Sorry, its a little rushed guys. Never did have great time management!
High Intensity Overtraining in Weightlifting
Overtraining (OT) has been defined as ‘An increase in training intensity or volume that results in a long term (>2 weeks) performance decrement’ (5). Alternative terms for OT include burn out, staleness and chronic fatigue. Overreaching has been used to define a milder form of OT where performance decrements are more short term. Interestingly and conversely, undertraining is defined as a decrease in training intensity or volume that leads to performance decrements. High intensity OT has been described as ‘Basedowic’ (or ‘sympathetic’) OT because the symptoms are believed to be similar to Basedow’s disease. This is a thyroid condition that causes increased metabolic and heart rate as well as weight loss and irritability (1,3).
Any training stimulus that is sufficiently strong to disrupt the body’s homeostasis will induce a short-term performance decrement. Depending on the magnitude of the stimulus that decrement may last a few hours or a few days. If subsequent training is undertaken before homeostasis has been restored an accumulation of fatigue occurs (11,14).
Planned, controlled overreaching is often called an ‘impact’ period. These cause an accumulation in fatigue but it is hypothesised, a greater adaptation stimulus when rest is finally taken. Commonly, impact periods are followed by periods of ‘unloading’ (lower intensity/volume) where ‘rebound’ super-compensation is able to occur (2,8,14). If impact periods continue beyond adaptation capacity over reaching will develop into OT. Often the effect of a stimulus lags the stimulus itself and this can cause difficulty when interpreting training effects (3)…
In order to help athletes optimise their training and train ‘smarter not harder’, it is important to understand the causes of OT and to highlight potential markers that could permit early detection. This paper will look specifically at high intensity OT in weightlifting, a sport where intensity can be easily quantified.
Resistance Exercise Variables
Before addressing OT it is first necessary to define and discuss the variables that interact, and that can be manipulated, to determine the training stress. The two most important variables and the ones that will be addressed in this paper are intensity and volume.
Intensity is regarded as the most powerful training variable and there is a threshold that must be breached to generate an adaptive stimulus. It is generally defined as the percentage of one repetition max (1RM) on a given exercise. It is also possible to measure it as a percentage of a multiple repetition max, e.g. 5RM or 10RM. When performing multiple repetitions it should be noted that, due to fatigue, relative intensity increases with each subsequent repetition. For example when performing a 5RM the load may only be 85% 1RM but the final repetition would constitute 100%.
The kinematics of an exercise may alter depending on the intensity. For example in the squat, as loads increase the lifter increases hip inclination during the concentric phase in order to shorten the knee’s moment arm and permit successful completion of the lift. In order to avoid risk of injury 1RM could be defined as the maximum load performed with strict form
Strength trainers often train at percentages of their (recent) 1RM. A 1RM however, is usually achieved when rested and with the added arousal of competition. Actual daily maximums may be more than ten percent less; therefore a load equal to 90% 1RM may actually constitute 100% on a particular day (2). Bulgarian weightlifting training utilises session maximums (there may be three per day) by having lifters work up to maximum and then take subsequent lifts at or below that load (11
Intensity can also be affected by the speed of a movement. In a concentric movement with a sub maximal load intensity is generally positively correlated with the speed of movement. For example a clean at 100kg is less stressful than a snatch at the same load. In contrast, for an eccentric movement intensity is negatively correlated with movement speed (14).
There is also a threshold of volume required to elicit a training adaptation. Volume is typically defined as the number of repetitions multiplied by the number of sets. Volume may also be measured over a specified length of time and could therefore incorporate frequency (see below). Additionally when the same muscles are targeted by different exercises (e.g. Snatch and clean) the number of exercises also contributes to total volume
Elite weightlifters typically perform sets of one to three repetition since this repetition range has been found to elicit optimal strength increases whilst also minimising ‘non- functional’ hypertrophy (i.e. of the sarcoplasm rather than of the myofibrils) (14). Additionally high repetitions lead to a deterioration in technique that increases risk of injury and which may reinforce incorrect movement patterns (2). Weightlifters therefore generally increase volume through sets and/or frequency.
Tonnage is defined as volume multiplied by load and hence interlinks both the previous variables. Taken alone however it can be a misleading since high volumes with low intensities could have greater tonnage than smaller volumes with higher intensities (e.g. 3x8r @ 75kg Vs 8x3r @ 90kg). As a lifter improves tonnage increases but this is primarily due to an increase in load. If volume continues to increase there will come a point where the lifter has insufficient ability to adequately recover.
Frequency is defined as the number of sessions in a particular time frame. It is generally accepted that a heavy training stimulus requires forty-eight hours recovery before any ‘super compensation’ is attained. In apparent contradiction however, elite weightlifters train six days per week and up to three times per day. The consecutive training days cause an accumulation of fatigue but increase the adaptation stimulus when a day’s recovery is finally taken. In contrast if training frequency is too low the athlete will detrain between sessions and no progress will be made
Length of rest permitted between sets is another (less powerful) training variable. Short rests reduce work capacity due to residual fatigue (PC has insufficient time to replenish) For example if 5 repetitions are performed at 90% 1RM with one minute recovery, the last set may actually constitute 93% maximum. Density incorporates this variable and is defined as volume divided by workout duration.
