Ann C. Snyder

Effects of specific versus cross-training on running performance

The cross-training (XT) hypothesis suggests that despite the principle of specificity of training, athletes may improve performance in one mode of exercise by training using another mode. To test this hypothesis we studied 30 well-trained individuals (10 men, 20 women) in a randomized longitudinal trail. Subjects were evaluated before and after 8 weeks of enhanced training (+10%/week), accomplished by adding either running (R) or swimming (XT) to baseline running, versus continued baseline running (C). Both R ( − 26.4s) and XT (− 13.2s) improved time trial (3.2 km) performance, whereas C did not (− 5.4s). There were no significant changes during treadmill running in maximum oxygen uptake (O2peak; − 0.2, − 6.0, and + 2.7%), steady state submaximal O2 at 2.68 m · s−1 ( − 1.2, − 3.3 and + 0.2 ml · kg−1 · min−1), velocity at O2peak (+0.05, +0.25 and +0.09 m · s−1) or accumulated O2 deficit (+ 11.2, − 6.1 and + 9.4%) in the R, XT or C groups, respectively. There was a significant increase in velocity associated with a blood lactate concentration of 4 mmol · l−1 in R but not in XT or C ( + 0.32, + 0.07 and + 0.08 m · s−1). There were significant changes in arm crank O2peak ( + 5%) and arm crank O2 at 4 mmol · l−1 ( + 6.4%) in XT. There was no significant changes in arm crank O2peak ( + 1.3 and − 7.7%) or arm crank O2 at 4 mmol · l−1 ( + 0.8 and + 0.4%) in R or C, respectively. The data suggest that muscularly non-similar XT may contribute to improved running performance but not to the same degree as increased specific tranining.

Overtraining following intensified training with normal muscle glycogen.

The purpose of this study was to determine if consumption of appropriate amounts of carbohydrate during a period of increased exercise training would protect the athletes from becoming overtrained. Eight male competitive cyclists were monitored and tested during three training periods: a) normal training (moderate intensity, long duration, 7 d, NORM); b) overtraining (high intensity training, 15 d, OVER); and c) recovery (minimal training, 6 d, REC). Throughout the training 160 g of liquid carbohydrate were consumed within the first 2 h after the daily exercise bout. Mean dietary intake (NORM = 13.7 +/- 1.6, OVER = 14.1 +/- 1.0 MJ.d-1) and carbohydrate percent (NORM = 64.0 +/- 2.1, OVER = 67.4 +/- 2.5%) were not different during the different training periods. Similarly, resting muscle glycogen levels were not different (NORM = 530.9 +/- 42.5, OVER = 571.2 +/- 27.5 mumol.g-1 dry weight). Five criteria were used to determine if overtraining occurred in a subject (decreased maximal workload, maximal heart rate, ratio of maximal lactate to rating of perceived exertion (HLa:RPE), and resting plasma cortisol levels, increased affirmative response to a daily questionnaire). All subjects met at least three of the five criteria and thus were classified as overtrained. Therefore, short-term overtraining may occur even when resting muscle glycogen levels are maintained.

Overtraining and glycogen depletion hypothesis.

Low muscle glycogen levels due to consecutive days of extensive exercise have been shown to cause fatigue and thus decrements in performance. Low muscle glycogen levels could also lead to oxidation of the branched chain amino acids and central fatigue. Therefore, the questions become, can low muscle glycogen not only lead to peripheral and central fatigue but also to overtraining, and if so can overtraining be avoided by consuming sufficient quantities of carbohydrates? Research on swimmers has shown that those who were nonresponsive to an increase in their training load had low levels of muscle glycogen and consumed insufficient energy and carbohydrates. However, cyclists who increased their training load for 2 wk but also increased carbohydrate intake to maintain muscle glycogen levels still met the criteria of over-reaching (short-term overtraining) and might have met the criteria for overtraining had the subjects been followed for a longer period of time. Thus, some other mechanism than reduced muscle glycogen levels must be responsible for the development and occurrence of overtraining.

Effects of low-level light therapy on hepatic antioxidant defense in acute and chronic diabetic rats

Diabetes causes oxidative stress in the liver and other tissues prone to complications. Photobiomodulation by near infrared light (670 nm) has been shown to accelerate diabetic wound healing, improve recovery from oxidative injury in the kidney, and attenuate degeneration in retina and optic nerve. The present study tested the hypothesis that 670 nm photobiomodulation, a low‐level light therapy, would attenuate oxidative stress and enhance the antioxidant protection system in the liver of a model of type I diabetes. Male Wistar rats were made diabetic with streptozotocin (50 mg/kg, ip) then exposed to 670 nm light (9 J/cm2) once per day for 18 days (acute) or 14 weeks (chronic). Livers were harvested, flash frozen, and then assayed for markers of oxidative stress. Light treatment was ineffective as an antioxidant therapy in chronic diabetes, but light treatment for 18 days in acutely diabetic rats resulted in the normalization of hepatic glutathione reductase and superoxide dismutase activities and a significant increase in glutathione peroxidase and glutathione‐S transferase activities. The results of this study suggest that 670 nm photobiomodulation may reduce, at least in part, acute hepatic oxidative stress by enhancing the antioxidant defense system in the diabetic rat model.

