Effect of Cadence on Time Trial Performance in Recreational Female Cyclists.

Graham, PL, Zoeller, RF, Jacobs, PL, and Whitehurst, MA. Effect of cadence on time trial performance in recreational female cyclists. J Strength Cond Res 32(6): 1739-1744, 2018-The impact of pedaling cadence on cycling performance remains unresolved especially in female cyclists. The purpose of this study was to determine the effect of cadence on time trial (TT) performance in recreational female cyclists. Ten recreational female cyclists volunteered to participate in this study. Subjects performed 3 exercise sessions: 1 to assess peak oxygen uptake (V[Combining Dot Above]O2peak) and 2 TTs. Cadence was randomly ordered and fixed for each TT (60 or 100 rpm), whereas power output (PO) was freely adjusted by the participant, as tolerated. Time trial time, heart rate (HR), blood lactate, PO, V[Combining Dot Above]O2, and ratings of perceived exertion were measured throughout the TTs. The major finding of this study was the significantly faster (p = 0.001) TT time during the 60-rpm condition (34:23 ± 4:21) vs. the 100-rpm condition (37:34 ± 5:53). Also the 60-rpm TT resulted in significant differences for HR (155.9 ± 3.97 vs. 161.2 ± 5.20 b·min, p = 0.04), gross efficiency, (21.1 ± 0.37 vs. 17.7 ± 0.85%, p < 0.001), and PO (147 ± 7.06 vs. 129 ± 10.62 W, p = 0.003). Thus, a slower cycling cadence was associated with greater mechanical efficiency and PO, resulting in significantly better performance in a TT. These results suggest that recreational female cyclists may benefit from adopting a low cadence during an 8-km TT.

Comparison of training methods to improve walking in persons with chronic spinal cord injury: a randomized clinical trial.

OBJECTIVE: To compare two forms of device-specific training - body-weight-supported (BWS) ambulation on a fixed track (TRK) and BWS ambulation on a treadmill (TM) - to comprehensive physical therapy (PT) for improving walking speed in persons with chronic, motor-incomplete spinal cord injury (SCI). METHODS: Thirty-five adult subjects with a history of chronic SCI (>1 year; AIS 'C' or 'D') participated in a 13-week (1 hour/day; 3 days per week) training program. Subjects were randomized into one of the three training groups. Subjects in the two BWS groups trained without the benefit of additional input from a physical therapist or gait expert. For each training session, performance values and heart rate were monitored. Pre- and post-training maximal 10-m walking speed, balance, muscle strength, fitness, and quality of life were assessed in each subject. RESULTS: All three training groups showed significant improvement in maximal walking speed, muscle strength, and psychological well-being. A significant improvement in balance was seen for PT and TRK groups but not for subjects in the TM group. In all groups, post-training measures of fitness, functional independence, and perceived health and vitality were unchanged. CONCLUSIONS: Our results demonstrate that persons with chronic, motor-incomplete SCI can improve walking ability and psychological well-being following a concentrated period of ambulation therapy, regardless of training method. Improvement in walking speed was associated with improved balance and muscle strength. In spite of the fact that we withheld any formal input of a physical therapist or gait expert from subjects in the device-specific training groups, these subjects did just as well as subjects receiving comprehensive PT for improving walking speed and strength. It is likely that further modest benefits would accrue to those subjects receiving a combination of device-specific training with input from a physical therapist or gait expert to guide that training.

Acute enhancement of lower-extremity dynamic strength and flexibility with whole-body vibration.

