain was feasible in all subjects. The limited number of subjects did not allow to detect statistically significant differences between the groups, despite the higher values of Lo Strain values in apical segments. CONCLUSIONS: There is evidence of feasibility of Lo ST evaluation in post transplant patients. Lo Strain confirms the normal LV function in renal recipients and plays a role in following the progressive improvement of the myocardial function in post transplant renal syndrome submitted to the exercise program. More studies are necessary to evaluate the possible contribution of physical exercise to the improvement of deformation parameters.

Effect of Resistance Exercise Intensity on the Strength and Lymphedema of Upper Extremity in Patients with Breast Cancer

Purpose: The purpose of this study was to determine the effects of high and low resistance exercise using an elastic band on the strength and lymphedema of upper extremity in patients with breast cancer. Methods: Seventeen female patients with breast cancer related lymphedema were randomly allocated...

Low- and High-Resistance Exercise: Long-Term Adherence and Motivation among Older Adults

Background: In terms of motivation and long-term adherence, low-resistance exercise might be more suitable for older adults than high-resistance exercise. However, more data are needed to support this claim. Objective: The objective was to investigate the effect of low- and high-resistance exercise protocols on long-term adherence and motivation. Methods: This study was designed as an exploratory 24-week follow-up of a randomized 12-week resistance training intervention in older adults. Participants were free to decide whether or not they continued resistance training at their own expense following the intervention. Fifty-six older adults were randomly assigned to HIGH [2 × 10-15 repetitions at 80% of one repetition maximum (1RM)], LOW (1 × 80-100 repetitions at 20% of 1RM), or LOW+ (1 × 60 repetitions at 20% of 1RM + 1 × 10-20 repetitions at 40% 1RM). Motivation, self-efficacy and the perceived barriers for continuing resistance exercise were measured after cessation of each supervised intervention and at follow-up, while long-term adherence was probed retrospectively at follow-up. Results: Participants reported high levels of self-determined motivation before, during, and after the supervised intervention, with no differences between groups (p > 0.05). Nevertheless, only few participants continued strength training after the intervention: 17% in HIGH, 21% in LOW+, and 11% in LOW (p > 0.05). The most commonly reported barriers for continuing resistance exercise were perceived lack of time (46%), being more interested in other physical activities (40%), seasonal reasons (40%), and financial cost (28%). Conclusion: The results suggest no difference in long-term adherence after the end of a supervised exercise intervention at high or low external resistances. Long-term adherence was limited despite high levels of self-determined motivation during the interventions. These findings highlight the importance of further research on developing strategies to overcome barriers of older adults to adhere to resistance exercise without supervision.

Crossfit Vs. Circuit-training

CrossFit (CF) emphasizes constantly varied, high-intensity, functional movement by performing strength and conditioning exercises, gymnastics movements, Olympic weightlifting, and sport/specialty movements. A major component of CF is that many workouts are completed as quickly as possible, emphasizing power and speed over strength. Conversely, circuit training (CT) programs aim to improve strength and cardiovascular health by using a series of high volume, low resistance exercises in progressive overload principle. To the authors’ knowledge, no empirical research currently exists comparing CF and CT individuals after a longitudinal training program. PURPOSE: To determine if differences exist in anaerobic, aerobic and flexibility measures in participants who have completed a CF or CT training program METHODS: Recreationally active females (CF: N=9, age: 29.2 + 8.4 yr; CT: N=14, age: 29.7 + 8.4 yrs) participated in a 10 week exercise intervention. Participants were randomly assigned to the CF or CT group and trained 3 days a week with certified trainers. Investigators examined Wingate Anaerobic test, Graded Exercise test and Sit and Reach test. Repeated measures ANOVA were used for statistical analysis with an alpha level of < 0.05. RESULTS: Both groups increased significantly in VO2max (p=0.006; CFpre: 35.0 + 5.5 mL/kg/min - CFpost: 37.1 + 7.19 mL/kg/min; CTpre: 32.9 + 6.8 mL/kg/min - CTpost: 37.1+ 7.1 mL/kg/min ), Wingate peak power (p=0.001; CFpre: 427.4 + 91 W - CFpost: 483.5 + 88.4 W; CTpre: 511.5 + 99.1 W - CTpost: 539.4+ 66.8 W ), mean power (p=0.001; CFpre: 326.6 + 69.1 W - CFpost: 361 + 49.7 W; CTpre: 371.4 + 64.6 W - CTpost: 404.7+ 49.6 W) .The sit and reach test showed singnificantly increased measures in both groups (p=0.002; CFpre: 35.4 + 6.28 cm - CFpost: 37.5 + 5.16 cm; CTpre: 33.5 + 7.8 - CTpost: 35.3 + 7.9 cm). There were no statistical significance noted in between the two groups. CONCLUSION: It was hypothesized that the high intensity intervals of CF would elicit higher VO2max, anaerobic power, as well as flexibility. Participating in CF and CT showed significant increase in aerobic, anaerobic fitness, and flexibilty. Future investigations should continue to explore the safety and efficacy of CF and CT.

