Increasing Meal Frequency in Isoenergetic Conditions Does Not Affect Body Composition Change and Appetite During Weight Gain in Japanese Athletes.

For athletes to gain body mass, especially muscle, an increase in energy consumption is necessary. To increase their energy intake, many athletes consume more meals, including supplementary meals or snacks. However, the influence of meal frequency on changes in body composition and appetite is unclear. The aim of this study was to determine the effect of meal frequency on changes in body composition and appetite during weight gain in athletes through a well-controlled dietary intervention. Ten male collegiate rowers with weight gain goals were included in this study. The subjects were randomly classified into two groups, and dietary intervention was implemented using a crossover method. During the intervention period, all subjects were provided identical meals aimed to provide a positive energy balance. The meals were consumed at a frequency of either three times (regular frequency) or six times (high frequency) a day. Body composition was measured using dual energy X-ray absorptiometry, and the visual analog scale was used for the evaluation of appetite. In both trials, body weight, fat-free mass, and fat mass significantly increased; however, an interaction (Trial × Time) was not observed. Visual analog scale did not vary between trials. Our data suggest that partitioning identical excess dietary intakes over three or six meals does not influence changes in body composition or appetite during weight gain in athletes.

High cardiovascular reactivity and muscle strength attenuate hypotensive effects of isometric handgrip training in young women: A randomized controlled trial.

OBJECTIVE: Isometric resistance training may reduce resting blood pressure (BP); however, the magnitude of this effect varies among individual subjects and few studies attempted to predict it. This study aimed to investigate the potential hypotensive effects of isometric training and their association with cardiovascular reactivity to acute isometric exercise and muscle strength in young women. METHODS: In this randomized trial, twenty young women were randomly assigned to either the training (n = 10) or control (n = 10) group. Women from the training group performed unilateral isometric handgrip sessions for 8 weeks (4 × 2 min at 25% of maximal voluntary contraction [MVC]; 3 days/week). Cardiovascular reactivity to acute isometric exercise and MVC were measured at baseline. Resting BP was assessed during and after the intervention. RESULTS: Resting systolic BP significantly lowered only in the training group. The change in resting systolic BP following an 8-week intervention was significantly associated with the systolic BP and diastolic BP reactivity to the acute exercise at baseline during set 3 and 4 (P <.05). The handgrip MVC was associated with changes in systolic BP (r = 0.79, P =.007), diastolic BP (r = 0.68, P =.032), and mean arterial pressure (r = 0.79, P =.006). These results indicated that high cardiovascular reactivity and strength attenuate the hypotensive effects following isometric training in young women. CONCLUSIONS: The hypotensive effects following isometric training may be identified by BP reactivity to acute isometric exercise or handgrip strength in young women.

The effect of endurance training on resting oxygen stores in muscle evaluated by near infrared continuous wave spectroscopy.

The purpose of this study was to examine the effects of endurance training (ET) on resting oxygen store (r-O(2)mus) using near infrared continuous wave spectroscopy (NIR(CWS)), and the validity of using this method for the evaluation of resting muscle oxygen consumption (r-VO(2)mus) in a training study. Ten female subjects were tested in the following study. All subjects were physically active, but did not participate in any regular training besides this study. The subjects were fully informed of the risks and gave their consent before the start of the experiments. For ET subjects cycled for 40 min at 60-70% VO(2)peak, three times a week, for 4 weeks. Before and after the period of ET, VO(2)peak and r-O(2)mus for the vastus lateralis muscle were measured. r-O(2)mus was defined as the amount of O(2) consumed by the muscle, which was determined from r-VO(2)mus measured by NIR(CWS) (HEO200, Omron) during arterial occlusion induced by a pneumatic tourniquet. In order to verify the measurements using NIR(CWS), oxygen consumption for both the whole body (40%-VO(2)) and vastus lateralis muscle (40%-VO(2)mus) were measured at pre and post ET. 40%-VO(2)mus was calculated from the ratio of the declining rates of Hb/MbO(2) immediately post-exercise and during rest (r-VO(2)mus). As a result, VO(2)peak significantly increased after ET. r-O(2)mus also significantly increased (p < 0.05). Neither 40%-VO(2) nor 40%-VO(2)mus changed following ET. Therefore these findings suggest the increase in r-O(2)mus calculated from r-VO(2)mus reflects an increase in resting oxygen stores in the trained muscle. Under the condition when resting muscle oxygen consumption is unchanged, NIR(CWS) can be a useful non-invasive tool for measuring muscle oxygen stores.

