The effects of the load mass and load position on body sway in supporting a load on the back

We examined the effects of a load's mass and position on body sway during standing with a load on the back. Three healthy male subjects participated in this experiment. The subjects supported loads of 23kg, 33kg, and 43kg on their backs using a carrier frame. They were asked to stand for 75s on a force platform with their eyes open while being as quiet as possible. Time series data of center-of-pressure (COP) were collected at a sampling rate of 50Hz during the last 60s of the 75s standing period. The COP was measured under three conditions in terms of the load position on the frame: lower (close to the hip), middle, and upper (close to the shoulder). All subjects showed that the lower the position of the load, the more anteriorly the mean COP coordinate was located in the anteroposterior (AP) direction, and the smaller the total distance of the COP trajectories became. Regarding carrying the heavier loads, each subject showed a specific tendency in the mean AP coordinate. The three subjects had different physical characteristics in terms of body height and experience at carrying heavy loads. These results suggest that the examintion of the COP in a static posture can help our understanding of individual information on the posture supporting loads and the general positioning of the body.     

Influence of training and maturity status on the cardiopulmonary responses to ramp incremental cycle and upper body exercise in girls

It has been suggested that the potential for training to alter the physiological responses to exercise in children is related to a "maturational threshold". To address this, we investigated the interaction of swim-training status and maturity on cardiovascular and metabolic responses to lower and upper body exercise. Twenty-one prepubertal [Pre: 11 trained (T), 10 untrained (UT)], 30 pubertal (Pub: 14 T, 16 UT), and 18 postpubertal (Post: 8 T, 10 UT) girls completed ramp incremental exercise on a cycle and an upper body ergometer. In addition to pulmonary gas exchange measurements, stroke volume and cardiac output were estimated by thoracic bioelectrical impedance, and muscle oxygenation status was assessed using near-infrared spectroscopy. All T girls had a higher peak O(2) uptake during cycle (Pre: T 49 ± 5 vs. UT 40 ± 4; Pub: T 46 ± 5 vs. UT 36 ± 4; Post: T 48 ± 5 vs. UT 39 ± 8 ml·kg(-1)·min(-1); all P < 0.05) and upper body exercise (Pre: T 37 ± 6 vs. UT 32 ± 5; Pub: T 36 ± 5 vs. UT 28 ± 5; Post: T 39 ± 3 vs. UT 28 ± 7 ml·kg(-1)·min(-1); all P < 0.05). T girls also had a higher peak cardiac output during both modalities, and this reached significance in Pub (cycle: T 21 ± 3 vs. UT 18 ± 3; upper body: T 20 ± 4 vs. UT 15 ± 4 l/min; all P < 0.05) and Post girls (cycle: T 21 ± 4 vs. UT 17 ± 2; upper body: T 22 ± 3 vs. UT 18 ± 2 l/min; all P < 0.05). None of the measured pulmonary, cardiovascular, or metabolic parameters interacted with maturity, and the magnitude of the difference between T and UT girls was similar, irrespective of maturity stage. These results challenge the notion that differences in training status in young people are only evident once a maturational threshold has been exceeded.     

The effect of handgrip position on upper extremity neuromuscular responses to arm cranking exercise.

The purpose of this study was to determine if handgrip position during arm cranking exercise influences the neuromuscular activity of muscles biceps brachii (BB), lateral head of triceps brachii (TB), middle deltoid (DT), infraspinatus (IS) and brachioradialis (BR). Fifteen participants cranked an arm ergometer using three different handgrip positions (supinated, pronated, and neutral). Electromyographic (EMG) data were recorded from the aforementioned muscles, and relative duration of EMG activation and amplitude were quantified for the first and second 180 degrees of crank angle. EMG measures were analyzed with MANOVA and follow-up univariate procedures; alpha was set at 0.01. The relative durations of EMG activation did not differ between handgrip positions. Muscle IS exhibited 36% less amplitude in the supinated versus neutral handgrip position (second half-cycle), and muscle BR displayed 63% greater amplitude across cycles in the neutral versus supinated and pronated handgrip positions. The greater BR activity displayed in the neutral handgrip position may reflect its anatomical advantage as an elbow flexor when the forearm is in neutral position. Muscle IS exhibited less activity in the supinated position and may be clinically relevant if it allows arm cranking to occur without subsequent shoulder pain, which is often the aim of shoulder rehabilitation.     