The load and volume a lifter can employ without OT can be described as tolerance. Tolerance is a long-term adaptation to training and is also influenced by outside factors such as length/quality of sleep, diet, life stresses and supplemental training.
There is currently limited research available that addresses the question of the relationship between intensity and OT in weightlifting. A major problem for physiologists has been designing a protocol that elicits an OT response as defined in the introduction. Much work in designing a protocol to elicit an OT training response has been done by Fry and Kraemer. Below I outline the protocol of three studies and comment on their design and results. All three studies used subjects that were ‘recreational’ strength athletes able to squat more than 1.5 times body weight
Study 1 (5): 3 weeks; 5 days per week; 8 single repetitions at 95% 1RM; Machine squat.
This protocol surprisingly resulted in an increase in average, one repetition maximum. Other non-specific performance parameters however did show a decline. Sprint times over 10 and 30 metres increased and isokinetic knee extension strength decreased. These markers could therefore be utilised as potential markers for OT. The findings have obvious implications to sports people who have a strength component in their training.
It appears from this evidence that maximum force (i.e. ‘limit’ strength) is maintained longer than speed strength (i.e. power) during periods of high intensity training. It is interesting therefore to consider how the results might alter if a dynamic exercise such as the clean was substituted for the squat. I contend that the importance of rate of force development in this exercise would increase the possibility of a specific performance decrement.
The squat has been described as the ‘King of Exercises’ due to the muscle mass that is activated during the lift. The researchers in this study decided to use a squat machine rather than the ‘free weight’ barbell squat. This may have been a safety precaution since when lifting at maximum with free weights there may be alterations in technique that increase risk of injury. A machine squat however moves only through one plane and therefore does not require the synergistic muscle support necessary in the free weight variation. It has been suggested therefore that when using a squat machine, the volume required to induce OT increases (11). It is intuitive to expect greater volumes also to be required for exercises that utilise less muscle mass and/or motor control.
It has been recognised by researchers that the training stress required to induce OT is subject to wide individual variation hence the choice of subjects is important when interpreting results. Unfortunately elite level subjects are unlikely to participate in a study that’s intention is to induce a prolonged drop in performance. The subjects in this study were described as ‘recreational’, an open term that permits wide variations in factors such as training age, typical training volume/intensity, exercise selection, supplements, diet, life stress etc. Tolerance to training increases with training age whilst trainability is typically inversely proportional to training age (2). That is as a lifter improves subsequent improvements are more difficult to achieve.
The training volume is significant since elite weightlifters rarely perform more than three repetitions per set whilst ‘recreational’ lifters typically perform a higher number of repetitions at a much lower absolute intensity. This protocol may therefore induce neural adaptations in a recreational population tsuch as increased motor unit recruitment, decreased inhibition and increased inter muscular coordination (7).
Study 2 (6): 4 weeks; 3 days per week; 2 singles at 95% 1RM and 3 at 90% 1RM; Free weight squat
This protocol resulted in a 1RM plateau and decreases in sprint performance over 10m but not 30m. The investigators recognised the likely increased stress of performing a free weight variation of the squat lift and reduced volume and intensity accordingly. They also decreased frequency of sessions from five to three that is more typical for strength training for other sports.
It is possible that the plateau in strength in this study resulted from a decrease in volume rather than an increase in intensity. Also the investigators used loads that were fixed percentages of a pre test maximum. Therefore, due to day-to-day variations, subjects may have actually used loads that were relatively more (or less!) intense than those specified. As for study 1, greater information regarding past training of the subjects would be useful in more accurately assessing the results.
Study 3: 2 weeks; 6 days per week; 10 single repetitions at 100% 1RM; Machine squat.
This protocol despite being only two weeks in duration did appear to be sufficiently stressful to elicit an OT response. Results showed a significant (>10%) decrease in maximum strength that required between two and eight weeks to recover from. As expected, in conjunction with study 1, there were also decreases in none specific tests such as isokinetic knee extensions and short sprint performance.
An important question is what the strength decrements resulted from maladaptions at the periphery or from decreased central drive. To investigate this the quadriceps muscle group was maximally activated through cutaneous stimulation of the femoral nerve. Force output was found to decrease implying that at least some of the decrements resulted from maladaption of the peripheral muscles.
Maximum intensity was defined in these studies to be 1RM but how powerful would the stress have been if sets were performed instead at multiple repetition maximums? If volume was equalised (e.g. 5 doubles at 2RM or 2 sets at 5RM!) absolute intensity would decrease but exercise density would increase. I hypothesise that the former variable is more powerful and that it would necessitate greater volumes of work when using multiple repetition maximums to elicit the same response. Further research is required to improve our understanding of how intensity and volume interact.
The catecholamines, adrenaline and noradrenaline are secreted from the chromaffin cells of the adrenal medulla. Noradrenaline constitutes less than 20% of medulla secretion since it is primarily secreted from adrenergic neuron boutons. Plasma NE concentration has been suggested as an indirect measure of sympathetic nerve activity (6).