Muscle oxidative metabolism accelerates with mild acidosis during incremental intermittent isometric plantar flexion exercise.

BACKGROUND: It has been thought that intramuscular ADP and phosphocreatine (PCr) concentrations are important regulators of mitochondorial respiration. There is a threshold work rate or metabolic rate for cellular acidosis, and the decrease in muscle PCr is accelerated with drop in pH during incremental exercise. We tested the hypothesis that increase in muscle oxygen consumption (o2mus) is accelerated with rapid decrease in PCr (concomitant increase in ADP) in muscles with drop in pH occurs during incremental plantar flexion exercise. METHODS: Five male subjects performed a repetitive intermittent isometric plantar flexion exercise (6-s contraction/4-s relaxation). Exercise intensity was raised every 1 min by 10% maximal voluntary contraction (MVC), starting at 10% MVC until exhaustion. The measurement site was at the medial head of the gastrocnemius muscle. Changes in muscle PCr, inorganic phosphate (Pi), ADP, and pH were measured by 31P-magnetic resonance spectroscopy. o2mus was determined from the rate of decrease in oxygenated hemoglobin and/or myoglobin using near-infrared continuous wave spectroscopy under transient arterial occlusion. Electromyogram (EMG) was also recorded. Pulmonary oxygen uptake (o2pul ) was measured by the breath-by-breath gas analysis. RESULTS: EMG amplitude increased as exercise intensity progressed. In contrast, muscle PCr, ADP, o2mus, and o2pul did not change appreciably below 40% MVC, whereas above 40% MVC muscle PCr decreased, and ADP, o2mus, and o2pul increased as exercise intensity progressed, and above 70% MVC, changes in muscle PCr, ADP, o2mus, and o2pul accelerated with the decrease in muscle pH (~6.78). The kinetics of muscle PCr, ADP, o2mus, and o2pul were similar, and there was a close correlation between each pair of parameters (r = 0.969~0.983, p < 0.001). CONCLUSION: With decrease in pH muscle oxidative metabolism accelerated and changes in intramuscular PCr and ADP accelerated during incremental intermittent isometric plantar flexion exercise. These results suggest that rapid changes in muscle PCr and/or ADP with mild acidosis stimulate accelerative muscle oxidative metabolism.

Post-exercise hyperemia after ischemic and non-ischemic isometric handgrip exercise.

Post-exercise related time course of muscle oxygenation during recovery provides valuable information on peripheral vascular disease. The purpose of the present study was to examine post-exercise hyperemia (forearm blood flow; FBF, Doppler ultrasound) assessed by peak FBF, excess FBF and the time constant for FBF (FBF(Tc)) following isometric handgrip exercise (IHE). Post-exercise hyperemia was assessed in an ischemic and non-ischemic state at different exercise intensities and durations. Peak FBF and excess FBF were defined as the maximum FBF during recovery, and the total amount of FBF volume, respectively. FBF(Tc) represents the time to reach approximately 37% of the change in FBF between peak FBF and resting FBF (delta peak FBF). Ten subjects performed IHE at "10% and 30% maximum voluntary contraction (MVC)" for 2 min with or without arterial occlusion (AO), followed by 2 min of AO alone (Study I). In Study II, six subjects performed 30%MVC-IHE with AO for "100%, 66%, 33% and 10% of the exhausted exercise duration" (time to exhaustion). In Study I, although peak FBF and excess FBF were significantly higher in ischemic than non-ischemic IHE for both 10% and 30%MVC (p<0.05), FBF(Tc) was similar in the ischemic and non-ischemic conditions. The peak FBF, excess FBF and FBF(Tc) were all significantly higher at 30% than at 10%MVC (p<0.05). In Study II, the peak FBF and excess FBF increased linearly compared to the absolute and relative exercise durations for ischemic IHE. FBF(Tc) increased exponentially when compared to the absolute and relative exercise durations. These data suggest the ischemic exercise has a larger hyperemic response compared to the non-ischemic exercise. In conclusion, the peak FBF, excess FBF and FBF(Tc) seen during post-exercise hyperemia are closely correlated with exercise intensity and duration, not only in non-ischemic, but also in the ischemic exercise. In combination with the ischemic exercise, these parameters could potentially prove to be valuable indicators of peripheral vascular disease.