Crossfit Vs. Circuit-trained Individuals

CrossFit (CF) emphasizes constantly varied, high-intensity, functional movement including strength and conditioning exercises, gymnastics, Olympic lifting, and specialty movements. Many workouts are completed as quickly as possible, emphasizing power and speed over strength. In contrast, the purpose of circuit training (CT) programs is to improve strength and cardiovascular health by utilizing the progressive overload principle, high volume, low resistance exercises, similar movements weekly, and specific work-to-rest ratios. To the authors’ knowledge, no empirical research currently exists comparing the effects of CF or CT on individuals after a longitudinal training program. PURPOSE: : To determine if differences exist in body composition (BC) and bone mineral density (BMD) measures in participants who have completed a CF or CT training program. METHODS : Recreationally active females (CF: N=9, age: 29.2 + 8.4 yr; CT: N=14, age: 29.7 + 8.4 yrs) participated in a 10 week exercise intervention. Participants were randomly assigned to the CF or CT group and trained 3 days a week with certified trainers. Investigators examined BC utilizing a 7-site skinfold formula; and BMD of the lumbar spine, hip, and wrist were measured using dual-energy X-ray absorptiometry. Repeated measures ANOVA were used for statistical analyses with an alpha level of < 0.05. RESULTS: There were no differences within or between the groups for body weight (CFpre: 67.3 + 16.08 - CFpost: 67.3 + 17.0 kg; CTpre: 66.5 + 14.0 - CTpost: 68.7 + 16.0 kg), body fat percentage (CFpre: 27.4 + 7.7 - CFpost: 28.0 + 9.8 %; CTpre: 26.0 + 8.5 - CTpost: 26.4 + 8.7 %), or BMD of the lumbar spine (CFpre: 1.1 + .0 - CFpost: 1.1+ .07 g/cm2; CTpre: 1.0 + .11 - CTpost: 1.0 + .11 g/cm2), hip (CFpre: .93 + .12 - CFpost: .93 + .11 g/cm2; CTpre: .94 + .10 - CTpost: .95 + .10 g/cm2), and wrist (CFpre: .54 + .10 - CFpost: .53 + .10 g/cm2; CTpre: .52 + .02 - CTpost: .54 + .10 g/cm2). CONCLUSIONS: Neither CF nor CT was effective in changing body weight, BC, or BMD of the lumbar spine, hip, or wrist. The lack of change in BC may be due to increased appetite resulting from the training volume. Although the changes in BMD did not reach significance, the percentage of change may be clinically relevant. Further research is needed to understand the effects of CF training on BC and BMD compared to traditional training styles.

Effects of loaded voluntary wheel exercise on performance and muscle hypertrophy in young and old male C57Bl/6J mice.

This study compared the capacity of young and old male C57Bl/6J mice to exercise with increasing resistance over 10 weeks, and its impact on muscle mass. Young mice (aged 15-25 weeks) were subjected to low (LR) and high (HR) resistance exercise, whereas only LR was used for old mice (107-117 weeks). Weekly patterns of voluntary wheel activity, food consumption and body weights were measured. Running patterns changed over time and with age, with two peaks of activity detected for young, but only one for old mice: speed and distance run was also less for old mice. The mass for six limb muscles was measured at the end of the experiment. The most pronounced increase in mass in response to exercise was for the soleus in young and old mice, and also quadriceps and gastrocnemius in young mice. Soleus and quadriceps muscles were analyzed histologically for myofiber number and size. A striking feature was the many small myofibers in response to exercise in young (but not old) soleus, whereas these were not present after exercise in young or old quadriceps. Overall, there was a striking difference in response to exercise between muscles and this was influenced by age.