The purpose of this investigation was to examine the acute effects of whole-body vibration (WBV) on muscular strength, flexibility, and heart rate (HR). Twenty adults (10 men, 10 women) untrained to WBV participated in the study. All subjects completed assessment of lower-extremity isokinetic torque, flexibility, and HR immediately before and after 6 minutes of WBV and 6 minutes of leg cycling ergometry (CYL), in randomized order. During WBV, subjects stood upright on a vibration platform for a total of 6 minutes. Vibration frequency was gradually increased during the first minute to a frequency of 26 Hz, which was maintained for the remaining 5 minutes. During CYL, power output was gradually increased to 50 W during the first minute and maintained at that power output for the remaining 5 minutes. Lower-extremity flexibility was determined using the sit-and-reach box test. Peak and average isokinetic torque of knee extension and flexion were measured by means of a motor-driven dynamometer with velocity fixed at 120 degrees .s. Change scores for the outcome measures were compared between treatments using Student's paired t-tests. Analysis revealed significantly greater HR acceleration with CYL (24.7 bpm) than after WBV (15.8 bpm). The increase of sit-and-reach scores after WBV (4.7 cm) was statistically greater (p < 0.05) than after CYL (0.8 cm). After WBV, increases in peak and average isokinetic torque of knee extension, 7.7% and 9.6%, were statistically greater than after CYL (p < 0.05). Average torque of knee flexion also increased more with WBV (+7.8%) than with CYL (-1.5%) (p < 0.05). The findings of this study indicate that short-term WBV standing elicits acute enhancements of lower-extremity muscular torque and flexibility, suggesting the application of this technology as a preparatory activity before more intense exercise.

The acute effects of different durations of static stretching on dynamic balance performance.

The purpose of this study was to examine the effects of different durations of static stretching on dynamic balance. Women (N = 28) were tested before and after 2 stretching interventions and a control condition on 3 separate days, at least 48 hours apart. The stretching sessions involved a cycle ergometer warm-up at 70 rpm and 70 W followed by passive stretching of the lower-body muscles. Each stretching position was held at a point of mild discomfort and repeated 3 times with 15 seconds between stretches. In the 2 stretching protocols, the positions were maintained for 15 or 45 seconds. The control condition involved the same cycle ergometer warm-up, with a 26-minute rest period between pre- and posttests. Balance was assessed using the Biodex Balance System. A 2-way repeated-measures analysis of variance was used with the effects of study condition (control, 15 seconds, 45 seconds) and time (pre-, postscores). Post hoc paired t-tests were used when appropriate to determine possible statistical significance between pre- and posttest scores. Analyses indicated no significant main effects for either study condition or time. However, there was a significant condition x time interaction (p < 0.05). Post hoc analyses indicated that the 15-second condition produced a significant improvement in the balance scores (p < 0.01), with no significant effects with the control condition or the 45-second treatment. The results of this study reveal that a stretching protocol of 45-second hold durations does not adversely affect balance when using the current stabilometry testing procedure. Furthermore, a stretching intervention with 15-second hold durations may improve balance performance by decreasing postural instability. Strength and conditioning professionals concerned with reported performance limitations associated with static stretching should consider applying shorter-duration stretching protocols when aiming to improve balance performance.

New functional electrical stimulation approaches to standing and walking.

Spinal cord injury (SCI) is a devastating neurological trauma that is prevalent predominantly in young individuals. Several interventions in the areas of neuroregeneration, pharmacology and rehabilitation engineering/neuroscience are currently under investigation for restoring function after SCI. In this paper, we focus on the use of neuroprosthetic devices for restoring standing and ambulation as well as improving general health and wellness after SCI. Four neuroprosthetic approaches are discussed along with their demonstrated advantages and their future needs for improved clinical applicability. We first introduce surface functional electrical stimulation (FES) devices for restoring ambulation and highlight the importance of these devices for facilitating exercise activities and systemic physiological activation. Implanted muscle-based FES devices for restoring standing and walking that are currently undergoing clinical trials are then presented. The use of implanted peripheral nerve intraneural arrays of multi-site microelectrodes for providing fine and graded control of force during sit-to-stand maneuvers is subsequently demonstrated. Finally, intraspinal microstimulation (ISMS) of the lumbosacral spinal cord for restoring standing and walking is introduced and its results to date are presented. We conclude with a general discussion of the common needs of the neuroprosthetic devices presented in this paper and the improvements that may be incorporated in the future to advance their clinical utility and user satisfaction.

Reliability of upper extremity anaerobic power assessment in persons with tetraplegia.