Effect of training on treadmill performance,aerobic capacity,and body responses to acute cold exposure

An attempt was made to test the hypothesis that regular physical activity at the anaerobic threshold can stimulate an increase in the amount of brown or beige body fat, which can manifest itself in increased lactate utilization during exercise and increased reactivity in response to acute regional cooling. The methods used in the study included the ramp test; regional acute cold exposure; measurement of gas exchange; lactate and glucose in the blood; heart rate; heart rate, blood pressure, and respiration variability at rest and during standard functional tests; infrared thermal imaging; and statistical methods of analysis of results. Training of ten physically active volunteers (7 males and 3 females) on a treadmill at a speed corresponding to 75–80% of personal maximum oxygen consumption \(\left( {V_{O_{2\max } } } \right)\) for 30 min 3 times per week at a fixed ambient temperature of 21–22°C for 6 weeks resulted in a significant (from 19 to 39%) increase in exercise duration in the ramp test, whereas \(V_{O_{2\max } }\) changed, on average, only slightly. The increase in the anaerobic threshold power was associated with a sharp slowdown in the accumulation of lactate during the ramp test. The lactate utilization rate during the recovery period, on the contrary, increased. In general, work efficiency during test load significantly increased. Noticeable changes in the condition and responses to the standard functional tests of the autonomic system were not found, as judged by the heart rate variability, blood pressure, and respiration variability at rest and during orthostatic tests and imposed breathing rhythm. The functional response of the body to acute cold exposure (1-min cooling of the feet in ice water) did not change after a cycle of training, both in terms of metabolism (oxygen consumption, etc.) and the skin temperature dynamics in the areas of most probable location of brown adipose tissue (BAT). These data do not confirm our previous hypothesis (2010) about the function of BAT as a universal homeostatic instrument in the body. Probably, if the formation of the beige adipose tissue is stimulated by physical activity and hormone irisin, produced by muscles, this tissue is involved in lactate utilization but is not involved in the thermoregulatory responses.     

Monitoring the effects of training load changes on stress and recovery in swimmers

This study was designed to investigate if monitoring of stress and recovery may be useful to detect overreaching in its early stages and may be used to evaluate effects of changes in training load. Nine swimmers were applied the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) in four different occasions (M1, M2, M3, M4) along a 6-week training period prior to a competition. During the basal training period (M1), recovery scales scored higher than stress scales, being the scales General well-being, Social recovery and Being in shape those reaching higher scores. Following the measure corresponding to the second training period (M2), in which training volume reached a maximum, there were significant increases in two stress scales (Injury and Emotional exhaustion), and decreases in three recovery scales (Success, Physical recovery, and Self-efficacy). Values increased again and did not significantly differ from those corresponding to the first measure during measures M3 and M4, in which there was a decrease in training volume and training time. Only a recovery scale score (Success) increased significantly from period M2 to period M4. When the recovery-stress (total recovery - total stress) state was calculated, it was found that there was a significant decreases in M2, and values progressively increased in measures M3 and M4, with no significant difference from M1. Results obtained indicate that the RESTQ-Sport is able to show significant changes concurrently with training loads. Regular monitoring of stress and recovery by these measures may help to detect overreaching in its early stages.     