Strength training at high versus low external resistance in older adults: Effects on muscle volume, muscle strength, and force–velocity characteristics

Muscle adaptations can be induced by high-resistance exercise. Despite being potentially more suitable for older adults, low-resistance exercise protocols have been less investigated. We compared the effects of high- and low-resistance training on muscle volume, muscle strength, and force–velocity characteristics. Fifty-six older adults were randomly assigned to 12weeks of leg press and leg extension training at either HIGH (2×10–15 repetitions at 80% of one repetition maximum (1RM)), LOW (1×80–100 repetitions at 20% of 1RM), or LOW+ (1×60 repetitions at 20% of 1RM, followed by 1×10–20 repetitions at 40% of 1RM). All protocols ended with muscle failure. Leg press and leg extension of 1RM were measured at baseline and post intervention and before the first training session in weeks 5 and 9. At baseline and post intervention, muscle volume (MV) was measured by CT-scan. A Biodex dynamometer evaluated knee extensor static peak torque in different knee angles (PTstat90°, PTstat120°, PTstat150°), dynamic peak torque at different speeds (PTdyn60°s−1, PTdyn180°s−1, PTdyn240°s−1), and speed of movement at 20% (S20), 40% (S40), and 60% (S60) of PTstat90°. HIGH and LOW+ resulted in greater improvements in 1RM strength than LOW (p<0.05). These differences were already apparent after week 5. Similar gains were found between groups in MV, PTstat, PTdyn60°s−1, and PTdyn180°s−1. No changes were reported in speed of movement. HIGH tended to improve PTdyn240°s−1 more than LOW or LOW+ (p=0.064). In conclusion, high- and low-resistance exercises ending with muscle failure may be similarly effective for hypertrophy. High-resistance training led to a higher increase in 1RM strength than low-resistance training (20% of 1RM), but this difference disappeared when using a mixed low-resistance protocol in which the resistance was intensified within a single exercise set (40% of 1RM). Our findings support the need for more research on low-resistance programs in older age, in particular long-term training studies and studies focusing on residual effects after training cessation.

MMP−2 Expression in Skeletal Muscle after Strength Training

The aim of this study was to assess the effects of resistance training on ladders (RTL) on MMP(-2) expression and blood lactate concentration [La-]. 30 male (3 months of age), albino rats were divided into 3 groups: sedentary control (SC, n=10), low resistance exercise training (Low-IntRT, n=10) and high-intensive exercise training (High-IntRT, n=10). Animals of High-IntRT were submitted to a progressively increasing overload in relation to body weight until exhaustion, while the Low-IntRT group performed the same exercise regimen with no external load. The program had a frequency of 3 times per week over 8 weeks. MMP(-2) expression of tibialis anterior muscle and [La-] were measured. While there was a significant increase of MMP(-2) (pro-form) in both groups, only High-IntRT significantly increased MMP(-2) in active-form (p<0.05). Both trained groups exhibited an increase in [La-] when compared to controls, however, the increase in [La-] was significantly higher in the High-IntRT compared to Low-IntRT (p<0.05). Strong correlation was found between MMP(-2) (active form) and [La-] in High-IntRT (r=0.91). RTL in using low and high-intensity exercise can serve as a model to demonstrate different responses of MMP(-2) expression in an animal model. It appears active form expression of MMP(-2) is modulated by exercise intensity.