BACKGROUND/OBJECTIVE: Reliable assessment of upper extremity anaerobic power in persons with cervical spinal cord injury (SCI) may indicate the ability to successfully and safely perform many daily activities. PURPOSE: To examine test-retest reliability of upper extremity Wingate anaerobic testing (WAnT) in persons with motor/sensory complete tetraplegia. METHODS: Forty-five persons with cervical-level SCI (15 individuals each at C5, C6, and C7 levels of injury) performed 2-arm WAnT bouts, with 2 to 4 days between bouts. Subjects performed the WAnT seated in their wheelchairs using a tabletop-mounted Monarch 834E ergometer. Resistance loads were applied relative to injury level, with 1%, 2%, and 3% of body mass applied to subjects with C5, C6, and C7 level injuries, respectively. All subjects were directed to crank the ergometer at maximal velocity for a 30-second period. Values of peak power (Ppeak) and mean power (Pmean) were determined using an SMI OptoSensor 2000 system. Ppeak and Pmean were compared between trials and between groups using 2-way analyses of variance for repeated measures. Coefficients of determination (r2) were calculated between trials. RESULTS: There were no significant differences in Ppeak or Pmean detected between the 2 trials of WAnT in the C5, C6, or C7 groups. Regression analyses revealed statistically significant associations between bouts for Pmean and Ppeak in each of the 3 groups (P < 0.05). CONCLUSIONS: Upper extremity WAnT is reliable for upper extremity anaerobic power assessment in persons with cervical SCI at or below the C5 level.

Exercise recommendations for individuals with spinal cord injury.

Persons with spinal cord injury (SCI) exhibit deficits in volitional motor control and sensation that limit not only the performance of daily tasks but also the overall activity level of these persons. This population has been characterised as extremely sedentary with an increased incidence of secondary complications including diabetes mellitus, hypertension and atherogenic lipid profiles. As the daily lifestyle of the average person with SCI is without adequate stress for conditioning purposes, structured exercise activities must be added to the regular schedule if the individual is to reduce the likelihood of secondary complications and/or to enhance their physical capacity. The acute exercise responses and the capacity for exercise conditioning are directly related to the level and completeness of the spinal lesion. Appropriate exercise testing and training of persons with SCI should be based on the individual's exercise capacity as determined by accurate assessment of the spinal lesion. The standard means of classification of SCI is by application of the International Standards for Classification of Spinal Cord Injury, written by the Neurological Standards Committee of the American Spinal Injury Association. Individuals with complete spinal injuries at or above the fourth thoracic level generally exhibit dramatically diminished cardiac acceleration with maximal heart rates less than 130 beats/min. The work capacity of these persons will be limited by reductions in cardiac output and circulation to the exercising musculature. Persons with complete spinal lesions below the T(10) level will generally display injuries to the lower motor neurons within the lower extremities and, therefore, will not retain the capacity for neuromuscular activation by means of electrical stimulation. Persons with paraplegia also exhibit reduced exercise capacity and increased heart rate responses (compared with the non-disabled), which have been associated with circulatory limitations within the paralysed tissues. The recommendations for endurance and strength training in persons with SCI do not vary dramatically from the advice offered to the general population. Systems of functional electrical stimulation activate muscular contractions within the paralysed muscles of some persons with SCI. Coordinated patterns of stimulation allows purposeful exercise movements including recumbent cycling, rowing and upright ambulation. Exercise activity in persons with SCI is not without risks, with increased risks related to systemic dysfunction following the spinal injury. These individuals may exhibit an autonomic dysreflexia, significantly reduced bone density below the spinal lesion, joint contractures and/or thermal dysregulation. Persons with SCI can benefit greatly by participation in exercise activities, but those benefits can be enhanced and the relative risks may be reduced with accurate classification of the spinal injury.

Peak exercise capacity of electrically induced ambulation in persons with paraplegia.

