3-minute Rest Period Research Articles

Impact of assisted exercises on skeletal muscle oxygenation levels in men with acutely decompensated heart failure.

The complex clinical status of modern day patients hospitalized due to acute heart failure (AHF) results from their advanced age, comorbidities, frailty, heart failure symptoms (including massive swelling of the lower limb), and dramatic reduction of exercise tolerance. Hence, there is a need to implement physiotherapeutic procedures as early as possible, aiming to both accelerate the restoration of clinical stabilization and prevent post-hospital disability. We investigated whether assisted lower limb exercises have an impact on perfusion and oxygenation in skeletal muscle and if they are feasible in patients with AHF. We examined 34 men (age: 66 ±11 years; left ventricular ejection fraction (LVEF): 34 ±11%; clinical presentation: 31 wet-warm and 3 wet-cold). The intervention (carried out on the 2nd day of hospitalization) included: 1) a 3-minute rest period; 2) an exercise phase (45 repetitions of assisted flexion and extension of the lower limb; and 3) a 10-minute relaxation period. We analyzed blood pressure (BP), heart rate (HR), respiratory rate (RR), tissue oxygenation (reflected by oxygen saturation measured with a pulse oximeter), and changes in peripheral tissue perfusion (reflected by the tissue oxygenation index (TOI) measured with near-infrared spectroscopy (NIRS)). The hemodynamic parameters (both ΔHR and Δsystolic BP) and oxygen saturation did not change (all p > 0.05), whereas the RR declined (p < 0.001). The exercises improved venous outflow (reflected by decreased oxygenated, deoxygenated and total hemoglobin, all p < 0.05) and increased peripheral tissue perfusion, as reflected by the TOI (p < 0.05). The patients reported relief and lack of dyspnea during and after the assisted exercises. The physiotherapeutic intervention improved both venous outflow and muscle oxygenation in men with AHF. The presented protocol was safe, feasible and well-tolerated, and resulted in relief for the patients. We believe that such procedures might be recommended for the initial period of rehabilitation in this challenging subgroup of patients.

Isometric Resistance Training Is Recommended as a Safe and Effective Adjunct Therapy to Reduce Blood Pressure

ABSTRACT Most scientific organizations recommend isometric resistance training (IRT) to manage blood pressure (BP), whereas some still do not. A typical grip IRT program of 4 × 2-minute 30%-intensity efforts with 1–3-minute rest periods, performed ≥3×/week for ≥8 weeks, can be efficient, safe, and relatively inexpensive. It can help decrease resting BP at least as much as aerobic or dynamic resistance training. IRT can be as effective as one antihypertensive medication and likely lessens strokes and myocardial infarctions. It can be as safe as other exercise modes regarding acute BP rise and safer than aerobic exercise regarding cardiac demand. Grip IRT is currently more conducive than leg IRT to program delivery. These highlights come from an expert-panel consensus reached through a largely anonymous multistep process, agreeing with the organizations that support IRT. To follow the science on IRT and BP, exercise and health care practitioners should seek corroboration from the guidelines of multiple organizations.

Effect of 4 weeks of High-Intensity Interval Training on P53 and Caspase-3 Proteins Content in the Heart Muscle Tissue of Rats with Type 1 Diabetes

Introduction: Type 1 diabetes can lead to muscle apoptosis and a defect in the structure of the heart tissue. One of the main pathways of apoptosis is the pathway activated by the P53 and Caspase-3 proteins. Therefore, the aim of this study was to investigate the effect of 4 weeks of high intensity interval training on the content of P53 and Caspase-3 proteins in heart muscle tissue of Sprague-Dawley rats with type 1 diabetic rats. Methods: In this experimental study, twelve 2-month-old Sprague-Dawley male rats with mean weight of 300±20 gr were selected and after induction of diabetes through streptozotocin solution, randomly divided into 2 groups: experimental (n= 6) and control (n= 6). The training program consisted of 5 stages of 4-minute with an intensity of 85 to 95% of the maximum speed and 3-minute active rest periods with an intensity of 50 to 60% of the maximum speed. Proteins were measured by Western-Blot in vitro. SPSS software version 16 and independent t-test were used to analyze the data. Results: High intensity interval training resulted in a significant reduction in the P53 protein content of the training group compared to the control group (P=0.003). However, there was no significant change in the content of Caspase-3 in the activated form (P=0.71) and the initial form (P=0.15) in the training group compared to the control group. Conclusion: High intensity interval training, by reducing the content of the P53 protein and preventing the activation of the caspase-3 protein, may have inactivated the apoptosis pathway of these two proteins in heart cells in type 1 diabetic subjects.

