Long-term effectiveness of the New Zealand Green Prescription primary health care exercise initiative.

OBJECTIVES: The rising incidence of non-communicable diseases in western countries is being driven by poor lifestyle choices, including increasingly inadequate physical activity. The aim of this study was to quantify the effectiveness of a physical activity primary care intervention named the 'Green Prescription' on changes in physical activity levels 2-3 year's following original prescription. STUDY DESIGN: A retrospective study design using a telephone interview. METHODS: Physical activity and health information was gathered from participants in June-September 2015, who were originally prescribed a primary care physical activity intervention 2-3 years ago. Respondents were classified as either having completed the programme (adherence group, n = 91) or having not completed the programme (non-adherence group, n = 56). RESULTS: Participants who had completed the programme within the past 2-3 years reported an additional 64 min (95% CI = 16-110) of total physical activity per week compared to those who had dropped out. Forty-two percent of participants in the adherence group reported increased physical activity levels after receiving the Green Prescription compared to 29% in the non-adherence group. The adherence group were less likely to be sedentary (odds ratio 0.7, 95% CI = 0.5-0.9) and more likely to meet the current physical activity guidelines of at least 150 min of physical activity per week (OR = 1.1, 95% CI = 1.0-1.3). CONCLUSIONS: The findings indicate a long-term benefit is likely to participants who completed Green Prescription.

The effect of short-term intermittent hypoxic exposure on heart rate variability in a sedentary population.

While the effects of instantaneous, single-bout exposure to hypoxia have been well researched, little is known about the autonomic response during, or as an adaptation to, repeated intermittent hypoxic exposure (IHE) in a sedentary population. Resting heart rate variability (HRV) and exercise capacity was assessed in 16 participants (8 receiving IHE, [Hyp] and 8 receiving a placebo treatment [C]) before and after a 4-week IHE intervention. Heart rate variability was also measured during an IHE session in the last week of the intervention. Post-intervention, the root mean squared successive difference (rMSSD) increased substantially in Hyp (71.6 ± 52.5%, mean change ± 90% confidence limits) compared to C suggesting an increase in vagal outflow. However, aside from a likely decrease in submaximal exercise heart rate in the Hyp group (-5.0 ± 6.4%) there was little evidence of improved exercise capacity. During the week 4 IHE measurement, HRV decreased during the hypoxic exposure (reduced R-R interval: -7.5 ± 3.2%; and rMSSD: -24.7 ± 17.3%) suggesting a decrease in the relative contribution of vagal activity. In summary, while 4 weeks of IHE is unlikely to improve maximal exercise capacity, it may be a useful means of increasing HRV in people unable to exercise.

Popularity of hypoxic training methods for endurance-based professional and amateur athletes.

Scientific debate continues into whether hypoxic training has any performance benefit for athletes, and although this type of training seems popular, to our knowledge little empirical evidence on its popularity with endurance-based athletes exists. To quantify the usage of hypoxic training in endurance-based athletes we asked 203 athletes (amateur = 108, professional = 95) to complete a 17-question survey during 2013-2014 season. Compared to amateurs, professional athletes were 4.5 times (3.0-6.8, odds ratio, 95% confidence limits) more likely to undertake hypoxic training. Live-high train-low was the most popular hypoxic training protocol for athletes (52% professional and 80% amateur) with live-high train-high also used (38% professional, 20% amateur). Compared to amateurs, professional athletes tended to use evidence-based hypoxic training methods, seek advice on hypoxic training from reliable sources and were generally more realistic about the potential performance gains as a result of hypoxic training. Almost one third (25-30%) of all athletes suffered illness during their hypoxic training. Compared to amateurs, professional athletes are more likely to undertake hypoxic training and tend to follow current scientific guidelines. Attenuation of the ill effects that occur during hypoxic training may be accomplished if athletes give more attention to monitoring stress and training levels.

Effect of intermittent hypoxic training on 20 km time trial and 30 s anaerobic performance.