INTRODUCTION: Persons with spinal cord injury (SCI) are generally limited to exercise activities using the relatively smaller, less productive upper extremities with limited benefits as compared with leg exercise training. Functional electrical stimulation (FES) assisted ambulation has previously been demonstrated to allow persons with paraplegia to stand and ambulate limited distances. PURPOSE: This study compared the peak physiological responses of persons with paraplegia during FES ambulation and voluntary arm exercise. METHODS: Fifteen subjects (T -T ) previously habituated to FES ambulation, completed peak testing of both arm cranking (AC) and FES walking to the point of exhaustion. The AC tests were performed using a graded incremental protocol to exhaustion in 3-min stages and 10-W power output increments. The FES walking test consisted of successive 10-m walking bouts, each trial progressively increased in pace. Metabolic activity was continuously monitored via open-circuit spirometry with heart rate (HR) determined by a 12-lead electrocardiograph for AC and by direct palpation during FES. RESULTS: Peak VO(2) did not differ between AC (22.9 +/- 3.8 mL x kg x min(-1)) and FES (22.7 +/- 3.9 mL x kg x min(-1)). FES ambulation elicited significantly greater peak values of HR (191 beats x min(-1) versus 179 beats x min(-1)) and lower peak values of respiratory exchange ratio (1.06 vs 1.12) compared with AC. There were no significant differences in peak values of any other variables. CONCLUSION: This study indicates that FES ambulation performance, in persons with paraplegia, elicits similar exercise capacity, as indicated by similar peak oxygen consumption, as voluntary arm exercise.

Physiological responses to high-speed, open-wheel racecar driving.

UNLABELLED: High-speed auto racing has been demonstrated to produce accelerated heart rate (HR) during competition. However, it has not been determined whether the increase in HR was due to physical work efforts or a result of emotional stress. PURPOSE: The purpose of this investigation was to examine the physiological responses associated with open-wheel automobile driving at competitive speeds. METHODS: Oxygen consumption and HR were assessed in seven professional automobile racing drivers during two incrementally paced driving sessions. A portable metabolic analyzer and EKG were directly attached to the subjects as they participated in driving tests on an oval speedway and a roadway course. Maximal physiological responses of the subjects were also determined during a graded treadmill test. RESULTS: During treadmill testing, maximal oxygen consumption (VO2max) ranged from of 42.0 to 59.7 mL x kg(-1) x min(-1) (mean +/- SD = 47.6+/-8.1). The road course and oval speedway testing at competitive speeds elicited mean VO2 values of 38.5 and 21.9 mL x kg(-1) x min(-1), respectively, which correspond to 79% and 45% of VO2max. Road course driving produced mean HR values of 152 beats x min(-1) with 142 beats x min(-1) recorded when driving at competitive speed on the speedway course. CONCLUSIONS: Professional open-wheel race drivers possess cardiorespiratory capacity similar to athletes participating in sports such as basketball, football, and baseball. The VO2 and HR responses to road course driving were similar to those previously reported in traditional sports settings. The findings of this study suggest that professional open-wheel racing drivers should be regarded as athletes that encounter significant physiological stresses.(2)

Hypokinetic circulation in persons with paraplegia.

INTRODUCTION: It is well established that hemodynamic dysfunction, resulting in diminished upper-extremity work capacity, occurs in persons with spinal cord injury (SCI) as compared with those who are nondisabled (ND). Although it has been shown that persons with paraplegia display higher values of heart rate (HR) with lower values of stroke volume (SV) during exercise, it is not resolved whether there is adequate compensation to produce similar values of cardiac output (.Q) as in ND. PURPOSE: This study examined central cardiovascular responses (HR, SV, and .Q) of 20 subjects with complete thoracic level SCI (T(4)-T(11)) and 20 sedentary ND subjects during matched levels of arm-crank (AC) exercise. METHODS: All subjects performed an incremental peak AC test to volitional exhaustion with continuous metabolic analysis and HR measurement via open circuit spirometry and 12-lead electrocardiography, respectively. Stroke volume was assessed using transthoracic impedance. RESULTS: Heart rate was higher for SCI (P< 0.05) with significantly lower values for SV and .Q at rest (approximately 25%). Peak responses were significantly higher for ND in all factors except HR. Although subpeak HRs at matched absolute workloads were significantly higher for SCI (12-20 beats.min (-1) ), SV and .Q were significantly lower (P< 0.05). CONCLUSIONS: The results of this study indicate that .Q is significantly lower in SCI than in ND during AC, despite significantly greater values of HR. These findings also suggest that the disparity in exercise values of .Q is related to differences exhibited at rest.