Effect of 2- vs. 3-Minute Interrepetition Rest Period on Maximal Clean Technique and Performance.

Ammar, A, Riemann, BL, Abdelkarim, O, Driss, T, and Hökelmann, A. Effect of 2- vs. 3-minute interrepetition rest period on maximal clean technique and performance. J Strength Cond Res 34(9): 2548-2556, 2020-Currently, it is widely accepted that adopting a long rest period (3-5 minutes) during maximal strength and power exercise is of importance in reducing acute fatigue and maintaining power and technique proficiency. However, despite the fact that weightlifting is an example of maximal strength exercise, only 2 minutes are officially allowed when athletes attempt 2 successive lifts. The purpose of this study was to compare 3- vs. 2-minute intermaximal repetition rest periods (IMRRPs) on performance, rate of perceived exertion (RPE), technical efficiency, and power production during 2 successive maximal repetitions of clean & jerk (C&J). Nine elite weightlifters (age: 24.4 ± 3.6 years, body mass: 77.2 ± 7.1 kg, height 176.0 ± 6.4 cm, and 1 repetition maximum C&J: 170.0 ± 5.0 kg) performed 2 separate testing sessions using 2-minute IMRRP (IMRRP-2) and 3-minute IMRRP (IMRRP-3), in a randomized order, while barbell kinematics and kinetics were recorded. Results showed that the longer IMRRP-3 minutes led to the maintenance of clean technique (from the first to the second repetition) evidenced by a 1.86% lower decline in peak vertical displacement (p = 0.03) and attenuation of increased peak horizontal displacements with a 1.74% (p = 0.03) less backward movement during the first pull, a 3.89% (p = 0.008) less forward movement during the second pull, and a 4.7% (p = 0.005) less backward movement during the catch phase. In addition, attenuation of peak velocity (2.22%; p = 0.02), peak vertical ground reaction force (1.70%; p = 0.03), and peak power (2.14%; p = 0.02) declines were shown using IMRRP-3 compared with IMRRP-2. Increasing IMRRP from 2 to 3 minutes was also shown to decrease RPE values (8.02%; p = 0.008) and to enhance supramaximal C&J performance (1.55%; p = 0.003). The results of this study suggest 3 minutes to be the most advantageous IMRRP in terms of maintaining technical efficiency, power output, reducing fatigue perception, and enhancing performance in elite weightlifters.

The Perceptual Responses Of Multiple Sclerosis Patients To Traditional Versus Blood Flow Restriction Resistance Exercise