This study aimed to verify whether the "live low, train high" approach is beneficial for endurance and/or anaerobic cycling performance. Sixteen well-trained athletes completed 90 min of endurance training (60-70% of heart rate reserve), followed by two 30-s all-out sprints (Wingate test), daily, for 10 consecutive days. Nine subjects [intermittent hypoxic training (IHT) group] trained with an F(I)O(2) set to produce arterial oxygen saturations of approximately 88-82%, while seven subjects (placebo group) trained while breathing a normal gas mixture (F(I)O(2)=0.21). Four performance tests were conducted at sea level including a familiarization and baseline trial, followed by repeat trials at 2 and 9 days post-intervention. Relative to the placebo group, the mean power during the 30-s Wingate test increased by 3.0% (95% confidence limits, CL +/- 3.5%) 2 days, and 1.7% (+/- 3.8%) 9 days post-IHT. Changes in other performance variables (30 s peak power, 20 km mean power and 20 km oxygen cost) were unclear. During the time trial, the IHT participants' blood lactate concentration, respiratory exchange ratio, and SpO(2), relative to the placebo group, was substantially increased at 2 days post-intervention. The addition of IHT to the normal training program of well-trained athletes produced worthwhile gains in 30 s sprint performance possibly through enhanced glycolysis.

Validation of the New Zealand Physical Activity Questionnaire (NZPAQ-LF) and the International Physical Activity Questionnaire (IPAQ-LF) with accelerometry.

BACKGROUND: Validation of instruments used to measure physical activity patterns is essential when attempting to assess the effectiveness of physical activity interventions. OBJECTIVES: To assess the validity of two self-report physical activity questionnaires on a representative sample of New Zealand adults. METHODS: 70 adults aged 18-65 years from around Christchurch, New Zealand were required to wear an ActiGraph GT1M accelerometer during all waking hours for 7 consecutive days. Immediately following the 7 day accelerometer period participants were required to complete the long forms of both the New Zealand Physical Activity Questionnaire (NZPAQ-LF) and the International Physical Activity Questionnaire (IPAQ-LF). RESULTS: Both the NZPAQ-LF and the IPAQ-LF questionnaires showed small to moderate correlations with ActiGraph data for time spent in moderate-intensity physical activity (r=0.19-0.30) and total physical activity (sum of moderate and vigorous-intensity physical activity, r=0.30-0.32). In comparison with the ActiGraph data, both self-report questionnaires tended to overestimate activity levels by approximately 165%. Total physical activity levels gathered from both questionnaires were strongly correlated with each other (r=0.79) and showed good levels of agreement in the Bland-Altman plots. CONCLUSIONS: The long forms of the NZPAQ and IPAQ were found to have acceptable validity when detecting participants' ability to meet activity guidelines based on exercise duration, but a significant amount of overestimation was evident. This presents a need for both instruments to be further developed and tested in order to increase validity.

Secular trends and distributional changes in health and fitness performance variables of 10-14-year-old children in New Zealand between 1991 and 2003.

BACKGROUND: New Zealand children's health and fitness performance is declining over time, but whether this change is because of deterioration in all children's health and fitness performance or can be attributed to just a certain portion of the population, is unknown. OBJECTIVES: In this study, secular trends and distributional changes in health-related and performance-related fitness components among New Zealand primary school children aged 10 to 14 years between 1991 and 2003 were tracked. METHODS: Health- and performance-related fitness parameters including height, weight, body mass index (BMI), flexibility, standing broad jump, 4 x 9-m agility run, abdominal curl-ups, and 550-m run were collected up to twice a year from 3306 children (10-14 years old) from a New Zealand school between 1991 and 2003. RESULTS: Over the 12-year period, the boys' weight increased by 4.5 kg (95% CL 2.7 to 6.2, or 0.8% per year) and girls' by 3.9 kg (95% CL 2.0 to 5.9, or 0.7% per year). Mean BMI increased by 0.12 kg m(-2) (0.6%) and 0.11 kg m(-2) (0.5%) per year for boys and girls, respectively. Children's 550-m run performance declined by 1.5% and 1.7% per year for boys and girls, respectively. Little difference existed between children located in the highest performing and leanest percentiles in 1991 and 2003, but for children in the poorest performing and fattest percentiles, their results were substantially worse in 2003. CONCLUSIONS: These results suggest that the deterioration in the health-related and performance-related fitness components of New Zealand 10-14-year-olds is not homogeneous but skewed towards those children who are the heaviest and perform worst in fitness tests. Previous research on health-related fitness parameters among children in New Zealand is limited but shows secular trends of increasing body mass1 2 in conjunction with deteriorating aerobic fitness performance, muscular endurance and explosive muscular power.3 Internationally, similar increases in body mass have been observed in children since the 1980s.1 4 5 Secular trends of deteriorating health-related fitness performance have also been reported among children around the world,1 5 6 with the most significant decreases observed in aerobic performance. However, trends in health-related variables reported as changes in mean body mass index (BMI) and mean aerobic fitness performance do not reveal possible changes in the distribution of BMI or aerobic performance within the population. Changes in such measures may come about because of a shift in the entire population under investigation or a change in a portion of the population. It is not clear whether New Zealand's entire childhood population is becoming heavier and less aerobically fit or whether only a portion of the children are becoming even heavier and more unfit, with the remaining children showing little secular change. The aim of this study was to track secular trends and distributional changes in body weight and physical fitness parameters among New Zealand primary school children aged 10 to 14 years.