Carbohydrate consumption prior to repeated bouts of high-intensity exercise

SummaryRapid depletion of muscle glycogen occurs during activities greater than 100% of maximal oxygen uptake. While carbohydrate ingestion prior to an endurance event has been shown to be beneficial, the effects of carbohyrate ingestion on repeated bouts of high-intensity exercise are not known. Therefore, the purpose of this study was to determine if carbohydrate ingestion prior to repeated bouts of high-intensity, short-duration exercise would improve performance. Ten well-trained male cyclists performed two experimental rides, one 15 min after consumption of 5.0 ml·kg−1 body weight of a 19.7% carbohydrate drink and one following a placebo. The experimental ride consisted of four 1.6 km timed performance rides separated by 4.8 km steadystate rides at 80% of maximal oxygen uptake (between the last two performance rides the steady-state rides were 1.6 km at 80% and 1.6 km at 90%). Blood glucose levels were significantly increased following both the ingestion of the carbohydrate beverage and the performance of the exercise bout. Total exercise time following ingestion of the experimental drink [mean (SD); 25.6 (3.3) min] was not different from that following ingestion of the placebo [25.2 (3.3) min]. Similarly, the sum of all four timed performance rides following ingestion of the experimental drink [6.8 (0.9) min] was not different from that following ingestion of the placebo [6.6 (0.9) min]. In the present study, carbohydrate ingestion 15 min prior to exercise increased blood glucose levels, although performance time was not affected.

Analysis of Seated and Standing Triple Wingate Tests

Wilson, RW II, Snyder, AC, and Dorman, JC. Analysis of seated and standing triple Wingate tests. J Strength Cond Res 23(3): 868-873, 2009-Observations of athletes in seated and standing cycling positions in laboratory and field settings have led to the perception that they produce different outputs. The purpose of this study was to determine whether there are differences in power output and physiological responses between seated and standing positions of athletes during 3 consecutive Wingate tests. Seven (n = 7) elite-level speedskaters completed 3 × 30-second Wingate tests (resistance = 7.5% body weight) with 3.5 minutes of recovery between each test in both seated and standing positions. During the recovery period, athletes pedaled against no resistance in the seated position. Testing was randomized and separated by at least 48 hours. Power output, heart rate, blood lactate, and muscle oxygenation data were collected. Statistical analysis of comparable tests (i.e., seated Wingate test 1 [WinD1] compared with standing Wingate test 1 [WinU1]; WinD2:WinU2; WinD3:WinU3) revealed no significant differences between the seated and standing variables. Position during a short-duration maximal-effort exercise test on a stationary bike did not produce statistically different results in power, maximal heart rate, blood lactate, or muscle oxygenation. As no differences were detected between positions, practitioners can allow subjects to choose their position. Also, if a subject rises out of the seat during a “seated” test, this change may not affect the subjects physiological variables. However, transitioning from one position to the other during the test is not advised due to the possible chance of injury. It should be acknowledged that there may be reasons for stipulating one position over another (e.g., injuries, leg length).

Using Near-Infrared Spectroscopy to Determine Maximal Steady State Exercise Intensity

Snyder, AC and Parmenter, MA. Using near-infrared spectroscopy to determine maximal steady state exercise intensity. J Strength Cond Res 23(6): 1833-1840, 2009-Maximal steady state (MSS) speed can be determined from blood lactate concentration (HLa); however, this method is not optimal. The purpose of this study was to determine whether near-infrared spectroscopy (NIRS) technology could be used to detect a breakpoint in percent oxygen saturation (StO2) of the muscle and whether the determined breakpoint exercise intensity could be used to determine MSS exercise intensity. Sixteen distance runners and triathletes (men = 9, &OV0312;O2max = 64.9 ± 4.9 ml·kg−1·min−1, women = 7, &OV0312;O2max = 50.8 ± 7.0 ml·kg−1·min−1) completed an incremental exercise test. A change from linearity when plotting StO2 or HLa vs. running speed was defined as the breakpoint. The subjects then completed constant speed runs to determine maximal lactate steady state (MLSS). In 12 subjects, breakpoints were identified for both HLa and StO2 values. Predicted MLSS velocities from HLa breakpoint (12.76 ± 1.63 km·h−1), StO2 breakpoint (12.84 ± 1.58 km·h−1), and 4 mM HLa (13.49 ± 1.71 km·h−1) methods from the incremental test did not differ from MLSS speeds (13.04 ± 2.03 km·h−1). A Bland and Altman analysis of agreement between the MLSS and the StO2 breakpoint speeds resulted in a mean difference of 0.14 ± 0.36, whereas the mean difference between MLSS and HLa breakpoint speeds was 0.19 ± 0.43. During the incremental test, no StO2 breakpoint was determined in 2 subjects, whereas 2 subjects had no HLa breakpoint. The results of this study lead us to conclude that the NIRS determination of StO2 is a noninvasive technique that is comparable with HLa in determining MSS intensity and therefore appropriate for use in determining exercise training intensity.