The acute effects of different training loads of whole body vibration on flexibility and explosive strength of lower limbs in divers

The purpose of this study was to examine the acute effects of different vibration loads (frequency and amplitude) of whole-body vibration (WBV) on flexibility and explosive strength of lower limbs in springboard divers. Eighteen male and female divers, aged 19 ± 2 years, volunteered to perform 3 different WBV protocols in the present study. To assess the vibration effect, flexibility and explosive strength of lower limbs were measured before (Pre), immediately after (Post 1) and 15 min after the end of vibration exposure (Post 15). Three protocols with different frequencies and amplitudes were used in the present study: a) low vibration frequency and amplitude (30 Hz/2 mm); b) high vibration frequency and amplitude (50 Hz/4 mm); c) a control protocol (no vibration). WBV protocols were performed on a Power Plate platform, whereas the no vibration divers performed the same protocol but with the vibration platform turned off. A two-way ANOVA 3 x 3 (protocol × time) with repeated measures on both factors was used. The level of significance was set at p < 0.05. Univariate analyses with simple contrasts across time were selected as post hoc tests. Intraclass coefficients (ICC) were used to assess the reliability across time. The results indicated that flexibility and explosive strength of lower limbs were significantly higher in both WBV protocols compared to the no vibration group (NVG). The greatest improvement in flexibility and explosive strength, which occurred immediately after vibration treatment, was maintained 15 min later in both WBV protocols, whereas NVG revealed a significant decrease 15 min later, in all examined strength parameters. In conclusion, a bout of WBV significantly increased flexibility and explosive strength in competitive divers compared with the NVG. Therefore, it is recommended to incorporate WBV as a method to increase flexibility and vertical jump height in sports where these parameters play an important role in the success outcome of these sports.     

The effects of breathing pattern training on ventilatory function in patients with COPD

The purpose of this study was to assess the effects of a particular breathing pattern training (BPT) on forced expiratory volume during the first second (FEV₁) and forced vital capacity (FVC) in patients with chronic obstructive pulmonary disease (COPD). The subjects adjusted each breath to a target breath displayed on a video screen, by using visual feedback. This target was chosen in an individual sample recorded at rest. We used a randomized, controlled group design. Twenty patients with stable COPD, FEV₁ less than 1.5 liters, undergoing a traditional rehabilitation program were randomly assigned to the BPT group or to the control group. Each BPT subject underwent 30–35 training sessions spread out over four weeks, in addition to the traditional program. FEV₁ and FVC were performed before and after this program. ANOVAs showed that FEV₁ and FVC significantly improved in BPT subjects, with a mean percent increase of 22% and 19%, respectively. Corresponding changes in controls were not significant. This study showed short-term increases in FEV₁ and FVC in COPD patients practicing BPT in addition to respiratory rehabilitation, in comparison with controls. Further studies should incorporate outcome data to clarify the mechanisms and the duration of this effect.The authors express their gratitude to Philippe Carrias, Elizabeth Maclet, Françoise Tulane, and Bernard Cossalter for their contribution to this study, as well as to Michèle Delaire for her technical assistance.     

The simulation effects of mountain climbing training on selected endocrine responses

The simulation effects of mountain climbing exercise training on plasma testosterone, cortisol and luteinizing hormone (LH) levels were examined in ten recreational mountain male climbers. Subjects underwent a simulating mountain climbing exercise training 3 times a week for a total of eight weeks before an expedition to Mount Muztag Ata (7546 m, Xingian, China). During training, each subject carried a 40 kg back pack while walking on a treadmill at a speed of 1.9 mph for 60 min at sea level. Subjects completed an incremental treadmill test to exhaustion prior to training, after training, and one week after returning from Mount Muztag Ata. Blood samples were collected from antecubital vein at rest and at 5, 60, and 120 min post testing to determine the plasma testosterone, cortisol and LH levels. The basal plasma testosterone and cortisol concentrations were lower in both post-training and after-climbing conditions compared with that in the pre-training condition (p<0.01). The basal plasma LH concentration was remained unchanged after training and after the mountain climbing compared with levels measured in the pre-training phase. No correlation could be established between plasma LH and testosterone level. These results suggest that an eight-week period of mountain climbing training protocol may be beneficial in maintaining normal endocrine function during and after high altitude mountain expedition. Our results also indicate the decrease of plasma testosterone was LH independent.     