The Effects Of Different Mode Of Low-intensity Exercise Training On Bone Mineral Density And Bone Metabolism In Postmenopausal Woman

PURPOSE: To investigate the effects of 12-month low-intensity resistance training using the elastic band and brisk walking on bone mineral density, body composition, and bone formation marker in postmenopausal woman. METHODS:Thirty-two postmenopausal women (49-63 yr) were assigned to resistance training group (RTG) (n=11; 55.9 ± 4.28 yrs), brisk walking group (BWG) (n=10; 53.2 ± 4.24 yrs) and control group (CG) (n=11; 54.4 ± 3.42 yrs). The training program consisted of resistance exercises using elastic bands and brisk walking for 2 sessions and one hour for each session per week. Total bone mineral density (TBMD), total bone mineral content (TBMC), lumbar spine (LS), femoral neck (FN), body fat, and lean body mass were measured at baseline and after one year training. Duel-energy X-ray absorptiometry (DXA) was used to measure subjects' body composition, regional and total bone mineral density. Serum intact N-terminal propeptide of type I collagen (PINP) and carboxyterminal telopeptide of type I collagen (ICTP) were determined as indices of bone metabolism. The statistical comparisons for the changes of different variables among the three groups were performed by applying one-way ANOVA. RESULTS: The three groups had similar BMD and BC characteristics at baseline. After the training period, there was a tendency of decline in BMD with age, and group differences change were not significant (p > 0.05) except for the spine of BWG. The BWG increased significantly in TBMC (1.4%), lumbar spine (1.3%), and PINP (12%) among groups (p<.05). In body composition, RTG showed significant decrease in body fat in the arm, leg, and total body than the other two groups (p<0.05). Leg lean mass in the walking group increased significantly than both the RTG and CG (p<0.05). CONCLUSIONS: These findings suggest that brisk walking is a medium-impact and weight-bearing exercise which is beneficial on bone mass in postmenopausal woman. Therefore, the impact of exercise training on bone metabolism may depend on the type of exercise during the early phase of training. However, the different mode of low-resistance exercises training on body composition have the different effects which is relatively site specific to the working muscle, thus, brisk walking is more beneficial on the leg and resistance training benefits more towards the whole body.

Effect of Resistance Exercise on Serum Levels of Growth Factors in Humans

Studies have shown that, depending on intensity, endurance exercise increases neurotrophins and thereby induces neuroplasticity. However, data on the effect of acute resistance exercise at different intensities on neurotrophins is not yet available. Thus, we conducted 2 trials to determine the serum concentrations of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and insulin-like growth factor (IGF-1) before and after a low or high intensity resistance exercise in 11 healthy humans. Exercise load was related to 3 repetitions of maximal effort isokinetic work involving knee extension under alternating concentric and eccentric conditions for muscle work at a velocity of 60°s-1 registered during a familiarization session. The torque angle diagrams from these 3 repetitions were averaged and displayed as target curves in the test sessions, the intensity of resistance exercise was set at 40% (trial: R1) or 110% (trial: R2) of the averaged individual maximal effort curve, respectively. After resistance exercise, serum IGF-1 was increased significantly (p<0.01) by 28% in R1 and 16% in R2 compared to pre-exercise levels. Resistance exercise did not increase serum VEGF at any time point. Serum BDNF increased during exercise compared to post-exercise, but did not achieve significant difference from pre-exercise values. The present study shows that either low or high resistance exercise increases levels of IGF-1, but not of BDNF or VEGF. This finding is of importance for health promotion by means of resistance exercise because circulating serum IGF-1 has been demonstrated to mediate positive effects of exercise on brain functions.

Heart-Rate Variability and Blood-Lactate Threshold Interaction During Progressive Resistance Exercise in Healthy Older Men

The objective of this study was to (a) evaluate the impact of the leg press, at variable percentages of 1 repetition maximum (1RM), on heart rate variability (HRV) and blood lactate and (b) determine the relationship between HRV with blood lactate in a healthy elderly cohort. Ten healthy men (64 +/- 4 years) participated in a progressive leg-press protocol to maximal exertion. Initially, 1RM for the leg press was determined for all subjects. The protocol then began at 10% of 1RM, with subsequent increases of 10% until 30% of 1RM, followed by incremental adjustments of 5% until exhaustion. The measurement of instantaneous R-R interval variability from Poincare plots (SD1 and SD2) and time domain indexes (RMSSD and RMSM), blood pressure, and blood lactate were obtained at rest and all leg-press loads. Significant alterations of HRV and blood lactate were observed from 30% of 1RM leg press (p < 0.05). Additionally, significant correlations were found between the lactate threshold (LT) and the RMSSD threshold (r = 0.78; p < 0.01), and between the LT and SD1 threshold (r = 0.81, p < 0.01). We conclude that metabolic and cardiovascular alterations are apparent during relatively low resistance exercise (RE) loads in apparently healthy subjects. In addition, HRV indexes were associated with blood-lactate levels during RE. The practical applications is the possibility of using HRV as a noninvasive measure obtained at a relatively low cost may be used to identify neural and metabolic alterations during RE in older subjects.