Fatigue compensation during FES using surface EMG.

Muscle fatigue limits the effectiveness of FES when applied to regain functional movements in spinal cord injured (SCI) individuals. The stimulation intensity must be manually increased to provide more force output to compensate for the decreasing muscle force due to fatigue. An artificial neural network (ANN) system was designed to compensate for muscle fatigue during functional electrical stimulation (FES) by maintaining a constant joint angle. Surface electromyography signals (EMG) from electrically stimulated muscles were used to determine when to increase the stimulation intensity when the muscle's output started to drop. In two separate experiments on able-bodied subjects seated in hard back chairs, electrical stimulation was continuously applied to fatigue either the biceps (during elbow flexion) or the quadriceps muscle (during leg extension) while recording the surface EMG. An ANN system was created using processed surface EMG as the input, and a discrete fatigue compensation control signal, indicating when to increase the stimulation current, as the output. In order to provide training examples and test the systems' performance, the stimulation current amplitude was manually increased to maintain constant joint angles. Manual stimulation amplitude increases were required upon observing a significant decrease in the joint angle. The goal of the ANN system was to generate fatigue compensation control signals in an attempt to maintain a constant joint angle. On average, the systems could correctly predict 78.5% of the instances at which a stimulation increase was required to maintain the joint angle. The performance of these ANN systems demonstrates the feasibility of using surface EMG feedback in an FES control system.

Circuit resistance training in persons with complete paraplegia.

BACKGROUND/OBJECTIVE: We assessed the metabolic and heart rate (HR) responses to a single session of circuit resistance training (CRT) in six subjects with complete paraplegia (T5-T12 levels) in order to determine the caloric cost of the exercise. METHODS: Subjects underwent isoinertial weight training exercises with interspersed periods of high-cadence, low-resistance arm ergometry (AE). Following protocol familiarization, subjects completed one session of CRT during which continuous monitoring of HR, oxygen uptake (VO2), and respiratory exchange ratio (RER = VCO2/VO2) was performed. Caloric cost was calculated from the exercise VO2 values across the CRT session. A peak arm exercise test allowed data to be expressed as percentages of peak VO2 and HR. RESULTS: Subjects displayed mean VO2 values of 11.6 +/- 2.4 ml/kg/min (mean +/- SD) and a mean HR of 136 +/- 17 beats/min across the CRT session, corresponding with 49.0% of peak VO2 and 76.8% of peak HR. The RER values ranged from 0.96 to 1.19 and averaged above unity throughout the CRT session. CONCLUSION: Despite the modest absolute VO2 during exercise, CRT satisfies operational criteria developed for cardiorespiratory exercise prescriptions in persons without disability. The RER values recorded indicate that CRT is intense work that relies primarily on glycolytic metabolism.

Reliability of arm Wingate Anaerobic Testing in persons with complete paraplegia.

BACKGROUND: Accurate, reliable assessment of upper extremity muscular power in persons with paraplegia caused by spinal cord injury (SCI) would provide an objective indication of their ability to generate the forces necessary for the performance of daily activities. Wingate Anaerobic Testing (WAnT) consists of a 30-second sprint test on a cycle ergometer and has been used widely in both athletic and research settings. PURPOSE: To examine test-retest reliability of arm WAnT performance in persons with complete SCI and paraplegia. METHODS: Forty-three participants with thoracic-level paraplegia (T2 through T12) performed 2 trials of arm WAnT with 2 to 7 days between each trial. Testing was performed using a Monarch 834E ergometer with participants seated in their wheelchairs. Participants were directed to crank at maximal pace for 30 seconds against a resistance load equivalent to 3.5% of their body mass. The SMI OptoSensor 2000 system was used to determine values of peak power (P(peak)), mean power (P(mean)), minimum power, and rate of fatigue, which were compared between trials using 1-way analysis of variance for repeated measures. Coefficients of determination (r2) were calculated between trials for P(peak) and P(mean). RESULTS: No significant difference was found between trials for any of the power output variables. Regression analysis indicated that P(peak) and P(mean) were closely associated between the 2 trials (r2 = 0.92 and 0.94, respectively). CONCLUSION: Arm WAnT is a reliable measurement tool for the assessment of upper extremity muscular power in persons with complete paraplegia.