PURPOSE: To investigate the perceptual responses (ratings of perceived exertion [RPE] and discomfort [RD]) of multiple sclerosis patients (MS) to low-load resistance exercise (RE) with blood flow restriction (BFR) and to traditional high-load RE without BFR. METHODS: Thirteen individuals (males = 3, females = 10) with a confirmed diagnose of relapsing-remitting MS were randomly assigned to the following RE conditions: 1) low-load RE with BFR (LL-BFR) and 2) high-load RE without BFR (HI). Participants performed 4 sets (30-15-15-15 reps) of bilateral leg press (LP) and knee extension (KE), at 20% of their one-maximum repetition (1-RM), and with 50% of BFR for the LL-BFR exercise trial. For the HI exercise condition, participants completed 4 sets (10-10-10-10 reps) of the same exercises at 70% of 1RM. There was a 3-minute rest period between sets and 5 minutes between exercises. RPE was assessed after each set using the OMNI-RES scale, with scores ranging from 0 to 10. The RD were assessed immediately before and after each set using a visual numeric pain scale, with scores ranging from 0 to 10. Data were analyzed using the Friedman’s and the Wilcoxon non-parametric tests with Bonferroni correction, and with p set at 0.05. Data are winsorized means ± SD. RESULTS: Greater RPE values were observed for the HI exercise condition compared to LL-BFR following the first set of LP (6.83±1.17 vs 4.84±2.05, p < 0.05), but not after sets 2 (6.83±1.48 vs 4.2±2.14), 3 (7.62±1.63 vs 4.82±2.09), and 4 (7.94±1.44 vs 4.98 ± 1.87). During KE, HI elicited significantly (p < 0.05) higher RPE after sets 2 (8.07±1.06 vs 6.47±1.52), 3 (8.86±1.02 vs 6.84±1.26), and 4 (9.02±1.17 vs 6.84±1.26, but not set 1 (8.24±0.66 vs 6.54±1.74). For the RD, LL-BFR induced significantly (p < 0.05) greater RD than HI only after the first set of both LP (2.26±1.46 vs 0.80±0.54) and KE (4.69±1.80vs 2.52±1.65). For the RD measured immediately before each set, LL-BFR was significantly greater (p < 0.05) than HI only before sets 3 (3.13±1.41 vs 0.52±0.68) and 4 (3.14±1.92 vs 1.10±1.09) of LP, and before sets 2 (3.75±1.93 vs 0.94±1.10) and 3 (3.15±1.41 vs 1.15±0.96) of KE. CONCLUSION: LL-BFR results in similar RPE and RD compared to HI. However, the RD perceived immediately before a subsequent set remained partially elevated following some of the sets of LL-BFR.

Initial force production before sag is enhanced by prior contraction followed by a 3-minute rest period in fast motor units of the rat medial gastrocnemius

Unfused tetanic contractions evoked in fast motor units exhibit extra-efficient force production at the onset of contraction, an effect called “boost”. Boost is diminished in subsequent contractions if there is a short rest period between contractions, but can be re-established with a longer period of rest. We tested the hypothesis that contractile activity and rest could enhance boost-related metrics. Two sets of 3 unfused tetani were evoked 3 min apart in fast fatigable (FF) and fast fatigue-resistant (FR) motor units of the rat medial gastrocnemius. The greatest changes occurred in the first unfused tetanic contractions. Relative to the first contraction in the first set, the first contraction in the second set exhibited higher peak force during boost in a subset of motor units (76% of FF and 48% of FR). Enhanced force during boost was influenced by interaction of slowing of twitch contraction time (up to 20% and 25%, for FF and FR motor units, respectively), half-relaxation time (up to 37% and 49% for FF and FR motor units, respectively), and potentiation of the first twitch (up to 13% and 5% for FF and FR motor units, respectively). Examination of twitches evoked between sets suggested opportunity for greater enhancement of boost with shorter intervening rest periods. The phenomenon of enhanced boost following motor unit activity may interest sports scientists.

Comparison of 2- and 3-Minute Inter-Repetition Rest Periods on Maximal Jerk Technique and Power Maintenance

ABSTRACTPurpose: The aim of this study was to examine the effect of 3- vs. 2-minute inter maximal-repetition rest period (IMRRP) on maintaining jerk technical efficiency and power production during two successive maximal repetitions of Clean & Jerk (C&J). Methods: In a randomized, within subject, repeated measures design, nine elite-weightlifters (age: 24.4 ± 3.6 years, body mass: 77.2 ± 7.1 kg, height 176.0 ± 6.4 cm and 1RM C&J: 170.0 ± 5.0 kg) performed 2-separate testing sessions using 2 (IMRRP-2) and 3 (IMRRP-3) -minute IMRRP, while barbell kinematics and kinetics and joint kinematics were recorded. Results: Statistical analysis showed that one minute longer IMRRP enhanced the maintenance of optimal jerk technique evidenced by reducing declines in peak vertical barbell displacement (2.74%; p = .03), peak barbell velocity (2.89%; p = .03), and peak knee (1.61%; p = .03) and hip extensions (1.59%; p = .03) during the drive phase of the jerk. Additionally, IMRRP-3 led to maintaining optimal lifting strategy by reducing the increase in horizontal displacement during the descending (3.85%; p = .04) and ascending (5.42%; p = .02) phases. Increasing IMRRP from 2min to 3min was also shown to enhance kinetic variables evidenced by prompting higher peak vGRF (2.01%; p = .04) and power (2.55%; p = .04). Conclusion: To better identify an athlete’s maximal jerk technique and power maintenance, the results of this study suggest 3min as more appropriate IMRRP during successive C&J at 100% 1RM.