Muscle oxygen consumption at onset of exercise by near infrared spectroscopy in humans.

In this study, we tried to continuously measure muscle oxygen consumption (m-VO2) by near infrared spectroscopy (NIRS) without arterial occlusions. We used an intermittent isometric exercise at high intensity, which elicits a spontaneous occlusion of the blood flow to the muscle due to an increase in intramuscular pressure. Changes in muscle oxygenation and phosphocreatine (PCr) concentration were monitored in 5 subjects during an intermittent isometric exercise (5 sec. contraction/5 sec. relaxation) at 50% of maximum voluntary contraction for 3 minutes. The rate of deoxygenation was measured from the 2nd sec. to the 3rd sec. of each muscle contraction. The rate of deoxygenation at the onset of exercise followed an exponential time course with a time constant of 42.0 +/- 12.5 sec. (mean +/- SD). This value agreed with the time constant of the decrease in PCr (48.2 +/- 10.2 sec.). This result suggests that m-VO2 was successfully monitored with a time resolution of 10 sec. by NIRS during exercise without arterial occlusion.

Muscle reoxygenation rate after isometric exercise at various intensities in relation to muscle oxidative capacity.

The purpose of this study was to determine whether the reoxygenation rate (Reoxy-rate) immediately after static exercise at various submaximal intensities would be related to muscle oxidative capacity. Seven healthy male subjects performed isometric handgrip exercise for 10 sec at 30%, 60% and 90% of maximal voluntary contraction (MVC). The Reoxy-rate and muscle oxygen consumption during exercise (muscle VO2EX) were monitored by near infrared continuous wave spectroscopy (NIRcws). The muscle oxidative capacity was evaluated by the time constant for phosphocreatine resynthesis (PCrTc) using 31-phosphorus magnetic resonance spectroscopy (31P-MRS). The Peak blood flow of brachial artery after exercise (BABFpeak) was measured using Doppler ultrasound. There was no correlation between PCrTc and Reoxy-rate at 30% and 60% MVC. In contrast, Reoxy-rate at 90% MVC was positively correlated to PCrTC (r = 0.825, p < 0.05). The muscle VO2EX increased 5.9, 8.8 and 12.6-fold of the resting on average at 30%, 60% and 90% MVC, respectively, and the muscle VO2EX at 90% MVC was significantly higher than that at 30% and 60% MVC. On the other hand, BABFpeak increased only just 1.9, 2.4 and 2.7-fold of the resting on average at 30%, 60% and 90% MVC, respectively (Fig. 4). These results suggest that the higher oxidative capacity muscle shows slower muscle reoxygenation after 10 sec isometric exercise at 90% MVC because the Reoxy-rate after this type of exercise may be influenced more by muscle VO2 than by O2 supply. In contrast, 60% MVC and lower exercise intensities may not be severe enough to influence the muscle VO2 dependent Reoxy-rate.

Creatine supplementation enhances anaerobic ATP synthesis during a single 10 sec maximal handgrip exercise.

Forearm muscles of twelve healthy male subjects (age = 22.3 +/- 1.1 years (mean +/- S.E.)) were examined during a 10 sec maximal dynamic handgrip exercise (Ex10) using 31-phosphorus magnetic resonance spectroscopy before and after ingestion with 30 g creatine (Cr) monohydrate or placebo per day for 14 days. Cr supplementation produced a 11.5 +/- 4.6% increase in the resting muscle phosphocreatine (PCr) concentration and a 65.0 +/- 4.2% increase in the PCr degradation during Ex10. ATP synthesis rate through PCr hydrolysis and total anaerobic ATP synthesis rate during Ex10 increased from 0.64 +/- 0.08 (pre-value) to 0.86 +/- 0.14 mmol/kg ww/sec (post-value, p < 0.05) and from 0.97 +/- 0.16 (pre-value) to 1.33 +/- 0.27 mmol/kg ww/sec (post-value, p < 0.05), respectively. An increase in total anaerobic ATP synthesis during Ex10 after Cr supplementation positively correlated with the increase in ATP synthesis through PCr hydrolysis. Cr supplementation produced a 15.1 +/- 3.8% increase in the mean power output during Ex10. There was no significant difference in the mean power output per unit of total anaerobic ATP synthesis during Ex10 between before and after Cr supplementation. ATP synthesis rate through PCr hydrolysis positively correlated with mean power output during Ex10 in all twelve subjects after treatment (r = 0.58, p < 0.05). The results suggest that Cr supplementation enhanced PCr degradation during Ex10. It is strongly indicated that an improvement in performance during Ex10 was associated with the increased PCr availability for the synthesis of ATP.