Physiologic responses to electrically assisted and frame-supported standing in persons with paraplegia.

BACKGROUND: Systems of functional electrical stimulation (FES) have been demonstrated to enable some persons with paraplegia to stand and ambulate limited distances. However, the energy costs and acute physiologic responses associated with FES standing activities have not been well investigated. OBJECTIVE: To compare the physiologic responses of persons with paraplegia to active FES-assisted standing (AS) and frame-supported passive standing (PS). METHODS: Fifteen persons with paraplegia (T6-T11) previously habituated to FES ambulation, completed physiologic testing of PS and AS. The AS assessments were performed using a commercial FES system (Parastep-1; Altimed, Fresno, Calif); the PS tests used a commercial standing frame (Easy Stand 5000; Altimed, Fresno, Calif). Participants also performed a peak arm-cranking exercise (ACE) test using a progressive graded protocol in 3-minute stages and 10-watt power output increments to exhaustion. During all assessments, metabolic activity and heart rate (HR) were measured via open-circuit spirometry and 12-lead electrocardiography, respectively. Absolute physiologic responses to PS and AS were averaged over 1-minute periods at 5-minute intervals (5, 10, 15, 20, 25, and 30 minutes) and adjusted relative to peak values displayed during ACE to determine percentage of peak (%pk) values. Absolute and relative responses were compared between test conditions (AS and PS) and across time using two-way analysis of variance. RESULTS: The AS produced significantly greater values of VO2 (43%pk) than did PS (20%pk). The mean HR responses to PS (100-102 beats per minute [bpm] throughout) were significantly lower than during AS, which ranged from 108 bpm at 5 minutes to 132 bpm at test termination. CONCLUSION: Standing with FES requires significantly more energy than does AS and may provide a cardiorespiratory stress sufficient to meet minimal requirements for exercise conditioning.

Combined hyperlipidemia in a single subject with tetraplegia: ineffective risk reduction after atorvastatin monotherapy.

BACKGROUND/OBJECTIVE: Effects of atorvastatin (Lipitor) drug monotherapy (10 mg daily) on fasting blood lipid profiles and cardiovascular disease (CVD) risks were examined for a single subject with C5-C6 tetraplegia. Routine fasting lipid profiles were analyzed by standard biochemistry techniques for total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C). Lipid profiles were analyzed on 3 occasions before drug therapy was initiated and 3 months after therapy commenced. The TC:HDL and LDL:HDL ratios were computed for all sampling times and used to assess pretreatment and post-treatment CVD risk. RESULTS: Fasting TC, TG, and LDL-C were all significantly reduced by therapy. The pretreatment HDL-C of 35 mg/dL was lowered to 21 mg/dL. As a result, the TC:HDL risk ratio was only marginally reduced from 6.6 to 6.4, whereas the LDL:HDL risk ratio remained unchanged by treatment. CONCLUSIONS: In this man with tetraplegia, atorvastatin drug monotherapy rapidly lowered TC, TG, LDL-C, and HDL-C. However, the TC:HDL ratio, considered the best predictor of CVD risk, was unchanged.

Metabolic and cardiac responses to robotic-assisted locomotion in motor-complete tetraplegia: a case report.