Single rescuer ventilation using a bag-valve mask with internal handle: a randomized crossover trial

ObjectiveTo compare tidal volume received during single rescuer ventilation with a modified bag-valve mask (BVM) with integrated internal handle vs standard BVM among healthy volunteers using a manikin model. MethodsThis study was a randomized crossover trial of adult healthcare provider volunteers performing ventilation on a manikin. We randomized participants to perform single rescuer ventilation first using either a modified BVM with integrated internal handle or a standard unmodified BVM. Participants were responsible for mask placement and delivery of 10 breaths per minute for 3 minutes as guided by a metronome. After a 3-minute rest period, they performed ventilation using the alternative device. The primary outcome measure was mean received tidal volume as measured by the manikin (IngMar RespiTrainer model). Secondary outcomes included participant reported device preference. ResultsOf 70 recruited participants, all completed the study. Mean received tidal volume was higher using the modified BVM with integrated internal handle vs standard BVM by 90 mL (95% confidence interval, 60-120 mL; P< .0001). There were no significant differences in mean received tidal volume based on the order of study arm allocation. Eighty percent of participants reported preference for the modified BVM over the standard BVM (95% confidence interval, 70.0%-80.0%). ConclusionsThe modified BVM with integrated internal handle results in greater mean received tidal volume compared with standard BVM during single rescuer ventilation in a manikin model. This modified BVM design may prove a useful airway adjunct for ventilation.

MAPK Signaling Following High Volume And High Intensity Resistance Exercise Protocols In Trained Men

Resistance exercise initiates a multifaceted series of events converting the stimulus of muscle contraction into biochemical responses regulating the rate of protein synthesis. The MAPK pathway appears to be a key signaling pathway involved in the regulation of skeletal muscle mass. While resistance exercise paradigms are often divided into high volume (HV) or high intensity (HI) protocols, it is unknown whether these protocols differentially stimulate MAPK signaling. PURPOSE: The purpose of this study was to examine MAPK signaling proteins following a typical HV and HI lower-body resistance exercise protocol. METHODS: Ten resistance-trained men (24.7±3.4y; 90.1±11.3kg; 176.0±4.9cm) performed each resistance exercise protocol in a random, counterbalanced order. The HV protocol utilized a load of 70% 1-RM for sets of 10-12 repetitions with a 1-minute rest period length between sets and exercises. The HI protocol utilized a load of 90% 1-RM for sets of 3-5 repetitions with a 3-minute rest period length between sets and exercises. Both protocols included six sets of barbell back squats and four sets of bilateral leg press, bilateral hamstring curls, bilateral leg extensions, and seated calf raises. Fine needle muscle biopsies of the vastus lateralis were completed at baseline (BL) and 1-hour post exercise (1H). RESULTS: No significant differences over time were noted for phosphorylation of ATF, ERK/MAPK, p53, p38, MEK1, MSK1, or c-Jun (p>0.05). No significant between trial interactions were noted for phosphorylation of ATF2, JNK, HSP27, ERK/MAPK, p53, p38, MEK1, MSK1, STAT1, or c-Jun (p>0.05). However, significant time effects were observed for phosphorylation of JNK (p=0.0001), HSP27 (p=0.002), and STAT1 (p=0.03). Phosphorylation of JNK, HSP27, and STAT1 were significantly elevated from BL at 1H for both HV and HI. CONCLUSION: HV and HI lower-body resistance exercise protocols appear to elicit similar MAPK activation in resistance-trained men.

