This page is going to cover several topics in fitness. We appreciate that there’s a lot of misconceptions spread around the internet where people are passing round information and when you ask where they got it from they say they got it from the well known reliable source of that guy who spotted him once who got it from a self-proclaimed fitness guru. We’ve tried to avoid any kind of “bro-science” by getting sourced material. The main source of this information at the moment is the Physiology of Exercise For Physical Education and Athletics, Fourth Edition, by Herbert A. deVries. All the studies backing up the information is towards the bottom of the page. For the most part we haven’t given definitive answers to questions rather we’ve stated what the evidence shows.
1 Interval Training
2 Frequency of Workout
3 Strength Training
4 Isometric Training
5 Disuse and Atrophy
6 Exercise Velocity
7 Recovery From Fatigue
8 On Warming Up
9 On Stretching
1: Interval Training
Interval training is when you alternate between periods of low- and high-intensity exercise. You might, for example jog for a few minutes and then sprint for periods of 40-60 seconds with a 2 minute jog in-between each interval. It’s advertised as a way of losing weight and improving endurance in a relatively short period of time. The weight loss aspect is covered in the “Weight Gain and Loss” chapter but a study by Scandinavian investigators showed that people using interval training could handle heavy exercise loads with low accumulation of oxygen debt and lactic acid which contribute to fatigue. Saltin (1), a Scandinavian authority in the area of the investigation concluded after reviewing the evidence that there was no apparent advantage over continuous training in improving the persons endurance.
Roskamm (2), compared the effect of continuous and interval training but only found small differences between the training response at maximal exercise. When heart rate at moderate exercise loads was tested, however, the continuous exercise produced better results. The advantage of interval training is that it may better replicate the demands of the activity the individual is training for; using the same muscles, fibre types and muscle recruitment patterns. Even though interval training has been shown to reduce the build up of lactic acid and oxygen debt, the interval training did not seem to improve endurance.
2: Frequency of Workout
Studies (3, 4, 5, 6) show that there is little if any improvement from working out once per week but improvement accelerates rapidly when you increase the frequency to 4-5 times per week. Above 6-7 times per week the improvements aren’t as substantial. Engaging in 7 heavy workouts per week is counter productive since it leaves no time for the muscle glycogen overshoot phenomenon to occur. When what we ingest is broken down into glucose, the glucose is trapped in muscle cells and can either be used directly or turned into glycogen and stored. The amount of glycogen stored in the muscle cell determines that muscles endurance for exercise. Bear in mind that protein, fat, and lactic acid can all be broken down to glucose and thus can be stored as glycogen in the muscle cells. This is the glycogen overshoot that is needed by muscles to contract. Therefore the optimal payoff from workouts occurs at between 3-5 workouts per week.
The question then becomes; when should I have these rest days for glycogen stores to build up and muscle to repair? Moffatt and associates (7) showed that there no difference in young males when training Monday, Tuesday, and Wednesday and resting for the remainder of the week. As opposed to resting on alternate days and so conducting workouts Monday, Wednesday, and Friday.
With a hectic lifestyle comes periods where you may not have the energy or time to exercise and then there comes the worry of how long you can wait before you begin to lose all that your training has accomplished. It has been shown, however, that once you have accomplished a conditioning effect, say completing 50 press ups, that effect can be maintained with as little as 2 workouts per week provided the intensity and duration of the workouts are maintained (8).
3: Strength Training
The best evidence available suggests that heavy resistance exercise results in a selective hypertrophy the fast twitch fibres (27, 28). Although there is no gain or loss of fast (FT) or slow (ST) twitch fibre numbers, the selective hypertrophy of the FT fibres has been reported to bring about marginally significant changes in the cross-sectional areas, with the FT increasing by 5%-12% as the ST decrease by roughly equivalent amounts (27). The increased area of FT fibres appears to be accounted for entirely by growth of the IIa (FOG) fibres, with no change in the IIb (G) fibres.