Dissimilar effects of one- and three-set strength training on strength and muscle mass gains in upper and lower body in untrained subjects

The purpose of this study was to compare the effects of single- and multiple-set strength training on hypertrophy and strength gains in untrained men. Twenty-one young men were randomly assigned to either the 3L-1UB group (trained 3 sets in leg exercises and 1 set in upper-body exercises; n = 11), or the 1L-3UB (trained 1 set in leg exercises and 3 sets in upper-body exercises; n = 10). Subjects trained 3 days per week for 11 weeks and each workout consisted of 3 leg exercises and 5 upper-body exercises. Training intensity varied between 10 repetition maximum (RM) and 7RM. Strength (1RM) was tested in all leg and upper-body exercises and in 2 isokinetic tests before training, and after 3, 6, 9, and 11 weeks of training. Cross sectional area (CSA) of thigh muscles and the trapezius muscle and body composition measures were performed before training, and after 5 and 11 weeks of training. The increase in 1RM from week 0 to 11 in the lower-body exercises was significantly higher in the 3L-1UB group than in the 1L-3UB group (41 vs. 21%; p < 0.001), while no difference existed between groups in upper-body exercises. Peak torque in maximal isokinetic knee-extension and thigh CSA increased more in the 3L-1UB group than in the 1L-3UB group (16 vs. 8%; p = 0.03 and 11 vs. 7%; p = 0.01, respectively), while there was no significant difference between groups in upper trapezius muscle CSA. The results demonstrate that 3-set strength training is superior to 1-set strength training with regard to strength and muscle mass gains in the leg muscles, while no difference exists between 1- and 3-set training in upper-body muscles in untrained men.     

10周核心力量练习对男性中老年人平衡能力的影响

目的：探讨核心力量练习对中老年男性平衡能力的影响,为运动锻炼改善老年人平衡能力和降低跌倒风险提供依据。方法：选取16名50~60岁男性中老年人,随机分为试验组（核心力量练习）和对照组,每组8人。利用悬吊绳和瑜伽垫进行动、静态支撑与推拉练习以及徒手下肢力量等间歇性组合核心力量训练,共练习10周,每周4~5次,每次50~60 min。对照组保持原有生活习惯。锻炼前后测定受试者静态平衡和动态平衡等指标。结果：①锻炼后试验组闭眼单脚站立时间和动态平衡得分较锻炼前显著升高分别为（9.00±2.27） s、（10.63±1.69） s,P<0.01;（77.38±10.94）、（89.50±5.53）,P<0.01。②锻炼后试验组星形伸展平衡测试（SEBT）,右腿支撑时左腿在8个方向、左腿支撑时右腿在6个方向的SEBT值均较锻炼前显著增加（P<0.01）。结论：10周核心力量练习显著提高男性中老年人的动、静态平衡能力。     