Game performance and intermittent hypoxic training.

Live high-train low altitude exposure simulated by hypoxic devices may improve athletic performance. In this study, intermittent normobaric hypoxia was achieved with the GO2altitude hypoxicator to determine its effects on sea level performance in rugby players. Ten players were randomly assigned to two groups. Players in each group received 14 sessions of either hypoxic (10-15% O(2)) or normoxic (21% O(2)) exposure at rest over 14 consecutive days in a single blind fashion. Various performance measures were obtained consecutively in a single testing session pre- and post-exposure. Effects of hypoxic exposure on maximum speed and sprint times were trivial (<1.0%) but unclear (90% likely range, +/-5% to +/-9%). In rugby simulation, hypoxic exposure produced impairments of peak power in two scrums (15%, +/-8%; 9%, +/-7%) and impairments of time in offensive sprints (7%, +/-8%) and tackle sprints (11%, +/-9%). Pending further research, rugby players would be unwise to use normobaric intermittent hypoxic exposure to prepare for games at sea level.

Self-reported health benefits in patients recruited into New Zealand's 'Green Prescription' primary health care program.

To assess the effectiveness of the 'Green Prescription' (GRx) program in promoting self-reported health benefits in previously inactive individuals, between 2001 and 2002, a retrospective survey was administered to 124 GRx patients throughout New Zealand. Participants were a non-randomized subset of a larger GRx population. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for differences in health outcomes between participants who had increased physical activity levels compared to participants who had decreased or not altered activity levels since first being prescribed the GRx. Completed surveys were obtained from 124 of 263 eligible participants; a response rate of 47%. Fifty-six percent of participants reported increases in physical activity levels after the GRx program, with 70% still undertaking some form of physical activity. Participants accumulated at least 30 minutes of physical activity per day on 3.4 +/- 2.5 days (mean +/- SD) per week. Participants who reported increased physical activity levels after the GRx reported substantially higher energy levels and improved breathing when compared to participants who reported less or about the same physical activity after the GRx intervention. Increased physical activity in GRx patients was associated with greater perceived health benefits. Effective and ongoing support networks were seen as important for behavior change.

Changes in physiological parameters in overtrained Standardbred racehorses.

Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial increased by 4.0% (95% probable range of true value 1.7-5.8) and peak velocity decreased by 6.9% (4.7-8.9), indicating that overtraining had occurred. Acute overtraining coincided with an increase in blood lactate concentration after the time trial and submaximal test. There were also substantial decreases in bodyweight, plasma cortisol concentration and packed cell volume after the time trial, and in the velocity at a heart rate of 200/min (V200). Parameters that showed no clear-cut change with overtraining included maximal and recovery heart rate, basal plasma cortisol, plasma and red cell volume, and markers of skeletal damage (plasma concentrations of creatine kinase and aspartate aminotransferase). Bodyweight, V200, postexercise blood lactate and plasma cortisol concentrations may all be useful for detecting acute overtraining in equine athletes.

