Muscle spindle feedback differs between the soleus and gastrocnemius in humans

The Hoffmann (H) reflex and motor (M) response were studied in soleus and gastrocnemius during voluntary contraction in eight male volunteers. Aims: To determine if the strength of spindle input to the muscles is the same. To assess if the M response size changes during contraction. Results: The size of the maximum M response (M max) changed during contraction in each subject. Hence, all H reflex measurements were normalized to the M max at each level of contraction for each subject. The largest H/M max was bigger in soleus than gastrocnemius at every contraction level. The overall largest H/M max for soleus (97%) and gastrocnemius (55%) were achieved at 40 and 100% maximum voluntary contraction (MVC), respectively. Conclusion: Soleus receives greater spindle feedback than the gastrocnemius both at rest and during voluntary contraction.     

Muscle spindle feedback differs between the soleus and gastrocnemius in humans

The Hoffmann (H) reflex and motor (M) response were studied in soleus and gastrocnemius during voluntary contraction in eight male volunteers. AIMS: To determine if the strength of spindle input to the muscles is the same. To assess if the M response size changes during contraction. RESULTS: The size of the maximum M response (M max) changed during contraction in each subject. Hence, all H reflex measurements were normalized to the M max at each level of contraction for each subject. The largest H/M max was bigger in soleus than gastrocnemius at every contraction level. The overall largest H/M max for soleus (97%) and gastrocnemius (55%) were achieved at 40 and 100% maximum voluntary contraction (MVC), respectively. CONCLUSION: Soleus receives greater spindle feedback than the gastrocnemius both at rest and during voluntary contraction.     

Characterization of the mechanical and neural components of spastic hypertonia with modified H reflex.

As the H reflex remains unable to assess mechanical changes intrinsic to a muscle, the aim of this study was to modify the H reflex techniques and to characterize the neural and mechanical components of muscle spasticity, relating the two components to clinical observations. Thirty-four patients featuring either a spinal-cord lesion (n=15) or stroke (n=19) and 23 neurologically normal subjects were recruited. Soleus H reflex and maximal M response (M(max)) were measured with electromyography and mechanomyography (MMG). The motoneuronal excitability was represented with the adjusted ratio of the H reflex to the M(max) (H/M(max)) and the ratio of the paired H reflexes (H(2)/H(1)). Muscle mechanical properties were characterized by the amplitude and median frequency of maximal M response recorded with MMG (MMG(Mmax)). The results showed that spastic patients exhibited a larger H/M(max), H(2)/H(1) and amplitude of MMG(Mmax) than the control group. H/M(max) and amplitude of MMG(Mmax) accounted for 55.7% of the variance in the Modified Ashworth Scale, the clinical hypertonia assessment. The amplitude of MMG(Mmax) correlated with functional impairments, as assessed with the Barthel index and Fugl-Meyer motor-assessment scale. It was concluded that spastic hypertonia involved an atypical increase in motoneuronal excitability and muscle mechanical properties, while impairment of functional performance and daily activity was attributable primarily to altered mechanical properties of a spastic muscle.     

Dissociation of peak vascular conductance and V(O2) max among highly trained athletes.

Previously, a strong relationship has been found between whole body maximal aerobic power (VO(2 max)) and peak vascular conductance in the calf muscle (J. L. Reading, J. M. Goodman, M. J. Plyley, J. S. Floras, P. P. Liu, P. R. McLaughlin, and R. J. Shephard. J. Appl. Physiol. 74: 567-573, 1993; P. G. Snell, W. H. Martin, J. C. Buckley, and C. G. Blomqvist. J. Appl. Physiol. 62: 606-610, 1987), suggesting a matching between maximal exercise capacity and peripheral vasodilatory reserve across a broad range of aerobic power. In contrast, long-term training could alter this relationship because of the unique demands for muscle blood flow and cardiac output imposed by different types of training. In particular, the high local blood flows but relatively low cardiac output demand imposed by the type of resistance training used by bodybuilders may cause a relatively greater development in peripheral vascular reserve than in aerobic power. To examine this possibility, we studied the relationship between treadmill VO(2 max) and vascular conductance in the calf by using strain-gauge plethysmography after maximal ischemic plantar flexion exercise in 8 healthy sedentary subjects (HS) and 28 athletes. The athletes were further divided into three groups: 10 elite middle-distance runners (ER), 11 power athletes (PA), and 7 bodybuilders (BB). We found that both BB and ER deviate from the previously demonstrated relationship between VO(2 max) and vascular conductance. Specifically, for a given vascular conductance, BB had a lower VO(2 max), whereas ER had a higher VO(2 max) than did HS and PA. We conclude that the relationship between peak vascular conductance and aerobic power is altered in BB and ER because of training-specific effects on central vs. peripheral cardiovascular adaptation to local skeletal muscle metabolic demand.     