Catacholamines act through interaction with alpha or beta adrenergenic membrane receptors of target cells. Secretion from the medulla, above basal levels, is controlled through innervation from the splananchic nerve. Basal levels are thought to be controlled by cortisol secreted from the surrounding adrenal cortex. Catecholamines are fast acting and have a multitude of roles within the body. Specific to this paper, they increase skeletal muscle contractility, by increasing transmembrane transport of potassium and sodium ions and increase the availability of energy substrates by stimulating lipolysis and glycogenolysis. (thus explaining its use as a fat burner!) (5,6,9,11).
Plasma catecholamine concentrations are positively correlated to exercise intensity and, for noradrenaline, also to exercise duration. Long term resistance training increases the acute response at any relative intensity and hence greater maximum concentrations are possible in chronic anaerobically trained populations (4,5,9).
OT does not influence resting catecholamine concentrations but does increase the acute response to training seen within one week of an over training protocol (5,6). This increase is believed to occur due to a decrease in utilisation resulting from down regulation of skeletal muscle beta receptors (5,6). This occurs despite of a decrease in absolute work due to strength decrements and an increased anticipatory response. In none overtrained athletes, post workout catacholamine concentrations are positively correlated with strength but this is not the case with overtrained subjects.
Acute post training catecholamine concentrations appear to be the most sensitive marker of high intensity OT currently available. Long term monitoring of athletes’ catecholamine concentrations may therefore permit individualised feedback regarding training status. Additionally it has been hypothesised that prolonged OT may also reveal altered resting catecholamine concentrations though ethical constraints may prevent laboratory analysis of this.
Peptide F is a molecule co-secreted with epinephrine from the chromaffin cells in the adrenal medulla. Its’ physiological function is not currently understood but has been linked to immune function. High intensity OT does not cause an increase in Peptide F concentrations at rest or in acute response to exercise (5,6). However, as previously discussed, acute epinephrine concentrations do increase hence the ratio between the two is altered. It has been hypothesised that epinephrine is preferentially secreted in order to preserve strength levels (6). Additionally the alteration in the ratio has been suggested as a contributor the increased frequency of illness/infections during OT (5).
Testosterone (T) is an anabolic and androgenic steroid hormone whose serum concentration is a limiting factor to muscle growth (12). T increases protein synthesis by increasing transport of amino acid across cell membranes and by increasing mRNA and DNA synthesis (5). T also has positive effects on the nervous system by increasing acetyl choline receptor density and size of motor end plates in some peripheral muscles (11).
T in males is secreted primarily from the Leydig cells of the testes. T secretion is regulated by Leutinizing Hormone secreted from the pituitary and Gonadotropin Releasing Hormone secreted from the hypothalamus in turn, regulates LH (13).
Since T is sparingly soluble in blood only approximately 2% of T is in the free, unbound form. Approximately 60% is bound to a protein synthesised in the liver called Sex Hormone Binding Globulin (SHBG). Due to the strength of the bond to this carrier the T is biologically inactive. The remaining T is bound to albumin but these bonds are weaker and hence the T remains ‘bio-available’ (5,13).
T increases acutely in response to weight training by as much as 70%. The increase is greater in response to bodybuilding training (i.e. moderate intensity, high repetitions and short rest periods) than weightlifting training (i.e. high intensity, low repetitions and long rest periods) but is not related to absolute strength (13). The mechanism(s) responsible for this acute increase is much debated. Decreased renal blood flow causing reduced metabolic clearance of T, altered testicular blood flow may increase T secretion and decreased plasma volume would cause an increase in T concentration without an increase in total T (5,13).
Long term resistance training causes an increase in bio-available T at rest due to a decrease in SHBG. This is a long-term adaptation to training that has been positively correlated with increased strength (9).
High intensity overtraining has not been found to effect resting total or bioavailable testosterone concentrations (4,5). It has been hypothesised however that if an OT protocol could ethically be allowed to continue eventually a decrease in resting T would occur. The acute T response to training has shown minor increases although this is thought to result from increased catecholamine levels (see previous) (5,7). T does not therefore appear to be a valid marker of high intensity overtraining.
Many texts site the following as physiological markers of high intensity overtraining: increased resting heart rate and blood pressure, disturbed sleep, decreased body mass and increased creatine kinase. Research however has been unable to substantiate these subjective findings.
Due to the difficulties in generating an OT response in controlled scientific settings there is currently only limited research on high intensity OT. The research cited in this review used repeated maximal squat lifts to induce an OT state. Further research is required to investigate the effects of other exercises and to improve our understanding of the interaction between intensity and volume.
An important finding was that none specific parameters linked to rate of force development (e.g. short sprint speed) were negatively affected prior to actual squat performance. Sports people should therefore be advised to monitor explosive strength (e.g. medicine ball throw) in addition to limit strength parameters.
Acute catecholamine response appears to be the only reliable physiological marker of this mode of OT. Future research is therefore required to investigate more fully this response in order to produce guidelines to help athletes and coaches monitor for the condition.
It is very possible that prolonged periods of OT may elicit responses that are not evident in the short duration studies currently available. Ethical constraints however may well prevent these investigations taking place.
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