Does power output vary accordingly with high load resistance training? - A comparative study between Bulk-up and Strength-up resistance training

&lt;p&gt;The objective of this study is to investigate the effects of six weeks of high-intensity resistance training on the power output of 14 university basketball players. The subjects were randomly divided into two groups: a hypertrophy-oriented group (bulk-up) and a neuromuscular improvement oriented-group (strength-up). The bulk-up group performed three sets of squat exercises at 75% of 1RM with 10 repetitions and 1-minute rest period between sets. The strength-up group performed six sets of squat exercises at 90% of 1RM with four repetitions and 3-minute rest period between sets. Both groups performed the squat exercises twice a week over a period of six weeks. The one repetition maximum (1RM) and muscle power of the squat were measured before training (0-wk), after three weeks of training (3-wk), and after six weeks of training (6-wk). The thigh circumference of each subject was measured at 0-wk and 6-wk. It is found that the 1RM of the squat increases significantly after the training period for both groups, and the rate of improvement does not differ between the groups at 6-wk (bulk-up group: 13.1 ± 9.3%, strength-up group: 12.6 ± 6.3%). It is also found that there is a significant increase in the thigh circumference (p &amp;lt; 0.01) in the left leg for the bulk-up group. In contrast, there is a significant increase in the peak muscle power (POWmax) (p &amp;lt; 0.05) for the strength-up group. The rate of increase for POWmax is different even after three weeks of training (bulk-up group: -4.5 ± 9.6%, strength-up group: 13.9 ± 13.6%). The results suggest that the effects of resistance training on the power output and thigh circumference vary according to the training programme even if the total work load remains the same. It is recommended that strength-up resistance training is implemented to increase muscle power. &lt;/p&gt;

Comparison of Two-Hand Kettlebell Exercise and Graded Treadmill Walking

Prevailing interest in the use of kettlebell (KB) exercises for rehabilitation and improvement of muscular strength has led to several recent studies, some suggesting that KB exercise may be useful for improvement of cardiorespiratory fitness. The purpose of this study was to determine whether KB exercise would produce similar cardiovascular stress to that of walking and thus provide an additional exercise mode for the improvement of cardiorespiratory fitness. It was hypothesized that a moderate-intensity, continuous KB protocol, would produce similar metabolic and cardiorespiratory responses as a brisk bout of graded treadmill (TM) walking, but greater rating of perceived exertion (RPE). Ten novice volunteers (5 men, 5 women) completed a preliminary session to determine body composition and VO2max and to familiarize participants with standardized KB exercise technique. Subsequently, they completed a 30-minute KB session that included 3 continuous 10-minute sets of 10 KB swings followed by 10 sumo deadlifts, with 3-minute rests between 10-minute exercise periods. The third session was a 30-minute TM regimen that began at the walking speed and 4% grade that matched the VO2 from the KB session and included 3-minute rest intervals after 10-minute TM exercise periods. VO2, respiratory exchange ratio, kcal·min, and blood pressure were similar for KB and moderate-intensity TM exercise, but RPE and heart rate were greater during KB exercise. Data indicate that a KB routine consisting of 2-hand swings and sumo deadlifts with 3-minute rest periods produces similar metabolic responses to those of a moderate-intensity TM walking protocol designed for the improvement of aerobic fitness.

The influence of firefighter boot type on balance

A firefighter's boots play a critical role in working effectiveness and personal safety. OSHA 1910.156 contains standards for personal protective equipment of fire brigades. Firefighters use either rubber or leather boots that meet these requirements. The purpose of the study was to examine the differences in balance in professional firefighters wearing rubber and leather boots when participating in a fire simulation activity. Twelve professional firefighters performed 2 sets of a three-minute simulated firefighter stair climb wearing a 50 lb weighted vest to simulate their typical personal protective equipment and two 5.68 kg weights on the shoulders to simulate the weight of a high-rise pack (hose bundle). On each condition day (leather, rubber) the firefighter conducted a balance assessment. Following the initial balance protocol, the firefighter conducted a Simulated Firefighter Stair Climb for 3 min at a rate of 60 steps per/min. At the completion of the stair climb, the firefighter repeated the balance procedure. Following a 3-minute rest period, the complete procedure (balance, stair climb) was repeated. A total of 3 balance procedures and 2 stair climbs were completed. Significant differences were found in sway velocity between the pre and post test measures and among the two different boots. These results suggest that the rubber boots elicit greater postural instability. These findings provide practical information on work practices and PPE usage decisions. Relevance to industryIndustry standards dictate the protective variables of boots used by fire brigades, but do not consider the influence on gait and balance. This study provides evidence that the rubber boots used by firefighters may impair specific balance parameters which are critical for firefighter safety.