Body composition and physical fitness of female volleyball and basketball players of the Japan inter-high school championship teams

This study evaluated the body composition (underwater weighing) and cardiorespiratory function (VO(2)max and O(2)debt max measured by the treadmill exercise test) in 12 members of the women's volleyball team (mean age 17.4 years) and 11 members of the women's basketball team (mean age 17.6 years) that won the championship in the Japan Inter-high School Meeting. We also examined differences in the physical abilities between the members of the top teams of different events. The following results were obtained. (1) The mean values of the height and body weight were 168.7+/-5.89 cm and 59.7+/-5.73 kg in the volleyball players and 166.5+/-7.87 cm and 58.8+/-6.85 kg in the basketball players. (2) The mean %Fat was 18.4+/-3.29% in the volleyball players and 15.7+/-5.05% in the basketball players, and was similar to the reported values in elite adult players. (3) The mean VO(2)max was 2.78+/-0.32 L x min(-1) (46.5+/-2.90 ml x kg(-1) x min(-1)) in the volleyball players and 3.32+/-0.31 L x min(-1) (56.7+/-4.17 ml x kg(-1) x min(-1)) in the basketball players, and was similar to the reported values in elite adult players. (4) The mean O(2)debt max was 6.18+/-1.15 L (103.2+/-12.40 ml x kg(-1)) in the volleyball players and 7.92+/-1.80 L (134.3+/-23.24 ml x kg(-1)) in the basketball players. These values were 2.6 times and 3.3 times as high as the average values in high school students in general. (5) No significant difference was observed in any measured item of the physique, skinfold thickness, or body composition between the volleyball players and basketball players. (6) The VO(2)max and O(2)debt max were 22% and 28% higher in the basketball players than in the volleyball players.From these results, the female volleyball players and basketball players evaluated in this study had the physical abilities needed to win the championship in the Japan Inter-high School Meets, i.e. a large FFM and excellent aerobic and anaerobic work capacities. Also, basketball appears to require higher aerobic and anaerobic work capacities than volleyball.     

Plantar flexor activation capacity and H reflex in older adults: adaptations to strength training.

The purpose of this study was to investigate whether the voluntary neural drive and the excitability of the reflex arc could be modulated by training, even in old age. To this aim, the effects of a 16-wk strengthening program on plantar flexor voluntary activation (VA) and on the maximum Hoffman reflex (H(max))-to-maximum M wave (M(max)) ratio were investigated in 14 elderly men (65-80 yr). After training, isometric maximum voluntary contraction (MVC) increased by 18% (P < 0.05) and weight-lifting ability by 24% (P < 0.001). Twitch contraction time decreased by 8% (P < 0.01), but no changes in half relaxation time and in peak twitch torque were observed. The VA, assessed by twitch interpolation, increased from 95 to 98% (P < 0.05). Pretraining VA, also evaluated from the expected MVC for total twitch occlusion, was 7% higher (P < 0.01) than MVC. This discrepancy persisted after training. The interpolated twitch torque-voluntary torque relationship was fitted by a nonlinear model and was found to deviate from linearity for torque levels >65% MVC. Compared with younger men (24-35 yr), the H(max)- to M(max) ratio and nerve conduction velocity (H index) of the older group were significantly lower (42%, P < 0.05; and 29%, P < 0.001, respectively) and were not modulated by training. In conclusion, older men seem to preserve a high VA of plantar flexors. However, the impaired functionality of the reflex pathway with aging and the lack of modulation with exercise suggest that the decrease in the H(max)- to M(max) ratio and H index may be related to degenerative phenomena.     