Neural Training for Quick Strength Gains in the Elderly: Strength as a Learned Skill

A sample of 20 older adults (76 +/- 6 years) participated in a two-session training intervention with the goal of eliciting rapid and functionally meaningful strength gains in the ankle plantarflexors. Tests were conducted on a Monday-Wednesday-Friday schedule with two training sessions after tests one and two. During each test, subjects performed five maximal explosive force production contractions (MVCs) from which maximal voluntary torque (MVT) and peak rates of torque development (RTDs) were obtained. To augment the quick strength gains typically observed in response to serial strength measurements, these MVCs were supplemented with exercises consisting of high-velocity, low-force movements at the ankle joint. These exercises were chosen to elicit high rates of neural stimulation without high resistance. Maximal voluntary torque increased by 15% from 53.9 +/- 36 to 62.2 +/- 36.2 N x m (p = 0.02). There was a parallel trend toward increases in RTD based on RTD measures computed over various timescales (0.11 < p < 0.21). The nonsignificant increase in RTD was from 223.9 +/- 153.6 to 248.4 +/- 147.8 N x m x s(-1). This preliminary study has determined that rapid strength gains of functional magnitude are possible in the plantarflexors of the elderly. Subsequent work is necessary to test the translation of such gains to function in the frail elderly and to determine the specific contributions of the selected low-resistance exercises to overall gains.

Investigation of Clinical Effects of High- and Low-Resistance Training for Patients With Knee Osteoarthritis: A Randomized Controlled Trial

Muscle strength training is important for people with knee osteoarthritis (OA). High-resistance exercise has been demonstrated to be more beneficial than low-resistance exercise for young subjects. The purpose of this study was to compare the effects of high- and low-resistance strength training in elderly subjects with knee OA. One hundred two subjects were randomly assigned to groups that received 8 weeks of high-resistance exercise (HR group), 8 weeks of low-resistance exercise (LR group), or no exercise (control group). Pain, function, walking time, and muscle torque were examined before and after intervention. Significant improvement for all measures was observed in both exercise groups. There was no significant difference in any measures between HR and LR groups. However, based on effect size between exercise and control groups, the HR group improved more than the LR group. Both high- and low-resistance strength training significantly improved clinical effects in this study. The effects of high-resistance strength training appear to be larger than those of low-resistance strength training for people with mild to moderate knee OA, although the differences between the HR and LR groups were not statistically significant.

Effects of Muscle Strength Training and Testosterone in Frail Elderly Males

Determine the independent and combined effects of progressive resistance muscle strength training (PRMST) and testosterone on strength, muscle mass, and function in hypogonadal elderly male recuperative care patients. Between 1999 and 2004, 71 subjects (mean age 78.2 +/- 6.4 yr, 86% white) were enrolled. After baseline one-repetition maximum (1RM) strength testing and then randomization to one of four treatment groups (low-resistance (20% of the 1RM) exercises and weekly injections of either 100 mg of testosterone enanthate or placebo or high-intensity PRMST (> or =80% 1RM) and weekly injections), each subject received training and injections for 12 wk. Ten subjects withdrew from the study before its completion. Based on intent-to-treat analyses, strength improved in all groups, but was greater with high-intensity PRMST compared with low-resistance exercise (e.g., leg press, (mean +/- SE), 28 +/- 4 vs 13 +/- 4%, P = 0.009). Although testosterone led to significantly greater increases in midthigh cross-sectional muscle area compared with placebo (7.9 +/- 1.3 vs 2.4 +/- 1.4%, P = 0.005), it produced only a nonsignificant trend toward greater strength gains (e.g., leg press 25 +/- 4 vs 16 +/- 4%, P = 0.144). Change in aggregate functional performance score (the sum of 4 functional performance test scores) did not differ between the four intervention groups nor with high-intensity PRMST compared with low-resistance exercise (7 +/- 5 vs 15 +/- 5%, P = 0.263). There was not a significant interaction between exercise and testosterone for any outcome. High-intensity PRMST is as safe and well tolerated as a similarly structured low-resistance exercise regimen for very frail elderly patients, but produces greater muscle strength improvements. The addition of testosterone leads to greater muscle size and a trend toward greater strength but did not produce a synergistic interaction with exercise. Neither intervention had a significant effect on functional performance.