Eccentric training for shoulder abductors improves pain, function and isokinetic performance in subjects with shoulder impingement syndrome: a case series

Conservative treatments have been proposed for people with shoulder impingement syndrome (SIS), such as strengthening of the rotator cuff and scapular muscles and stretching of the soft tissues of the shoulder. However, there is a lack of studies analyzing the effectiveness of eccentric training in the treatment of SIS. To evaluate the effects of eccentric training for shoulder abductors on pain, function, and isokinetic performance during concentric and eccentric abduction of the shoulder in subjects with SIS. Twenty subjects (7 females, 34.2 SD 10.2 years, 1.7 SD 0.1 m, 78.0 SD 16.3 kg) with unilateral SIS completed the study protocol. Bilateral isokinetic eccentric training at 60º/s for shoulder abductors was performed for six consecutive weeks, twice a week, on alternate days. For each training day, three sets of 10 repetitions were performed with a 3-minute rest period between the sets for each side. The range of motion trained was 60° (ranging from 80° to 20°). The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire was used to evaluate functional status and symptoms of the upper limbs. Peak torque, total work and acceleration time were measured during concentric and eccentric abduction of the arm at 60º/s and 180º/s using an isokinetic dynamometer. DASH scores, peak torque, total work and acceleration time improved (p<0.05) after the period of intervention. This study suggests that isokinetic eccentric training for shoulder abductors improves physical function of the upper limbs in subjects with SIS.

Salivary Hormone and Immune Responses to Three Resistance Exercise Schemes in Elite Female Athletes

This study examined the salivary hormone and immune responses of elite female athletes to 3 different resistance exercise schemes. Fourteen female basketball players each performed an endurance scheme (ES-4 sets of 12 reps, 60% of 1 repetition maximum (1RM) load, 1-minute rest periods), a strength-hypertrophy scheme (SHS-1 set of 5RM, 1 set of 4RM, 1 set of 3RM, 1 set of 2RM, and 1set of 1RM with 3-minute rest periods, followed by 3 sets of 10RM with 2-minute rest periods) and a power scheme (PS-3 sets of 10 reps, 50% 1RM load, 3-minute rest periods) using the same exercises (bench press, squat, and biceps curl). Saliva samples were collected at 07:30 hours, pre-exercise (Pre) at 09:30 hours, postexercise (Post), and at 17:30 hours. Matching samples were also taken on a nonexercising control day. The samples were analyzed for testosterone, cortisol (C), and immunoglobulin A concentrations. The total volume of load lifted differed among the 3 schemes (SHS > ES > PS, p < 0.05). Postexercise C concentrations increased after all schemes, compared to control values (p < 0.05). In the SHS, the postexercise C response was also greater than pre-exercise data (p < 0.05). The current findings confirm that high-volume resistance exercise schemes can stimulate greater C secretion because of higher metabolic demand. In terms of practical applications, acute changes in C may be used to evaluate the metabolic demands of different resistance exercise schemes, or as a tool for monitoring training strain.