Physiological and sport-specific skill response of olympic youth soccer athletes

Although many studies have been focused on soccer athletes, no comprehensive studies have been conducted on adolescent soccer athletes in the United States. Therefore, the purpose of this study was to quantify the physiological and sport-specific skill characteristics of Olympic Developmental Program (ODP) soccer athletes by age group and game experience. Following written, informed consent, 59 male athletes (age = 14.6 +/- 2.0 years; wt = 60.5 +/- 1.4 kg; ht = 172.4 +/- 1.2 cm) completed a battery of tests to determine aerobic power (VO(2)max), heart rate (HR(max)), ventilation (VE(max)), respiratory exchange ratio (RER), anaerobic threshold (AT), blood pressure (BP(rest/max)), anaerobic power/capacity [peak power (PP), mean power (MP), total work output (TWO), fatigue index (FI)], leg power [vertical squat jump (VJS), countermovement jump (VJC)], body composition [percent body fat (%BF), lean body mass (LBM)], joint range of motion (trunk, back, hip, knee, and ankle), and agility/sport-specific skills (T-test, line drill test, juggling test, Johnson wall volley, and modified-Zelenka circuit). Factor analyses with subsequent multivariate analyses of variance (MANOVAs) indicated significant main effects across age (p = 0.0001) but not by game experience (p = 0.82). Older athletes exhibited greater height, weight, LBM, VE(max), Time(max), PP, TWO, and VSJ values than younger athletes. Although not significant, there were differences with increasing age in the agility tests (T-test, wall volley, and juggling test). In conclusion, improvements in anaerobic power, agility, and sport-specific skill should be addressed at this developmental level of competition.     

Validity of Carminatti's test to determine physiological indices of aerobic power and capacity in soccer and futsal players

The aim of this study was to verify the validity of a new progressive distance and fixed time test (Carminatti's test [TCAR]) in estimating the main physiological indices of aerobic fitness in team-sport players. Thirty professional national level team-sport players (n = 12 futsal players and 18 soccer players) volunteered to participate in this study. The subjects performed the TCAR and a laboratory incremental treadmill test (ITT). The TCAR required subjects to complete repeated sets of 5 × 12-second shuttle-running bouts at progressive speed until volitional exhaustion. Each 12-second bout and series were separated by a 6- and 90-second recovery periods, respectively. The initial distance was set at 15 m and was progressively increased by 1 m each set. The ITT commenced at a velocity of 9.0 km·h(-1) and was increased by 1.2 km·h(-1) each 3 minutes until volitional exhaustion. Peak TCAR running velocity resulted not significantly (p > 0.05) different from speed at VO2max (vVO2max) during ITT. Peak TCAR running velocity was significantly correlated (p < 0.01) with vVO2max (r = 0.55) and VO2max (r = 0.51). No significant differences were found (p > 0.05) among the mean values of velocity and heart rate at the anaerobic threshold, estimated in the TCAR test and measured in the ITT. In light of this study results, the TCAR can be considered as a viable field test to estimate aerobic power and capacity in team-sports players. The limited devices and space required by TCAR warrant consideration for those strength and conditioning professionals who deal with team sports.     

Radio Telemetry of the Electrocardiogram,Fitness Tests,and Oxygen Uptake of Water-Polo Players

During competitive water polo, heart rate in six subjects was monitored by cupped plastic and silver electrodes glued to the skin. Minimum rates during the game averaged 156 beats/min.; maximum rates averaged 186 beats/min. Mean maximum rate with bicycle exercise was 188 beats/min. Maximum oxygen (VO₂ max.) with bicycle exercise of 14 water-polo players was 53.3 ml./kg. Physical working capacity (PWC 170) was 1310 kilopond metres per square metre (k.p.m./sq.m.). PWC 170 correlated well with VO₂ max. in this small group (r = 0.77).Oxygen uptake was measured at three speeds of swimming and four levels of work on a bicycle ergometer. VO₂ max. of swimming was 88% of that obtained on bicycle exercise. The slope of the oxygen uptake vs. pulse rate curves was less for the swimming than for cycling, so that for a given oxygen uptake below the maximal, pulse rate was less in the swimmers. At near-maximal swimming, respiratory quotient was 0.95 compared with 1.27 for cycling, suggesting that the swimmers were underbreathing.     