BACKGROUND/OBJECTIVE: To examine acute metabolic responses to treadmill locomotion in a participant with motor-complete tetraplegia. METHODS: The participant--a woman with a chronic ASIA B C3-C4 spinal cord injury--walked on a treadmill with 40% body weight support (BWS) and robotic assistance. Oxygen consumption (VO2), minute ventilation (VE), and heart rate (HR) were measured during seated resting, supported standing, and 40 minutes of walking with stepping assistance from a Lokomat-driven gait orthosis. RESULTS: A resting VO2 equal to 50 milliliters per minute was predictably low, and did not change after the participant assumed an upright posture. Both VO2 and VE increased immediately upon onset of locomotion, suggesting a neurogenic rather than a humoral regulatory response to movement. VO2 averaged 2.4 metabolic units (METS) during locomotion at an average expenditure of 2.98 kilocalories per minute. HR was unaltered by standing, but during locomotion averaged 1 7 beats higher than during resting. Increases in VE but not VO2 upon standing, and decreases in VO2 but not VE immediately after walking, rule out changes in VE alone as the source for increased VO2 during walking. CONCLUSION: The data collected on this single participant show that treadmill locomotion with BWS and robotic assistance elicits a metabolic response to treadmill gaiting characterized by increased VO2, VE, HR, and caloric expenditure.

Yoga Nidra relaxation increases heart rate variability and is unaffected by a prior bout of Hatha yoga.

OBJECTIVE: The measurement of heart rate variability (HRV) is often applied as an index of autonomic nervous system (ANS) balance and, therefore, myocardial stability. Previous studies have suggested that relaxation or mind-body exercise can influence ANS balance positively as measured by HRV but may act via different mechanisms. No studies, to the authors' knowledge, have examined the acute response in HRV to interventions combining relaxation and mind-body exercise. The objective of this study was to compare the acute HRV responses to Yoga Nidra relaxation alone versus Yoga Nidra relaxation preceded by Hatha yoga. DESIGN: This was a randomized counter-balanced trial. SETTING: The trial was conducted in a university exercise physiology laboratory. SUBJECTS: Subjects included 20 women and men (29.15±6.98 years of age, with a range of 18-47 years). INTERVENTIONS: Participants completed a yoga plus relaxation (YR) session and a relaxation only (R) session. RESULTS: The YR condition produced significant changes from baseline in heart rate (HR; beats per minute [bpm], p<0.001) and indices of HRV: R-R (ms, p<0.001), pNN50 (%, p=0.009), low frequency (LF; %, p=0.008) and high frequency (HF; %, p=0.035). The R condition produced significant changes from baseline in heart rate (bpm, p<0.001) as well as indices of HRV: R-R (ms, p<0.001), HF (ms(2), p=0.004), LF (%, p=0.005), HF (%, p=0.008) and LF:HF ratio (%, p=0.008). There were no significant differences between conditions at baseline nor for the changes from baseline for any of the variables. CONCLUSIONS: These changes demonstrate a favorable shift in autonomic balance to the parasympathetic branch of the ANS for both conditions, and that Yoga Nidra relaxation produces favorable changes in measures of HRV whether alone or preceded by a bout of Hatha yoga.

Long-term glycine propionyl-l-carnitine supplemention and paradoxical effects on repeated anaerobic sprint performance.