Delayed reoxygenation after maximal isometric handgrip exercise in high oxidative capacity muscle.

We hypothesized that after maximal short-term isometric exercise, when O(2) demand is still high and O(2) supply is not fully activated, higher oxidative capacity muscle may exhibit slower muscle reoxygenation after the exercise than low oxidative capacity muscle. Seven healthy male subjects performed a maximal voluntary isometric handgrip exercise for 10 s. The reoxygenation rate after the exercise (Reoxy-rate) in the finger flexor muscle was determined by near infrared continuous wave spectroscopy (NIRcws) while phosphocreatine (PCr) was measured simultaneously by (31)P magnetic resonance spectroscopy. Muscle oxygen consumption (muscle VO(2)) and muscle oxidative capacity were evaluated using the rate of PCr resynthesis post-exercise. The forearm blood flow (FBF) index at the end of exercise was measured using NIRcws. There was a significant positive correlation between the Reoxy-rate, which ranged between 0.53% s(-1) and 12.47% s(-1), and the time constant for PCr resynthesis, which ranged between 17.8 s and 38.3 s (r(2)=0.939, P<0.001). At the end of the exercise, muscle VO(2) exceeded the resting level by approximately 25-fold, while the FBF index exceeded the resting level by only 3-fold on average. The Reoxy-rate closely correlated with muscle VO(2) (r(2)=0.727, P<0.05), but not with the FBF index. Also, the estimated O(2) balance (muscle VO(2) index/FBF index) was negatively correlated with the Reoxy-rate (r(2)=0.820, P<0.001). These results support our hypothesis that higher oxidative capacity muscle shows slower muscle reoxygenation after maximal short-term isometric exercise because the Reoxy-rate after this type of exercise may be influenced more by muscle VO(2) than by O(2) supply.

Oxygenation in vastus lateralis and lateral head of gastrocnemius during treadmill walking and running in humans.

The purposes of this study were to compare the deoxygenation patterns of the vastus lateralis (VL) and the lateral head of gastrocnemius (GL) and examine the relationship between the muscle oxygenation level and pulmonary oxygen uptake (VO(2)) during graded treadmill exercise. Changes in oxygenation in each muscle were measured using near infrared spectroscopy (NIRS). Eight healthy male subjects participated in this study. Two NIRS probes were placed on VL and GL, and thereafter the leg arteries were occluded in all subjects to enable normalization of the NIR signals. The subjects then walked at 4 km x h(-1) and 6 km x h(-1), and then ran continuously at speeds ranging from 8 km x h(-1) to 16 km x h(-1). The muscle oxygenation level was defined as being 100% at rest and 0% at its lowest value during occlusion. Pulmonary VO(2) was measured using indirect calorimetry. After the subjects had started walking, the muscle oxygenation in VL increased and exceeded the level at rest. Thereafter, the muscle oxygenation in both muscles decreased in relation to the increase in speed (P < 0.001). A significant difference in the level of muscle oxygenation between VL and GL was found at speeds of 10 km x h(-1) and 12 km x h(-1) (P < 0.05). The muscle oxygenation level at 16 km x h(-1) was [mean (SEM)] 51.9 (4.6)% in VL and 52.8 (3.6)% in GL. There was a negative relationship between pulmonary VO(2) and the muscle oxygenation level (VL: r=-0.803 to -0.986; GL: r=-0.848 to -0.963, P < 0.05). We concluded that the pattern of deoxygenation between VL and GL was somewhat different and that the muscle oxygenation level was associated with pulmonary VO(2).