Rating Perceived Exertion during Short Duration, Very High Intensity Cycle Exercise

This study compared undifferentiated ratings of perceived exertion (RPE) during short duration, very high intensity cycle exercise using high and low resistance. 30 recreationally trained males (24.2 +/- 2.4 yr.) were memory-anchored to the Borg 15-category scale. The high and low resistance exercises were defined by 30-sec. maximum tests assigned in counterbalanced order, with resistances set before testing during an orientation session. High resistance was 10% of body mass. Low resistance resulted in the same total work as the high resistance over the 30-sec. sessions (+/-5%) but increased pedal rate. RPE was taken at 8, 13, 18, 23, and 28 sec. during the high and the low resistance exercises. Measurements were compared using a 2-way repeated-measures analysis of variance. RPE was significantly greater (p=.005) for the high than the low resistance exercise at each interval. RPE increased when the subjects were required to pedal against a greater resistance and produce the highest forces. These RPE data are consistent with data from both aerobic cycle and resistance exercise. The data suggest that instantaneous force production, not summed work, is a primary determinant of RPE. All of these observations support Cafarelli's theoretical model of effort sense. In conclusion, as an individual generates more force during high resistance exercise than in light resistance exercise, a potential explanation of our results is that the increased motor outflow and corollary sensory signal lead to a greater sense of effort.

Changes In Postactivation Potentiation At The Onset Of Exercise Training In Older Adults

INTRODUCTION Postactivation potentiation (PAP) of resting twitch force is known to decline with age (Vandervoort and McComas, 1986). The inability to utilize enhanced muscular output may contribute to impaired motor function in the elderly. In daily tasks, older adults seldom experience the high-force muscular contractions that elicit PAP. PURPOSE The purpose of this experiment was to determine the extent to which PAP is recoverable in older adults due to exercise training. For specific applications to frail elderly adults, a low-force, high movement velocity training intervention was tested. The goal of this training protocol was to elicit a high volume of neural activation, which might have a positive impact on PAP and other neuromuscular factors. METHODS Seventeen healthy older adults, (7 males, 10 females; mean ± standard deviation: age 76±6.3 yrs.), who were not actively participating in a strength-training program involving dorsi/plantar flexion exercises, participated in this study. Each subject was required to attend three sessions, each 48 hours apart. At the start of each session subjects were evaluated for PAP by applying supramaximal stimuli to the tibial nerve before and after a 10 second maximal voluntary isometric contraction. Stimuli were applied three times within each of two stimulus trains in which the stimuli were separated by 2 seconds and the trains by approximately 3 seconds. Thus PAP was the difference between the average peak torques of 6 twitches. The training was conducted after testing on both days one and two and consisted of 4 exercises; up-tempo cycling, two plantar flexion exercises, and active and passive ankle rotations. RESULTS Older adults exhibited an average of 24.5 ± 17.7 % PAP at baseline. This is similar to the results of Petrella et al. (1989). In response to the combined effects of training and test contractions, there was a significant increase in PAP (F2.32=3.850, p=0.032). There was an 18.5% increase in PAP from day 1 to day 2, and a 37.0% increase from day 1 to day 3 (D1=24.5±17.7; D2=29.1±16.6; D3=33.6±16.9) There were no significant changes in resting twitch torque, or maximal voluntary torque in this group. CONCLUSIONS These results indicate that PAP is trainable in older adults. It must be noted however, that due to requirements for other aspects of this experiment, training stimuli included maximal voluntary contractions. Thus, we cannot isolate the low-resistance exercises as the only candidate stimuli for increased PAP.