Energy expenditure during tennis play: a preliminary video analysis and metabolic model approach

The aim of this study was to estimate, using video analysis, what proportion of the total energy expenditure during a tennis match is accounted for by aerobic and anaerobic metabolism, respectively. The method proposed involved estimating the metabolic power (MP) of 5 activities, which are inherent to tennis: walking, running, hitting the ball, serving, and sitting down to rest. The energy expenditure concerned was calculated by sequencing the activity by video analysis. A bioenergetic model calculated the aerobic energy expenditure (EEO2mod) in terms of MP, and the anaerobic energy expenditure was calculated by subtracting this (MP - EEO2mod). Eight tennis players took part in the experiment as subjects (mean ± SD: age 25.2 ± 1.9 years, weight 79.3 ± 10.8 kg, VO2max 54.4 ± 5.1 ml·kg(-1)·min(-1)). The players started off by participating in 2 games while wearing the K4b2, with their activity profile measured by the video analysis system, and then by playing a set without equipment but with video analysis. There was no significant difference between calculated and measured oxygen consumptions over the 16 games (p = 0.763), and these data were strongly related (r = 0.93, p < 0.0001). The EEO2mod was quite weak over all the games (49.4 ± 4.8% VO2max), whereas the MP during points was up to 2 or 3 times the VO2max. Anaerobic metabolism reached 32% of the total energy expenditure across all the games 67% for points and 95% for hitting the ball. This method provided a good estimation of aerobic energy expenditure and made it possible to calculate the anaerobic energy expenditure. This could make it possible to estimate the metabolic intensity of training sessions and matches using video analysis.     

Physical responses of different small-sided game formats in elite youth soccer players

A major use of small-sided games (SSGs) in soccer training is the concomitant development of game-specific aerobic fitness. We hypothesize that the SSG formats of 2 vs. 2, 3 vs. 3, and 4 vs. 4 players reveal game-like intensities and therefore are most adequate to increase game-specific aerobic fitness. Heart rate (HR), percentage of maximum heart rate (HRmax), blood lactate concentration (La), and time-motion characteristics of 17 elite male youth soccer players (aged 14.9 ± 0.7 years, V[Combining Dot Above]O2max 61.4 ± 4.5 ml·kg·min, HRmax 199.6 ± 7.3 b·min) were collected by global positioning systems while performing the SSG formats. Repeated-measures analysis of variance and effect sizes were calculated to demonstrate the differences between SSG formats. Highest physiological responses were obtained in 2 vs. 2 (HR: 186 ± 7 b·min, HRmax: 93.3 ± 4.2%, La: 5.5 ± 2.4 mmol·L) followed by 3 vs. 3 (HR: 184 ± 8 b·min, HRmax: 91.5 ± 3.3%, La: 4.3 ± 1.7 mmol·L) and 4 vs. 4 (HR: 179 ± 7 b·min, HRmax 89.7 ± 3.4%, La: 4.4 ± 1.9 mmol·L). Pronounced differences were found for most physiological parameters and for time spent in the speed zones "walking" (<5.3 km·h), "moderate-speed running" (10.3-13.9 km·h), and "maximum sprinting" (≥26.8 km·h). The findings suggest that all the formats reveal game-like intensities and are suitable for aerobic fitness improvements. However, we found pronounced demands on the anaerobic energy supply in 2 vs. 2, whereas 3 vs. 3 and 4 vs. 4 remain predominantly on an aerobic level and differ mainly in the HR response. We suggest using 3 vs. 3 for soccer-specific aerobic fitness training.     

Oxygen Demand and Energy Cost of Intense Muscular Activity in Humans

Changes in the kinetics of aerobic and anaerobic metabolism were studied in 26 highly profiled athletes performing bicycle ergometer exercise. The different intensity exercise sessions included those with a critical intensity corresponding to the maximum oxygen consumption up to value of the maximum anaerobic intensity of about 10 MMR units. The maximal aerobic metabolism was maintained in the exercises with a relative intensity of 1.0 to 2.5 MMR units. At the higher values of the exercise relative intensity, the oxygen current consumption exponentially decreased. An increase in the rate of anaerobic glycolytic energy production, which was first recorded at the threshold of anaerobic metabolism (W _AT = 0.5 MMR units), increased linearly with a further increase in the exercise relative intensity up to the level of the exhaustion intensity (W _ex = 4.7 MMR units). A sharp increase in the rate of an alactic anaerobic process was found at the relative intensity values of 2.5 MMR units, and this increase grew linearly up to values of the maximal anaerobic intensity (W _max = 9.5 MMR units).     

Quantification of T- and H-responses before and after a period of endurance training.