BACKGROUND: It has been demonstrated that acute GPLC supplementation produces enhanced anaerobic work capacity with reduced lactate production in resistance trained males. However, it is not known what effects chronic GPLC supplementation has on anaerobic performances or lactate clearance. PURPOSE: The purpose of this study was to examine the long-term effects of different dosages of GPLC supplementation on repeated high intensity stationary cycle sprint performance. METHODS: Forty-five resistance trained men participated in a double-blind, controlled research study. All subjects completed two testing sessions, seven days apart, 90 minutes following oral ingestion of either 4.5 grams GPLC or 4.5 grams cellulose (PL), in randomized order. The exercise testing protocol consisted of five 10-second Wingate cycle sprints separated by 1-minute active recovery periods. Following completion of the second test session, the 45 subjects were randomly assigned to receive 1.5 g, 3.0 g, or 4.5 g GPLC per day for a 28 day period. Subjects completed a third test session following the four weeks of GPLC supplementation using the same testing protocol. Values of peak power (PP), mean power (MP) and percent decrement of power (DEC) were determined per bout and standardized relative to body mass. Heart rate (HR) and blood lactate (LAC) were measured prior to, during and following the five sprint bouts. RESULTS: There were no significant effects of condition or significant interaction effects detected for PP and MP. However, results indicated that sprint bouts three, four and five produced 2 - 5% lower values of PP and 3 - 7% lower values of MP with GPLC at 3.0 or 4.5 g per day as compared to baseline values. Conversely, 1.5 g GPLC produced 3 - 6% higher values of PP and 2 -5% higher values of MP compared with PL baseline values. Values of DEC were significantly greater (15-20%) greater across the five sprint bouts with 3.0 g or 4.5 g GPLC, but the 1.5 g GPLC supplementation produced DEC values -5%, -3%, +4%, +5%, and +2% different from the baseline PL values. The 1.5 g group displayed a statistically significant 24% reduction in net lactate accumulation per unit power output (p < 0.05). CONCLUSIONS: The effects of GPLC supplementation on anaerobic work capacity and lactate accumulation appear to be dosage dependent. Four weeks of GPLC supplementation at 3.0 and 4.5 g/day resulted in reduced mean values of power output with greater rates of DEC compared with baseline while 1.5 g/day produced higher mean values of MP and PP with modest increases of DEC. Supplementation of 1.5 g/day also produced a significantly lower rate of lactate accumulation per unit power output compared with 3.0 and 4.5 g/day. In conclusion, GPLC appears to be a useful dietary supplement to enhance anaerobic work capacity and potentially sport performance, but apparently the dosage must be determined specific to the intensity and duration of exercise.

Caffeine enhances upper body strength in resistance-trained women.

BACKGROUND: Research has indicated that low-to-moderate dosages of caffeine supplementation are ergogenic for sustained endurance efforts as well as high-intensity exercise. The effects of caffeine supplementation on strength-power performance are equivocal, with some studies indicating a benefit and others demonstrating no change in performance. The majority of research that has examined the effects of caffeine supplementation on strength-power performance has been carried out in both trained and untrained men. Therefore, the purpose of this study was to determine the acute effects of caffeine supplementation on strength and muscular endurance in resistance-trained women. METHODS: In a randomized manner, 15 women consumed caffeine (6 mg/kg) or placebo (PL) seven days apart. Sixty min following supplementation, participants performed a one-repetition maximum (1RM) barbell bench press test and repetitions to failure at 60% of 1RM. Heart rate (HR) and blood pressure (BP) were assessed at rest, 60 minutes post-consumption, and immediately following completion of repetitions to failure. RESULTS: Repeated measures ANOVA indicated a significantly greater bench press maximum with caffeine (p

Effects of resistance and endurance training in persons with paraplegia.

INTRODUCTION: The specific effects of resistance and endurance training on upper extremity work capacity, muscular strength, and anaerobic power in chronic survivors of paraplegia have not been previously determined. PURPOSE: This study compared the effects of 12 wk of endurance training (ET) with 12 wk of resistance training (RT) on VO(2peak), upper extremity strength, and power output in persons with chronic paraplegia. METHODS: Eighteen subjects with neurologically complete paraplegia, T6-T10, participated in three weekly exercise sessions during a 12-wk training period. Subjects were matched into pairs (body mass and gender) and were randomly assigned to ET or RT. The ET group performed 30 min of arm cranking at 70%-85% of HR(peak). The RT group performed three sets of 10 repetitions at six exercise stations with an intensity of ranging from 60% to 70% of 1 repetition maximum (1RM). Values of upper extremity strength (1RM) were established using the Mayhew regression equation. VO(2peak) was determined during arm ergometry testing using open circuit spirometry. Arm Wingate anaerobic testing (WAnT) was used to determine subjects' peak and mean anaerobic power output. RESULTS: VO(2peak) values were significantly greater after RT (15.1%) and ET (11.8%). Muscular strength significantly increased for all exercise maneuvers in the RT group (P values < 0.01) with no changes detected in the ET group. Mean WAnT power increased in the RT and ET groups by 8% and 5%, respectively. The RT group displayed significantly greater gains in peak WAnT power (P < 0.001) than ET, 15.6% and 2.6%, respectively. CONCLUSION: Persons with paraplegia can significantly improve their upper extremity work capacity, muscular strength, and power by participating in RT.