Microfracture for grade IV chondral lesions of the hip (SS-89)

Articular lesions are the second most common pathology encountered among patients undergoing hip arthroscopy. It is postulated that the microfracture principle may have application in the hip. This study reports the results of this technique in a series of hip arthroscopy patients. Methods: All patients undergoing arthroscopy are prospectively assessed. Twenty-one patients were identified that had undergone microfracture and had achieved a minimum two year follow-up. The indications for the procedure were a well circumscribed Grade IV articular lesion with intact subchondral bone and healthy surrounding cartilage, and ability of the patient to participate in the 3 month structured postoperative rehabilitation protocol. This protocol included 10 weeks of protected weight bearing, emphasizing range of motion and low resistance exercises, followed by transition to a weight bearing program and gradual resumption of normal activities. Results: There was 100% follow-up at an average of 32.6 months. The average age was 35.0 years. Work up included radiographs in all cases, 17 MRIs, 8 intra-articular injections, 2 MRAs, 2 CT scans, and 2 bone scans. Radiographs were normal in 13 cases (62%) and revealed evidence of degenerative changes in 8 cases (38%). MRI or MRA revealed evidence of articular pathology in only 4 cases (19%) and was inadequate at grading the lesion. Indirect findings of articular damage was evidenced by subchondral cyst formation (4 cases), edema or stress reaction of the subchondral bone (4 cases), and effusion (3 cases). At arthroscopy, the Grade IV lesion addressed was on the acetabular surface in 19 cases, the femoral surface in 1 case, and both surfaces in 1 case. Among the 19 acetabular lesions, 17 had associated labral pathology, 3 had accompanying Grade III lesions of the femoral head, and there were 3 degenerate ruptures of the ligamentum teres. The mean dimensions of the Grade 4 lesions were 12.2mm2 (range 6–17.5mm2). The mean improvement was 23.9 points (preoperative 51.4; postoperative 75.2). Quantitative improvement was maintained in 18 patients (86%). There was no correlation with radiographic findings, other imaging findings, associated pathology, dimensions of the lesions, or CE angle. There were no complications and all patients demonstrated compliance with the rehabilitation process. Discussion and Conclusions: Radiographs were poorly reflective of Grade IV articular lesions amenable to microfracture. Other investigative studies were unreliable at detecting these lesions and are incapable of assessing the necessary parameters for selecting the microfracture method. The decision to perform microfracture is based on the arthroscopic appearance of the defect. Thus, the surgeon must maintain an index of suspicion and include the ramifications of the postoperative rehabilitation in the preoperative discussion. The results are encouraging, although some patients did poorly despite proper selection for the procedure and compliance with the rehabilitation. In absence of controls, it is impossible to compare these results to the natural history of this process; but it is speculated that, when successful, this technique may positively influence the expected progression of these Grade IV lesions.

Perceived exertion responses to novel elbow flexor eccentric action in women and men.

The primary aim was to describe perceived exertion responses to different intensities of eccentric exercise in women and men. 42 adults (21 men and 21 women, 7 per condition) completed elbow extension exercises with a weight corresponding to 80%, 100%, or 120% of maximal voluntary concentric strength. Total work was equated by manipulating the number of repetitions in the 80% (N = 45), 100% (N = 36), and 120% (N = 30) conditions. A two-way ANOVA showed significant main effects for the intensity and sex factors. Perceived exertion ratings were strongly dependent on exercise intensity, and women reported lower RPEs than men. A separate three-way mixed model ANOVA that included a repetition factor showed that perceived exertion ratings increased similarly across the first 30 repetitions in all exercise conditions. Significant partial correlations were found between mean RPE during the eccentric exercise bout, and the mean intensity of delayed-onset muscle pain measured from 12- to 72-h postexercise after controlling for the relative exercise intensity (r12.3 = 0.28) or the maximum concentric strength of the elbow flexors (r12.3 = 0.33). 1) for both women and men, there is a positive association between the intensity of eccentric exercise performed with the elbow flexors and RPE; 2) perceived exertion ratings increase significantly then plateau when repeated eccentric muscle actions are performed at constant, submaximal absolute intensities; 3) women rate eccentric exercise performed at the same intensity (relativized to MVC-C) as being less effortful compared with men; and 4) RPE during eccentric exercise can account for a small but significant amount of variability in delayed-onset muscle pain after statistically controlling for differences in strength or relative intensity.