4: Isometric Training
In 1953 Hettinger and Mueller’s studies on isometric training (44) it was found that that a maximum training effect could be obtained from one daily 6-second isometric contraction against 67% of an individual’s maximal contraction strength. Greater force, duration, or repetitions did not seem to increase the rate of strength gain, which they found averaged 5% per week when training was performed five times per week. Strength improved in various muscles from 33% to 181%. However, recent work from the same German laboratory (45) has modified the work of Hettinger and Mueller, and it now appears that the rate of strength gain approximately doubles when maximal contraction strength is used instead of two-thirds maximum. Also, a higher end strength can be reached by increasing the number of 6-second repetitions to between five and ten. The work of Mueller and Rohmert (45) seems to be definitive, so there are few choices to be made as to frequency, intensity, and the like. Best results appear to be obtained by using maximal contraction strength, held for 5 seconds and repeated for 5-10 repetitions times daily. If a well-rounded workout is desired it is best to apply these contractions at varying points in the range of motion or, if the activity that is trained for demands strength or power, throughout the entire range of motion. For a press-up, for example, this means starting with straight arms, lowering yourself until your chest touches the ground, lifting your hands from the ground, quickly returning them to the ground and then pressing up until arms are once again straight leaving as little time as possible with the chest resting on the ground. In some cases, as in ballistic movements, analysis many indicate the need for maximal power at the beginning of the motion, and exercises should be designed accordingly. In the press-up example this would mean an explosive upward motion. The work of De Lorme and Watkins (46) recommended the following program:
1 set of 10 repetitions with 1/2 10 RM
1 set of 10 repetitions with 3/4 10 RM
1 set of 10 repetitions with full 10 RM
(10 RM (rep-max) is the greatest weight that can be lifted 10 times)
Other investigators have furnished support for the effectiveness of this method of weight training (34). However, systematic investigations of the value of varying numbers of repetitions seem to indicate that fewer repetitions may be even more effective: four, five, or six. Berger’s data (36) provides rather good evidence that between 4 and 8 repetitions provide maximal results in terms of strength gain. Another approach that has been validated under laboratory conditions as being very effective is that of doing 10 repetitions in which each repetition is done against the maximum possible for that particular execution (47). In other words, completing a repetition with the heaviest load possible, then decreasing the weight such that you can only do one repetition of that load and so on. Individuals start with their own 1 RM and use as large a weight as possible for each successive lift. In comparison with the use of 1 set of 10 repetitions with the full 10 RM, it was shown that significantly greater gain in strength was achieved. Muscle hypertrophy seems to be best brought about by the De Lorme and Watkins procedure (34). The optimal number of workouts per week is probably between 3-5, depending on the amount of other vigorous activity a given individual may be indulging in (work or play) beyond the weight training program (48). In summery, reaching maximal contraction produces the fastest strength gains (training to failure). A duration of 5 seconds is optimal for these exercises. 5 second contractions doesn’t mean that exercise has to be sacrificed. Many exercises will involve lowering a weight with gravity as part of a repetition. For the press-up example this would be lowering yourself to the ground. If you do this quickly then gravity is doing the work for you and you have nothing to gain from that part of the repetition. Instead the muscle can be worked by slowly lowering yourself to the ground. Therefore you could lift your body from the ground explosively and then lower yourself slowly back to the ground thus getting the best of both worlds. Higher end strength values can be achieved by increasing repetitions from 1 to 5 to 10 times a day.