Effect of tapered normal and interval training on performance of Standardbred pacers.

Human athletes taper or reduce their training load before a race to enhance performance, apparently because recovery from the effects of fatigue occurs faster than the loss of fitness from the reduced training. However, there appear to be no previous studies of tapering of equine athletes. Our aim in the present study was, therefore, to investigate the efficacy of tapering with Standardbred pacers. We determined the effect of repeated cycles of tapered training on performance of Standardbred pacers. After 8 weeks of jogging and 3 x 2 week cycles of pace work, 19 horses were randomised to a taper and a control group. The taper group completed 5 consecutive 2 week cycles, each incorporating a 7 day taper; some cycles included high-intensity interval training. The control group continued with 5 more cycles of pace work. All horses completed a 2400 m individual time trial after each cycle. Peak and mean speed of the taper group were faster than those of the control group in all cycles; the differences were clear-cut in all cycles for peak speed (overall 4.4%, 95% confidence interval 1.7 to 7.1%), but only in one of the interval-training cycles for mean speed (2.4%, 0.3 to 4.7%). Four horses in the taper group were injured during interval training. Repeated tapering produces a worthwhile enhancement of performance in Standardbreds, but the addition of interval training appears to increase the risk of injury.

Quadriceps concentric and eccentric exercise 2: differences in muscle strength, fatigue and EMG activity in eccentrically-exercised sore and non-sore muscles.

The purpose of this study was to determine whether the previously reported muscle weakness and increases in EMG and EMG/force ratio after eccentric exercise were related to ensuing soreness or simply to the exercise mode. Delayed-onset muscle soreness, maximal voluntary force and the surface electromyogram (EMG) of the quadriceps were studied in 10 healthy male subjects following 20 min of bench-stepping with a constant leading leg. Prior to stepping and at 0, 0.25, 0.50, 0.75, 1, 3, 24 and 48 h afterwards the subjects performed a 30 s isometric maximal voluntary contraction (MVC) of the extensors of each leg during which the isometric force and the root mean square voltage of the surface EMG (rms EMG) were recorded. Muscle soreness was recorded prior to and at 0, 0.75, 3, 24 and 48 h after the stepping task by means of a force probe. No soreness was experienced in the concentrically exercised muscles, but in the eccentrically exercised muscles 5 subjects were not sore and 5 experienced soreness after 24 h, increasing to 48 h. There were no significant differences between sore and non-sore muscles in muscle weakness, fatigue during 30 s, the EMG amplitudes or the EMG/force ratios during peak force and the 30 s MVC (p >0.05). Muscle weakness following eccentric exercise was related to the exercise mode and was independent of subsequent soreness. Both weakness and soreness may be related to muscle damage, but involve different mechanisms.

Quadriceps concentric and eccentric exercise 1: changes in contractile and electrical activity following eccentric and concentric exercise.

The purpose of this study was to determine whether or not losses of strength or endurance following eccentric and concentric exercise are associated with reduced excitation. The effects of eccentric and concentric work on maximal voluntary isometric contraction (MVC) and surface electromyogram (EMG) of the quadriceps were studied in 10 healthy male subjects following bench-stepping for 20 min with a constant leading leg. Prior to stepping and at 0, 0.25, 0.50, 0.75, 1, 3, 24 and 48 h afterwards the subjects performed a 30 s leg extension MVC with each leg during which the isometric force and the root mean square voltage of the EMG were recorded. In the eccentrically exercised muscles (ECC), MVC0-3 (force during the first 3 s of contraction) fell immediately after the bench-stepping exercise to 88+/-2% (mean+/-SE) of the pre-exercise value and remained significantly lower than the concentrically exercised muscles (p<0.05). The muscle weakness in the ECC could not be attributed to central fatigue as surface EMG amplitude at MVC0-3 increased during the recovery period. Muscle weakness after eccentric exercise appears to be due to contractile failure, which is not associated with a reduction in excitation as assessed by surface EMG. Muscular fatigue over 30 s did not change in the two muscle groups after exercise (p = 0.79), indicating that the ECC were weaker but not more fatiguable after exercise.