Acute Salivary Hormone Responses to Complex Exercise Bouts

The combination of resistance and plyometric training, or complex training, may yield greater functional gains than either method alone. As steroid hormones respond to exercise stimuli and modulate the functional outcomes, it is possible that complex training creates an enhanced anabolic physiological milieu for adaptation. We investigated acute responses of salivary testosterone and cortisol to complex exercise bouts. After a standardized warm-up, 16 semiprofessional rugby players performed 1 of 4 exercise bouts in a cross-over manner: power-power; power-strength; strength-power; or strength-strength. Each player completed each of the 4 bouts twice over a 4-week period in a balanced random order such that each player performed a total of 8 bouts. The power block consisted of 3 sets of 3 repetitions of jump squat exercise at 50% of 1-repetition maximum load. The strength block consisted of three sets of three repetitions of box squat exercise at a 3-repetition maximum load. There were 3-minute rest periods between sets and 4-minute rest periods between exercise blocks. Saliva was sampled before, during, and immediately after the exercise bout. The greatest overall hormonal responses were a small increase in testosterone (13%; 90% confidence limits ± 7%) and a trivial increase in cortisol (27%; ± 30%) after the strength-power bout. A clear difference was observed between the strength-power and the power-power bouts immediately after exercise for testosterone (10%; ± 8%) and cortisol (29%; ± 17%). The preceding exercise block had little effect on subsequent strength and power performance. The hormonal response after the strength-power bout suggests that this exercise sequence provides an enhanced anabolic milieu for adaptation.

Comparison of Methods to Quantify Volume During Resistance Exercise

The purpose of this investigation was to compare 4 different methods of calculating volume when comparing resistance exercise protocols of varying intensities. Ten Appalachian State University students experienced in resistance exercise completed 3 different resistance exercise protocols on different days using a randomized, crossover design, with 1 week of rest between each protocol. The protocols included 1) hypertrophy: 4 sets of 10 repetitions in the squat at 75% of a 1-repetition maximum (1RM) (90-second rest periods); 2) strength: 11 sets of 3 repetitions at 90% 1RM (5-minute rest periods); and 3) power: 8 sets of 6 repetitions of jump squats at 0% 1RM (3-minute rest periods). The volume of resistance exercise completed during each protocol was determined with 4 different methods: 1) volume load (VL) (repetitions [no.] x external load [kg]); 2) maximum dynamic strength volume load (MDSVL) (repetitions [no.] x [body mass--shank mass (kg) + external load (kg)]); 3) time under tension (TUT) (eccentric time +milliseconds] + concentric time +milliseconds]); and 4) total work (TW) (force [N] x displacement [m]). The volumes differed significantly (p , 0.05) between hypertrophy and strength in comparison with the power protocol when VL and MDSVL were used to determine the volume of resistance exercise completed. Furthermore, significant differences in TUT existed between all 3 resistance exercise protocols. The TW calculated was not significantly different between the 3 protocols. These data imply that each method examined results in substantially different values when comparing various resistance exercise protocols involving different levels of intensity.

The Contribution of Volume, Technique, and Load to Single-Repetition and Total-Repetition Kinematics and Kinetics in Response to Three Loading Schemes

This study examined the effect of volume, technique, and load upon single-repetition and total-repetition kinematics and kinetics during three loading schemes. Eleven recreationally trained males each performed a power (8 sets of 6 repetitions at 45% of one-repetition maximum [1RM], 3-minute rest periods, explosive and ballistic movements), hypertrophy (10 sets of 10 repetitions at 75% 1RM, 2-minute rest periods, controlled movements), and maximal strength (6 sets of 4 repetitions at 88% 1RM, 4-minute rest periods, explosive intent) scheme involving squats. Examination of repetition data showed that load intensity (% 1RM) generally had a direct effect on forces, contraction times, impulses, and work (i.e., increasing with load), whereas power varied across loads (p < 0.001). However, total-repetition forces, contraction times, impulses, work, and power were all greater in the hypertrophy scheme (p < 0.001), because of the greater number of repetitions performed (volume) as well as lifting technique. No differences in total forces were found between the equal-volume power and maximal strength schemes, but the former did produce greater total contraction times, work, and power (p < 0.001), which may also be attributed to repetition and technique differences. Total impulses were the only variable greater in the maximal strength scheme (p < 0.001). Thus, the interaction of load, volume, and technique plays an important role in determining the mechanical responses (stimuli) afforded by these workouts. These findings may explain disparities cited within research, regarding the effectiveness of different loading strategies for hypertrophy, maximal strength, and power adaptation.