Tendon (T-) and Hoffmann (H-) responses in the soleus muscle were quantified either separately or in association to compare the mononeurons activated and to study their changes after a period of endurance training. In a first experiment T- and H-responses of the same amplitude were compared: the electrical stimulus (inducing the H-response) and the Achilles tendon tap (inducing the T-response) were associated so that the T-response firstly was concomitant with the H-response, and secondly shifted 10 ms forward or back compared to the H-response. From the study of these combined reflexes we would suggest that the same motoneurons are involved in T- or H-responses of the same amplitude. In a second experiment the maximal H-responses, the T-responses and maximal aerobic power (Waer,max) were measured on 20 subjects before and after a period of endurance training. For 75% of the subjects the Waer,max and the reflex parameters (T or H) varied in the same direction: most of them exhibited higher values of both Waer,max and reflex amplitudes while the others had Waer,max and reflex values hardly modified or decreased. The different effects of the training period could reflect the heterogeneity of the subject's status and involvement in sport. In most cases the T:Hmax ratios were also influenced, reflecting the fact that T- and H-responses were not identically affected by training. Thus it is suggested that an endurance training programme can influence not only the excitability of the motoneurons but also the response of the muscle receptors to stretch. An interpretation in terms of a change of spindle receptivity and/or a change in their recruitment due to a greater stiffness of the trained muscles is suggested.     

“Negative phase” of the heart rate and stroke volume in young athletes after the Harvard step test

Changes in the heart rate (HR) and stroke volume (SV) after the Harvard step test have been studied in young athletes at different stages of multiyear training. At the initial stage of training, the HR of young swimmers and skiers transiently decreased after the test below the starting values; i.e., during the recovery period, a “negative phase” of the HR was observed. After the test, the SVs of these athletes also decreased below the starting values, following the pattern of the pulse negative phase. However, the HR and SV negative phases were not synchronous. With advancement in the training level of the young swimmers and skiers, decreases in the HR and SV below the starting values were observed more seldom, and such decreases were virtually absent at the advanced stage. No decreases in the HR or SV after the Harvard step test were observed in young ice hockey players or gymnasts.     

少年足球运动员运动性疲劳后的差异代谢物筛选*

目的: 探索少年足球运动员在运动性疲劳后的差异代谢物变化。方法: 以12名男性少年足球运动员(14～16岁)为试验对象,用功率自行车建立包含有氧运动和无氧运动的训练模型:完成6 min 150 W负荷、60～65 r/min的踏骑运动和30 s的负荷按照测试者体重而设定的最大速度踏骑运动,中间休息1 min,重复运动3组,组间休息3 min;测定运动员每组运动后的最大摄氧量值和平均无氧功率值,采集运动训练前后的尿液样本,利用气相-质谱联用(GC-MS)法检测尿液样本,通过数据库筛选潜在的差异代谢物。结果: 与运动前相比较,少年足球运动员运动疲劳后的平均无氧功率显著下降(P＜0.05),筛选出25个差异代谢物,其中3个代谢物显著升高(P＜0.05,0.01),22个代谢物显著降低(P＜0.05,0.01);上述差异代谢物的相关代谢通路归属为甘氨酸-丝氨酸-苏氨酸代谢、三羧酸循环、酪氨酸代谢、氮代谢和甘油磷酯代谢通路。结论: 少年足球运动员发生运动性疲劳后,机体的代谢物:肌氨酸、L-别苏氨酸、肌酸、丝氨酸、琥珀酸、柠檬酸、4-羟基苯乙酸、羟胺和乙醇胺产生明显的变化,上述差异代谢物可作为少年足球运动员疲劳评价的指标。     

Do hockey players need aerobic fitness? Relation between VO2max and fatigue during high-intensity intermittent ice skating

The primary objective of this study was to assess the relationship between aerobic capacity, as measured by the VO(2)max test, and recovery from high-intensity intermittent exercise. Eleven female collegiate hockey players agreed to participate. Subjects skated 5 1-lap intervals around the hockey rink at maximal intensity with a 30-second recovery period between skates. The VO(2)max test was performed on a motor-driven treadmill after a modified Bruce protocol. A fatigue index was calculated by measuring the total increase in skate time from trial 1 to trial 5. This fatigue index was then correlated to VO(2)max. This correlation coefficient (-0.422) was not significant (p > 0.05) and indicated that only 17.8% of the variance in VO(2)max could be explained by the fatigue index. It was concluded that ability to recover from high-intensity intermittent exercise is not related to aerobic capacity. Coaches and trainers probably do not need to include aerobic training in their practices, because the high-intensity interval training commonly seen in hockey training also improves aerobic capacity, as reflected in the high VO(2)max values of these subjects.     