5: Disuse and Atrophy
Evidence has been presented (28, 29) to show that immobilisation of a limb results in decreased fibre size but no loss in number off fibers. Bear in mind that we saw in the previous section that exercise increases the size of muscle fibres rather than the number of muscle fibres. Since muscle fibre size decreases with disuse we may say that all changes in muscle tissue brought about by exercise are impermanent, and that training must be carried on systematically throughout a lifetime. Otherwise, a degree of atrophy from disuse will set in. There is also evidence that stretch of muscle may not only retard atrophy of a denervated muscle but may even induce muscular atrophy (30, 31). This is because the transport of amino acid into the stretched muscle is improved. We must load the muscle beyond its normal everyday use to bring about an adaptive response. Hettinger and Mueller (33) defined 20% maximal voluntary contraction (MVC) for 1 sec/day as the load required to prevent atrophy and 35% MVC as the threshold value at which training response began to appear. Where MVC is the when you have trained to failure and you cant complete another full repetition without breaking form. However, holding muscle tensions between 35% and 100% MVC brings an increase tension in the muscle and connective tissue (33), gradual occlusion of blood flow (34), increased local temperature (35), hypoxia (36), and increased levels of metabolic products (37). At Harvard, Goldberg and associates (38) point out that the factor that best explains all those experimental observations with respect to muscle hypertrophy, including the fact that even passive stretching can improve protein turnover and amino acid transport and can stimulate muscle O2 consumption, is tension development in the muscle.
6: Exercise Velocity
The strength gains from heavy resistance exercise appear to be limited to velocities at or below those used in training. Two studies using isokinetic methods have agreed that the significant strength benefits gained in training could not be demonstrated when the velocity of contraction in the test was greater than that at which training occurred (39, 40). This effect was best demonstrated by Ikai (41) who found that training at 100% MVC improved force but not velocity; training at 30%-60% MVC improved both force and velocity; training with no load and maximum velocity improved velocity but not force. So when the load was light enough such that it required 30%-60% of MVC to complete a repetition at maximum speed that persons force and strength and velocity improved. More recent work supports Ikai’s findings (42, 43). This means that although the idea of using TUT training (time under tension) does result in greater strength gains, it means that you wouldn’t be able to utilise that strength if you tried to complete a similar exercise at speed which might be necessary in a fight or sporting scenario.
7: Recovery From Fatigue
It has been shown that recovery of maximal strength after isometrically induced fatigue is complete in about ten minutes (49). Interestingly, the recovery of endurance function is related to the tension of the fatiguing contraction, whereas strength recovery is not (49).
Clarke and Still (50, 51) conducted two series of training experiments, one of which used low resistance and high repetitions, a combination that is ordinarily considered to be endurance-type training. In the other experiment they used the De Lorme technique of heavy resistance and low repetitions (strength-type training). Surprisingly, the gains in strength were as great from endurance training as from strength training, and the gains in absolute endurance were also similar in the two training experiments although relative endurance did not change. Two other investigations support their findings (52, 53), which leads to the conclusion that the first order of business in improving athletes’ muscular endurance is to optimise their strength. Since heavy resistance training such as weight training is more time efficient, this would seem to be the method to choose.The overload principle applies to muscular endurance as well as to strength. This is not to be confused with repetitions of easy work loads which do not bring about optimal improvement in muscular endurance. In general, suitable overload training brings about improvement in strength and muscular endurance simultaneously. The power (work per unit time) of muscular contracting seems to be more important than the total amount of work in brining about a training effect. Although fat produces more than twice as much energy per gram as carbohydrate, it requires more oxygen for each calorie (213ml/cal of fat compared with 198/cal of carbohydrate). Increased muscular efficiency of up to 10% had been shown experimentally for high carbohydrate diets (54). It had also been shown experimentally that fatigue occurred earlier on high fat diets (55).
8: On Warming Up
On theoretical grounds it might be expected that a warming-up that resulted in increased blood and muscle temperatures should improve performance through the following mechanisms:
1 Muscles relax and contract faster.
2 Lower viscous resistance in the muscles increases efficiency.
3 Haemoglobin gives up more oxygen at higher temperatures and also dissociates much more rapidly.
4 Myoglobin shows temperature effects similar to those of haemoglobin.
5 Metabolic process rates increase with increasing temperature.
6 Resistance of the vascular bed decreases with increasing temperature.
Gutin and his co-workers have suggested another rationale for the use of warm-up, based on a mobilisation hypothesis (59, 60, 61, 62). They view exercise prior to working out as a mobilising stimulus for the systems involved in O2 transport, thereby allowing the subject to reach a high level of aerobic metabolism more quickly doing the subsequent athletic task. This reduces the initial O2 deficit, thus leaving more of the anaerobic capacity for later use.