Effect of fitness on arm vascular and metabolic responses to upper body exercise

We investigated arm perfusion and metabolism during upper body exercise. Eight average, fit subjects and seven rowers, mean +/- SE maximal oxygen uptake (VO2 max) 157 +/- 7 and 223 +/- 14 ml O2. kg(-0.73).min(-1), respectively, performed incremental arm cranking to exhaustion. Arm blood flow (ABF) was measured with thermodilution and arm muscle mass was estimated by dual-energy X-ray absorptiometry. During maximal arm cranking, pulmonary VO2 was approximately 45% higher in the rowers compared with the untrained subjects and peak ABF was 6.44 +/- 0.40 and 4.55 +/- 0.26 l/min, respectively (P < 0.05). The arm muscle mass for the rowers and the untrained subjects was 3.5 +/- 0.4 and 3.3 +/- 0.1 kg, i.e., arm perfusion was 1.9 +/- 0.2 and 1.4 +/- 0.1 l blood.kg(-1).min(-1), respectively (P < 0.05). The arteriovenous O2 difference was 156 +/- 7 and 120 +/- 8 ml/l, respectively, and arm VO2 was 0.98 +/- 0.08 and 0.60 +/- 0.04 l/min corresponding with 281 +/- 22 and 181 +/- 12 ml/kg, while arm O(2) diffusional conductance was 49.9 +/- 4.3 and 18.6 +/- 3.2 ml.min(-1).mmHg(-1), respectively (P < 0.05). Also, lactate release in the rowers was almost three times higher than in the untrained subjects (26.4 +/- 1.1 vs. 9.5 +/- 0.4 mmol/min, P < 0.05). The energy requirement of an approximately 50% larger arm work capacity after long-term arm endurance training is covered by an approximately 60% increase in aerobic metabolism and an almost tripling of the anaerobic capacity.     

Adrenocorticotropic hormone and corticosterone responses to acute hypoxia in the neonatal rat: effects of body temperature maintenance

The corticosterone response to acute hypoxia in neonatal rats develops in the 1st wk of life, with a shift from ACTH independence to ACTH dependence. Acute hypoxia also leads to hypothermia, which may be protective. There is little information about the endocrine effects of body temperature maintenance during periods of neonatal hypoxia. We hypothesized that prevention of hypothermia during neonatal hypoxia would augment the adrenocortical stress response. Rat pups separated from their dams were studied at postnatal days 2 and 8 (PD2 and PD8). In one group of pups, body temperature was allowed to spontaneously decrease during a 30-min prehypoxia period. Pups were then exposed to 8% O(2) for 3 h and allowed to become spontaneously hypothermic or externally warmed (via servo-controlled heat) to maintain isothermia. In another group, external warming was used to maintain isothermia during the prehypoxia period, and then hypoxia with or without isothermia was applied. Plasma ACTH and corticosterone and mRNA expression of genes for upstream proteins involved in the steroidogenic pathway were measured. Maintenance of isothermia during the prehypoxia period increased baseline plasma ACTH at both ages. Hypothermic hypoxia caused an increase in plasma corticosterone; this response was augmented by isothermia at PD2, when the response was ACTH-independent, and at PD8, when the response was ACTH-dependent. In PD8 rats, isothermia also augmented the plasma ACTH response to hypoxia. We conclude that maintenance of isothermia augments the adrenocortical response to acute hypoxia in the neonate. Prevention of hypothermia may increase the stress response during neonatal hypoxia, becoming more pronounced with increased age.     

The effects of arm crank training on the physiological responses to submaximal wheelchair ergometry

The purpose of this investigation was to examine the cardiovascular and metabolic effects of a 5 wk arm crank (AC) training program on submaximal wheelchair (WC) ergometry in able-bodied women. The 6 subjects in the training group (TG) and 4 in the control group (CG) performed a 10 min WC exercise prior to and following the training period at a power output (PO) that elicited 70% of the pre-training peak oxygen uptake (VO2). Steady state VO2, heart rate (HR), cardiac output (Qc) and stroke volume (Vs) were measured. Resting and post-exercise blood lactate concentrations (LA) were measured, the difference was recorded as net LA. The TG exercised on the AC 3 d.wk-1 at a PO that elicited 85% of each subject's recorded peak HR. Each session consisted of four 4 min exercise bouts preceded by a 2 min warm-up and interspersed with 2 min rest periods. After training, the TG had a significantly (p less than 0.05) lower HR, larger Vs and lower LA in response to the WC exercise. Qc and VO2 were not significantly altered. The results demonstrate that the AC exercise program used in this study produced a physiological training effect which was observed during submaximal WC exercise of an intensity frequently encountered during daily WC ambulation. It appears that short-term, moderate intensity AC training offers an adequate stimulus to reduce the stress imposed by wheelchair locomotion.     