Aerobic parameters of exercise as a function of body size during growth in children

To examine the relationship between body weight in children and aerobic parameters of exercise, we determined the anaerobic threshold (AT), maximum O2 uptake (VO2max), work efficiency, and response time for O2 uptake (RT-VO2) in 109 healthy children (51 girls and 58 boys, range 6-17 yr old) using a cross-sectional study design. Gas exchange during exercise was measured breath by breath. The protocol consisted of cycle ergometry and a linearly increasing work rate (ramp) to the limit of the subject's tolerance. Both AT and VO2max increased systematically with body weight, whereas work efficiency and RT-VO2 were virtually independent of body size. The ratio of AT to VO2max decreased slightly with age, and its mean value was 60%. AT scaled to body weight to the power of 0.92, not significantly different from the power of 1.01 for VO2max. Thus both the AT and the VO2max increase in a highly ordered manner with increasing size, and as judged by AT/VO2max, the onset of anaerobic metabolism during exercise occurred at a relatively constant proportion of the overall limit of the gas transport system. We conclude that in children cardiorespiratory responses to exercise are regulated at optimized values despite overall change in body size during growth.     

THE ASSOCIATION BETWEEN ACE GENE VARIATION AND AEROBIC CAPACITY IN WINTER ENDURANCE DISCIPLINES

The aim of the study was to examine the possible relationship between I/D polymorphism of ACE gene and selected indices of aerobic capacity among male and female athletes practising winter endurance sports. Sixty-six well-trained athletes (female n = 26, male n = 40), aged 18.4 ± 2.8 years, representing winter endurance sports (cross-country skiing, n = 48; biathlon, n = 8; Nordic combined, n = 10) participated in the study. Genotyping for ACE I/D polymorphism was performed using polymerase chain reaction. Maximal oxygen consumption (VO₂max), maximal running velocity (V_max) and running velocity at anaerobic threshold (V_AT4) were determined in an incremental test to volitional exhaustion on a motorized treadmill. The ACE genotype had no significant effect on absolute VO₂max, relative VO₂max (divided by body mass or fat free body mass), V_AT4 or V_max. No interaction effect of gender x ACE genotype was found for each of the examined aerobic capacity indices. ACE gene variation was not found to be a determinant of aerobic capacity in either female or male Polish, well-trained endurance athletes participating in winter sports.     

Adaptation of motor nerve fibers to physical activity

The effects induced by training on the H-reflex of soleus and lateral gastrocnemius muscles have been studied on 19 adult male volunteers; out of these, 10 were non-trained subjects and the remaining 9 were top level athletes engaged in sports requiring very rapid and intense contractions (sprinters and volley-ball players). It has been observed that the latency of the M response is significantly higher in the athletes than in the non-trained subjects. Instead, no significant differences were observed between these two groups, concerning the latency of H response. The increase of M response latency is likely due to a decrease of nerve conduction velocity in the terminal part of motor fibers. The possibility that this conduction speed decrease could be dependent on sprouting and/or terminal branching growth of the motor nerve ending is discussed.     

Production of polyhydroxybutyrate by activated sludge performing enhanced biological phosphorus removal

In this study, polyhydroxybutyrate (PHB) – a biodegradable plastics material – was produced by activated sludge performing enhanced biological phosphorus removal (EBPR) in batch experiments under anaerobic, aerobic and anaerobic/aerobic conditions. Under anaerobic conditions, the maximum PHB content of the dry biomass was 28.8% by weight, while under aerobic or anaerobic/aerobic conditions, the maximum PHB content was about 50%. The PHB production rate with respect to the volatile suspended solids (VSS) was: (i) 70 mg/(g VSS) h under aerobic conditions that followed anaerobic conditions, (ii) 156 mg/(g VSS) h under anaerobic condition, and (iii) 200 mg/(g VSS) h under aerobic conditions with energy also supplied from polyphosphate. A side stream, with initially anaerobic conditions for PHB accumulation and phosphorus release, and then aerobic conditions for PHB accumulation, was proposed. In this side stream, biomass with a high PHB content and a high PHB production rate could be both achieved.