The Salivary Testosterone and Cortisol Response to Three Loading Schemes

This aim of this study was to examine the free hormone (in saliva) responses to squat workouts performed by recreationally weight-trained males, using either a power (8 sets of 6 reps, 45% 1 repetition maximum [1RM], 3-minute rest periods, ballistic movements), hypertrophy (10 sets of 10 reps, 75% 1RM, 2-minute rest periods, controlled movements), or maximal strength scheme (6 sets of 4 reps, 88% 1RM, 4-minute rest periods, explosive intent). To determine the relative importance of the different training variables, these schemes were equated by workout duration with the power and strength schemes also equated by load volume. Salivary testosterone (T) and cortisol (C) both increased following the hypertrophy scheme (P < 0.05), with little to no hormonal change across the power and maximal strength schemes (P > 0.05). In general, the postexercise T and C responses to the hypertrophy scheme exceeded the other two schemes (P < 0.05). The greater volume of load lifted in the hypertrophy protocol over the same workout duration may explain the endocrine differences observed. The similar T and C responses to the power and maximal strength schemes (of equal volume) support such a view and suggest that differences in load intensity, rest periods, and technique are secondary to volume. Because the acute hormonal responses to resistance exercise contribute to protein metabolism, then load volume may be the most important workout variable activating the endocrine system and stimulating muscle growth.

Effect of Two Different Rest Period Lengths on the Number of Repetitions Performed During Resistance Training

The purpose of this study was to compare the effects of 2 different rest period lengths during a resistance training session with the number of repetitions completed per set of each exercise, the volume completed over 3 sets of each exercise, and the total volume during a training session. Fourteen experienced, weight-trained men volunteered to participate in the study. All subjects completed 2 experimental training sessions. Both sessions consisted of 3 sets of 8 repetitions with an 8 repetition maximum resistance of 6 upper body exercises performed in a set manner (wide grip lat pull-down, close grip pull-down, machine seated row, barbell row lying on a bench, dumbbell seated arm curl, and machine seated arm curl). The 2 experimental sessions differed only in the length of the rest period between sets and exercises: 1 session with a 1-minute and the other with a 3-minute rest period. For all exercises, results demonstrate a significantly lower total number of repetitions for all 3 sets of an exercise when 1-minute rest periods were used (p < or = 0.05). The 3- and 1-minute protocols both resulted in a significant decrease from set 1 to set 3 in 4 of the 6 exercises (p < or = 0.05), whereas the 1-minute protocol also demonstrated a significant decrease from set 1 to set 2 in 2 of the 6 exercises (p < or = 0.05). The results indicate that, during a resistance training session composed of all upper body exercises, 1-minute rest periods result in a decrease in the total number of repetitions performed compared with 3-minute rest periods between sets and exercises.

Effect of Potentiation and Stretching on Maximal Force, Rate of Force Development, and Range of Motion

The purpose of this investigation was to compare the effects of stretching vs. potentiation on subsequent maximal force and rate of force development capabilities of subjects in an isometric squat. Ten male collegiate athletes participated as subjects in this study. Subjects were tested during 3 separate sessions that involved joint range of motion (ROM) measurements of the lower body and isometric squat trials on a force plate to determine peak force (PF) and rate of force development (RFD) values. One testing session was preceded by 10 minutes of quiet sitting (C), 1 by a 30-minute lower-body stretching protocol (S), and 1 by 3 sets of a leg press exercise using 90% of the subjects' previously determined 1 repetition maximum (P). Three repetitions were performed for each set of the leg press, with a 3-minute rest period between each set. PF during the isometric squat was not significantly different following any of the 3 conditions (C: 100.0 +/- 0.0%, S: 101.2 +/- 6.5%, P: 98.6 +/- 6.2%). However, RFD was significantly lower in P (87.5 +/- 12.8%) compared with both C (100.0 +/- 0.0%) and S (102.6 +/- 18.5%). Significant improvement in ROM occurred only following P. It appears the potentiation protocol used in the current investigation may actually have had fatiguing effects instead of potentiating effects, but it did result in significant increases in ROM.