A systematic review of the effects of physical training on load carriage performance

Soldiers are often required to carry heavy loads during military operations. This article reports on a systematic literature review examining the influence of physical training on load carriage performance. Several literature databases, reference lists, and other sources were explored to find studies that quantitatively examined the effects of physical training on the time taken for individuals to complete a set distance carrying an external load, with the majority of the load contained in a backpack. Effect sizes (Cohen's d statistic) were used in meta-analyses to examine the changes in load carriage performance after various modes of physical training. Effect sizes quantified training-related changes in terms of SD units. Ten original research studies met the review criteria. Meta-analysis indicated that large training effects (≥0.8SD units) were apparent when progressive resistance training was combined with aerobic training and when that training was conducted at least 3 times per week, over at least 4 weeks. When progressive load-carriage exercise was part of the training program, much larger training effects were evident (summary effect size [SES] = 1.7SD units). Field-based training that combined a wide variety of training modes and included progressive load-carriage exercise was also very effective in improving load carriage performance (SES = 1.1SD units). Aerobic training alone or resistance training alone had smaller and more variable effects, depending on the study. This review indicates that combinations of specific modes of physical training can substantially improve load carriage performance.     

The effects of defensive style and final game outcome on the external training load of professional basketball players

This study aimed to analyse the influence of different contextual factors (i.e., defensive style and game outcome) on basketball players’ external load during games-based drills using ultrawideband (UWB) technology. Fourteen male professional basketball players belonging to an elite reserve Spanish club (ACB) participated in this study. The games-based drills consisted of one bout of 10 min played 5vs5 in which players were instructed to use man-to-man defence (MMD) and/or zone defence (ZD). In addition, the final game outcome (i.e., winning or losing) of the game-based drill was registered. External load variables per minute were recorded: total distance covered, distance covered in different speed zones, distance covered while accelerating and decelerating, maximum speed, steps, jumps and player load. A two-way ANOVA with the Tukey post hoc test was used to assess the impact of defensive style and final game outcome and the interaction of both factors on the external load encountered by basketball players. No meaningful differences (unclear) were found in the external loads between playing with MMD and with ZD and between winning and losing teams except for greater distance at high-speed running (18.0–24.0 km·h^-1) in winning teams (p < 0.05, ES = 0.68, moderate). A significant interaction between defensive style and final game outcome was found for high decelerations (> -2 m·s^-2) (p = 0.041; ES = 0.70) and jumps (p = 0.037; ES = 0.68). These results could potentially help coaching staff in prescribing an appropriate workload during basketball-specific game-based drills, and ultimately enhance the match performance.     

Short-term effects of selected exercise and load in contrast training on vertical jump performance

The present study examined the short-term effects of loaded half squats (HSs) and loaded jump squats (JSs) with low and moderate loads on the squat jump (SJ) and the countermovement jump (CMJ) performance using a contrast training approach. Ten men (mean +/- SD age, 23 +/- 1.8 years) performed the HS and JS exercises twice with loads of 30% of 1 repetition maximum (1RM) (HS30% and JS30%, respectively) and 60% of 1RM (HS60% and JS60%, respectively). On each occasion, 3 sets of 5 repetitions with 3 minutes of rest were performed as fast as possible. Vertical jump performance was measured before exercise, 1 minute after each set, and at the fifth and 10th minutes of recovery. The CMJ increased significantly after the first and second set (3.9%; p < 0.05) compared with preexercise values following the JS30% protocol and 3.3% after the second and third sets of the JS60% protocol. Following the HS60% protocol, CMJ increased after the first and the second sets (3.6%; p < 0.05) compared with preexercise values, whereas SQ increased only after the first set (4.9%; p < 0.05) in this condition. These data show that contrast loading with the use of low and moderate loads can cause a short-term increase in CMJ performance. The applied loads do not seem to present different short-term effects after loaded JSs. When the classic form of dynamic HS exercise is performed, however, at least a moderate load (60% of 1RM) needs to be applied.