Although there is still some uncertainty about the value of warm-up in improving performance, warming up has been retained as standard practice on the grounds that it might prevent injury to muscles. However, there is no direct evidence to support this contention, although considerable data exists showing that deep muscle temperature and compliance should be very important factors in the incidence of athletic injuries (63).
9: On Stretching
Static stretching is effective at increasing range of motion (ROM). The greatest change in ROM with a static stretch occurs between 15 and 30 seconds (64,65); most authors suggest that 10 to 30 seconds is sufficient for increasing flexibility (65-68). In addition, no increase in muscle elongation occurs after 2 to 4 repetitions (69-79). Static stretching as part of a warm-up immediately prior to exercise has been shown detrimental to dynamometer-measured muscle strength (80, 89) and performance in running and jumping (80-89).
In 1983 Ekstrand et al (90) found that a group of elite soccer teams randomised to an intervention of warming up and stretching before exercise, leg guards, special shoes, taping ankles, controlled rehabilitation, education, and close supervision had 75% fewer injuries than the control group. There was one other randomised controlled trial (RCT) and a quasi-experimental study that also supported this conclusion, (91, 92) both using at least warm up as a co-intervention.
Clinical evidence suggesting that stretching before exercise does not prevent injuries has also been reported. Van Mechelen (93) published an RCT showing that the intervention had no effect, but many subjects were non-compliant. If we look at “less strong evidence”, both Walter et al (94) and Macera et al (95) published cohort studies that suggested that stretching before exercise was not beneficial, and there have been several cross sectional studies as well. (96, 97) Of course, there were significant limitations to all of these studies.
Some people believe that a compliant muscle is less likely to be injured. From the basic science research, we find that an increase in tissue compliance due to temperature (98), immobilisation (99), or fatigue (100, 101) is associated with a decreased ability to absorb energy. Although this is not the equivalent of stretching, no basic science research shows that an increase in compliance is associated with a greater ability to absorb energy. Most injuries are believed to occur during eccentric contractions (102), which can cause damage within the normal range of motion because of heterogeneity of sarcomere lengths (103-106). If injuries usually occur within the normal range of motion, why would an increased range of motion prevent injuries? Even mild stretching can cause damage at the cytoskeletal level (107). There is no basic scientific evidence to suggest that stretching would decrease injuries. Understanding these principles, we can now explain the apparent contradiction in the clinical literature. Re-examining the RCTs that support stretching before exercise, one finds that all of them included at least one other effective co-intervention—for example, warm up, leg guards, etc. (90-92) Therefore it is not surprising that these RCTs found less injuries in the intervention group. On the other hand, the cohort studies, (94, 95) and the RCT by van Mechelen et al, (93) controlled for these co-interventions in the analysis stage. Therefore, although formally a “weaker design”, the studies suggesting that stretching before exercise is not beneficial should be weighted as stronger because the analysis was more appropriate. However, this was only recognised because the basic science was reviewed. There’re people who say that warming up and stretching does prevent injury because they didn’t do it a few times and got injured and they haven’t been injured once after warming up and stretching. There’re 3 main issues with this. Firstly, that is an embarrassingly small sample size for their experiment. Secondly, I somewhat doubt the test was controlled in any way. And thirdly, argument by anecdote is a logical fallacy. For example: Jason said that that was all cool and everything, but his grandfather smoked, like, 30 cigarettes a day and lived until 97 – so don’t believe everything you read about meta analyses of methodologically sound studies showing proven casual relationships.
One the other hand. you could take the “better safe than sorry” approach and stretch anyway just in case it does inexplicably prevent injury. But bear in mind there’s no conclusive evidence to back you.
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