The Endocrine System in Overtraining

Athletes typically train to enhance performance and competition goals; however, too much training with insufficient recovery can result in the athlete becoming overtrained. When the overtraining syndrome occurs, decrements in performance are the most prominent symptom, but others include fatigue, changes in mood state, competitive incompetence, and changes in sleep patterns, just to name a few. As the endocrine system is very involved in physiological adaptations and recovery to stress, two hypothesized mechanisms by which endocrine function affects exercise performance and may lead to the overtraining syndrome have been proposed, the sympathetic/parasympathetic imbalance and neuroendocrine dysfunction. The sympathetic/parasympathetic imbalance hypothesis states that during the early stages of overtraining, the sympathetic system is activated, while in the later stages of overtraining, the sympathetic system is inhibited and the parasympathetic system predominates. In the neuroendocrine dysfunction hypothesis, a disruption occurs in the anabolic (i.e., testosterone) to catabolic (i.e., cortisol) balance which affects performance and prolongs recovery. However, due to the difficulty in studying overtrained athletes, neither of these hypotheses has been supported well by the literature. Since the primary symptom of overtraining is a decrement in performance, proper exercise training planning is important which includes sufficient recovery such that overtraining does not occur as few markers of its progression have been shown to be of value.

Stress fractures of male distance runners: Lack of association with nutritional practices

Abstract The incidence of stress fractures has been reported frequently in the literature. Since physical activity and nutritional intake influence bone growth, the purpose of this study was to investigate if food intake could influence the occurrence of stress fractures in highly trained distance runners. A question-naire dealing with incidence of stress fractures, training schedule and aating patterns was completed by 80 male runners competing on the national road race circuit. The subjects were grouped relative to their having previously had a stress fracture (SF, n=24) or not (NF, n=56). The two groups of runners had similar physical characteristics, and reported comparable training and racing patterns, although, the SF athletes were significantly faster over the 10 km distance than the NF athletes. Dairy product intake was similar in the two groups, both being lower than recommended. The consumption of meat, chicken and fish was also similar between the two groups of athletes, however, 41.7% of the SF and 32.1% of the NF group restricted red meat consumption. Since reported consumption of different food groups was similar between the two groups of male runners, perhaps other factors, such as hormonal influences, were involved in the occurrence of the stress fractures.

Oxygen Saturation in Right and Left Vastus Lateralis During Split Squat Exercise in Speed Skaters

Many athletes use resistance training to enhance muscular strength and endurance, with resistance determined as a percentage of a repetition maximum. However, the stress placed on the muscles is rarely determined. During a split squat exercise, it is essential to distribute weight equally in both legs to insure equal development. Near-infrared spectroscopy (NIRS) allows for noninvasive examination of muscle oxygenation during exercise. PURPOSE: The purpose of this study was to examine the right and left leg muscle oxygen usage during a typical split squat exercise workout to assess whether proper muscle emphasis could be determined. We hypothesized that muscle oxygen usage would be tractable by NIRS during resistance training exercise and that with elite athletes muscle oxygen usage would be similar in both legs during the split squat exercise. METHODS: Six (5 male and 1 female) National and International caliber speed skaters (aged 24 6 6 yrs) were monitored while performing a split squat training session. The procedure consisted of three sets of fifteen repetitions. A set consisted of fifteen repetitions with both the left and right legs forward. After each leg and between sets the athletes had a one minute rest period. The exercise protocol used was similar to the athletes’ regular workout. Percent oxygen saturation (StO2) of the right and left vastus lateralis muscles was measured continuously throughout the individual’s exercise. RESULTS: The results showed a large variation between subjects. Resting StO2 ranged from 96-53%, while the exercising StO2 ranged from 68-0%. With the left leg forward there was a large difference between subjects on which leg the emphasis was placed. Two placed greater emphasis on the left leg, three on the right leg and one subject put equal emphasis on both. When the right leg was forward, all subjects but one placed the emphasis on that right leg; the one placed greater emphasis on the left leg. CONCLUSION: Our results indicate that StO2 should be able to be used as an indicator of leg preference during the performance of a split squat training session. However, further research is needed on the usage of StO2 to monitor muscle utilization during resistance exercise. PRACTICAL SIGNIFICANCE: The use of muscle oxygenation to determine muscle usage during exercises such as the split squat has the potential to assist coaches and athletes to correctly critique and modify activity during a training session to maximize adaptations, especially at the elite level.